Solid organ and bone marrow transplant recipient patients are prone to develop infections particularly Cytomegalovirus (CMV) infection which is associated with the development of CMV disease,allograft dysfunction, and death. First line treatment is ganciclovir but these days patients have developed resistance to ganciclovir. Mechanism of action of ganciclovir:
Ganciclovir –an antiviral agent ,inhibit CMV DNA polymerase, first approved by the FDA in 1989.Various different gene mutations are responsible for resistance. Gene UL97, and gene UL54, both causes resistance individually and in combination if it occurs, then very high level of resistance.Risk factors which increase the resistance to ganciclovir include: CMV D+/R-,Prolong exposure to ganciclovir ,intense immunosuppression, and heavy viral load.
According to the data of two Chicago transplant centers,from 1994-2001,Lung transplant represent highest level of resistance comprising about 15%. Prevention of Ganciclovir-resistant CMV infection:
Drugs which can be used for ganciclovir resistance include : valganciclovir, foscarnet, cidofovir or Leflunomide Valganciclovir (VGC): 10 times more potent than ganciclovir Foscarnet: Inhibit CMV DNA polymerase-competitive.
Side effects-nephrotoxicity, electrolyte abnormalities, and seizures. Cidofovir: FDA approved in 1996, monophosphorylated cytosine analogue that needs phosphorylation to inhibit DNA polymerase activity.
Side effects of cidofovir is nephrotoxic and ocular toxicity Leflunomide-immunomodulatory drug, and is a protein kinase inhibitor and also competitive inhibitor of dihyrdoorotate dehydrogenase
Side effects: raised liver enzymes,alopecia , skin rash , hypertension and pancytopenia.
In my practice,valganciclovir is used for prophylaxis ,however, for mild –moderate disease valganciclovir and ganciclovir for severe infection. Unfortunately we don’t have facility of drug resistance testing and non availability of drugs like cidofovir ,foscarnet so no experience ,But leflunomide is available,have used this drug in BK nephropathy.
This review is discussing the treatment strategies available to treat ganciclovir-resistant CMV infection. Ganciclovir resistance can be assayed either phenotypically or genotypically. The “gold standard” test is the plaque reduction assay in which human fibroblasts are cultured with ganciclovir at various defined concentrations. The concentration of ganciclovir required to inhibit 50% of CMV growth is the IC50 value. Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml.
Valganciclovir has offered a potential means to decrease ganciclovir resistance. valganciclovir was shown to be superior to oral ganciclovir for the prevention of resistant CMV infection.
Foscarnet can lead to clearance of blood and urine cultures as well as stabilization of retinitis.The major limitation to greater use of foscarnet has been its adverse effect profile. Foscarnet is associated with renal toxicity, electrolyte abnormalities, and seizures.
combined ganciclovir and foscarnet at reduced doses as ganciclovir and foscarnet resistance are usually associated with different gene mutations. combination therapy has been shown to be effective in pre-emptive therapy of CMV antigenemia in non-ganciclovir resistant bone marrow transplant patients, permit lower dosing of each agent and consequent mitigation of their different toxicity profiles.
Cidofovir was approved by the FDA in 1996 for the treatment of cytomegalovirus infection. The pharmacology of cidofovir is such that it has to be given intravenously but need only be administered once or twice per week. Like ganciclovir and foscarnet, resistance to cidofovir is low at baseline but rises under sustained drug pressure. it has been noted in case reports to cause bone marrow suppression and ocular disease including iritis, uveitis, and vitreous hypotonicity.
Leflunomide has attracted particular interest from the transplant community because in addition to immunosuppressive properties it is active against viruses. It has a long-half life on the order of 15-18 days potentiated by substantial enterohepatic recirculation. Without a loading dose it is estimated that it would take nearly two months to achieve steady-state plasma concentrations. Likewise, after discontinuation of the medication it can take as long as two years for the body to entirely clear the drug. Renal excretion is limited. Its potential to inhibit a multidrug-resistant CMV isolate was confirmed in vitro by plaque reduction assays using a virus recovered from a heart transplant patient with CMV pneumonitis. Cases of hepatic necrosis and death from liver failure have been reported but are rare.
Our local practice is limited by the un-accessible alternative medications
1. Please summarise this article
Cytomegalovirus (CMV) infection is a common and serious complication of immunosuppression in solid organ transplantation and in AIDs. If not treated it is associated with a high risk for the development and progression of CMV disease, allograft dysfunction, and death.
First line treatment for CMV infections and disease is ganciclovir, but some centres have reported a small but rising incidence of ganciclovir resistant CMV infections.
Strategies available to treat ganciclovir-resistant CMV infection include approved alternative agents foscarnet and cidofovir, the use of combination ganciclovir and foscarnet at reduced doses, and the novel immunomodulatory agent, leflunomide.
Mutations arising in UL97 phosphotransferase lead to ganciclovir resistance. Similarly, mutations arising in the DNA polymerase gene UL54 also confer resistance to ganciclovir. Different UL97 mutations are associated with different degrees of ganciclovir resistance. Definition
Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml. Options for treatment of ganciclovir resistant CMV: Foscanet Cidofovir Lefluconamide.
Foscarnet and cidofovir limits their attractiveness as anti-CMV agents. The use of reduced dose combination therapy appears to deliver potent antiviral therapy with less risk of nephrotoxicity but this approach requires further study.
The novel immunomodulatory agent leflunomide holds promise as a future agent for the management of CMV since it both potentiates immunosuppression and suppresses CMV reproduction. 2. Please reflect on your practice: We use gancicolovir/valganciclovir for treatment of CMV infection. We did not face a case ganciclovir resistance. We do not have tests for ganciclovir resistance. If we face such case we need to ask for referral to higher center for treatment.
Treatment of Ganciclovir Resistant Cytomegalovirus Infection
Cytomegalovirus (CMV) infection is a common and serious complication of immunosuppression
in solid organ and bone marrow transplant recipients, and in patients with AIDS.
Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase.
Ganciclovir resistance can be assayed either phenotypically or genotypically.
Ganciclovir resistance has been
defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml.5
Ganciclovir resistance is uncommon at baseline amongst untreated patients but arises rapidly after prolonged exposure to antiviral agents
Risk factors for the acquisition of ganciclovir resistance include CMV seronegativity at
transplant when receiving a seropositive organ, degree of immunosuppression, magnitude of
CMV viremia, and prolonged exposure to anti-CMV medication.
The alternative therapies foscarnet and cidofovir both appear to have good in
vivo activity against cytomegalovirus but both are limited by their propensity to cause acute renal failure.
Ganciclovir resistance is uncommon but can arises rapidly after prolonged exposure to antiviral agents.
The prevalence of CMV resistance in solid organ transplant recipients, ranges between 0 and 15%. The risk of developing ganciclovir resistance differs according to organ transplanted .
Definition
Ganciclovir resistance can be assayed either phenotypically or genotypically. The standard test is the plaque reduction assay. The human fibroblasts are cultured with ganciclovir at various defined concentrations. CMV growth can be quantified by counting viral plaque formation or by a DNA hybridization technique. The concentration of ganciclovir required to inhibit 50% of CMV growth is the IC50 value. Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6μg/ml.
Ganciclovir resistance can also be detected by genotype analysis. Prevalence and Risk Factors for Resistance :
Risk factors for ganciclovir resistance include :
1- CMV seronegativity at transplant when receiving a seropositive organ
2- degree of immunosuppression
3- magnitude of CMV viremia
4- prolonged exposure to anti-CMV medication. Prevention of Ganciclovir Resistant CMV Infection : 1- Valganciclovir which is valyl ester prodrug of ganciclovir
2- Foscarnet
The side effect include renal toxicity, electrolyte abnormalities and seizures
3- Combination therapy with low dose ganciclovir and foscarnet
4- Cidofovir
5- Leflunomide
the main side effect is transaminase elevation
Please summarize this article Ganciclovir resistant CMV is suspected if CMV PCR is not falling by >1copies/ml after 2 weeks or if there is no clinical improvement. Risk factors for ganciclovir resistant CMV: CMV D+/R-, prolonged exposure, UL97 gene mutation and lung transplantation. Treatment of ganciclovir resistant CMV: 1-Foscarnet: side effects include nephrotoxicity, metabolic changes, cardiac arrhythmias, and genital ulceration. 2-Cidofovir: side effects include nephrotoxicity, neutropenia, metabolic acidosis and ocular hypotony. 3-Letemovir: can be used with other anti-CMV drugs, its dose should be adjusted in renal and hepatic impairment, it can interact with other immune-suppressive medications. 4-Maribavir: is effective against viral UL97 kinase, less hepatotoxic and nephrotoxic compared to ganciclovir and valganciclovir. 5-CMV IVIG: especially in cmv pneumonitis.
Untreated CMV is associated with CMV progression, allograft dysfunction and death.
First line of treatment for CMV infection is Ganciclovir, but there is small increasing incidence of Ganciclovir resistant CMV infection reported by many centers.
Mechanism of action and drug resistance of Ganciclovir
Ganciclovir is a guanosine analog that inhibits CMV DNA polymerase. The drug to be active need to be phoshorylated by the gene UL97. Mutation of this gene leads to Ganciclovir resistance. Also Mutation of the DNA polymerase gene UL54 leads to Ganciclovir resistance.
Ganciclovir resistance can be detected either phenotypically or genotypically
Ganciclovir resistance is defined as a plaque reduction DNA hybridization IC50 of > 6ug/ml.
Also can be detected via genotype analysis to assess for mutation in the UL54 and UL97 genes.
The prevelance of CMV resistance ranges between 0 to 15 %.
Risk factors for Ganciclovir resistance: CMV seronegativity at transplant when receiving a seropositive organ, degree of immunosuppression, magnitude of CMV viremia and prolonged exposure to anti CMV medication.
Prevention and treatment of Ganciclovir resistant CMV infection
1. Valganciclovir is more potent option for CMV prophylaxis and maintenance therapy compared to Ganciclovir. Valganciclovir is ten times more bioavialable than Ganciclovir. So it can decrease resistance.
2. Foscarnet
Foscarnet is a direct competitive inhibitor of DNA polymerase. Unlike Ganciclovir, it doesn’t need to be phoshorylated to become active, so it doesn’t affected by mutation in the UL97 gene.
The risk of resistance increases with the duration of drug and drug resistance is associated with an increased risk of retinitis progression.
The main limitation to the use of foscarnet is its side effect as it is associated with renal toxicity, electrolyte abnormalities and seizures.
The efficacy of foscarnet is similar to Ganciclovir, so it is a useful agent can be used in Ganciclovir resistance, but its side effects especially nephrotoxicity and electrolyte disturbance limit its use .
3. Combination therapy with dose reduced Ganciclovir and Foscarnet
4. Cidofovir
It is a monophosphorylated cytosine analogu and inhibits DNA polymerase activity .
It is given intravenously once or twice per week.
5. Leflunomide
It is immunomodulatory drug and it is active against viruses, it is protein kinase inhibitor and inhibits activated lymphocytes.
cmv resistant is in the range of 0-15, usually GCV resistant due to genetic mutation in UL97, UL54, carry high morbidity and mortality risk and is associated with graft loss and many risk factors related to the CMV serostatus of the recipient and donor (D+ve /R-ve, the immunosuppression type and intensity, duration of antiviral use and the subtherapeutic dosing, types of organ transplantation like higher risk in lung and heart transplantation while kidney transplantation have a lower risk
treatment for GCV-resistant CMV includes second-line traditional therapy with a wide range of side effects like foscarnet and cidofovir, leflunomide.
new novel oral treatment and is FDA-approved and recommended for treatment of R/R CMV disease after SOT, HSCT including the nice guideline 2023, can be given as oral medication with fewer side effects and cost-effective compared to early preemptive therapy in prevention and treatment for R/R CMV
screening for UL97 genetic mutation should be considered in suspected cases of CMV resistance.
narrative review level 5
My experience with resistant CMV infection was two cases from hematology after HSCT , and a second case of resistant PNH was on regular eculizumab both died with massive GI bleeding from confirmed CMV invasive colitis resistant to first-line treatment which is IV GCV and even second-line treatment
we use GCV IV as the standard of care for the treatment of CMV disease alternative oral valganciclovir 900mg BID for 3 weeks followed by 900mg OD for another 28 days or till two CMV PCR tests turned negative
we don’t have reported resistant CMV disease after kidney transplantation
Ganciclovir resistance should be suspected in patients who have rising or persistently elevated viral loads despite treatment with appropriately dosed ganciclovir for more than two weeks .
Ganciclovir Mechanism of Action and Drug Resistance-
Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase.In order to become active it must first be phosphorylated in three steps to a triphosphorylated form. Once phosphorylated, it acts as a competitive substrate for DNA polymerase and slows the replication of CMV DNA by DNA polymerase. Phosphorylation is accomplished by the phosphotransferase produced by the gene UL97. Mutations arising in UL97 phosphotransferase lead to ganciclovir resistance. Similarly, mutations arising in the DNA polymerase gene UL54 also confer resistance to ganciclovir
UL54 mutations are much less common and confer various patterns of cross-resistance depending on the specific mutation .UL54 mutations confer dual ganciclovir-cidofovir resistance. A significant number of patients with clinically ganciclovir-resistant CMV disease have no detectable mutation.
Definition-
Ganciclovir resistance can be assayed either phenotypically or genotypically. The “gold standard” test is the plaque reduction assay in which human fibroblasts are cultured with ganciclovir at various defined concentrations. Ganciclovir resistance can also be detected via genotype analysis to assess for known mutations in the UL54 and UL97 genes. Detection of resistance via gene mutations is attractive since it is less labour intensive, less time consuming.
Prevalence and Risk Factors for Resistance
Ganciclovir resistance is uncommon at baseline amongst untreated patients but arises rapidly after prolonged exposure to antiviral agents.The risk of developing ganciclovir resistance does seem to vary according to the organ transplanted (Lung most common,kidney least common).Risk factors for the acquisition of ganciclovir resistance include CMV seronegativity at transplant when receiving a seropositive organ, degree of immunosuppression, magnitude of CMV viremia, and prolonged exposure to anti-CMV medication.
Prevention of Ganciclovir Resistant CMV Infection
Valganciclovir is approximately ten times more bioavailable than oral ganciclovir. Since ganciclovir resistance is thought to be related to prolonged exposure to subtherapeutic plasma concentrations of ganciclovir, valganciclovir offered a potential means to decrease resistance while retaining the convenience and safety of an oral agent.
Treatment–
Foscarnet -A pyrophosphate analog that inhibits viral replication by selectively binding to viral DNA polymerase and requires IV administration. it is active against CMV with UL97 and UL54 mutations.Foscarnet is dosed at 60 mg/kg IV every 8 hours or 90 mg/kg every 12 hours, with dose adjustment for kidney function impairment. Foscarnet is highly nephrotoxic and patients should receive pre- and postinfusion hydration, and close monitoring of electrolytes, creatinine, magnesium, and phosphorus is essential given that acute kidney injury is common with foscarnet.
Cidofovir –t is active against CMV with UL97 mutations but not against CMV with UL54 mutations. It is also highly nephrotoxic. it can also cause uveitis .Cidofovir can be dosed at 1 mg/kg IV three times a week. Cidofovir should be given with aggressive hydration.
Leflunomide-Leflunomide has attracted particular interest from the transplant community because in addition to immunosuppressive properties it is active against viruses.Experimental data on the use of leflunomide in human beings is extremely limited and remains on the case report level. The largest series published to date describes the experiences of four renal transplant patients from India with symptomatic gastrointestinal CMV disease who were treated with leflunomide because they could not afford intravenous ganciclovir. All four patients had detectable CMV viremia via quantitative PCR. The patients were treated with a 100mg oral loading dose once daily for three days followed by 20mg/day for three months. All experienced clinical and endoscopic resolution of their disease as well as clearance of serum viremia. No significant adverse effects were reported.The major toxicity of leflunomide is transaminase elevation.
Conclusion–
The risk of renal failure with foscarnet and cidofovir limits their attractiveness as anti-CMV agent. The novel immunomodulatory agent leflunomide holds promise as a future agent for the management of CMV since it both potentiates immunosuppression and suppresses CMV reproduction.Unlike foscarnet and cidofovir it does not appear to be nephrotoxic but can cause transaminase elevation.But it has limited experience in human subjects.
Newer agent to treat drug-resistant CMV–
Maribavir – An oral drug that inhibits UL97 phosphotransferase and stops viral maturation and egress. Maribavir is active against CMV with UL97 and UL54 mutations. Maribavir is dosed at 400 mg orally twice daily for eight weeks. Dysgeusia is a frequent side effect, and maribavir cannot be coadministered with ganciclovir or valganciclovir.Key advantages of maribavir over other agents are lack of bone marrow and kidney toxicity. Due to a drug interaction with calcineurin inhibitors and mammalian (mechanistic) target of rapamycin (mTOR) inhibitors, close monitoring of these immunosuppressive agents is required.
Our institute protocol–
Since we lack the facility to test cmv resistance,we refer them to higher center.We dont have experience of treating resistant cmv cases.
Treatment of Ganciclovir Resistant Cytomegalovirus Infection: Ganciclovir Resistant:
it is suspected when no clinical improvement despite treatment or CMV PCR failed to decrease by at least >1copies /ml after 2 weeks of treatment Mechanism of ganciclovir resistance:
mutation in UL97 phosphotransferase Risk factors: – D+/R- – excessive using antiviral agent – Lung transplantation
Treatment: second line of treatment:
-Foscarnet but it is nephrotoxic.
-Cidovir: also nephrotoxic
-letemovir
-Maribavir
Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase. In order to become active, it must first be phosphorylated in three steps to a triphosphorylated form. Once phosphorylated, it acts as a competitive substrate for DNA polymerase and slows the replication of CMV DNA by DNA polymerase.
Ganciclovir resistance can be assayed either phenotypically or genotypically. The “gold standard” test is the plaque reduction assay in which human fibroblasts are cultured with ganciclovir at various defined concentrations. CMV growth can be quantified by counting viral plaque formation or by a DNA hybridization technique. The concentration of ganciclovir required to inhibit 50% of CMV growth is the IC50 value. Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6μg/ml.
Ganciclovir resistance is uncommon at baseline amongst untreated patients but arises rapidly after prolonged exposure to antiviral agents. In one cohort of AIDS patients newly diagnosed with CMV retinitis, samples of vitreous were assayed for baseline gene mutations associated with ganciclovir resistance. A UL97 mutation was found in only 1 out of 195 eyes tested.
Prevention of Ganciclovir Resistant CMV Infection
The treatment of ganciclovir resistant CMV infections has not been comprehensively studied. The existing literature consists exclusively of case reports and case series describing the outcomes of treatment for patients with resistant infections. Controlled trials comparing various alternative strategies have yet to be published. In light of the serious morbidity associated with ganciclovir resistant infection and the lack of a clearly efficacious second line therapy, efforts to prevent the emergence of ganciclovir resistance are warranted.
Foscarnet
The primary alternative to ganciclovir for the treatment of CMV viremia and disease is foscarnet. Foscarnet was approved by the FDA in 1991. Foscarnet is a direct competitive inhibitor of DNA polymerase. Unlike ganciclovir, it does not need to be phosphorylated in order to inhibit CMV DNA polymerase. Since it is not dependent on the CMV phosphotransferase UL97 it retains activity against CMV isolates with UL97 mutations that are resistant to ganciclovir.
Cidofovir
Cidofovir was approved by the FDA in 1996 for the treatment of cytomegalovirus infection. It is a monophosphorylated cytosine analogue which, like ganciclovir, is further phosphorylated intracellularly to form a compound that impedes DNA polymerase activity. The pharmacology of cidofovir is such that it has to be given intravenously but need only be administered once or twice per week. Like ganciclovir and foscarnet, resistance to cidofovir is low at baseline but rises.
under sustained drug pressure. In a series of 122 treatment naïve AIDS patients with CMV retinitis, cidofovir resistance was identified in 4.1 and 6.6% of blood and urine culture specimens respectively. After three months of cidofovir therapy, 29% of patients had a resistant blood or urine isolate.
Leflunomide
Leflunomide is an immunomodulatory drug originally developed for the treatment of rheumatoid arthritis and approved for that indication by the FDA in 1998. Leflunomide has attracted particular interest from the transplant community because in addition to immunosuppressive properties it is active against viruses. Since the medical management of transplant patients is often a fine balance between maximising immunosuppression to prevent allograft rejection and minimizing immunosuppression to prevent infection, an agent with simultaneous immunosuppressive and anti-infective properties is particularly alluring.
Conclusion
The management of CMV infection remains a substantial challenge for clinicians caring for immunocompromised patients. While there are a number of agents active against the virus, effective therapy requires prolonged drug use which in turn is associated with emergence of drug resistant virus. CMV resistance to ganciclovir has been reported with increasing frequency in both AIDS patients treated for CMV retinitis and in recipients of both bone marrow and solid organ transplants.
Protocol for prophylaxis, surveillance, and treatment of CMV after renal transplantation: Principles:
§ The risk of disease determined by serological status of the donor and recipient and intensity of immunosuppression.
§ Valganciclovir is licensed for prophylaxis but is often also used for the treatment of disease.
§ High-risk patients (D+R-) remain at risk of CMV viraemia and disease after they complete the prophylaxis. Prophylaxis:
1) D+/R- 200 days of valganciclovir.
2) D-/R+ and D+/R+ 100 days of valganciclovir, 200 days after ATG or Alemtuzumab.
3) D-/R- No valganciclovir.
4) Any patient receiving intensified immunosuppression at any time point beyond 100 days consider prophylaxis.
5) Prophylaxis dose is 900mg od adjusted in renal impairment. Surveillance and testing by indication in suspected CMV viraemia or disease: 1. Routine surveillance for viraemia is not required during prophylaxis.
2. D+/R- patients should have their serostatus (CMV IgG) checked at or around 200 days.
3. D+/R- patients should start surveillance with CMV PCR once they finish prophylaxis.
This may be more frequent than clinic visits and can be achieved with extra “Bloods and Go” visits to RAU if required as per the following schedule:
– 2 weeks
– 4 weeks
– 8 weeks
– 12 weeks
The recipient team will coordinate this.
4. CMV PCR on blood is the standard test for all transplant patients where CMV viraemia or disease is suspected or a possibility in outpatients or inpatients, irrespective of whether on prophylaxis or not. Thresholds for treatment:
A. Patients that develop viraemia or disease whilst not on prophylaxis
1. Treatment is mandatory in all cases of suspected tissue-invasive CMV disease, irrespective of viral load.
2. Consider appropriate reduction in immunosuppression in R+ patients with a viral load of fewer than 3 logs 10. Page 3 of 3
3. Consider treatment with valganciclovir when the viral load exceeds 3 logs 10 if symptomatic or rapidly rising titre in high-risk patients.
4. Treatment with valganciclovir or IV ganciclovir is mandatory when the viral load exceeds 4 logs 10.
5. IV ganciclovir is indicated where enteric absorption is likely to be compromised (proven GI involvement, diarrhea or vomiting).
6. IV ganciclovir is indicated in any patient with severe organ involvement (e.g. pneumonitis, encephalitis) – Consultant decision.
B. Patients that develop viraemia or disease whilst on prophylaxis
1. Discuss all such cases with a consultant virologist to agree best treatment regime and discuss resistance testing. Treatment:
The choice of oral versus IV therapy is determined by the abovementioned thresholds and criteria. There are three options:
1. Oral valganciclovir 900mg bd* for 21 days, then 900mg od* for 28 days or until 2 x PCR negative, whichever occurs first (off-label drug use).
2. IV ganciclovir 5mg/kg bd* for 5 days followed by oral valganciclovir 900mg od* until 2 x PCR negative.
3. IV ganciclovir 5mg/kg bd* for 14-21 days, stop date determined by 2 x PCR negative.
Please note dose reductions for renal impairment are commonly needed with valganciclovir and ganciclovir therapy; please consult the Renal Drug Handbook or pharmacist for an appropriate regime and revise in the event of changing renal function.
Virological, pharmacy and other specialist advice should be sought in less straightforward cases. Additional therapy may be appropriate following the discussion.
Treatment of Ganciclovir Resistant Cytomegalovirus Infection: Ganciclovir Resistant: should be suspected if CMV PCR count has not fallen by >1copies/ml after two weeks of therapy or if there is no clinical improvement despite treatment. Mechanism of ganciclovir resistance:
After phosphorylation it acts as a competitive substrate for DNA polymerase. Phosphorylation is accomplished by the phosphotransferase produced by the gene UL97. Mutation in UL97 phosphotransferase leading to ganciclovir resistance. Risk factors:
1) Serostatus- D+/R-
2) Prolong exposure to antiviral agent
3) UL97 gene mutation
4) Lung transplantation Prevention:
By prophylaxis oral valganciclovir Treatment:
§ Exclude other causes of symptoms.
§ Switch to second line: 1) Foscarnet: nephrotoxic, it can result in metabolic changes as well as cardiac arrythmias and genital ulceration. 2) Cidovir: nephrotoxic and causes neutropenia, metabolic acidosis, and ocular hypotony. 3) Letemovir: is newly approved anti-CMV antiviral which inhibits the viral terminase complex. It interacts with immunosuppression, require dose adjustment in renal and hepatic impairment and can be used with other anti-CMV medication. 4) Maribavir: is a promising new antiviral against the viral UL97 kinase. Reduced haematotoxicity and nephrotoxicity compared to GCV and VGCV and so could eventually replace these older compounds.co-administration of with GCV is not advised as maribovir is an inhibitor of the UL97enzyme required for anabolism of the later.
§ Consider further reduction in immunosuppression.
§ Consider immunoglobulins (especially if pneumonitis). CMVIG can be used to induce a passive immune resistant infection and side effects of VGC.
§ Request for genotypic resistance.
Introduction :
Cytomegalovirus (CMV) infection is a common and serious complication of immunosuppression in solid organ and bone marrow transplant recipients, and in patients with AIDS. Untreated CMV infection is associated with a high risk for the development and progression of CMV disease, allograft dysfunction, and death
Recently we started to see cases of Ganciclovir Resistant Cytomegalovirus Infection due to mutation arising in UL97 phosphotransferase or UL54 lead to ganciclovir resistance.
Ganciclovir resistance can be assayed either phenotypically or genotypically.
phenotypically : plaque reduction or DNA hybridization IC50 of > 6µg/ml.
genotypically : genotype analysis to assess for known mutations in the UL54 and UL97 genes.
Risk factors for resistant CMV infection .
1- prolonged exposure to antiviral agents
2- which organ is transplanted ( most common in Lung )
3- CMV seronegativity at transplant when receiving a seropositive organ degree of immunosuppression, magnitude of CMV viremia, and prolonged exposure to anti-CMV medication
Prevention of Ganciclovir Resistant CMV Infection
valganciclovir is superior to oral ganciclovir for the prevention of resistant CMV infection
Foscarnet
it is not dependent on the CMV phosphotransferase UL97 so it retains activity against CMV isolates with UL97 mutations that are resistant to ganciclovir but Mutations in the DNA polymerase gene UL54, however, do confer foscarnet resistance and can sometimes be selected for by prolonged ganciclovir therapy .
The major limitation to greater use of foscarnet has been its adverse effect profile. Foscarnet is associated with renal toxicity, electrolyte abnormalities, toxic reactions and seizures .
Overall, it seems that foscarnet and ganciclovir are of similar efficacy but that foscarnet is less well tolerated. As such, foscarnet is useful agent to use against ganciclovir resistant CMV but treatment will be limited in some patients by nephrotoxicity and/or electrolyte abnormalities. In the inpatient setting where both these variables can be closely monitored and often pre-empted foscarnet seems to be a reasonable choice but a more challenging option in the management of outpatients.
Combination therapy with dose reduced ganciclovir and foscarnet
combination therapy in Ganciclovir resistant cases : All patients had a clinical response within 72-96 hours and completely cleared their antigenemia within 4-8 weeks. No relapses were seen after 12-36 months of follow-up.
combination therapy in Ganciclovir sensitive cases : Patients treated with combination therapy were less likely to have PCR negative blood at 14 days, although the difference was not statistically significant (50% vs 71%, P=.12). Combination therapy was also more likely to cause renal dysfunction and electrolyte abnormalities (seen in 25% of combination patients versus 0% of monotherapy patients, P=.009)
Cidofovir
prolonged treatment of CMV infection with ganciclovir can also lead to the development of cross-resistance to cidofovir .
Likewise, treatment with cidofovir alone can confer resistance to ganciclovir
Cidofovir can cause nephrotoxicity In addition, cidofovir has been noted in case reports to cause bone marrow suppression and ocular disease including iritis, uveitis, and vitreous hypotonicity.
Leflunomide
The novel immunomodulatory agent leflunomide holds promise as a future agent for the management of CMV since it both potentiates immunosuppression and suppresses CMV reproduction. Unlike foscarnet and cidofovir it does not appear to be nephrotoxic but can cause transaminase elevation. The longterm effectiveness, tolerability, and ideal settings for the use of leflunomide remain to be defined by ongoing and future studies.
1- summarise the article: Treatment of Ganciclovir Resistant Cytomegalovirus Infection
Cytomegalovirus (CMV) infection is a common and serious complication, If untreated , can result in allograft dysfunction and might cause death as well.
Some time the patient is resistant to the standard treatment hence another line of treatment being proposed and approved for such patients. Ganciclovir Mechanism of Action and Drug Resistance
Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase
first be phosphorylated in three steps to a triphosphorylated form. then, it acts as a competitive substrate for DNA polymerase and slows the replication of CMV DNA by DNA polymerase.
Phosphorylation is accomplished by the phosphotransferase produced by the gene UL97.
· Mutations arising in UL97 phosphotransferase lead to ganciclovir resistance
· mutations arising in the DNA polymerase gene UL54 also confer resistance to ganciclovir.
· prolonged exposure to ganciclovir can give rise to simultaneous UL54 and UL97 mutations. This is associated with higher level resistance to ganciclovir.
· UL54 mutations can confer cross resistance to foscarnet and cidofovir since these agents also target CMV DNA polymerase. Definition
Ganciclovir resistance can be assayed either phenotypically or genotypically.
The “gold standard” test is the plaque reduction assay in which human fibroblasts are cultured with ganciclovir at various defined concentrations.
CMV growth can be quantified by
· counting viral plaque formation
· or by a DNA hybridization technique.
The concentration of ganciclovir required to inhibit 50% of CMV growth is the IC50 value.
Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml
Ganciclovir resistance can also be detected via genotype analysis to assess for known mutations in the UL54 and UL97 genes.
Detection of resistance via gene mutations is attractive since it is less labour intensive, less time consuming, and is not limited by the need to culture CMV from patient specimens.
The correlation between genotype and phenotype, however, is imperfect so genotype-based resistance reports need to be interpreted with caution. Prevalence and Risk Factors for Resistance
· Ganciclovir resistance is uncommon at baseline amongst untreated patients but arises rapidly after prolonged exposure to antiviral agents.
· Among solid organ transplant recipients, the prevalence of CMV resistance ranges between 0 and 15%. The risk of developing ganciclovir resistance does seem to vary according to the organ transplanted
· This is felt to reflect different degrees of immunosuppression and different protocols for the prophylaxis of CMV. Risk factors for the acquisition of ganciclovir resistance include
1. CMV sero-negativity at transplant when receiving a sero-positive organ
2. degree of immunosuppression
3. magnitude of CMV viremia
4. prolonged exposure to anti-CMV medication.
· Patients with ganciclovir resistant disease suffered a statistically significant decrease in survival compared to those with ganciclovir sensitive disease.
· Ganciclovir resistant CMV disease was diagnosed a median of 10 months after transplant (range 7-12 months) suggesting an association with prolonged ganciclovir exposure.
· It is reported that outcomes for patients with ganciclovir resistance were poor.
· The patient usually treated with reduced immunosuppression and CMV immunoglobulin. Prevention of Ganciclovir Resistant CMV Infection
· The treatment of ganciclovir resistant CMV infections has not been comprehensively studied.
· It is based on case reports and case series
· Valganciclovir is approximately ten times more bioavailable than oral ganciclovir.
· valganciclovir offered a potential means to decrease resistance while retaining the convenience and safety of an oral agent.
· valganciclovir was shown to be superior to oral ganciclovir for the prevention of resistant CMV infection.
· Another report noted that CMV viremia was less frequent during the prophylactic period
· valganciclovir had a higher incidence of neutropenia Foscarnet
· The primary alternative to ganciclovir for the treatment of CMV viremia and disease is foscarnet.
· Foscarnet is a direct competitive inhibitor of DNA polymerase.
· Unlike ganciclovir, it does not need to be phosphorylated in order to inhibit CMV DNA polymerase. Since it is not dependent on the CMV phosphotransferase UL97 it retains activity against CMV isolates with UL97 mutations that are resistant to ganciclovir.
· Like ganciclovir, the risk of resistance increases with the duration of foscarnet therapy.
· Treatment with foscarnet led to clearance of blood and urine cultures as well as stabilization of retinitis for 12-25 weeks in a large trial.
· The major limitation to greater use of foscarnet has been its adverse effect profile. Foscarnet is associated with renal toxicity, electrolyte abnormalities, and seizures.
· Nephrotoxicity was more likely to occur in patients assigned to foscarnet who were taking additional nephrotoxic agents.
· In the inpatient setting where both these variables can be closely monitored and often pre-empted foscarnet seems to be a reasonable choice but a more challenging option in the management of outpatients. Combination therapy with dose reduced ganciclovir and foscarnet
· A promising avenue for the future treatment of ganciclovir resistant CMV infection has been the use of combination ganciclovir and foscarnet at reduced doses.
· The rationale for this strategy stems from the recognition that ganciclovir and foscarnet resistance are usually associated with different gene mutations, in vitro demonstration of synergy between the two agents even against ganciclovir resistant isolates.
· trial data from the AIDS literature showing that combination therapy is superior to monotherapy with the alternative agent alone.
· Moreover, investigators reasoned that synergy between the two agents would permit lower dosing of each agent and consequent mitigation of their different toxicity profiles.
· In a trial, Patients were treated with ganciclovir at half the usual therapeutic dose (5mg/kg IV q24h) combined with foscarnet at two-thirds the usual induction dose (125mg/kg IV q24h).
· Dosages were adjusted for renal dysfunction and foscarnet was titrated to a therapeutic dose over a few days.
· All patients also received CMV hyperimmunoglobulin.
· All patients had a clinical response within 72-96 hours and completely cleared their antigenemia within 4-8 weeks.
· No relapses were seen after 12-36 months of follow-up. Treatment of Ganciclovir Resistant CMV
significant hypomagnesemia requiring 10-24g of magnesium replenishment per day was noted.
No other adverse effects were reported.
Cidofovir
· Cidofovir was approved by the FDA in 1996 for the treatment of cytomegalovirus infection.
· It is a monophosphorylated cytosine analogue which, like ganciclovir, is further phosphorylated intracellularly to form a compound that impedes DNA polymerase activity.
· it has to be given intravenously, to be administered once or twice per week.
· Like ganciclovir and foscarnet, resistance to cidofovir is low at baseline but rises under sustained drug pressure.
· prolonged treatment of CMV infection with ganciclovir can also lead to the development of cross-resistance to cidofovir.
· Cross-resistance to cidofovir in transplant patients treated with ganciclovir alone has also been reported Likewise, treatment with cidofovir alone can confer resistance to ganciclovir.
· The popularity of cidofovir therapy has been limited by its adverse effect profile.
· Cidofovir can cause nephrotoxicity in as many as half of all patients. This can be attenuated by pre-hydration Treatment of Ganciclovir Resistant CMV Klompas
· cidofovir has been noted in case reports to cause bone marrow suppression and ocular disease including iritis, uveitis, and vitreous hypotonicity.
· Clinical reports of the use of cidofovir in ganciclovir-resistant infection are scarce.
· Cidofovir at high dose significantly delayed progression of however, nephrotoxicity occurred in 24% of patients and proteinuria was detected in 39%.34 in a study with AID patients. Leflunomide
· Leflunomide is an immunomodulatory drug originally developed for the treatment of Rheumatoid arthritis and approved for that indication by the FDA in 1998.
· Leflunomide has attracted particular interest from the transplant community because in addition to immunosuppressive properties it is active against viruses.
· It is an an agent with simultaneous immunosuppressive and anti-infective properties .
· Leflunomide acts as a protein kinase inhibitor and as a competitive inhibitor of dihydroorotate
· Leflunomide is a prodrug that is rapidly metabolized to the active metabolite, A77 1726. With long-half life 15-18 days, potentiated by substantial enterohepatic recirculation.
· Without a loading dose it is estimated that it would take nearly two months to achieve steady-state plasma concentrations.
· Likewise, after discontinuation of the medication it can take as long as two years for the body to entirely clear the drug.
· Renal excretion is limited.
· Leflunomide’s immunomodulatory properties were the first aspect of the drug to be probed. In a single center, retrospective review, 53 liver and kidney transplant patients who were failing conventional immunosuppressive therapy were treated with leflunomide. Two thirds of renal patients were able to reduce their dose of cyclosporine and prednisone by about a third. Treatment of Ganciclovir Resistant CMV Klompas
· four out of five patients with liver transplants who tolerated leflunomide were able to stop cyclosporine or FK-506 entirely, while the fifth reduced his dose by 65%.
· There were no cases of allograft rejection.
· adverse effects includes (predominantly anemia, one case of liver enzyme elevation).
· Human CMV isolates were tested for susceptibility to leflunomide using a plaque reduction assay and proved vulnerable.
· the viral target for leflunomide is distinct from that targeted by ganciclovir, foscarnet, and cidofovir.
· The major toxicity of leflunomide is transaminase elevation (less than three times the upper limit of normal) that generally resolve with discontinuation of the drug.
· Cases of hepatic necrosis and death from liver failure have been reported but are rare. (0.02 to 0.04%)
· Patients with pre-existing liver disease, heavy alcohol intake, or concurrent viral hepatitis should not be given leflunomide.
· Other adverse effects reported diarrhea (17-33%), hypertension (6-12%), reversible alopecia (8-11%), and rash (10-14%).
· In addition, there have been case reports of weight loss and pancytopenia.
· Leflunomide is contraindicated in pregnancy due to reports of fetal death and teratogenesis in human subjects. Treatment of Ganciclovir Resistant CMV Klompas
Leflunomide caused hyperbilirubemia in patient with allogeneic bone marrow transplant necessitate stopping treatment. Four weeks after stopping therapy, the patient’s CMV viremia recurred.
Anecdotal evidence also exists on the use of leflunomide to treat CMV viremia in solid organ transplant patients at the Cleveland Clinic. Patients treated with leflunomide in combination with ganciclovir or valganciclovir. All had sustained reduction or clearance of viremia but CMV viremia recurred at a low level when the ganciclovir was discontinued. There is speculation that this is related to underdosing of leflunomide. None of these patients suffered any hepatotoxicity .
2- reflect on your practice
among our transplant patient , positive CMV infection being treated with valgancyclovir orally treatment dose 900mg bd until we get 2 negative PCR, no resistance cases were observed.
Summary:
Cytomegalovirus (CMV) infection is a common and serious complication of immunosuppression
in solid organ and bone marrow transplant recipients, and in patients with AIDS. Untreated
CMV infection is associated with a high risk for the development and progression of CMV
disease, allograft dysfunction, and death. First line treatment is
ganciclovir, but , a lot off centres have reported a little but rising incidence of ganciclovir
resistant .
Ganciclovir Mechanism of Action and Drug Resistance:
Ganciclovir is a guanosine analogue that inhibits DNA polymerase. Mutations arising in UL97 phosphotransferase lead to ganciclovir resistance. mutations arising in the DNA polymerase gene UL54 also confer resistance to ganciclovir. Different UL97 mutations are associated with different degrees of ganciclovir resistance .
Definition:
Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml.
Ganciclovir resistance can also be detected via genotype analysis to assess for known mutations in the UL54 and UL97 genes. Ganciclovir resistance is uncommon at baseline amongst untreated patients but arises rapidly after prolonged exposure to antiviral agents
Among solid organ transplant recipients, the prevalence of CMV resistance ranges between 0
and 15%.
Risk factors for ganciclovir resistance include
1- CMV seronegativity at transplant when receiving a seropositive organ .
2- degree of immunosuppression .
3- magnitude of CMV viremia .
4- prolonged exposure to anti-CMV medication.
Note: D-VE TO R –VE appear to be at particular risk of both CMV infection and ganciclovir Resistance.
In one study Patients with ganciclovir resistant disease suffered a statistically significant decrease in survival compared to those with ganciclovir sensitive disease.
Prevention of Ganciclovir Resistant CMV Infection:
In light of the serious morbidity associated with ganciclovir resistant infection and the lack of a clearly efficacious second line therapy, efforts to prevent the emergence of ganciclovir resistance are warranted.
The FDA approval of the valyl ester prodrug of ganciclovir valganciclovir in 2001, introduced a
more potent option for CMV prophylaxis and maintenance therapy of disease in both transplant
recipients and AIDS patients. Valganciclovir is approximately ten times more bioavailable than
oral ganciclovir. Since ganciclovir resistance is thought to be related to prolonged exposure to
sub therapeutic plasma concentrations of ganciclovir, valganciclovir offered a potential means to
in solid organ transplant population, valganciclovir was shown to be superior to oral ganciclovir for the prevention of resistant CMV infection decrease resistance while retaining the convenience and safety of an oral agent.
Foscarnet :
The primary alternative to ganciclovir for the treatment of CMV viremia and disease is foscarnet.
Foscarnet was approved by the FDA in 1991. Foscarnet is a direct competitive inhibitor of DNA
polymerase.
The major limitation to greater use of foscarnet has been its adverse effect profile. Foscarnet is
associated with renal toxicity, electrolyte abnormalities, and seizures.
Patients treated with ganciclovir were significantly more likely to suffer neutropenia while those
treated with foscarnet had a greater incidence of nephrotoxicity and electrolyte abnormalities.
The toxic reactions usually resolved after discontinuing foscarnet. No permanent disability or death resulted from toxic reactions was reported .
Overall, foscarnet and ganciclovir are of similar efficacy but that foscarnet is less well tolerated. foscarnet is useful agent to use against ganciclovir resistant CMV but treatment will be limited in some patients by nephrotoxicity and/or electrolyte abnormalities.
Combination therapy with dose reduced ganciclovir and foscarnet :
The investigators reasoned that synergy between the two agents would permit lower dosing of each agent and consequent mitigation of their different toxicity profiles.
Cidofovir:
Cidofovir was approved by the FDA in 1996 for the treatment of cytomegalovirus infection. it inhibits DNA polymerase activity.
it should given intravenously but need only be administered once or twice per week. Like ganciclovir and foscarnet, resistance to cidofovir is low at baseline but rises .
in one study cidofovir resistance was identified in 4.1 and 6.6% of blood and urine culture specimens
respectively. After three months of cidofovir therapy, 29% of patients had a resistant blood or
urine isolate. Notably, prolonged treatment of CMV infection with ganciclovir can also lead to the
development of cross-resistance to cidofovir.
The popularity of cidofovir therapy has been limited by its adverse effect profile. Cidofovir can
cause nephrotoxicity in as many as half of all patients. Clinical reports of the use of cidofovir in ganciclovir-resistant infection are scarce.
Leflunomide:
Leflunomide is an immunomodulatory drug originally developed for rheumatoid
arthritis and approved by the FDA in 1998. Leflunomide has attracted particular interest from the transplant community because in addition to immunosuppressive properties it is active against viruses.
Leflunomide acts as a protein kinase inhibitor and as a competitive inhibitor of dihyrdoorotate
dehydrogenase, the intracellular enzyme required for pyrimidine synthesis. It specifically
inhibits denovo pyrimidine synthesis and hence selectively inhibits activated lymphocytes since
resting lymphocytes are able to synthesize pyrimidines via a salvage pathway. Leflunomide is a
prodrug that is rapidly metabolized to the active metabolite, A77 1726. The drug has a long-half life on the order of 15-18 days potentiated by substantial enterohepatic recirculation. Without a
loading dose it is estimated that it would take nearly two months to achieve steady-state plasma
concentrations. Likewise, after discontinuation of the medication it can take as long as two year
for the body to entirely clear the drug. Renal excretion is limited.
The major toxicity of leflunomide is transaminase elevation. Patients with pre-existing liver disease, heavy alcohol intake, or concurrent viral hepatitis should not be given leflunomide
Other adverse effects reported include diarrhea, hypertension ,reversible alopecia , rash and case reports of weight loss and pancytopenia .
Leflunomide is contraindicated in pregnancy due to fetal death and teratogenesis in human .
Experimental data on the use of leflunomide in human beings is extremely limited and remains
Conclusion:
The management of CMV infection remains a substantial challenge for clinicians caring for
immunocompromised patients. While there are a number of agents active against the virus,
effective therapy requires prolonged drug use which in turn is associated with emergence of drug
resistant virus. CMV resistance to ganciclovir has been reported with increasing frequency in
both AIDS patients treated for CMV retinitis and in recipients of both bone marrow and solid
organ transplants. The alternative therapies foscarnet and cidofovir both appear to have good in
vivo activity against cytomegalovirus but both are limited by their propensity to cause acute
renal failure. Given the often tenuous medical status of immuncompromised patients and the
frequent need to simultaneously administer nephrotoxic agents, the risk of renal failure with foscarnet and cidofovir limits their attractiveness as anti-CMV agents. The use of reduced dose
combination therapy appears to deliver potent antiviral therapy with less risk of nephrotoxicity
but this approach requires further study. The novel immunomodulatory agent leflunomide holds
promise as a future agent for the management of CMV since it both potentiates
immunosuppression and suppresses CMV reproduction. Unlike foscarnet and cidofovir it does not appear to be nephrotoxic but can cause transaminase elevation. The longterm effectiveness,
tolerability, and ideal settings for the use of leflunomide remain to be defined by ongoing and
future studies.
Q2 – reflect on your practice .
In our center
1- We have no facility to prove CMV drug resistance .
2- Clinically we did not face drug resistant CMV .
3- We never used second line anti CMV drug .
4- We have no facility to diagnose the UL97 and UL 54 gen mutation.
5- We have no experience with foscarnet and cidofovir drug use .
6- We never use combined anti viral drug therapy.
7- We never use leflonmide in the treatment of CMV .
-Definition of ganciclovir resistance
It can be tested either phenotypically or genotypically. The gold standard test is plaque reduction assay( plaque reduction or DNA hybridization IC50 of> 6 ug/ ml). It can also be tested via genotype analysis ( mutation in UL54 and UL97 gene)
–Mechanism of gancyclovir resistance
Activation of ganciclovir require phospho
rylation. After phosphorylation it acts as a competitive substrate for DNA polymerase. Phosphorylaion is accomplished by the phosphotransferase produced by the gene UL97. Mutation in UL97 phosphotransferase leading to ganciclovir resistance.
Oral valganciclovir prophylaxis with adequate dose and duration.
–Treatment of ganciclovir resistance
Ganciclovir resistant CMV infections has not been comprehensively studied. The existing literature consists exclusively of case reports & case series describing the outcomes of treatment for patients with resistant infection.
-Foscarnet The primary alternative to ganciclovir for the treatment of CMV viremia and disease is foscarnet.
Foscarnet was approved by the FDA in 1991. Foscarnet is a direct competitive inhibitor of DNA polymerase.Unlike ganciclovir, it does not need to be phosphorylated in order to inhibit CMV DNA polymerase.
Since it is not dependent on the CMV phosphotransferase UL97 it retains activity against CMV isolates with UL97 mutations that are resistant to ganciclovir.
Mutations in the DNA polymerase gene UL54.
The risk of resistance increases with the duration of foscarnet therapy.
The major limitation to greater use of foscarnet has been its adverse effect profile: Nephrotoxicity, Electrolytes Disturbances (Hypocalcemia , Hypomagnesemia , Hypokalemia, Hypophosphatemia), Seizures, Genital ulcers, Infusion-related symptoms (fatigue, anxiety, nausea, numbness/tingling).
-Dose reduced ganciclovir and foscarnet combination Combined Ganciclovir and Foscarnet offer more promising treatment with less dose and side effects. Other observations show less target treatment response and more side effects as electrolyte abnormality.
–Cidofovir It is a monophosphorylated cytosine analogue, require phosphorylation to impedes DNA polymerase activity.
Given IV once or twice per week.
Prolonged treatment with ganciclovir can also lead to cross-resistance to cidofovir. Likewise, treatment with cidofovir alone can confer resistance to ganciclovir
Adverse effect profile; nephrotoxicity reduced by (pre-hydration and the use of probenecid), bone marrow suppression and ocular disease.
-Leflunomide It specifically inhibits activated lymphocytes as a protein kinase inhibitor and competitive inhibitor of dihyrdoorotate dehydrogenase, the intracellular enzyme needed for pyrimidine production. It has immunomodulatory, immunosuppressive, and anti-viral effects. Inhibits CMV via final virion assembly rather than DNA synthesis. It lasts 15–18 days. It has the potential to inhibit a multidrug-resistant CMV. Side effects include in Transaminases, diarrhea, hypertension, reversible alopecia, dermatitis, weight loss, and pancytopenia.
Treatment of Ganciclovir Resistant Cytomegalovirus Infection :
Summary:
Ganciclovir Mechanism of Action and Drug Resistance:
Once active it is a competitive substrate for DNA polymerase and slows the replication of CMV DNA by DNA polymerase. UL54 and UL97 genes mutations lead to resistance
Definition:
Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml. Where the IC50 is the concentration value required to inhibit 50% of CMV growth. Genotype analysis helps to assess known mutations in the UL54 and UL97 genes.
Prevalence:
Prevalence ranges from 0-15 % and it is higher with the lung transplant. Renal is around 2%.
Other agents for Ganciclovir Resistant CMV Infection :
Oral valganciclovir higher bioavailability, better than oral ganciclovir and it is equivalent to IV ganciclovir
Foscarnt: Direct inhibitor of CMV DNA polymerase ( no need for viral phosphorylation). Associated with nephrotoxicity, electrolytes disturbance , and convulsions
Combination therapy with dose reduced ganciclovir and foscarnet: may be superior to use of drug alone, Synergistic with less SE
Cidofovir: Monophosphorylated cytosine analogue,inhibits CMV DNA polymerase. Dosing IV once or twice weekly. SE: nephrotoxicity 50 % , BM suppression, and ocular toxicity.
Leflunomide: Protein kinase inhibitor, de novo pyrimidine synthesis inhibitor, Interfering virion assembly and not CMV DNA polymerase. It needs a loading dose, t1/2 2 weeks and slow clearance 2 years. IT requires monitoring LFT and FBC routinely and can cause reversible alopecia
Reflection:
It looks like very old article as the most recent evidence was 2004 and they accessed FDA webpage Oct 2004 (Ref 40).
No information about the article, where and when it was published and if it peer reviewed or not therefore it is hard to assess the accuracy of the information given.
We haven’t seen such case in our center
Ganciclovir is the first line treatment for CMV infections in transplanted patients
However resistance to this agent is manifesting
Alternative therapies have been discussed in this article
Mechanism of Action of Ganciclovir and Drug Resistance
Ganciclovir enters the virus and is activated by phosphotransferase
The UL97 gene codes for this phosphotransferase enzyme
Activated Ganciclovir inhibits viral DNA polymerase to prevent replication
Mutations of the UL97 and UL54 gene result in resistance to ganciclovir
Definition of resistance to ganciclovir
Genetic test is positive for presence of mutations of the UL97 and UL54 gene
Culture of CMV within human fibroblasts produce viral plaques which can be inhibited by Ganciclovir. CMV is deemed resistant if plaque reduction (gold standard test) is sub-optimal despite using higher concentrations of ganciclovir.
Prevalence and Risk Factors for Resistance
Prevalence of CMV resistance ranges from 0 to 15% among solid organ transplant recipients
At baseline, ganciclovir resistance is uncommon amongst untreated patients but after prolonged sub-optimal dose exposure to this agent it rises rapidly
CMV Positive organ transplanted into CMV negative patient
Higher magnitude of CMV viremia also leads to prolonged dosing and resistance
Treatment of Ganciclovir Resistant CMV Infection
————————————————————————————————— Foscarnet
Direct competitive inhibitor of DNA polymerase requiring no phosphorylation (thus uaffected by UL97 mutation)
Associated with electrolyte abnormalities and renal toxicity as well as seizures.
Neutropenia is less common with Foscarent than with Ganciclovir
Combination therapy with dose reduced ganciclovir and foscarnet
Combination therapy is superior to monotherapy with the alternative agent alone
Dosage guideline: Half the dose of gancyclovir and two-thirds of the dose of foscarnet
Results in better efficacy and reduced side effects than either agent alone
Cidofovir
Monophosphorylated cytosine analogue which requires further phosphorylation like ganciclovir leading to DNA polymerase inhibition
Given IV once or twice weekly
Causes nephrotoxicity (50% of cases), myelosuppression and ocular disease – hence not widely used
Leflunomide:
Possibly inhibits final virion assembly
Causes transaminase elevation, diarrhoea, rash and hypertension
Dose: a 100mg oral loading dose once daily for three days followed by 20mg/day for three months
Reflection in practice:
We have used oral valganciclovir for routine CMV prophylaxis. We did not encounter any CMV disease or resistance to this agent.
1. Please summarise this article. Introduction Gancyclovir and Valagancyclovir has been recommended as the first line of treatment and prophylaxes for CMV infection post-transplant. Many centres have reported rising incidence of ganciclovir resistant CMV infections.
Ganciclovir Mechanism of Action and Drug Resistance
Ganciclovir is a guanosine analogue that after phosphorylation in 3 steps to “tri-phosphorylated form” that acts as a competitive inhibitor of DNA polymerase and thus slows the replication of CMV DNA.
Phosphorylation is accomplished by the phosphotransferase produced by the gene UL97, thus its mutations lead to ganciclovir resistance.
Similarly, mutations in Gene UL54 that codes for DNA polymerase, confer resistance to ganciclovir.
Most patients develop only UL97 mutations, but prolonged exposure to ganciclovir can give rise to simultaneous UL54 and UL97 mutations, associated with higher level resistance. UL54 mutations can confer cross resistance to foscarnet and cidofovir which target CMV DNA polymerase.
Definition of resistance:
Phenotypic “plaque reduction assay” is the gold standard test, in which human fibroblasts cultured with ganciclovir at various concentrations.
– CMV growth can be quantified by counting viral plaque formation or by a DNA hybridization technique. – The concentration of ganciclovir required to inhibit 50% of CMV growth is the IC50 value. – Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml. · Genotype analysis to detect mutations on UL97 and UL54 genes can also assess Ganciclovir resistance.
– It takes less time and labour, and is not limited by the need to culture CMV Prevalence and Risk Factors for Resistance Around 2 % for Gancyclovir, around 4% cross resistance to Foscarnet Risk factors: · CMV seronegativity at transplant (D+/R-) · degree of immunosuppression, · magnitude of CMV viremia, · prolonged exposure to anti-CMV medication. Prevention and treatment of Ganciclovir Resistant CMV Infection Valganciclovir – valyl ester prodrug of ganciclovir
· Ten times more bioavailable and more potent than Gancyclovir for CMV prophylaxis and treatment of CMV disease in both transplant recipients and AIDS patients.
. Since ganciclovir resistance is thought to be related to prolonged exposure to subtherapeutic plasma concentration, valganciclovir offered a potential means to decrease resistance while retaining the convenience and safety of an oral agent.
In a study CMV prophylaxis given 100 days – the rate of CMV disease associated with ganciclovir resistant virus remained at 0% for the valganciclovir group but had risen to 6% in the oral ganciclovir group during 1 year follow up.16
Foscarnet · direct competitive inhibitor of DNA polymerase.
Unlike ganciclovir, it does not need to be phosphorylated, thus not dependent on the CMV phosphotransferase – so, it retains activity against CMV isolates with UL97 mutations which are resistant to ganciclovir,
Side effects: renal toxicity, electrolyte abnormalities, and seizures
– Because of different mechanisms of action and gene mutations, synergistic action demonstrated in vitro by the two agents even against ganciclovir resistant isolates. – Result of Reduced dose ganciclovir and foscarnet Combination therapy was good in a study, while clinically not translated in the other. Cidofovir
Monophosphorylated cytosine analogue – further phosphorylated intracellularly to form a compound that inhibits DNA polymerase.
Intravenously administered once or twice a week.
Resistance to Cidofovir by CMV is low at baseline, but rises with sustained use.
Has shown better results in a series of Gcv-resistant CMV retinitis in AIDS patients
Significant nephrotoxicity and bone marrow suppression
Leflunomide
A novel immunomodulator, Protein Kinase Inhibitor
Inhibits pyrimidine synthesis de novo through competitive inhibition of intracellular enzyme di-hyrdo-orotate dehydrogenase – selectively in activated lymphocytes
Long-half-life of 5-18 days – without a loading dose, steady state concentration achieved by 2months, and remains in body for as long as 2years after discontinuation.
Human CMV isolates were tested for susceptibility to leflunomide using a plaque reduction assay and proved vulnerable.
Leflunomide inhibits CMV byinterfering with final virion assembly rather than DNA synthesis – distinct from that targeted by ganciclovir, foscarnet, and cidofovir – thus has potential to inhibit a multidrug-resistant CMV isolate, which was also confirmed in vitro by plaque reduction assays.
Side effect: LFT derangement (transaminitis)
Conclusions:
Foscarnet and Cidofovir both appear to have good in vivo activity against cytomegalovirus, as alternative to Gancyclovir, but are limited by severe nephrotoxicity (acute renal failure).
Reduced dose combination therapy (Gancyclovir + Foscrnet) appears to deliver potent antiviral therapy with less risk of nephrotoxicity, require further studies.
Novel immunomodulator leflunomide holds promise as a future agent for the management of CMV
Unlike foscarnet and cidofovir it does not appear to be nephrotoxic but can cause transaminase elevation, but long-term effectiveness, tolerability, and ideal settings for its use remain to be defined by ongoing and future studies.
2. Reflect on Practice In India, due to less use of Induction ATG, we don’t see much of CMV infection, although we don’t routinely monitor CMV viremia due to cost. Many years back, I have seen 3 patients in my practice in India – 2005 and 2010- 2 patients with CMV disease involving Renal allograft dysfunction – responded to IV Gancyclovir for 1 week followed by oral Valgancyclovir – responded well. 2014 – 1 patient with extensive CMV disease, encephalitis, colitis, graft dysfunction associated with rejection (ACR + ABMR), flared up very fast, and in spite of IV antiviral therapy succumbed to the illness. In my current practice in Kenya, we don’t see symptomatic CMV disease, although we don’t routinely monitor CMV DNA on follow up.
1. Please summarise this article. CMV infection is prevelant in immunocompromised recipient in solid organ transplantation. Valagancyclovir, Gancyclovir has been recommended as the first line of treatment and prophylaxes. The incidence of resistance has been reported increasing. Also it has association with prolong exposure to genciclovir. Mechanism of action, The drug gancyclovir is a guanosine analogue when phosphorelated it competitively inhibits viral DNA polymerase and inhibit CMV replication. It became active in three steps, it has association with prolong exposure to genciclovir. Mutations are firstly, UL97 in which enzyme will affect active drug generation adherence resistance development, second, UL54 it makes mutation in DNA polymerase and resistance. The risk of developing ganciclovir resistance looks to very according to the organ transplantation, immunosuppression load and protocol. Risk and prevalence. The prevalence of resistance in solid organ transplant is around <15%. Risk increases with immunosuppression load and protocol, Seropositivity and negativity, Magnitude of CMV load, Prolong exposure to gencyclovir. Prevention of Resistance. Valganciclovir is 10 times more potent than ganciclovir. Incidence of resistance is more in ganciclovir than valganciclvir. Foscarnet; It’s a competitive inhibitor of DNA polymerase. It was approved by FDA at 1991 for second line treatment of resistant vs alternate treatment of CMV. Side effects are nephrotoxicity, electrolyte misbalance, and fits. It can be used combined with ganciclovir with better effect with low dose and less side effect. Other second line drugs are Cidofovir, and Leflonamide, 2. Please reflect on your practice; We have treated patients with CMV disease and syndrome, firtunatly they had responded to ganciclovir very well.
Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase.
In order to become active it must first be phosphorylated in three steps to a triphosphorylated form.
Once phosphorylated, it acts as a competitive substrate for DNA polymerase and slows the replication of CMV DNA by DNA polymerase.
Phosphorylation is accomplished by the phosphotransferase produced by the gene UL97.
Mutations arising in UL97 phosphotransferase lead to ganciclovir resistance.
Definition of resistance:
The “gold standard” test is the plaque reduction assay in which human fibroblasts are cultured with ganciclovir at various defined concentrations.
CMV growth can be quantified by counting viral plaque formation or by a DNA hybridization technique.
The concentration of ganciclovir required to inhibit 50% of CMV growth is the IC50 value.
Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml.5
Ganciclovir resistance can also be detected via genotype analysis to assess for known mutations in the UL54 and UL97 genes
Prevalence and Risk Factors for Resistance
Around 2 %
Risk factors for the acquisition of ganciclovir resistance include CMV seronegativity at transplant when receiving a seropositive organ, degree of immunosuppression, magnitude of CMV viremia, and prolonged exposure to anti-CMV medication.
Prevention of Ganciclovir Resistant CMV Infection
Valganciclovir
Valganciclovir is approximately ten times more bioavailable than oral ganciclovir.
Since ganciclovir resistance is thought to be related to prolonged exposure to subtherapeutic plasma concentrations of ganciclovir, valganciclovir offered a potential means to decrease resistance while retaining the convenience and safety of an oral agent.
Foscarnet
Mechanism of action: It is a direct competitive inhibitor of DNA polymerase.
Unlike ganciclovir, it does not need to be phosphorylated in order to inhibit CMV DNA polymerase.
Since it is not dependent on the CMV phosphotransferase UL97 it retains activity against CMV isolates with UL97 mutations that are resistant to ganciclovir
Side effects: renal toxicity, electrolyte abnormalities, and seizures
Combination therapy with dose reduced ganciclovir and foscarnet
They are usually associated with different gene mutations, in vitro demonstration of synergy between the two agents even against ganciclovir resistant isolates
Cidofovir
Mechanism of action: It is a monophosphorylated cytosine analogue which, like ganciclovir, is further phosphorylated intracellularly to form a compound that impedes DNA polymerase activity.
It is given intravenously, once or twice per week.
The resistance to cidofovir is low at baseline but rises under sustained drug pressure
Leflunomide
Mechanism of action: It acts as a protein kinase inhibitor and as a competitive inhibitor of dihyrdoorotate dehydrogenase, the intracellular enzyme required for pyrimidine synthesis.
It specifically inhibits denovo pyrimidine synthesis and hence selectively inhibits activated lymphocytes since resting lymphocytes are able to synthesize pyrimidines via a salvage pathway.
Leflunomide is a prodrug that is rapidly metabolized to the active metabolite, A77 1726.
long-half life: 15-18 days
the viral target for leflunomide is distinct from that targeted by ganciclovir, foscarnet, and cidofovir.
Side effect: transaminase elevation.
Conclusion:
The alternative therapies foscarnet and cidofovir both appear to have good in vivo activity against cytomegalovirus but both are limited by their propensity to cause acute renal failure.
The use of reduced dose combination therapy appears to deliver potent antiviral therapy with less risk of nephrotoxicity.
The novel immunomodulatory agent leflunomide holds promise as a future agent for the management of CMV since it both potentiates immunosuppression and suppresses CMV reproduction.
Unlike foscarnet and cidofovir it does not appear to be nephrotoxic but can cause transaminase elevation
Ganciclovir Mechanism of Action and Drug Resistance:
Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase.
Mutations arising in UL97 phosphotransferase lead to ganciclovir resistance.
Also mutation in the DNA polymerase gene UL54 also confer ganciclovir resistance.
Most patients develop only UL97 mutations, however, prolonged exposure to ganciclovir can give rise to simultaneous UL54 and UL97 mutations.
UL54 mutations can confer cross resistance to Foscarnet and cidofovir since these agents also target CMV DNA polymerase.
Ganciclovir resistance:
Can be assayed either phenotypically or Geno typically.
The “gold standard” test is the plaque reduction assay:
In which human fibroblasts are cultured with ganciclovir at various defined concentrations.
Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml. Genotype analysis mutations in the UL54 and UL97 genes.
Prevalence and Risk Factors for Resistance:
The prevalence of CMV resistance ranges between 0 and 15%.
Arises rapidly after prolonged exposure to antiviral agents.
The risk of developing ganciclovir resistance does seem to vary according to the organ transplanted, highest in lung transplant lower in renal and liver transplant.
CMV seronegativity at transplant when receiving a seropositive organ,
Degree of immunosuppression,
Magnitude of CMV viremia, And Prevention of Ganciclovir Resistant CMV Infection prolonged exposure to anti-
CMV medication.
Valganciclovir:
Ability to temper ganciclovir resistance has been demonstrated in comparative studies.
Valganciclovir shown to be superior to oral ganciclovir for the prevention of resistant CMV infection.
Foscarnet:
Foscarnet is a direct competitive inhibitor of DNA polymerase.
Unlike ganciclovir, it does not need to be phosphorylated in order to inhibit CMV DNA polymerase. Since it is not dependent on the CMV phosphotransferase UL97 it retains activity against CMV isolates with UL97 mutations that are resistant to ganciclovir.
Mutations in the DNA polymerase gene UL54, however, do confer Foscarnet resistance and can sometimes be selected for by prolonged ganciclovir therapy.
Combination therapy with dose reduced ganciclovir and Foscarnet:
A promising avenue for the future treatment of ganciclovir resistant CMV infection has been the use of combination ganciclovir and Foscarnet at reduced doses.
Cidofovir:
A monophosphorylated cytosine analogue which, like ganciclovir, is further phosphorylated intracellularly to form a compound that impedes DNA polymerase activity.
Cross-resistance to cidofovir in transplant patients treated with ganciclovir alone has also been reported in other series. Likewise, treatment with cidofovir alone can confer resistance to ganciclovir.
Cidofovir therapy has been limited by its adverse effect profile, nephrotoxicity.
Case reports to cause bone marrow suppression and ocular disease including iritis, uveitis, and vitreous hypotonicity.
Leflunomide:
Acts as a protein kinase inhibitor and as a competitive inhibitor of dihydroorotate dehydrogenase, the intracellular enzyme required for pyrimidine synthesis.
Its potential to inhibit a multidrug-resistant CMV isolate was confirmed in vitro by plaque redز Major toxicity
of Leflunomide is transaminase elevation,
Diarrhea (17-33%), hypertension (6-12%), reversible alopecia (8-11%), and rash (10-14%).
Weight loss44 and pancytopenia.45 Among 39 renal transplant patients treated with high-dose Leflunomide as an immunosuppressant, the mean hematocrit dropped by an average of 15%
Contraindication in pregnancy due to reports of fetal death and teratogenesis in human Conclusion:
The use of reduced dose combination therapy appears to deliver potent antiviral therapy with less risk of nephrotoxicity but this approach requires further study. The novel immunomodulatory agent Leflunomide holds promise as a future agent for the management of CMV .
Please reflect on your practice
Fortunately we don’t encountered resistance in our practice.
In this article Michael Kloamps has tried to look into treatment strategies for Ganciclovir resistant CMV.
Ganciclovir Mechanism of Action and Drug Resistance
Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase. In order to become active it must first be phosphorylated in three steps to a triphosphorylated form. Once phosphorylated, it acts as a competitive substrate for DNA polymerase and slows the replication of CMV DNA by DNA polymerase. Phosphorylation is accomplished by the phosphotransferase produced by the gene UL97. Mutations arising in UL97 phosphotransferase lead to ganciclovir resistance. Similarly, mutations arising in the DNA polymerase gene UL54 also confer resistance to ganciclovir. Different UL97 mutations are associated with different degrees of ganciclovir resistance.
UL54 mutations can confer cross- resistance to foscarnet and cidofovir since these agents also target CMV DNA polymerase. Ganciclovir resistance does not appear to impair viral virulence.
Ganciclovir resistance can be assayed either phenotypically or genotypically.
Prevention of Ganciclovir Resistant CMV Infection
The treatment of ganciclovir resistant CMV infections has not been comprehensively studied. The existing literature consists exclusively of case reports and case series describing the outcomes of treatment for patients with resistant infections. Controlled trials comparing various alternative strategies have yet to be published. In light of the serious morbidity associated with ganciclovir resistant infection and the lack of a clearly efficacious second line therapy, efforts to prevent the emergence of ganciclovir resistance are warranted.
The FDA approval of the valyl ester prodrug of ganciclovir valganciclovir in 2001, introduced a more potent option for CMV prophylaxis and maintenance therapy of disease in both transplant recipients and AIDS patients. Valganciclovir is approximately ten times more bioavailable than oral ganciclovir. Since ganciclovir resistance is thought to be related to prolonged exposure to subtherapeutic plasma concentrations of ganciclovir, valganciclovir offered a potential means to decrease resistance while retaining the convenience and safety of an oral agent.
Treatment of Ganciclovir Resistant CMV
Foscarnet
The primary alternative to ganciclovir for the treatment of CMV viremia and disease is foscarnet. Foscarnet was approved by the FDA in 1991. Foscarnet is a direct competitive inhibitor of DNA polymerase. Unlike ganciclovir, it does not need to be phosphorylated in order to inhibit CMV DNA polymerase. Since it is not dependent on the CMV phosphotransferase UL97 it retains activity against CMV isolates with UL97 mutations that are resistant to ganciclovir. Mutations in the DNA polymerase gene UL54, however, do confer foscarnet resistance and can sometimes be selected for by prolonged ganciclovir therapy. Like ganciclovir, the risk of resistance increases with the duration of foscarnet therapy.
The major limitation to greater use of foscarnet has been its adverse effect profile. Foscarnet is associated with renal toxicity, electrolyte abnormalities, and seizures.
Combination therapy with dose reduced ganciclovir and foscarnet
A promising avenue for the future treatment of ganciclovir resistant CMV infection has been the use of combination ganciclovir and foscarnet at reduced doses.
Cidofovir
Cidofovir was approved by the FDA in 1996 for the treatment of cytomegalovirus infection. It is a monophosphorylated cytosine analogue which, like ganciclovir, is further phosphorylated intracellularly to form a compound that impedes DNA polymerase activity. The pharmacology of cidofovir is such that it has to be given intravenously but need only be administered once or twice per week.
Anecdotal evidence also exists on the use of leflunomide to treat CMV viremia in solid organ transplant patients at the Cleveland Clinic.
We at our center have never observed any Ganciclovir resistance so have no real experience of dealing with such patients
Dear All
I’m very pleased with your summary and the feedback of some of you suggesting the article might be old in view of the emergence of new treatments for CMV resistant cases. Most of the alternatives for Gancyclvir/valgancyclovir have untoward side effects. Hence the emergence of other alternatives such as maribavir which is unfortunately very expensive.
Please read the attached NICE guidance published few days ago for Maribavir as an alternative treatment for CMV resistant cases.
Treatment of Ganciclovir Resistant Cytomegalovirus Infection
Summary:
Ganciclovir Mechanism of Action and Drug Resistance: Once active it is a competitive substrate for DNA polymerase and slows the replication of CMV DNA by DNA polymerase. UL54 and UL97 genes mutations lead to resistance
Definition: Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml. Where the IC50 is the concentration value required to inhibit 50% of CMV growth. Genotype analysis helps to assess known mutations in the UL54 and UL97 genes.
Prevalence: ranges from 0-15 % and it is higher with the lung transplant. Renal is around 2%.
Risk Factors for Resistance D+ / R- Lymphocyte depleting agent at induction time. CMV viral load Prolonged antiviral ttt
Other agents for Ganciclovir Resistant CMV Infection
Oral valganciclovir higher bioavailability, better than oral ganciclovir and it is equivalent to IV ganciclovir
Foscarnt: Direct inhibitor of CMV DNA polymerase ( no need for viral phosphorylation). Associated with nephrotoxicity, electrolytes disturbance , and convulsions
Combination therapy with dose reduced ganciclovir and foscarnet: may be superior to use of drug alone, Synergistic with less SE
Cidofovir: Monophosphorylated cytosine analogue,inhibits CMV DNA polymerase. Dosing IV once or twice weekly. SE: nephrotoxicity 50 % , BM suppression, and ocular toxicity.
Leflunomide: Protein kinase inhibitor, de novo pyrimidine synthesis inhibitor, Interfering virion assembly and not CMV DNA polymerase. It needs a loading dose, t1/2 2 weeks and slow clearance 2 years. IT requires monitoring LFT and FBC routinely and can cause reversible alopecia
Reflection:
It looks like very old article as the most recent evidence was 2004 and they accessed FDA webpage Oct 2004 (Ref 40).
No information about the article, where and when it was published and if it peer reviewed or not therefore it is hard to assess the accuracy of the information given.
Summary
· Definition of ganciclovir resistance: detected by either human fibroblasts culture with ganciclovir at various defined concentrations. (The concentration of ganciclovir required to inhibit 50% of CMV growth is the IC50 value) . Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6μg/ml.5 Or by genotype analysis to assess for known mutations in the UL54 and UL97 genes.
· Prevalence in SOT: varies from 0-15 %.
· Risk factors: prolonged use of antiviral prophylaxis as in high risk recipients for CMV infection as heart-lung transplantation, use of induction therapy, intensive IS or repeated courses of anti rejection therapy.
· The higher bioavailability of valganciclovir contributed to decrease in ganciclovir resistance.
· Lines of ttt of ganciclovir resistant CMV:
o Foscarnet: but it causes nephrotoxicity, electrolyte disturbance.
o Cidofovir: needs hepatic and renal adjustment.
o Although foscarnet and cidofovir are potent, but their side effects limit their use.
o Combination ganciclovir and foscarnet at reduced doses is better than monotherapy due to synergistic effect, also decrease side effects of both.
o Novel immunomodulatory agent, leflunomide: better safety profile but can cause mild transaminitis, but not used in combination with ganciclovir. Reflect on our practice”
I don’t have experience on ganciclovir resistant CMV, but we use oral valganiclovir in prophylaxis and IV ganciclovir for ttt of tissue invasive disease .
Treatment of Ganciclovir Resistant Cytomegalovirus Infection
Mechanism of Action and Drug Resistance
Ganciclovir is a guanosine analogue – inhibits CMV DNA polymerase
phosphorylated in three steps to a triphosphorylated form – acts as a competitive substrate for DNA polymerase and slows the replication of CMV DNA by DNA polymerase – accomplished by the phosphotransferase produced by the gene UL97
Ganciclovir resistance-assayed phenotypically or genotypically
CMV growth can be quantified by counting viral plaque formation or by a DNA hybridization technique
concentration of ganciclovir required to inhibit 50% of CMV growth is the IC50 value
Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6μg/ml
Prevalence and Risk Factors for Resistance
Resistance – uncommon at baseline amongst untreated patients but arises rapidly after prolonged exposure to antiviral agents
one cohort of AIDS patients newly diagnosed with CMV retinitis-UL97 mutation was found in only 1 out of 195 eyes tested
similar cohort of untreated patients-CMV cultured from blood or urine was resistant to ganciclovir in 2% of patients and resistant to foscarnet in 4% of patients
Another study- baseline prevalence of ganciclovir resistance was 0.9% in blood specimens and 2.7% in urine specimens
-After six months of treatment predominantly with intravenous ganciclovir, the prevalence of patients with resistant blood or urine isolates rose to 11.4%. By nine months of therapy, resistant virus was cultured from 27.5% of patients
Risk factors
CMV seronegativity at transplant when receiving a seropositive organ
degree of immunosuppression
magnitude of CMV viremia
prolonged exposure to anti-CMV medication
Foscarnet
primary alternative to ganciclovir
direct competitive inhibitor of DNA polymerase
does not need to be phosphorylated in order to inhibit CMV DNA polymerase
lead to clearance of blood and urine cultures as well as stabilization of retinitis for 12-25 weeks
foscarnet and ganciclovir are of similar efficacy but that foscarnet is less well tolerated
treatment will be limited in some patients by nephrotoxicity and/or electrolyte abnormalities
Combination therapy with dose reduced ganciclovir and foscarnet
rationale for this strategy stems from the recognition that ganciclovir and foscarnet resistance are usually associated with different gene mutations, in vitro demonstration of synergy between the two agents even against ganciclovir resistant isolates
trial data from the AIDS literature – combination therapy is superior to monotherapy with the alternative agent alone, and that combination therapy has been shown to be effective in pre-emptive therapy of CMV antigenemia in non-ganciclovir resistant bone marrow transplant patients
Cidofovir
monophosphorylated cytosine analogue-further phosphorylated intracellularly to form a compound that impedes DNA polymerase activity
administered once or twice per week
resistance to cidofovir is low at baseline but rises
Trial showed Cidofovir reasonably active in this series; 61% of patients had a clinical or virological response but 21/82 (26%) suffered renal toxicity that failed to reverse in most patients (57%) upon dis
Cidofovir can cause nephrotoxicity in as many as half of all patients.33 This can be attenuated by pre-hydration continuation of the drug and the use of probenecid but these two interventions can also limit tolerance
reports to cause bone marrow suppression and ocular disease including iritis, uveitis, and vitreous hypotonicity
Leflunomide
protein kinase inhibitor and as a competitive inhibitor of dihyrdoorotate dehydrogenase, the intracellular enzyme required for pyrimidine synthesis
Without a loading dose it is estimated that it would take nearly two months to achieve steady-state plasma concentrations
major toxicity of leflunomide is transaminase elevation, others -diarrhea (17-33%), hypertension (6-12%), reversible alopecia (8-11%), and rash (10-14%)
Leflunomide is contraindicated in pregnancy due to reports of fetal death and teratogenesis in human subjects
novel immunomodulatory agent leflunomide holds promise as a future agent for the management of CMV since it both potentiates immunosuppression and suppresses CMV reproduction
Cytomegalovirus (CMV) is a serious infection, seen in immunosuppressed patients, and if untreated, is associated with increased risk of CMV disease, graft dysfunction and mortality. Injection Ganciclovir is first-line treatment for CMV infection and disease.
Ganciclovir mechanism of action and drug resistance:
UL97 phosphotransferase phosphorylates Ganciclovir, which inhibits CMV DNA polymerase. Ganciclovir resistance can be assayed genotypically by mutations in UL97 and UL54 genes , and phenotypically by plaque reduction or DNA hybridization IC50 (concentration of ganciclovir required to inhibit 50% of CMV growth) value of >6 microgram/ml.
Risk factors for ganciclovir resistance include CMV seronegativity of recipient with donor being seropositive, degree of immunosuppression, magnitude of CMV viremia, and prolonged exposure to anti-CMV medications. All these risk factors lead to reduced survival. Ganciclovir resistance prevalence rages from 0-15% in solid organ transplants (SOT), with increased prevalence in lung transplant and least among kidney transplant recipients.
Prevention: Valganciclovir use, in convenient oral formulation, has helped in reducing ganciclovir resistance and has been shown to be superior to oral ganciclovir to reduce ganciclovir resistance in SOT. Valganciclovir has been associated with neutropenia.
Treatment:Foscarnet inhibits CMV polymerase and UL54 mutations (but not UL97 mutations) confer foscarnet resistance. Foscarnet has efficacy similar to ganciclovir, but is associated with increased incidence of seizures, infusion-related symptoms, genital ulcers, nephrotoxicity, hypocalcemia, hypomagnesemia, hypophosphatemia, and hypokalemia, and, hence, is less well tolerated. Combination of low dose ganciclovir and foscarnet has not been shown to be superior to full dose ganciclovir. Cidofovir can be given intravenously once or twice a week, but a prolonged use of ganciclovir leads to cross-resistance to cidofovir. Cidofovir is associated with nephrotoxicity in 50% cases, bone marrow suppression, and ocular disease. Leflunomide inhibits pyrimidine synthesis (inhibiting activated lymphocytes), and has anti-viral properties in addition to immunosuppressive effects. It inhibits CMV by interfering with final virion assembly, and is associated with anemia, diarrhea, hypertension, alopecia, rash, loss of weight, and elevated liver enzymes. When used in combination with ganciclovir, CMV viremia improved, but recurred on stopping ganciclovir.
Conclusion: CMV treatment is challenging, especially once ganciclovir resistance develops. Foscarnet and cidofovir have been used in such a scenario, but are associated with nephrotoxicity. Reduced ganciclovir dose with other agents in combination needs further evaluation. Leflunomide use has potential due to lack of nephrotoxicity, but needs further evaluation.
2. Please reflect on your practice
Tablet Valganciclovir is used as CMV prophylaxis in transplant patients in our unit. CMV infection is very rarely seen in our unit. In a scenario with CMV infection, we use Injection Ganciclovir and have not come across any patient with Ganciclovir resistance till now.
-Its plaque reduction or DNA hybridization IC50 of >6 microgram/mls. Plaque reduction is the gold standard for testing resistance.
-Can also be assessed genotypically using UL54 & UL 97 mutation. This is cheap and needs less time to get results.
PREVALENCE & RISK FACTORS.
-In SOT,CMV Resistance it is varied between 0-15% irrespective of organ transplanted.
-Risk factors;
Immunosuppression -AIDS,SOT,BM Transplant.
-Prolonged exposure to antivirals esp anti CMV therapy, most infection occur after a median of 10/12 after treatment.
CMV D+/R-
Degree of immunosuppression -Pancreas more than other SOT due to more potent immunosuppressive meds used.
High CMV VL.
PREVENTION OF GANCICLOVIR RESISTANT CMV INFECTION.
1.VALGANCICLOVIR.
-Valganciclovir is x10 more bioavailable than PO ganciclovir and thus decreased resistance with same efficacy orally. It has also demonstrated superiority to PO valganciclovir for prevention of resistant CMV infection.
2.FOSCARNET.
-Main alternative for treatment of CMV infection and disease,
-Direct competitive inhibitor of DNA polymerase and doesn’t need to be phosphorylated to block CMV DNA polymerase.
-Effective against UL97 but not UL54 mutation.
-Risk for foscarnet resistance increases with prolonged foscarnet therapy .
-Has an extensive SE compared to ganciclovir; Neutropenia ,seizures, genital ulcers and infusion related symptoms(More nephrotoxicity and les neutropenia compared to ganciclovir with a x4 probability of switching to alternative treatment compared to foscarnet)
-In HIV studies and BM transplant recipients, combined therapy has so far shown some superiority to monotherapy. This is an option but more studies are needed in ganciclovir resistance cohort to get more evidence for this to be applied in clinical practice beyond studies.
4.CIDOFOVIR.
-Given parenterally x1/x2 per week.
-Resistance increases with more drug exposure.
-Its resistance has also been associated with ganciclovir resistance.
-Associated with nephrotoxicity in up to 50% of patients on it which can be decreased with proper rehydration.
5.LEFLUNOMIDE.
-Its a protein kinase inhibitor and a competitive inhibitor of dihydoorotate dehydrogenase.
-Has been found to be able to inhibit multidrug resistant CMV but with a major side effect of transaminase elevation.
-Cheaper and effective but more studies needed in various SOT.
CONCLUSION.
-Ganciclovir resistant CMV treatment is challenging. It is mostly associated with prolonged use ,Cidofovir and foscarnet are good alternatives but associated with renal toxicities. Use of reduced dose combination therapy is a potential option with less nephrotoxicity but needs more studies before application in clinical studies.
REFLECTION ON PRACTICE.
Limited resources has limited my exposure to this and as such I haven’t been able to work up a pt fully, appropriately manage and follow up as required by protocol. I will definitely put into practice the above going forward.
Treatment of Ganciclovir Resistant Cytomegalovirus Infection
Introduction
Cytomegalovirus (CMV) infection is a common and serious complication of immunosuppression in solid organ and bone marrow transplant recipients, and in patients with AIDS.
Untreated CMV infection is associated with a high risk for the development and progression of CMV disease, allograft dysfunction, and death. Ganciclovir is the first line treatment for CMV infections in transplanted patients However, resistance to this agent is manifesting Alternative therapies have been discussed in this article Mechanism of Action of Ganciclovir and Drug Resistance Ganciclovir enters the virus and is activated by phosphotransferase The UL97 gene codes for this phosphotransferase enzyme Activated Ganciclovir inhibits viral DNA polymerase to prevent replication Mutations of the UL97 and UL54 gene result in resistance to ganciclovir Definition of resistance to ganciclovir Genetic test is positive for presence of mutations of the UL97 and UL54 gene Culture of CMV within human fibroblasts produce viral plaques which can be inhibited by Ganciclovir. CMV is deemed resistant if plaque reduction (gold standard test) is sub-optimal despite using higher concentrations of ganciclovir. Prevalence and Risk Factors for Resistance Prevalence of CMV resistance ranges from 0 to 15% among solid organ transplant recipients At baseline, ganciclovir resistance is uncommon amongst untreated patients but after prolonged sub-optimal dose exposure to this agent it rises rapidly CMV Positive organ transplanted into CMV negative patient Higher magnitude of CMV viremia also leads to prolonged dosing and resistance Treatment of Ganciclovir Resistant CMV Infection
Foscarnet: Direct competitive inhibitor of DNA polymerase requiring no phosphorylation (thus unaffected by UL97 mutation) Associated with electrolyte abnormalities and renal toxicity as well as seizures. Neutropenia is less common with Foscarent than with Ganciclovir Combination therapy with dose reduced ganciclovir and foscarnet Combination therapy is superior to monotherapy with the alternative agent alone Dosage guideline: Half the dose of gancyclovir and two-thirds of the dose of foscarnet Results in better efficacy and reduced side effects than either agent alone Cidofovir: Monophosphorylated cytosine analogue which requires further phosphorylation like ganciclovir leading to DNA polymerase inhibition Given IV once or twice weekly Causes nephrotoxicity (50% of cases), myelosuppression and ocular disease – hence not widely used Leflunomide: Leflunomide is an immunomodulatory drug originally developed for the treatment of rheumatoid arthritis. In addition to immunosuppressive properties, it is active against viruses.
Leflunomide acts as a protein kinase inhibitor and as a competitive inhibitor of dihydroorotate dehydrogenase, the intracellular enzyme required for pyrimidine synthesis.
It has the potential to inhibit a multidrug-resistant CMV isolate.
There were reported clinical and endoscopic resolution of GI CMV after using leflunomide in 4 renal transplant patients from India.
Adverse effects; hepatic necrosis, death from liver failure, diarrhea, hypertension, reversible alopecia, and rash. Leflunomide is contraindicated in pregnancy due to reports of fetal death and teratogenesis in human subjects. Causes transaminase elevation, diarrhoea, rash, and hypertension Dose: a 100mg oral loading dose once daily for three days followed by 20mg/day for three months Reflection in practice:
I Have one patient Resistant to PO valganciclovir and IV Ganciclovir and we started on Fosacarnet waiting for Genetic tests for Mutations of the UL97 and UL54 gene
Treatment of Ganciclovir Resistant Cytomegalovirus Infection.
Definition
Ganciclovir resistance can be assayed either phenotypically or genotypically which is defined as a plaque reduction or DNA hybridization IC50 of > 6μg/ml and also can be detected by genotype analysis to assess for known mutations in the UL54 and UL97 genes.
Among solid organ transplant recipients, the prevalence of CMV resistance ranges between 0 and 15%. Risk factors of ganciclovir resistance :
=CMV seronegativity at transplant when receiving a seropositive organ, =Degree of immunosuppression.
=Magnitude of CMV viremia.
=Prolonged exposure to anti-CMV medication. Ganciclovir Mechanism of Action and Drug Resistance.
Ganciclovir is a competitive substrate for DNA polymerase that inhibit CMV DNA replications but it become activated when be phosphorylated by the phosphotransferase produced by the gene UL97 and so mutations arising in the DNA polymerase gene UL54 also confer resistance to ganciclovir. Prevention of Ganciclovir Resistant CMV Infection.
=Val ganciclovir offered a potential means to decrease resistance while retaining the convenience and safety of an oral agent. =Foscarnet: is considered an alternative to ganciclovir for the treatment of CMV viremia and disease and it does not need to be phosphorylated.Like ganciclovir, the risk of resistance increases with the duration of Foscarnet therapy. in AIDS patients with CMV retinitis, for example, the incidence of resistance at 6, 9, and 12 months of therapy rose from 13% to 24% to 37% respectively.
Foscarnet is as effective as Val ganciclovir but had a greater incidence of nephrotoxicity and electrolyte abnormalities and less well tolerated but is considered an option for resistance. =Combination therapy with dose reduced ganciclovir and Foscarnet.
Combination therapy is superior to monotherapy with the alternative agent alone, and also shown less side effects revealed by many studies. =Cidofovir.
Cidofovir is a monophosphorylated cytosine analogue which, like ganciclovir impedes DNA polymerase activity, given intravenously but need only be administered once or twice per week. Also, prolonged treatment of CMV infection with ganciclovir can also lead to the development of cross-resistance to Cidofovir and Cidofovir can cause nephrotoxicity in as many as half of all patients. Leflunomide.
Leflunomide’s immunomodulatory properties and considered prodrug that is rapidly metabolized to the active metabolite, A77 1726. The drug has a long-half life on the order of 15-18 day. It has a good role as antiviral and can discontinue CNI or substituted by MMF to avoid the risk of rejection and the major toxicity of leflunomide is transaminase elevation and anemia .
It is considered an option for CMV viremia treatment in VGC resistance with good outcome but bear in mind the side effects. Conclusion .
CMV is one of the most common infection in immunocompromised patient such as AIDS and in solid organ transplant recipients, VGC resistance is a rare condition but it is still challenges and many alternative medications can be used such as Foscarnet, Cidofovir, Leflunomide and combinations of small doses of these medications. Please reflect on your practice.
CMV screening post kidney transplant and importance of prophylactic treatment is better than treatment.
VGC is the most common drug used in CMV treatment and VGC resistance is uncommon and I had never met it before, but keeping the other option in mind is important and to be familiar with these medications and their side effects.
Introduction : Immunosuppressive status in solid organ and bone marrow transplant recipients, and in patients with AIDS will lead to many complications including opportunistic infections , CMV is one of the common and serious infections which if left untreated is associated with a high risk for the development serious complication can lead to graft loss and even death . ganciclovir is the mainstay of treatment but unfortunately many centres reported increasing incidence of resistance . Ganciclovir Mechanism of Action and Drug Resistance Ganciclovir is a guanosine analogue which acts by inhibition of CMV DNA polymerase that slows the replication of CMV DNA,this occur by phosphorylation of ganciclovir with the enzyme phosphotransferase which is produced by the gene UL97,mutation of this gene will lead to ganciclovir resistance . Similarly, mutations arising in the DNA polymerase gene UL54 also confer resistance to ganciclovir which also causes cross resistance to foscarnet and cidofovir since these agents also target CMV DNA polymerase. Definition: Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml (plaque reduction assay is the gold standard test, ). Ganciclovir resistance can also be detected via genotype analysis to assess for known mutations in the UL54 and UL97 genes.
Prevalence and Risk Factors for Resistance : Ganciclovir resistance arises rapidly after prolonged exposure to antiviral agents . In a prospective study done to illustrate the impact of treatment upon the prevalence of ganciclovir resistance,blood and urine cultures from 108 AIDS patients newly diagnosed with CMV retinitis were tested for ganciclovir resistance .After six months of treatment predominantly with intravenous ganciclovir, the prevalence of patients with resistant blood or urine isolates rose to 11.4%. By nine months of therapy, resistant virus was cultured from 27.5% of patients. Risk factors for the acquisition of ganciclovir resistance include : CMV seronegativity at transplant when receiving a seropositive organ, degree of immunosuppression, magnitude of CMV viremia, and prolonged exposure to anti-CMV medication. Seronegative recipients of seropositive organs appear to be at particular risk of both CMV infection and ganciclovir resistance.
Prevention of Ganciclovir Resistant CMV Infection The treatment of ganciclovir resistant CMV infections has not been comprehensively studied. Because of serious morbidities associated with emergence of ganciclovir resistance every effort to prevent it is warranted . When compared to oral ganciclovir valganciclovir is approximately ten times more bioavailable this why valganciclovir is more effective in prophylaxis than oral ganciclovir . Foscarnet : Foscarnet is a direct competitive inhibitor of DNA polymerase.It does not need to be phosphorylated in order to inhibit CMV DNA polymerase so it is not affected by mutation in UL97 gene however prolog ganciclovir therapy can cause UL54 gene mutation that lead to foscarnet resistant . Combination therapy with dose reduced ganciclovir and foscarnet : Ganciclovir and foscarnet resistance are usually associated with different gene mutations which promising avenue for the future treatment of ganciclovir resistant CMV infection , Moreover, investigators reasoned that synergy between the two agents would permit lower dosing of each agent and consequent mitigation of their different toxicity profiles.
Cidofovir : Is a monophosphorylated cytosine analogue which, like ganciclovir, is further phosphorylated intracellularly to form a compound that impedes DNA polymerase activity .Resistance to cidofovir is low at baseline but unfortunately rises.
Leflunomide: It is an immunomodulatory drug but also has antiviral activity .It act as a protein kinase inhibitor and as a competitive inhibitor of dihydroorotate dehydrogenase, the intracellular enzyme required for pyrimidine synthesis , leflunomide inhibits CMV by interfering with final virion assembly rather than with DNA synthesis evident by electron microscopy . As such, the viral target for leflunomide is distinct from that targeted by ganciclovir, foscarnet, and cidofovir,,
Conclusion : The management af CMV is still challenging especially with rising resistant to ganciclovir and toxicity of other medications hence the novel immunomodulatory agent leflunomide holds promise as a future agent for the management of CMV since it both potentiates immunosuppression and suppresses CMV reproduction.
Please reflect on your practice:
in our centre we used to give valganciclovir as prophylaxis to CMV post kidney transplant we didn’t encounter any resistance of valganciclovir or even iv ganciclovir .
II. Treatment of Ganciclovir Resistant Cytomegalovirus Infection
Summarise this article
Introduction
– CMV is a common infection among immunosuppressed individuals. It is associated with graft dysfunction, graft loss and even death in severe cases.
– Ganciclovir is the drug of choice but there is associated drug resistance hence the need for alternative regimens.
Ganciclovir mechanism of action
– Ganciclovir is a guanosine analogue which inhibits CMV DNA polymerase. It has to undergo phosphorylation for it to become active.
Ganciclovir mechanism of drug resistance
– Mutation in the UL97 gene which is responsible for phosphorylation
– Mutations in the DNA polymerase gene UL54. This mutation can also confer cross-resistance to foscarnet and cidofovir since they also target CMV DNA polymerase
– Prolonged exposure to subtherapeutic plasma concentrations of ganciclovir can cause simultaneous UL54 and UL97 mutation which is associated with a higher level of resistance to ganciclovir.
Definition of ganciclovir resistance
– Ganciclovir resistance can be determined phenotypically or genotypically.
– The plaque reduction assay in which human fibroblasts are cultured with ganciclovir at different concentrations is the gold standard test.
– Ganciclovir resistance is defined as a plaque reduction or DNA hybridisation IC50 of > 6µg/ml.
– Genotypic analysis involves assessment for mutations in the UL54 and UL97 genes. This method is faster, less labour intensive and there is no need for cultured specimens.
Prevalence of ganciclovir resistance
0-15% among SOT recipients
Risk factors for ganciclovir resistance
– Prolonged exposure to subtherapeutic plasma concentrations of ganciclovir
– Degree of immunosuppression
– Donor/ recipient CMV serostatus (D+/ R-)
– Magnitude of CMV viremia
Prevention of ganciclovir resistant CMV infection
– Use of valganciclovir which is a prodrug of ganciclovir and is almost 10 times more bioavailable than oral ganciclovir.
Treatment for ganciclovir resistant CMV
Options available include: –
Foscarnet
– It is a direct competitive inhibitor of DNA polymerase. It does not require phosphorylation for it to be active hence is not affected by UL97 gene mutation.
– However, UL54 gene mutation confers foscarnet resistance. Risk of resistance increases with the duration of foscarnet therapy.
– Side effects include: – nephrotoxicity, seizure, electrolyte abnormalities
Combination of low dose ganciclovir and foscarnet
– Ganciclovir and foscarnet resistance are associated with different gene mutations.
– Effective in pre-emptive treatment of CMV.
Cidofovir
– It is a monophosphorylated cytosine analogue, it requires further phosphorylation.
– It is given intravenously once or twice per week.
– Prolonged ganciclovir use can result in the development of cidofovir cross-resistance.
– Side effects – nephrotoxicity, bone marrow suppression, ocular disease
Leflunomide
– It is an immunomodulatory drug with immunosuppressive and antiviral properties.
– It acts as a protein kinase inhibitor with limited renal excretion
– Side effects – anaemia, elevated transaminases, diarrhoea, hypertension
– Avoid leflunomide in pregnancy, in patients with heavy alcohol intake, pre-existing liver disease, concurrent viral hepatitis
Conclusion
Ganciclovir resistant CMV is more prevalent among AIDs patients managed for CMV retinitis and recipients of SOTs and BMTs.
Foscarnet and cidofovir are the alternative therapies but are nephrotoxic making the risks greater than the benefits involved.
Although studies are still ongoing, leflunomide seems to be a promising agent since it potentiates immunosuppression as well as suppresses CMV replication. It is not nephrotoxic but it can cause an elevation in the transaminases.
Reflect on your practice
Unfortunately, we do not have the expertise to assess for ganciclovir resistance at our transplant center. And again, we do not routinely use ganciclovir due to the cost implications.
Generally, we offer valganciclovir as treatment for CMV disease.
Treatment of Ganciclovir Resistant Cytomegalovirus Infection
Michael Klompas in this review article explained the diagnosis and mechanism of ganciclovir resistance, prevalence of risk factors, and the strategies of treatment and prevention.
Mechanism of action of ganciclovir and resistance to ganciclovir
Ganciclovir is an analogue of guanosine and inhibits DNA polymerase by competitive inhibition. Before the formation of the nucleoside analogue, it undergoes phosphorylation by viral and cellular kinases mediated by UL97 gene, hence mutation of this gene can lead to drug resistance. Prolonged exposure to ganciclovir can lead to simultaneous UL54 and UL97 mutations which leads to cross resistance of the virus to other inhibitors of DNA polymerase like cidofovir and foscarnet.
Definition of ganciclovir resistance
Phenotypic definition: Ganciclovir resistance is defined as a plaque reduction or DNA hybridization IC50 (the concentration of ganciclovir required to inhibit 50% of CMV growth) value of > 6µg/ml.
Genotypic definition: Detection of UL54 and UL97 genetic mutation.
Prevalence and risk factors for ganciclovir resistance The prevalence of CMV resistance among recipients of solid organ transplant ranges between 0 and 15%. Ganciclovir resistance is uncommon, but risk tend to rise following a prolonged exposure to antiviral agents.
In a study of 108 patients with AID having CMV retinitis, baseline prevalence of ganciclovir resistance was 0.9% and 2.7% from blood and urine respectively. At 6 months of treatment with ganciclovir, 11.4% had resistance with both urine and blood isolates and this rose to 27.5% at 9 months (OR -9.06; P =0.003).
According to a study of prevalence of drug resistant isolates among transplant recipients infected with CMV at two Chicago transplant centres, between 1994-2001.The risk of developing ganciclovir resistance is highest with lung transplant and least with kidney transplant recipients. Heart and liver transplantation is in between but the risk is higher in heart compared with liver transplant recipients.
Risk factors for development of ganciclovir resistance include CMV seronegative recipient transplanted with a CMV positive donor, intense immunosuppression, magnitude of CMV viremia, and prolonged use of anti-CMV medication.
Prevention of Ganciclovir Resistant CMV Infection
Use of valganciclovir, valyl ester prodrug of ganciclovir valganciclovir with 10 times better bioavailability. In an open label trial comparing valganciclovir to intravenous ganciclovir in 148 AIDS patients with CMV retinitis, valganciclovir was superior to oral ganciclovir for the prevention of resistant CMV infection. Other studies also demonstrate similar results. Other treatment options are foscarnet, ganciclovir and foscarnet combination, Cidofovir, Leflunomide.
Conclusion
Treatment of ganciclovir resistance is still a difficult job for clinicians as the available options such as foscarnet and cidofovir are nephrotoxic. However, leflunomide is promising but will require long term studies.
Reflecting on my own practice
Honestly, I have never treated a patient with CMV disease before and never had to treat a resistant case. But this definitely has enriched my knowledge on the approach when confronted with such.
# Introduction:
* (CMV) infection is frequent and severs complication of immunosuppression post SOT, BMT as well as patients with AIDS.
*The first line for treatment of CMV infections and disease is ganciclovir, but, drug resistant may develop.
*The objective of this review to emphasise treatment strategies available to treat ganciclovir-resistant CMV infection including the currently approved alternative agents foscarnet and cidofovir, the use of combination ganciclovir and foscarnet at reduced doses, and the novel immunomodulatory agent, leflunomide.
# Ganciclovir Mechanism of Action and Drug Resistance
*Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase.
*For activation it should be first be phosphorylated in three steps to a triphosphorylated.
*Phosphorylation is associated with phosphotransferase produced by the gene UL97.
* Mutations arising in UL97 phosphotransferase lead to ganciclovir resistance.
* Also mutations arising in the DNA polymerase gene UL54 also confer resistance to ganciclovir.
# Definition:
*Ganciclovir resistance can be assayed either phenotypically or genotypically.
* The “gold standard” test is the plaque reduction assay.
*The concentration of ganciclovir required to inhibit 50% of CMV growth is the IC50 value. Resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6μg/ml.5
*Genotype analysis when there is a mutation in the UL54 and UL97 genes.
# Prevalence and Risk Factors for Resistance:
*Ganciclovir resistance is not frequent at baseline between untreated patients but arises rapidly following prolonged exposure to antiviral agents.
*In SOT, the prevalence of CMV resistance ranges between 0 and 15%.
*The risk of developing ganciclovir resistance does seem to vary according to the organ transplanted.
# The risk factors include:
* CMVseostutus (D+ /R-).
*The degree of immunosuppression.
*Magnitude of CMV viremia.
*Prolonged exposure to anti-CMV medication.
# Prevention of Ganciclovir Resistant CMV Infection:
* The FDA approval of the valyl ester prodrug of ganciclovir valganciclovir in 2001.
# Valganciclovir:
Is approximately ten times more bioavailable than oral ganciclovir.
*Valganciclovir offered a potential means to decrease resistance while retaining the convenience and safety of an oral agent.
# Foscarnet:
*Is a primary alternative to ganciclovir for the treatment of CMV viremia and disease.
*It is a direct competitive inhibitor of DNA polymerase, and does not need to be phosphorylated, so UL97 it retains activity against CMV isolates with UL97 mutations that are resistant to ganciclovir.
* Mutations in the DNA polymerase gene UL54, however, do confer foscarnet resistance
*The risk of resistance increases with the duration of foscarnet therapy.
*The major limitation to greater use of foscarnet has been its adverse effect profile (associated with renal toxicity, electrolyte abnormalities, and seizures).
*Patients treated with ganciclovir were suffer from neutropenia.
*Foscarnet is useful agent against ganciclovir resistant CMV but treatment will be limited in some patients by nephrotoxicity and/or electrolyte abnormalities.
# Combination therapy with dose reduced ganciclovir and foscarnet:
*The rationale for this strategy stems from the recognition that ganciclovir and foscarnet resistance are usually associated with different gene mutations.
*Trial data from the AIDS literature showing that combination therapy is superior to monotherapy with the alternative agent alone.
* synergy between the two agents would permit lower dosing of each agent and consequent mitigation of their different toxicity profiles.
# Cidofovir:
*It is a monophosphorylated cytosine analogue which need further phosphorylated to impedes DNA polymerase activity.
*Given I/V once or twice per week.
*Like ganciclovir and foscarnet, resistance to cidofovir is low at baseline but rises under sustained drug pressure.
*The use of cidofovir has been limited due to its adverse effect profile, it lead to nephrotoxicity in half of all patients. This can be degraded by pre-hydration and use of probenecid.
*Also it causes bone marrow suppression, iritis, uveitis, and vitreous hypotonicity.
# Leflunomide:
*Is an immunomodulatory drug, in addition to immunosuppressive properties it is active against viruses.
*It inhibits denovo pyrimidine synthesis and inhibits activated lymphocytes.
* Leflunomide is a prodrug that is rapidly metabolized to the active metabolite, A77 1726.
*Has a long-half life on the order of 15-18 days potentiated by substantial enterohepatic recirculation.
*It is potential to inhibit a multidrug-resistant CMV isolate was confirmed in vitro by plaque reduction assays using a virus recovered from a heart transplant patient with CMV pneumonitis.
*The major toxicity of leflunomide is transaminase elevation, diarrhea, hypertension, reversible alopecia, rash, weight loss and pancytopenia, and the effect appeared to be dose related.
*It is contraindicated in pregnancy due to reports of fetal death and teratogenesis.
* The novel immunomodulatory agent leflunomide holds promise as a future agent for the management of CMV since it both potentiates immunosuppression and suppresses CMV reproduction.
* Unlike foscarnet and cidofovir it does not appear to be nephrotoxic but can cause transaminase elevation.
*The longterm effectiveness, tolerability, and ideal settings for the use of leflunomide remain to be defined by ongoing and future studies.
# Please reflect on your practice:
I have not seen gancyclovir resistance case in my center, we use valgancyclovir and gancyclovir. I think this article will help us in the future to deal with such case.
CMV infection is a common and serious complication in solid organ transplant.
First line treatment for CMV infections and disease is ganciclovir.
There is small but rising incidence of ganciclovir resistant CMV infections.
Ganciclovir: Mechanism of Action and Drug Resistance:
Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase.
The active form is a phosphorelated one, this phosphorylation is achieved by the enzyme phosphotransferase produced by the gene UL97.
Mutations arising in UL97 phosphotransferase and UL54 lead to ganciclovir resistance.
The concentration of ganciclovir required to inhibit 50% of CMV growth is the IC50 value.
Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml.
Ganciclovir resistance can be assayed either phenotypically or genotypically.
Detection of resistance via gene mutations is attractive.
Ganciclovir resistance is uncommon at baseline but arises rapidly after prolonged exposure to antiviral agents.
Among solid organ transplant recipients, the prevalence of CMV resistance ranges between 0 and 15%.
Other risk factors for the development of ganciclovir resistance in addition to prolong use of ganciclovir include CMV seronegativity at transplant when receiving a seropositive organ, degree of immunosuppression and magnitude of CMV viremia.
Prevention of Ganciclovir Resistant CMV Infection
The lack of a clearly efficacious second line therapy necessitates efforts to prevent the emergence of ganciclovir resistance.
The use of valganciclovir offered a potential means to decrease resistance as it is ten times more bioavailable than oral ganciclovir.
In the solid organ transplant population, valganciclovir was shown to be superior to oral ganciclovir for the prevention of resistant CMV infection
Options for treatment of ganciclovir resistant CMV: 1. Foscarnet:
Foscarnet is a direct competitive inhibitor of DNA polymerase that does not need to be phosphorylated in order to inhibit CMV DNA polymerase. Hence it retains activity against CMV isolates with UL97 mutations that are resistant to ganciclovir.
However, mutations in the DNA polymerase gene UL54, do confer foscarnet resistance.
Foscarnet is useful agent to use against ganciclovir resistant CMV.
Treatment is limited by nephrotoxicity and/or electrolyte abnormalities.
2. Combination therapy with dose reduced ganciclovir and foscarnet:
The rationale for this strategy comes from the recognition that ganciclovir and foscarnet resistance are usually associated with different gene mutations and in vitro demonstration of synergy between the two agents.
This approach seems attractive as would permit lower dosing of each agent and consequently reducing their different toxicity profiles.
3. Cidofovir:
It is a monophosphorylated cytosine analogue which, like ganciclovir needs to be phosphorylated.
Like ganciclovir and foscarnet, resistance to cidofovir is low at baseline but rises with prolong use.
Prolonged treatment of CMV infection with ganciclovir can also lead to the development of cross-resistance to cidofovir.
Clinical reports of the use of cidofovir in ganciclovir-resistant infection are scarce.
The popularity of cidofovir therapy has been limited by its adverse effect profile. Cidofovir can cause nephrotoxicity in as many as half of all patients.
4. Leflunomide:
Leflunomide is an immunomodulatory drug.
In addition to immunosuppressive effects, it is active against viruses.
It is suggested that leflunomide inhibits CMV by interfering with final virion assembly rather than with DNA synthesis.
· Its potential to inhibit a multidrug-resistant CMV isolate was confirmed in vitro by plaque reduction assays.
leflunomide holds promise as a future agent for the management of CMV since it both potentiates immunosuppression and suppresses CMV reproduction.
Unlike foscarnet and cidofovir it does not appear to be nephrotoxic, but can cause transaminase elevation.
The long-term effectiveness and tolerability for the use of leflunomide remain to be defined by ongoing and future studies.
. We have good experience with the use oral valganciclovir for the treatment of CMV infection (combined with the reduction of antimetabolite dose). Followed by Prophylactic dose of valganciclovir for 3 months. Probably we don’t see resistant cases because we usually use oral valganciclovir rather than ganciclovir.
Summary of the article Treatment of Ganciclovir Resistant Cytomegalovirus Infection
Ganciclovir is the first line treatment for CMV infections and disease, however, many centres have reported a small but rising incidence of ganciclovir resistant CMV infections. Ganciclovir Mechanism of Action and Drug Resistance a) Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase. · The active substance is the triphosphorylated form. · Phosphorylation is accomplished by the phosphotransferase produced by the gene UL97. · Prolonged exposure to ganciclovir can give rise to simultaneous UL54 and UL97 mutations. · The concentration of ganciclovir required to inhibit 50% of CMV growth is the IC50 value. b) Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6μg/ml. c) Ganciclovir resistance can be detected via genotype analysis for mutations in the UL54 and UL97 genes. d) Identification of a ganciclovir resistant isolate was correlated with the development of CMV retinitis in the contralateral eye. Prevalence of Ganciclovir resistance
According to Chicago transplant centres, 1994-2001, the prevalence of CMV resistance ranges between 0 and 15%. With highest resistance in lung transplants and lowest one in kidney and liver transplants. Risk Factors for Ganciclovir Resistance
a) CMV seronegativity at transplant when receiving a seropositive organ.
b) Degree of immunosuppression.
c) Magnitude of CMV viremia.
d) Prolonged exposure to anti-CMV medication. Prevention of Ganciclovir Resistant CMV Infection a) Valgancicloviris approximately ten times more bioavailable than oral ganciclovir. It offered a potential means to decrease resistance while retaining the convenience and safety of an oral agent. b) valganciclovir was shown to be superior to oral ganciclovir for the prevention of resistant CMV infection.
Treatment of ganciclovir resistant CMV infection 1. Foscarnet
a) Foscarnet is the primary alternative to ganciclovir for the treatment of CMV viremia and disease.
b) Foscarnet is a direct competitive inhibitor of DNA polymerase, it does not need to be phosphorylated in order to inhibit CMV DNA polymerase.
c) It retains activity against CMV isolates with UL97 mutations.
d) Like ganciclovir, the risk of resistance increases with the duration of foscarnet therapy.
e) Foscarnet is associated with renal toxicity, electrolyte abnormalities, seizures and infusion related symptoms(fatigue, anxiety, nausea, numbness/tingling).
2. Combination therapy with dose reduced ganciclovir and foscarnet
a) combination therapy is superior to monotherapy with the alternative agent alone.
b) Combination therapy has been shown to be effective in pre-emptive therapy of CMV antigenemia in non- ganciclovir resistant bone marrow transplant patients.
c) Synergy between the two agents would permit lower dosing of each agent and consequent mitigation of their different toxicity profiles.
d) Ganciclovir at half the usual therapeutic dose (5mg/kg IV q24h) combined with Foscarnet at two-thirds the usual induction dose (125mg/kg IV q24h).
e) According to British investigators:
· Combination therapy were less likely to have PCR negative blood at 14 days(the difference wasn’t statistically significant).
· Combination therapy was also more likely to cause renal dysfunction and electrolyte abnormalities. 3. Cidofovir
a) It is a monophosphorylated cytosine analogue, to be given intravenously once or twice per week.
b) Prolonged treatment of CMV infection with ganciclovir can also lead to the development of cross-resistance to cidofovir.
c) Cidofovir can cause nephrotoxicity in as many as half of all patients, bone marrow suppression and ocular disease including iritis, uveitis, and vitreous hypotonicity. 4. Leflunomide a) Leflunomide is an immunomodulatory drug originally developed for the treatment of rheumatoid arthritis. In addition to immunosuppressive properties it is active against viruses.
b) Leflunomide acts as a protein kinase inhibitor and as a competitive inhibitor of dihyrdoorotate dehydrogenase, the intracellular enzyme required for pyrimidine synthesis.
c) It has the potential to inhibit a multidrug-resistant CMV isolate.
d) There were reported clinical and endoscopic resolution of GI CMV after using leflunomide in 4 renal transplant patients from India.
e) Adverse effects; hepatic necrosis, death from liver failure, diarrhea, hypertension, reversible alopecia, and rash.
f) Leflunomide is contraindicated in pregnancy due to reports of fetal death and teratogenesis in human subjects. 5. Combination of leflunomide and foscarnet
a) After starting a combination of leflunomide and foscarnet,for patient with BM transplant, the patient’s CMV viral load decreased from 226,000 copies per ml to an undetectable level over the course of six weeks.
b) Leflunomide was stopped after three weeks of therapy due to hyperbilirubinemia.
c) While the agent was clearly effective in clearing the patient’s CMV viremia, it is possible that it contributed to her death from progressive liver failure.
Please reflect on your practice
Encountered cases of CMV infection were responding well to Valganciclovir and no noticed resistance to the drug.
Treatment of Ganciclovir Resistant Cytomegalovirus Infection:
Introduction
Cytomegalovirus (CMV) infection is a common and serious complication of immunosuppression in solid organ and bone marrow transplant recipients, and in patients with AIDS.
Ganciclovir Mechanism of Action and Drug Resistance:
Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase Once phosphorylated, it acts as a competitive substrate for DNA polymerase and slows the replication of CMV DNA by DNA polymerase. Phosphorylation is accomplished by the phosphotransferase produced by the gene UL97.
Mutations arising in UL97 phosphotransferase lead to ganciclovir resistance.
Definition:
Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml.5
Prevalence and Risk Factors for Resistance:
Risk factors for the acquisition of ganciclovir resistance include CMV sero negativity at transplant when receiving a sero positive organ, degree of immunosuppression, magnitude of CMV viremia, and prolonged exposure to anti-CMV medication.
Seronegative recipients of seropositive organs appear to be at particular risk of both CMV infection and ganciclovir resistance.
Ganciclovir resistant CMV disease was diagnosed a median of 10 months after transplant (range 7-12 months) suggesting an association with prolonged ganciclovir exposure. The outcomes for patients with ganciclovir resistance in this study were poor
Prevention of Ganciclovir Resistant CMV Infection:
The treatment of ganciclovir resistant CMV infections has not been comprehensively studied. The existing literature consists exclusively of case reports and case series describing the outcomes of treatment for patients with resistant infections
Valganciclovir:
Valganciclovir’s ability to temper ganciclovir resistance has been demonstrated in comparative studies
Foscarnet :
The primary alternative to ganciclovir for the treatment of CMV viremia and disease
Combination therapy with dose reduced ganciclovir and foscarnet
A promising avenue for the future treatment of ganciclovir resistant CMV infection has been the use of combination ganciclovir and foscarnet at reduced doses
Cidofovir :
Cidofovir was approved by the FDA in 1996 for the treatment of cytomegalovirus infection. It is a monophosphorylated cytosine analogue which, like ganciclovir, is further phosphorylated intracellularly to form a compound that impedes DNA polymerase activity
Leflunomide
Leflunomide’s activity against cytomegalovirus was discovered when investigators hypothesized that the predominance of phosphoproteins within CMV might imply that intracellular construction of virions is dependent upon protein kinase
Conclusion :
The novel immunomodulatory agent leflunomide holds promise as a future agent for the management of CMV since it both potentiates immunosuppression and suppresses CMV reproduction Unlike foscarnet and cidofovir it does not appear to be nephrotoxic but can cause transaminase elevation
In solid organ and bone marrow transplant recipients and AIDS patients, cytomegalovirus (CMV) infection is a common and significant immunosuppressive consequence. CMV illness, allograft malfunction, and death are more likely with an untreated CMV infection.
Ganciclovir Mechanism of Action and Drug Resistance Guanosine analogue ganciclovir inhibits CMV DNA polymerase. It must be phosphorylated three times to become active. Phosphorylated, it competes with DNA polymerase and reduces CMV DNA replication. UL97 phosphotransferase phosphorylates. UL97 phosphotransferase mutations cause ganciclovir resistance. Similarly, DNA polymerase gene UL54 mutations cause ganciclovir resistance.
Definition Ganciclovir resistance can be tested phenotypically or genotypically. Ganciclovir-cultured human fibroblasts are the “gold standard” test. Plaque formation or DNA hybridization can measure CMV growth. Ganciclovir’s IC50 inhibits 50% of CMV growth. Plaque reduction or DNA hybridization IC50 > 6μg/ml indicates ganciclovir resistance.
Resistance Risk and Prevalence Solid organ transplant recipients have up to 15% CMV resistance. Ganciclovir resistance is rare in untreated patients, although it rapidly builds after sustained sub-optimal dosage exposure. Higher CMV viremia prolongs dosing and resistance.
Prevention of Ganciclovir Resistant CMV Infection In 2001, the FDA approved valganciclovir, a strong valyl ester prodrug of ganciclovir, for CMV prevention and disease maintenance in transplant recipients and AIDS patients. Valganciclovir is ten times bioavailable. Valganciclovir may reduce ganciclovir resistance by reducing prolonged exposure to subtherapeutic plasma concentrations. In solid organ transplant patients, valganciclovir reduced resistant CMV infection better than oral ganciclovir, whereas in AIDS patients with CMV retinitis, it was equivalent to intravenous ganciclovir.
Foscarnet Foscarnet, an alternative to ganciclovir, inhibits DNA polymerase directly without phosphorylation. -Active against UL97 but not UL54 CMV isolates. Foscarnet treatment lengthens resistance risk. Renal toxicity, electrolyte imbalances, and convulsions are all adverve effects of Foscarnet use. Foscarnet withdrawal eliminated all adverse affects.
Combination therapy with dose reduced ganciclovir and foscarnet In vitro synergy between dose-reduced ganciclovir and foscarnet against ganciclovir-resistant isolates supports combination therapy. Combination therapy outperformed alternative agent monotherapy in trials. Reduce agent dose and toxicity.
Cidofovir Monophosphorylated cytosine analogues inhibit DNA polymerase activity through phosphorylation. It is given IV twice weekly. Long-term ganciclovir treatment can also cause cidofovir resistance. Cidofovir alone can make ganciclovir resistant. Pre-hydration and probenecid minimize nephrotoxicity, bone marrow suppression, and eye disease.
Leflunomide It specifically inhibits activated lymphocytes as a protein kinase inhibitor and competitive inhibitor of dihyrdoorotate dehydrogenase, the intracellular enzyme needed for pyrimidine production. It has immunomodulatory, immunosuppressive, and anti-viral effects. Inhibits CMV via final virion assembly rather than DNA synthesis. It lasts 15–18 days. It has the potential to inhibit a multidrug-resistant CMV. Side effects include in Transaminases, diarrhea, hypertension, reversible alopecia, dermatitis, weight loss, and pancytopenia.
In conclusion, clinicians treating immunocompromised patients struggle with CMV infection. There are several antiviral medications, however extended drug use leads to drug-resistant virus. AIDS patients treated for CMV retinitis and bone marrow and solid organ transplant recipients are increasingly resistant to ganciclovir. Foscarnet and cidofovir have strong in vivo action against CMV but cause acute renal failure.
Ganciclovir is the first line treatment for CMV infections in transplanted patients
However resistance to this agent is manifesting
Alternative therapies have been discussed in this article
Mechanism of Action of Ganciclovir and Drug Resistance
Ganciclovir enters the virus and is activated by phosphotransferase
The UL97 gene codes for this phosphotransferase enzyme
Activated Ganciclovir inhibits viral DNA polymerase to prevent replication
Mutations of the UL97 and UL54 gene result in resistance to ganciclovir
Definition of resistance to ganciclovir
Genetic test is positive for presence of mutations of the UL97 and UL54 gene
Culture of CMV within human fibroblasts produce viral plaques which can be inhibited by Ganciclovir. CMV is deemed resistant if plaque reduction (gold standard test) is sub-optimal despite using higher concentrations of ganciclovir.
Prevalence and Risk Factors for Resistance
Prevalence of CMV resistance ranges from 0 to 15% among solid organ transplant recipients
At baseline, ganciclovir resistance is uncommon amongst untreated patients but after prolonged sub-optimal dose exposure to this agent it rises rapidly
CMV Positive organ transplanted into CMV negative patient
Higher magnitude of CMV viremia also leads to prolonged dosing and resistance
Treatment of Ganciclovir Resistant CMV Infection
————————————————————————————————— Foscarnet
Direct competitive inhibitor of DNA polymerase requiring no phosphorylation (thus uaffected by UL97 mutation)
Associated with electrolyte abnormalities and renal toxicity as well as seizures.
Neutropenia is less common with Foscarent than with Ganciclovir
Combination therapy with dose reduced ganciclovir and foscarnet
Combination therapy is superior to monotherapy with the alternative agent alone
Dosage guideline: Half the dose of gancyclovir and two-thirds of the dose of foscarnet
Results in better efficacy and reduced side effects than either agent alone
Cidofovir
Monophosphorylated cytosine analogue which requires further phosphorylation like ganciclovir leading to DNA polymerase inhibition
Given IV once or twice weekly
Causes nephrotoxicity (50% of cases), myelosuppression and ocular disease – hence not widely used
Leflunomide:
Possibly inhibits final virion assembly
Causes transaminase elevation, diarrhoea, rash and hypertension
Dose: a 100mg oral loading dose once daily for three days followed by 20mg/day for three months
Reflection in practice: We have used oral valganciclovir for routine CMV prophylaxis. We did not encounter any CMV disease or resistance to this agent.
Introduction:
In patients with AIDS and transplant recipients who are immunosuppressed, CMV infection poses a major risk for illness onset, disease progression, allograft failure, and mortality. Ganciclovir resistant CMV infections are rising.
Ganciclovir Mechanism of Action and Drug Resistance
Ganciclovir inhibits CMV DNA polymerase and resistance to Ganciclovir resulted from mutations in UL97 phosphotransferase and UL54, which can also confer cross-resistance to Foscarnet and Cidofovir. Prolonged exposure to Ganciclovir can give rise to these mutations simultaneously.
Definition
Ganciclovir resistance can be assayed either; Phenotypically: (Gold Standard): plaque reduction or DNA hybridization IC50 of > 6µg/ml. Genotypically: Analysis to assess for known mutations in the UL54 and UL97 genes.
Prevalence and Risk Factors for Resistance
Ganciclovir resistance is uncommon at baseline amongst untreated patients but arises rapidly after prolonged exposure to antiviral agents
The prevalence of CMV resistance ranges (from 0 -15%). The risk is varying according to the organ transplanted.
This is felt to reflect different degrees of immunosuppression and different protocols for the prophylaxis of CMV. Being the most among Lung transplant recipients 15.2% followed by heart transplant recipients at 5.3%.
Risk factors for the acquisition of ganciclovir resistance include:
· CMV seronegativity at transplant when receiving a seropositive organ,
· Degree of immunosuppression,
· Magnitude of CMV viremia,
· Prolonged exposure to the anti-CMV medication.
Prevention of Ganciclovir Resistant CMV Infection
Valganciclovir offered a potential means to decrease resistance while retaining the convenience and safety of an oral agent
Foscarnet
Foscarnet is the main substitute for ganciclovir in the management of CMV viremia and illness. Ganciclovir and foscarnet have comparable efficacy, although foscarnet is less well tolerated.
The major limitation to the greater use of foscarnet has been its adverse effect profile.
· Renal toxicity,
· Electrolyte abnormalities,
· Seizures.
Combination therapy with dose-reduced ganciclovir and foscarnet
Researchers reasoned that a synergistic interaction between the two drugs would allow for lower doses of each agent, so reducing their disparate toxicity profiles. AIDS trial data demonstrating that combination treatment outperforms monotherapy with the substitute drug alone,
Cidofovir
Another effective alternative. It must be taken intravenously, although just once or twice a week is necessary to be successful.
At first, cidofovir resistance is minor, but it increases when the drug is used frequently.
Notably, prolonged use of ganciclovir to treat CMV infection can also result in the emergence of cross-resistance to cidofovir.
The major toxicity
· Nephrotoxicity in as many as half of all patients.
· Bone marrow suppression
· Ocular disease including iritis, uveitis, and vitreous hypotonicity.
Leflunomide
Leflunomide is an immunomodulatory medication that was first created for the treatment of rheumatoid arthritis and was given FDA approval for its use in 1998. sparked a lot of interest because it has antiviral effects in addition to immunosuppressive ones.
The major toxicity of leflunomide is
· Transaminase elevation.
· Diarrhea
· Hypertension
· Reversible alopecia
· Rash
· Leflunomide is contraindicated in pregnancy due to reports of fetal death and teratogenesis in human subjects.
Conclusion
· The management of CMV infection is a challenge for clinicians caring for immunocompromised patients, as effective therapy requires prolonged drug use and is associated with the emergence of a drug-resistant virus.
· CMV resistance to ganciclovir is increasing in both AIDS patients and transplant recipients.
· Alternative therapies foscarnet and cidofovir have good in vivo activity against cytomegalovirus, but can cause acute renal failure.
· Reduced dose combination therapy may deliver potent antiviral therapy with less risk of nephrotoxicity, but further study is needed.
· Leflunomide is a novel immunomodulatory agent that both potentiate immunosuppression and suppresses CMV reproduction, but its long-term effectiveness, tolerability, and ideal settings remain to be determined.
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Please reflect on your practice
Generally, in our center, we see a good response to Ganciclovir provided that the patient has had a good preoperative risk assessment, proper prophylaxis & good compliance in a way that we didn’t have to resort to other agents in the treatment of CMV-infected patients.
CMV infection is a serious complication of immunosuppression in transplant recipients. Untreated infection carries the risk of allograft dysfunction, and death. First line treatment is ganciclovir, there is rising incidence of ganciclovir resistant. Ganciclovir Mechanism of Action and Drug Resistance
Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase. It undergoes phosphorylation to a triphosphorylated form that acts as a competitive substrate for DNA polymerase and slows DNA replication. Phosphorylation occurs by phosphotransferase produced by UL97 gene. Mutations in UL97 phosphotransferase lead to resistance. Mutations in DNA polymerase gene UL54 also confer resistance. Different UL97 mutations causes different degrees of resistance. Most patients develop only UL97 mutations, prolonged ganciclovir exposure can lead to simultaneous UL54 and UL97 mutations which cause higher level resistance. UL54 mutations can confer cross resistance to foscarnet and cidofovir as they target CMV DNA polymerase. Ganciclovir resistance does not impair viral virulence. Definition
Resistance can be assayed phenotypically or genotypically. The “gold standard” is the plaque reduction assay; fibroblasts are cultured with ganciclovir at various concentrations. CMV growth is quantified by viral plaque formation or DNA hybridization technique. Concentration required to inhibit 50% of growth is the IC50 value. Resistance is defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml. Analysis for mutations is less labour intensive, time consuming, and doesn’t need culture from patient. The correlation between genotype and phenotype is imperfect so genotype-based resistance needs to be interpreted cautiously. Prevalence and Risk Factors for Resistance
Resistance arises rapidly after prolonged exposure to antivirals. In s study of AIDS patient with CMV retinitis, resistance has increased from 0.9% in blood and 2.7% in urine at baseline to 11.4% after 6 months of treatment and 27.5% at 9 months.
Resistance varies according to the organ transplanted, which reflect different degrees of immunosuppression and prophylaxis protocols.
Risk factors for resistance include CMV seronegativity receiving a seropositive organ, degree of immunosuppression, magnitude of CMV viremia, and prolonged exposure to anti-CMV medication. Seronegative recipients of seropositive organs are at risk of both infection and ganciclovir resistance. Patients with resistant disease has significant decreased survival compared to ganciclovir sensitive disease. Prevention of Ganciclovir Resistant CMV Infection
The FDA approved valganciclovir in 2001 for prophylaxis and treatment, It is ten times more bioavailable than oral ganciclovir. As resistance is related to prolonged exposure to subtherapeutic doses, valganciclovir decrease resistance. It was equivalence to IV ganciclovir in risk of resistance in AIDS studies, while in transplant population, It was superior to oral ganciclovir for the prevention of resistant infection. Foscarnet
Foscarnet was approved by the FDA in 1991. It is a direct competitive inhibitor of DNA polymerase, it does not need to be phosphorylated, so it retains activity against CMV with UL97 mutations. However, UL54 mutations, do confer foscarnet resistance which can be induced by prolonged ganciclovir therapy. The risk of resistance increases with duration of foscarnet therapy.
It was proven to be effective in ganciclovir resistant disease.
Studies showed that Foscarnet and ganciclovir have similar efficacy, Foscarnet is associated with renal toxicity, electrolyte abnormalities, and seizures but less neutropenia.
Combination therapy with dose reduced ganciclovir and foscarnet
Ganciclovir and foscarnet resistance are associated with different mutations, Trials showed that combination therapy is superior to monotherapy. Synergy between the two permit lower dosing and mitigation of toxicity.
In a study of six patient with infection refractory to IV ganciclovir. Patients were treated with half dose ganciclovir and foscarnet at two-thirds dose. Foscarnet was titrated to a therapeutic dose over a few days, patients also received CMV hyperimmunoglobulin. All patients had a clinical response in 72-96 hours and cleared their antigenemia in 4-8 weeks. No relapses seen after 12-36 months. All patients had significant hypomagnesemia requiring replacement.
In another trial, half-dose ganciclovir and half-dose foscarnet was associated with less negative PCR at 14 days compared to full dose ganciclovir which reflects the advantage of treating ganciclovir sensitive disease with full dose ganciclovir. Cidofovir
Cidofovir was approved by FDA in 1996. It is a monophosphorylated cytosine analogue which is phosphorylated to a compound that impedes DNA polymerase. It is given intravenously once or twice per week. Resistance to cidofovir rises with exposure, prolonged treatment with ganciclovir lead to cross-resistance to cidofovir.
In series of 240 transplant recipients prophylaxed with oral ganciclovir, five had ganciclovir resistance. Four of them also had resistant to cidofovir. Likewise, treatment with cidofovir can confer resistance to ganciclovir.
In a cohort of AIDS patients with retinitis, 3 of 9 patients treated with cidofovir developed ganciclovir resistance.
Cidofovir can cause nephrotoxicity, this can be prevented by pre-hydration and probenecid, cidofovir can cause bone marrow suppression and ocular disease and proteinuria. Cidofovir at high dose significantly delayed progression of retinitis. Leflunomide
Leflunomide was approved for rheumatoid arthritis in 1998. It is and immunosuppressant and antiviral. It a protein kinase competitive inhibitor of dihyrdoorotate dehydrogenase, an enzyme required for pyrimidine synthesis. It inhibits pyrimidine synthesis so inhibits activated lymphocyte.
It has a half-life of 15-18 days due to enterohepatic recirculation.
In a study transplant patients failing conventional immunosuppression, two thirds of patients treated with leflunomide were able to reduce cyclosporine and prednisone dose by a third.
Four out of five liver transplants who tolerated leflunomide were able to stop cyclosporine or FK-506 and the fifth reduced his dose by 65% with no cases of rejection.
In another study, leflunomide was substituted for antimetabolite in 22 kidney transplant failing conventional immunosuppression due to rejection, cyclosporine toxicity, or progressive dysfunction. Six months after conversion, creatinine declined by a mean of 5%, no episodes of rejection.
Leflunomide inhibits CMV by interfering with final virion assembly rather than with DNA synthesis. As such, its viral target is distinct from that targeted by ganciclovir, foscarnet, and cidofovir. So can inhibit a multidrug-resistant CMV.
The major toxicity is transaminitis. Hepatic necrosis and death from liver failure was reported but rare. It should be avoided in patient with pre-existing liver disease, heavy alcohol, or concurrent viral hepatitis. Other adverse effects include diarrhoea, hypertension, reversible alopecia and rash, weight loss and pancytopenia. It is is contraindicated in pregnancy due to reports of fetal death and teratogenesis.
In our centre we mainly use Foscarnet for Gaciclovir resistant disease.
CMV infection is not uncommon complication in SOT.
CMV infection in immunosuppressed patient is associated with increased mortality as well as graft loss.
Timely diagnosis, treatment in addition to prophylaxis is the key.
Mechanism of action of Ganciclovir:
Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase.
To become active; phosphorylated in three steps to a triphosphorylated form.
Once phosphorylated, it acts as a competitive substrate for DNA polymerase and slows the replication of CMV DNA by DNA polymerase. And thus, it inhibit CMV DNA polymerase
Resistant definition:
Ganciclovir resistant either phenotypical or genotypical.
The “gold standard” test is the plaque reduction assay.
Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6μg/ml.
Ganciclovir resistance can also be detected via genotype analysis to assess for known mutations in the UL54 and UL97 genes.
Prevalence & risk factors for Ganciclovir resistant:
The prevalence of Ganciclovir resistant before treatment is low (0.9-2.7%), but it increased with prolonged use of the drugs reaching to 27.5% after 9 months of ganciclovir treatment.
Patients with ganciclovir resistant associated with lower survival compared to ganciclovir sensitive patients.
Prevention of ganciclovir resistant CMV infection:
The FDA approval of the valyl ester prodrug of ganciclovir valganciclovir in 2001, introduced a more potent option for CMV prophylaxis and maintenance therapy of disease in both transplant recipients and AIDS patients.
Valganciclovir is approximately ten times more bioavailable than oral ganciclovir
In SOT, Valganciclovir is superior to oral ganciclovir in prevention of resistant CMV infection.
Foscarnet:
It is an alternative to ganciclovir in treatment of CMV.
It is a direct competitive inhibitor of DNA polymerase.
The risk of resistance increases with the duration of foscarnet therapy.
Foscarnet is associated with renal toxicity, electrolyte abnormalities, and seizures.
Some studies found that combination of low doses of ganciclovir & foscarnet was superior to mono therapy to alternative agent alone.
Cidofovir:
It interferes with DNA polymerase activity.
It is effective in resistant CMV infection, but resistant increased with prolonged use.
Its use limited by side effects; nephrotoxicity, bone marrow suppression, & ocular disease.
Leflunomide:
Immuno-modulatory drugs with antiviral activity.
This drug originally developed for the treatment of rheumatoid arthritis.
Leflunomide is a prodrug that is rapidly metabolized to the active metabolite.
It suggested that leflunomide inhibits CMV by interfering with final virion assembly rather than with DNA synthesis.
Leflunomide is contraindicated in pregnancy due to reports of fetal death and teratogenesis in human subjects. Elevated liver enzyme is the most serious side effects.
It can be used in ganciclovir resistant CMV infection.
Reflection in our practice: In our practice we use oral valganciclovir as prophylaxis in all the cases. We are not using Gancyclovir at all.
Introduction
Ganciclovir is a guanosine analogue. It works by inhibiting CMV DNA polymerase. It is active in its triphosphorylated form which acts as a competitive substrate for DNA polymerase and slows down the replication of CMV DNA by DNA polymerase. Phosphorylation is achieved by phosphotransferase produced by the gene UL97. Mutations arising from UL97 phosphotransferase and from UL54 (DNA polymerase gene) lead to ganciclovir resistance. UL54 mutations can also lead to resistance in cidofovir and foscarnet and these agents also target CMV DNA polymerase. Ganciclovir resistance does not seem to impair the virulence of the virus.
Definition
There are 2 ways of assaying ganciclovir resistance:
Phenotypic assay
Genotypic assay
The ‘gold standard’ test to assay ganciclovir resistance is the plaque reduction assay. Human fibroblasts are cultured with ganciclovir at various different concentrations. Counting the viral plaque formations or DNA hybridization can be used to quantify the CMV growth. This method involves detection of mutations in the UL54 and UL97 genes. However, the correlation between the genotype and phenotype is not well founded, hence the genotype-based resistance reports need to be interpreted with caution.
Prevalence & risk factors for resistance
Among solid organ transplant recipients, the prevalence of CMV resistance to ganciclovir ranges from 0-15%. The risk factors for acquiring resistance to ganciclovir include:
CMV sero-negativity of the transplant recipient and seropositive donor
Degree of immune suppression
Level of CMV viremia
Prolonged exposure to anti-CMV medication
It was noted that patients with CMV that is resistant to ganciclovir had a significant reduction in survival compared to those with CMV that was sensitive to ganciclovir.
Patients who receive pancreas transplants receive more potent immune suppression. Investigators noted higher incidence rates of ganciclovir resistance among these patients.
Ganciclovir resistant to CMV disease has been diagnosed a median of 10 months after the transplant.
Treatment of Ganciclovir Resistant Infection Valganciclovir
Valganciclovir is a valyl ester prodrug of ganciclovir, approved by the FDA in 2001. It is approximately 10 times more bioavailable than ganciclovir, hence it is a more potent option for CMV prophylaxis and maintenance therapy for CMV disease.
Foscarnet
Foscarnet is a direct competitive inhibitor of DNA polymerase, approved by the FDA in 1991. It does not need to be phosphorylated in order to inhibit DNA polymerase. It is the primary alternative to ganciclovir for the treatment of CMV infection. As it is not dependent on UL97 gene for activation, it can act despite those mutations. However, mutation of UL54 may still lead to foscarnet resistance. Similar to ganciclovir, the risk of foscarnet resistance increases with the duration of therapy. It has also been noted that patients treated with ganciclovir had an increased incidence of neutropenia, while patients treated with foscarnet had an increased incidence of electrolyte abnormalities and nephrotoxicity.
Overall, studies have shown that foscarnet has a similar efficacy to ganciclovir, but as foscarnet is less well tolerated it may be a useful alternative agent to use in CMV that is resistant to ganciclovir.
Combination therapy with dose reduced ganciclovir and foscarnet
The rationale behind this approach is based on the fact that their resistance stems from different mutations, reducing their dosage may consequently mitigate their different toxicity profiles, and hence the medications may be better tolerated. One study demonstrated that combination therapy used for patients not responding to ganciclovir cleared the viremia and no relapses were seen. However, the incidence of nephrotoxicity was still increased despite the reduced dose of foscarnet.
Cidofovir
Cidofovir is a monophosphorylated cytosine analogue, which requires further phosphorylation intracellularly to form a compound that acts against DNA polymerase. It was approved by the FDA in 1996 for the treatment of CMV infection. It only requires to be administered once or twice a week. Sustained drug pressure increases the resistance to cidofovir. It has also been noted that prolonged treatment of CMV infection with ganciclovir can lead to the development of cross-resistance to cidofovir and likewise, treatment with cidofovir alone can lead to the resistance to ganciclovir. Cidofovir can lead to nephrotoxicity in as many as half of its patients. This adverse effect can be reduced by prehydration and probenecid, but these methods may also reduce its tolerance. Other adverse effects include bone marrow suppression and ocular disease.
Leflunomide
Leflunomide was approved by the FDA in 1998 to be used for the treatment rheumatic arthritis. Leflunomide acts as a protein kinase inhibitor and as a competitive inhibitor of dihyrdoorotate dehydrogenase, the intracellular enzyme required for pyrimidine synthesis. It is a prodrug that requires to be metabolized into an active form. It requires a loading dose as it has a long half life. It has limited renal excretion. It has been studies that leflunomide has the potential to inhibit multi-drug resistant CMV disease. Its major adverse effect is the elevation of transaminase. There have been cases reported of hepatic necrosis and liver failure due to leflunamide, but it is noted to be rare. Other adverse effects include diarrhea, hypertension, reversible alopecia and skin rashes. Further studies are required to ascertain the level of liver toxicity and its benefits in the use for multi drug resistant CMV infection.
Conclusion
Treatment of CMV disease is especially challenging in transplant recipients. There are a few drug options. Ganciclovir resistance is reportedly increasing, and the use of foscarnet and cidofovir is limited due to their nephrotoxic properties. Leflunomide appears to be promising, but it requires further studies and careful monitoring due to its potential to cause liver toxicity.
Local Practice:
In Kenya, we use IV ganciclovir for treating CMV disease for 5 – 7 days and then convert to valgancicovir once the patient is stable. We have not had a reported case of ganciclovir resistance. We also don’t routinely use valganciclovir for prophylaxis unless if we have used ATG. We monitor patients for CMV immediately post-transplant and then treat if we detect CMV disease
1. Please summarise this article Treatment of Ganciclovir Resistant Cytomegalovirus Infection Treatment strategies:
1. Ganciclovir Mechanism of Action & Resistance It is a guanosine analogue that inhibits CMV DNA polymerase. It must be phosphorylated (3 phases) before it may become active. The phosphotransferase produced by the UL97 gene is responsible for phosphorylation. Ganciclovir resistance results from UL97 phosphotransferase mutations. Changes in the DNA polymerase gene UL54 also result in ganciclovir resistance. Resistance assays: The plaque reduction assay: Is the “gold standard” test Human fibroblasts are grown with ganciclovir at different specified doses, CMV growth can be measured using a DNA hybridization method or by counting the number of viral plaques that develop. Genotyping analysis Mutations in the UL54 & UL97 genes indicate resistance. It takes less time and effort compared culture CMV method. Be aware of imperfection in the link between genotype and phenotype. Prevalence It is uncommon at first, but it quickly develops following prolonged antiviral exposure. The prevalence of CMV resistance in SOTs ranges from 0% to 15%. The risk of developing ganciclovir resistance is highest among lung TXs and is least among liver TXs; this may reflect the degree of IS & protocols used for CMV prophylaxis. Risk Factors for Resistance CMV seronegativity at TX when receiving a seropositive organ Degree of IS Magnitude of CMV viremia Number of CMV episodes in the past Prolonged exposure to anti-CMV medication Prior exposure to IV ganciclovir D+/R- organs are at particular risk of both CMV infection & ganciclovir resistance Pancreas recipients Prevention of Ganciclovir Resistant CMV Infection No published RCTs. No clearly efficacious 2ndline therapy. FDA approved valganciclovir (a prodrug of ganciclovir) in 2001 as a more potent option for CMV prophylaxis & maintenance therapy of disease. Through the use of valganciclovir, it may be possible to reduce resistance while maintaining the benefits and security of an oral medication. Foscarnet
A DNA polymerase that is direct competitive inhibitor.
The main substitute for ganciclovir in the management of CMV viremia & illness.
FDA approval in 1991.
It does not require phosphorylation, unlike ganciclovir, in order to prevent CMV DNA polymerase from working.
It retains effectiveness against CMV isolates that have UL97 mutations and are resistant to ganciclovir because it is not reliant on the CMV phosphotransferase UL97.
However, mutations in the DNA polymerase gene UL54 can sometimes give foscarnet resistance. Adverse effect profile has been the main barrier to wider adoption of Foscarnet; it is linked to electrolyte imbalances, convulsions, and kidney damage. Foscarnet & ganciclovir are of similar efficacy but foscarnet is less well tolerated. Combination therapy with dose reduced ganciclovir & foscarnet Rationale: Resistance to ganciclovir & foscarnet is linked to different gene alterations. Synergy between the two agents even against ganciclovir resistant isolates (in vitro). Combination is superior to monotherapy with the alternative agent alone. Synergy between the two agents would permit lower dosing of each agent & lower toxicity profiles. Cidofovir FDA approved in 1996 for the treatment of CMV infection. It is a monophosphorylated cytosine analogue that, similar to ganciclovir, further phosphorylation to be able to inhibits DNA polymerase activity. It is given IV once or twice/week. Similar to ganciclovir & foscarnet, cidofovir has modest baseline resistance that increases in response to persistent drug pressure. The toxicity profile of cidofovir restrict its appeal; nephrotoxicity in 50%. This can be mitigated by pre-hydrating & using probenecid. Other S/Es: iritis, uveitis, vitreous hypotonicity, & bone marrow suppression. Leflunomide Leflunomide is an immunomodulatory drug. It is active against viruses. It selectively inhibits activated lymphocytes. It is a prodrug that is rapidly metabolized to the active metabolite, A77 1726. Has a long-half life (15-18 days). Leflunomide has potential as a treatment for CMV since it potentiates immunosuppression & inhibits CMV reproduction. It is not nephrotoxic, in contrast to foscarnet and cidofovir, but it can raise transaminases. Leflunomide’s long-term efficacy, tolerability, & appropriateness are still being determined by research. //////////////////////////// 2. Please reflect on your practice
We have never encountered a true, or confirmed, ganciclovir resistant CMV infection in our transplant center. However, this does not necessarily reflect the real situation; it rather indicates under estimation of the problem. Due to financial issues, many of the logistics for confirming resistant case are lacking.
Summary Introduction.
Ganciclovir is a guanosine analogue that inhibits DNA polymerase. It is activated by phosphorylation to its triphosphorylated form.
Phosphorylation is accomplished by phosphotransferase produced by gene UL97.
Mutations in UL97 leads to ganciclovir resistance.
Other mutations that confer ganciclovir resistance is UL54 which also causes resistance to cidofovir and forscanet that also inhibit DNA polymerase.
Risk factors
1.Prolonged antiviral exposure.
Initially patients develop UL97 mutations but prolonged exposure to ganciclovir will lead to simultaneous UL54 and UL 97 mutations.
Similarly studies have shown patients with CMV disease not exposed to antivirals have low prevalence of mutations, but with prolonged exposure the prevalence increases.
2.Type of organ transplanted
The risk of resistance seem to be high in heart and lung transplants in comparison to kidney transplants.
This could be associated with the high degree of immunosuppression.
3.Donor and recipients CMV serostatus.
D+/R- have a high risk of CMV infection and resistance.
This could be due to repeated CMV episodes, high exposure of ganciclovir and higher degree of immunosuppression.
Prevention
1.Use of valganciclovir
Valganciclovir is 10 times more bioavailable than oral ganciclovir.
Resistance is thought to occur due to exposure of subtherapeutic plasma concentrations of ganciclovir.
Studies comparing IV ganciclovir and PO valganciclovir, have shown patients treated with IV ganciclovir have higher rate of resistance.
2.Forscanent
Direct inhibitor of DNA polymerase that doesn’t need phosphorylation hence retains activity against UL97 mutated CMV.
However it under goes UL54 mutation resistance which increases with increased exposure.
Forscanet is of similar efficacy as ganciclovir however it is less tolerated due to its side effects profile, thus reserved for ganciclovir resistant CMV.
3.Combination of ganciclovir and forscanet
One study compared the efficacy of combined ganciclovir and forscanet in reduced doses. The rationale behind this is, their activity is synergistic and they undergo different mutations thus can have activity against resistant strains.This study all patients cleared their antigenimia with no recurrence after. The only adverse effect was hypomagnesemia with no other adverse effects.
However a UK study that compared full dose ganciclovir compared with combined reduced forscanet and ganciclovir, had different results. Patients in the combined arm were less likely to have a negative CMV PCR at two weeks and were more likely to have nephrotoxicity and electrolyte imbalance.
4.Cidofovir
It is a monophosphorylated cytosine analogue that required phosphorylation to inhibit DNA polymerase.
Thus there is cross resistance between cidofovir and ganciclovir.
Its use is also limited by its side effect profile that include nephrotoxicity, bone marrow suppression and ocular disease.
Limited data on its use for ganciclovir resistant CMV.
5.Leflunomide
It’s an immunomodulatory drug with activity against viruses.
Its viral target is different from that of ganciclovir, cidofovir and forscanet hence permitting its use in ganciclovir resistant CMV.
Conclusion
Treatment of CMV in the immunocompromised patient is a challenge.
Effective therapy requires prolonged exposure which leads to resistance.
Cidofovir and forscanet have good activity against CMV but limited by their side effect profiles.
Use of combined reduced antivirals may deliver potent therapy with reduced nephrotoxicity though requires further research.
Leflonomide hold promise for the future further studies are thus required.
My practise
I have not come across any ganciclovir resistance could be due to the fact that we mainly use valganciclovir or we don’t routinely look for it.
Introduction.
CMV infection is usually treated with ganciclovir, treatment resistance have been reported. Different treatment strategies available to treat ganciclovir-resistant CMV infection.
Ganciclovir Mechanism of Action
GCV; guanosine analogue that competitively inhibits CMV DNA polymerase, to become active it first undergoes phosphorylation is accomplished by the phosphotransferase produced by the gene UL97.
Drug Resistance
Resulted from mutations in UL97 phosphotransferase or UL54, simultaneous UL54 and UL97 mutations resulted in higher level resistance.
Definition
Ganciclovir resistance can be assayed either :
– Phenotypically; plaque reduction or DNA hybridization IC50 of > 6μg/ml ( IC50 is the concentration value required to inhibit 50% of CMV growth )
-or Genotypically; analysis to assess for known mutations in the UL54 and UL97 genes.
Prevalence;
The prevalence in SOT ranges between 0 and 15%, it vary according to the organ transplanted likely reflect different degrees of immunosuppression.
Risk Factors;
CMV R-/ D+ ; risk of both CMV infection and ganciclovir resistance.
Degree of IS.
Magnitude of CMV viremia.
Prolonged exposure to anti-CMV medication. Prevention of Ganciclovir Resistant CMV Infection.
– Studies showed the resistance decrease with use of vGCV.
– Valganciclovir vGCV ; a more potent option for CMV prophylaxis and maintenance therapy, 10 times more bioavailable than oral ganciclovir , had similar safety profile except for higher incidence of neutropenia.
Foscarnet
-The primary alternative to ganciclovir, is a direct competitive inhibitor of DNA polymerase and does not need phosphorylation.
-Retains activity against CMV isolates with UL97 mutations, but not UL54
-Risk of resistance increases with the duration of foscarnet therapy.
– Adverse effect profile; renal toxicity, electrolyte abnormalities, and seizures.
-All toxic reactions resolved after discontinuing foscarnet. Combination therapy with dose reduced ganciclovir and foscarnet
-The rationale; ganciclovir and foscarnet resistance are usually associated with different gene mutations, in vitro demonstration of synergy between the two agents even against ganciclovir resistant isolates.
-Trial showed that combination therapy is superior to monotherapy with the alternative agent alone.
-Permit lower dosing of each agent and consequent mitigation of their different toxicity profiles.
Cidofovir
-It is a monophosphorylated cytosine analogue, require phosphorylation to impedes DNA polymerase activity.
– Given IV once or twice per week.
-Prolonged treatment with ganciclovir can also lead to cross-resistance to cidofovir. Likewise, treatment with cidofovir alone can confer resistance to ganciclovir
-Adverse effect profile; nephrotoxicity reduced by (pre-hydration and the use of probenecid), bone marrow suppression and ocular disease.
Leflunomide
– It is a protein kinase inhibitor and as a competitive inhibitor of dihyrdoorotate dehydrogenase, the intracellular enzyme required for pyrimidine synthesis hence selectively inhibits activated lymphocytes
-It is an immunomodulatory and additional activity against viruses, simultaneous immunosuppressive and anti-infective properties.
– Inhibits CMV by interfering with final virion assembly rather than with DNA synthesis
– It has a long-half life on the order of 15-18 days.
– Potential to inhibit a multidrug-resistant CMV
-The major toxicity; transaminase elevation. Others include; diarrhea, hypertension, reversible alopecia, and rash, weight loss and pancytopenia.
– It is contraindicated in pregnancy
Conclusion
-The management remains a challenge, effective therapy requires prolonged drug use which in turn is associated with emergence of drug resistant virus.
-The alternative therapies foscarnet and cidofovir both appear to have good in vivo activity against CMV, the adverse side effect limits their attractiveness as anti-CMV agents.
-The use of reduced dose combination therapy appears requires further study.
-The of leflunomide holds promise as a future agent for the management of CMV since it both potentiates immunosuppression and suppresses CMV reproduction.
Level of evidence: Level 5 narrative review.
Please reflect on your practice
I have not came across CMV resistance cases. Leflunomide therapy looks promising and has attractive properties .
● Management of CMV infection remains a substantial challenge for clinicians caring for immunocompromised patients
● Effective therapy requires prolonged drug use which associated with emergence of drug resistant virus
● Ganciclovir resistance can be assayed either phenotypically or genotypically.
● The “gold standard” test is the plaque reduction assay in which human fibroblasts are cultured with ganciclovir at various defined concentrations.
● IC50 is The concentration of ganciclovir required to inhibit 50% of CMV growth
● Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml.
● Ganciclovir resistance genotypically by detected mutations in UL54 , UL97 genes.
● Detection of resistance via gene mutations is :
• less labour intensive
• less time consuming
• is not limited by the need to culture CMV from patient specimens.
● Risk Factors for Resistance
☆ CMV seronegativity at transplant when receiving a seropositive organ
☆ Degree of immunosuppression
☆ Magnitude of CMV viremia
☆ prolonged exposure to anti-CMV medication.
● Seronegative recipients of seropositive organs appear to be at particular risk of both CMV infection and ganciclovir resistance.
● Patients with ganciclovir resistant suffered a significant decrease in survival ● valganciclovir offered a potential means to decrease resistance than gancyclovir in SOT transplants but more neutropenia
● Foscarnet is the primary alternative to ganciclovir for the treatment of CMV viremia and disease
● Foscarnet is a direct competitive inhibitor of DNA polymerase it does not need to be phosphorylated in order to inhibit CMV DNA polymerase.
● The risk of resistance increases with the duration of foscarnet therapy.
● Foscarnet is associated with renal toxicity, electrolyte abnormalities, and seizures.
● Foscarnet and ganciclovir are of similar efficacy but foscarnet is less well tolerated so treatment will be limited in some patients .
● Combination therapy of ganciclovir and foscarnet at reduced doses is A promising step for ganciclovir resistant CMV infection
● Cidofovir is further phosphorylated
intracellularly to form a compound that impedes DNA polymerase activity.
● cidofovir resistance was low but increases when :
Prolong treatment with cidofovir or ganciclovir ( cross-resistance )
● Cidofovir has nephrotoxicity “proteinuria”
, bone marrow suppression and ocular disease
● The risk of renal failure with foscarnet and cidofovir limits their attractiveness as anti-CMV agents
● Leflunomide is an immunomodulatory drug, in addition to immunosuppressive
properties it is active against viruses.
● Leflunomide has a long-half life “15-18” days it takes two months to achieve steady-state plasma concentrations and it can take two years to clear the drug.
● leflunomide inhibits CMV by interfering with final virion assembly rather than with DNA synthesis.
● The major toxicity of leflunomide is transaminase elevation
● Contraindications for leflunomide :
☆ Patients with pre-existing liver disease
☆ Heavy alcohol intake
☆ Concurrent viral hepatitis
☆ pregnancy
● In our centre we have CMV infection and CMV disease all of them were responsed to treatment with IV gancyclovir and oral valgancyclovir
We haven’t resistant cases
Other drugs aren’t avaliable
Introduction: Cytomegalovirus (CMV) infection is common in immunocompromised patients with serious complications, graft loss and death. The drug of choice of CMV infection is ganciclovir, that has reported drug resistance, mandating foundation of new drugs for prevention and treatment of it.
Ganciclovir Mechanism of Action and Drug Resistance Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase. Mutations arising in UL97 phosphotransferase lead to ganciclovir resistance. Simultaneous UL54 and UL97 mutations. This is associated with higher level resistance to ganciclovir. UL54 mutations can confer cross-resistance to foscarnet and cidofovir since these agents also target CMV DNA polymerase.
Definition Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml, or via genotype analysis to assess for known mutations in the UL54 and UL97 genes.( less labour intensive, less time consuming, and is not limited by the need to culture). The “gold standard” test is the plaque reduction assay in which human fibroblasts are cultured with ganciclovir at various defined concentrations. The concentration of ganciclovir required to inhibit 50% of CMV growth is the IC50 value.
Prevalence and Risk Factors for Resistance – Prolonged exposure to antiviral agents. – The baseline prevalence of ganciclovir resistance was 0.9% in blood specimens and 2.7% in urine specimens. – After six months of treatment prevalence of 11.4%, increased to almost third for those treated for 9 months. – The type of organ transplanted lung>heart>liver> kidney. – CMV –ve R /+ve D. – Potent immunosuppressive drugs. – Severity of viremia. – Almost 60% of patients treated for resistant CMV, suffered allograft loss, foscarnet nephrotoxicity, or rejection.
Prevention of Ganciclovir Resistant CMV Infection Valyl ester prodrug of ganciclovir= valganciclovir. CMV viremia was less frequent during the prophylactic period (2.9% versus 10.4%; P=.001), a mechanistically fitting observation for the observed difference in subsequent rates of resistance.
Treatment of Ganciclovir Resistant CMV Foscarnet – A direct competitive inhibitor of DNA polymerase. – It retains activity against CMV isolates with UL97 mutations that are resistant to ganciclovir. – Mutations in the DNA polymerase gene UL54, however, do confer foscarnet resistance. – The risk of resistance increases with the duration of foscarnet therapy. – Foscarnet is associated with renal toxicity, electrolyte abnormalities, and seizures. – Excess mortality in the ganciclovir group was unclear when compared to Foscrnet group in a trial treating AIDS associated retinitis, however the mortality difference might be explained by the fact that patients in the ganciclovir arm were significantly less likely to be receiving concurrent antiretroviral therapy. – In other study; Neutropenia significantly more in the ganciclovir group, genital ulcers, nephrotoxicity, electrolyte imbalance, and infusion related symptoms were more in foscarnet group and more patients were shifted to other treatment option. Combination therapy with dose reduced ganciclovir and foscarnet – The rationale for this strategy stems from the recognition that ganciclovir and foscarnet resistance are usually associated with different gene mutations, in vitro demonstration of synergy between the two agents even against ganciclovir resistant isolates. – All patients also received CMV hyperimmunoglobulin. All patients had a clinical response within 72-96 hours and completely cleared their antigenemia within 4-8 weeks. No relapses were seen after 12-36 months of follow-up. But experienced significant hypomagnesemia requiring treatment. Cidofovir – A monophosphorylated cytosine analogue which, like ganciclovir, is further phosphorylated intracellularly to form a compound that impedes DNA polymerase activity, administered IV once or twice a week. – Resistance increased by treatment time, even prolonged treatment of CMV infection with ganciclovir can also lead to the development of cross-resistance to cidofovir. – Nephrotoxicity occurs in 50% of cases that may halted by hydration and use of probenecid, bone marrow suppression and ocular disease including iritis, uveitis, and vitreous hypotonicity.
Leflunomide – An immunomodulatory drug, a protein kinase inhibitor and as a competitive inhibitor of dihyrdoorotate dehydrogenase, the intracellular enzyme required for pyrimidine synthesis, originally developed for the treatment of rheumatoid arthritis, e in addition to immunosuppressive properties it is active against viruses, so can reduce the risk of rejection and treating the virus. – It would take nearly two months to achieve steady-state plasma concentrations, and takes almost two years to clear the drug- not excreted by kidneys. – It inhibits CMV by interfering with final virion assembly rather than with DNA synthesis. – Side effects includes anemia, one case of liver enzyme elevation, drug drug interaction requiring CNI dose reduction by 70%, diarrhea, hypertension, reversible alopecia, and rash, hepatic necrosis and death(rare). – A 4 renal transplant patients from India with symptomatic gastrointestinal CMV disease who were treated with leflunomide because they could not afford intravenous ganciclovir. All four patients had detectable CMV viremia via quantitative PCR. The patients were treated with a 100mg oral loading dose once daily for three days followed by 20mg/day for three months. All experienced clinical and endoscopic resolution of their disease as well as clearance of serum viremia. No significant adverse effects were reported. – The data are limited with few case series, in BMT, lung transplant…etc. Conclusion: The management of CMV infection is challenging, requiring prolonged treatment course, increasing the risk of drug resistance. Foscarnet and cidofovir have ag good in vivo activity againt the virus but both can cause acute kidney injury. The use of reduced dose combination therapy appears to deliver potent antiviral therapy with less risk of nephrotoxicity but this approach requires further study. The longterm effectiveness, tolerability, and ideal settings for the use of leflunomide remain to be defined by ongoing and future studies.
Please reflect on your practice In our center we did not face any CMV resistant strains, this could be due to the use of Valgancyclovir. However, this review article makes us understand how to deal with such cases in the future.
CMV infection is a common complication of immune suppression.
The first line treatment isganciclovir. There is rising trend of drug resistance. This review explains the treatment strategies available to treat ganciclovir-resistant CMV infection. This also includes approved alternative agents foscarnet and cidofovir, the use of combination ganciclovir and foscarnet at reduced doses, and leflunomide.
Ganciclovir Mechanism of Action and Drug Resistance
Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase. It acts as a competitive substrate for DNA polymerase and slows the replication of CMV DNA by DNA polymerase. Phosphorylation is accomplished by the phosphotransferase produced by the gene UL97.
Mutations arising in UL97 phosphotransferase lead to ganciclovir resistance.
Different UL97 mutations are associated with different degrees of ganciclovir resistance.
Definition of resistane
The best test is the plaque reduction assay in which human fibroblasts are cultured with ganciclovir at various defined concentrations.
The concentration of ganciclovir required to inhibit 50% of CMV growth is the IC50 value.
Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml.
Prevalence and Risk Factors for Resistance
Among solid organ transplant recipients, the prevalence of CMV resistance ranges between 0 and 15%. The risk of developing ganciclovir resistance does seem to vary according to the organ transplanted.
Risk factors for the acquisition of ganciclovir resistance include –
CMV seronegativity at transplant when receiving a seropositive organ
Degree of immunosuppression, magnitude of CMV viremia
Prolonged exposure to anti-CMV medication
Treatment
Foscarnet
Foscarnet is a direct competitive inhibitor of DNA polymerase.
The risk of resistance increases with the duration of foscarnet therapy
Foscarnet is associated with renal toxicity, electrolyte abnormalities, and seizures
Foscarnet and ganciclovir are of similar efficacy but that foscarnet is less well tolerated
Combination therapy with dose reduced ganciclovir and foscarnet
The rationale for this strategy stems from the recognition that ganciclovir and foscarnet resistance are usually associated with different gene mutations
combination therapy has been shown to be effective in pre-emptive therapy of CMV antigenemia in nonganciclovir resistant bone marrow transplant patients
Cidofovir
It is a monophosphorylated cytosine analogue which is further phosphorylated intracellularly to form a compound that impedes DNA polymerase activity
Prolonged treatment of CMV infection with ganciclovir can also lead to the development of cross-resistance to cidofovir
Cidofovir can cause nephrotoxicity, bone marrow suppression and ocular disease including iritis, uveitis, and vitreous hypotonicity.
Leflunomide
Leflunomide is an immunomodulatory drug originally developed for the treatment of rheumatoid arthritis and approved for that indication by the FDA in 1998.
It is protein kinase inhibitor and as a competitive inhibitor of dihyrdoorotate dehydrogenase, the intracellular enzyme required for pyrimidine synthesis.
The half life on the order of 15-18 days
The major toxicity of leflunomide is transaminase elevation
Other side effects includes, diarrhoea, rash , hypertension and Pancytopenia.
Conclusions
The management of CMV infection remains a substantial challenge for clinicians
Effective therapy requires prolonged drug use which in turn is associated with emergence of drug resistant virus
CMV resistance to ganciclovir has been reported with increasing frequency
Foscarnet and cidofovir both appear to have good in vivo activity against cytomegalovirus but both are limited by their propensity to cause acute renal failure
The novel immunomodulatory agent leflunomide holds promise as a future agent for the management of CMV since it both potentiates immunosuppression and suppresses CMV reproduction.
Reflection on Practice
I have not seen a case of CMV resistance and have experience with its pharmacotherapy.
Treatment of Ganciclovir Resistant Cytomegalovirus Infection – Ganciclovir is a guanosine analogue when phosphorylated it competitively inhibits CMV DNA polymerase and decrease CMV replications. – Phosphorylation is accomplished by the phosphotransferase produced by the gene UL97 and UL54. So mutations cause ganciclovir resistance. – UL54 mutations can confer cross-resistance to foscarnet and cidofovir. Definition:
– Phenotypically: ganciclovir resistance has been defined as a plaque reduction
or DNA hybridization IC50 (The concentration of ganciclovir required to inhibit
50% of CMV growth) of > 6μg/ml.
– Genetically: mutations in genes UL97 and UL54.
Prevalence:
– Ganciclovir resistance is uncommon at baseline amongst untreated patients but
arises rapidly after prolonged exposure to antiviral agents.
– In solid organ transplant, the prevalence of CMV resistance ranges between 0 and
15% and does not vary according to the organ transplanted. Risk factors:
– CMV seronegativity at transplant when receiving a seropositive organ
– Degree of immunosuppression (with more potent IS ).
– Magnitude of CMV viremia
– Prolonged exposure to anti-CMV medication. Prevention of Ganciclovir Resistant CMV Infection:
1- Valganciclovir (10 time more bioavailable, FDA approved in 2001) offered a
potential means to decrease resistance while retaining the convenience and safety
of an oral agent.
2- Foscarnet:
– It is an alternative to ganciclovir for the treatment of CMV viremia and disease.
– Direct competitive inhibitor of DNA polymerase without need for phosphorylation.
– So, it retains activity against CMV isolates with UL97 mutations that are resistant
to ganciclovir.
– However, UL54 mutation does confer foscarnet resistance.
– The risk of resistance increases with the duration of foscarnet therapy.
– Foscarnet is associated with renal toxicity, electrolyte abnormalities
(hypocalcaemia, hypomagnesemia, hypokalemia and hypophosphatemia), genital
ulcers and seizures.
– Foscarnet is useful agent to use against ganciclovir resistant CMV but treatment will be limited by the increased side effects.
3- Combination therapy with dose reduced ganciclovir and foscarnet:
– The rationale for this strategy stems from the recognition that ganciclovir and
foscarnet resistance are usually associated with different gene mutations.
– Data on those with ganciclovir resistant CMV is limited to a retrospective study
included six SOT patients with good response.
4- Cidofovir:
– It is a monophosphorylated cytosine analogue which, like ganciclovir, is further
phosphorylated intracellularly to form a compound that impedes DNA polymerase
activity.
– It has to be given intravenously but need only be administered once or twice per
week
– Resistance to cidofovir is low at baseline but rises.
– Prolonged treatment of CMV infection with ganciclovir can also lead to the
development of cross-resistance to cidofovir.
– Its use is limited by its adverse effect profile. Cidofovir can cause nephrotoxicity in
as many as half of all patients, bone marrow suppression and ocular disease
including iritis, uveitis, and vitreous hypotonicity.
Clinical reports of the use of cidofovir in ganciclovir-resistant infection are scarce.
5- Leflunomide:
– An immunomodulatory drug with anti-viral activity.
– Leflunomide acts as a protein kinase inhibitor and as a competitive inhibitor of
dihyrdoorotate dehydrogenase required for pyrimidine synthesis. Thus inhibit
activated lymphocytes.
– It is rapidly metabolized to the active metabolite and has a long half-life (15-18
days)
– It is used for treatment of rheumatoid arthritis and can be used as IS for patients
with poor response to conventional IS in SOT.
– Reported complications includes: elevated liver enzymes, diarrhea, hypertension,
reversible alopecia, weight loss, pancytopenia and rash.
– It is contraindicated in patients with liver disease, viral hepatitis, alcoholic and in
pregnancy.
Leflunomide inhibits CMV by interfering with final virion assembly rather than with DNA synthesis. So, it has the potential to inhibit multi-drug resistant CMV.
The use of leflunomide in human beings for CMV infection is extremely limited and remains on the case report level.
Conclusion:
CMV resistance to ganciclovir has been reported with increasing frequency in
both AIDS patients treated for CMV retinitis and in recipients of both bone marrow
and SOT.
The alternative therapies foscarnet and cidofovir both appear to have good in vivo activity against CMV but both are limited by their propensity to cause acute renal failure.
The use of reduced dose combination therapy appears to deliver potent antiviral therapy with less risk of nephrotoxicity but this approach requires further study.
The novel immunomodulatory agent leflunomide holds promise as a future agent for the management of CMV since it both potentiates immunosuppression and suppresses CMV reproduction.
The long-term effectiveness, tolerability, and ideal settings for the use of leflunomide remain to be defined by ongoing and future studies.
II- In the last 2 years, was diagnosed few cases with CMV and they responded well with slandered treatment.
CMV infection is prevelant in solid organ transplantation( SOT ) patient and if not apprioratlytreated it will lead to graft failure and increased mortality gancyclover has been recommended as the 1st line of treatment and prophylaxis but a rising incidence of drug resistance incidence has been reported Mechanism of action
Gancyclover is a competitive inhibitor of DNA polymerase that is responsible for replication of CMV DNA
The medication become active through 3 steps enzymatic phosphorylation , mutation( UL 97) in such enzyme will affect active drug generation andhence resistance develop . Another well known mutation which is UL 54 which make DNA polymerase resistant to the effect of the active phosphorylated gancyclover metabolite , making drug resistance is possible . both mutation can present at same time Prevelance and risk factors Prevelance of Resistance in SOT is ranging from 0- 15% risk factors are
· CMV seronegativity at transplant when receiving a seropositive organ,
· degree of immunosuppression,
· magnitude of CMV viremia, and
· prolonged exposure to anti-CMV medication Prevention of Ganciclovir Resistant CMV Infection
· Use of Valganciclover which is FDA approved in 2001 and it is 10 times more potent than ganciclover so it will shorten the treatment course and reduce resistance . but on cohort studies which has small number of patients it showed no difference in incidence of resistance in some and others showed high resistance incidence with gancyclover
· Use of Foscarnet : it has a direct competitive inhibitor of DNA without the need for phosphorylation and hence is not affected by mutation in UL97 gen but mutation affecting DNA polymerase can create Foscarnet drug resistance .Foscarnet is associated with renal toxicity, electrolyte abnormalities, and seizures.Accordingly , Foscarnet is agood alternative for treatment of incase of Ganciclover resistance but the risk of nephrotoxicity limit its use
· Combination therapy with dose reduced ganciclovir and foscarnet: both medication has synrgitic effect and reduction of dose will reduce SideEffects the evidence to support this hypothesis is still low
· Cidofovir : approved for CMV treatment by FDA in 1994 and acting in away similar to Gancyclover but taken IV in twicewekly dose but again resistance incidence is rising . Notably, prolonged treatment of CMV infection with ganciclovir can also lead to the development of cross-resistance to cidofovir.
· Leflunomide: acts as a protein kinase inhibitor and as a competitive inhibitor of dihyrdoorotate dehydrogenase, the intracellular enzyme required for pyrimidine synthesis. It specifically inhibits denovo pyrimidine synthesis. It is immunomodulator and has antiviral activity and basically used ibn rheumatoid arthritis treatment but found to be helpful to reduce or completely stop immunsupression while using leflunoamide without incidence of acute rejection . it has long half-life and its side effected noted from clinical studies are anamia and elevation of liver function test in addition to minor incidence of diarrhea, hypertension, reversible alopecia , and rash . Conclusion
1. CMV resistance to ganciclovir has been reported with increasing frequency in recipients of both bone marrow and solid organ transplants.
2. The alternative therapies foscarnet and cidofovir both appear to have good in vivo activity against cytomegalovirus but both are limited by their propensity to cause acute renal failure.
3. The use of reduced dose combination therapy appears to deliver potent antiviral therapy with less risk of nephrotoxicity but this approach requires further study
4. leflunomide holds promise as a future agent for the management of CMV since it both potentiates immunosuppression and suppresses CMV reproduction
reflection on practice
balancing approach with use of antiviral reduction of IS with close monitoring shorten course of antiviral to reduce resistance keeping patient oriented by the risk andbenefit of each sttigy accordingly
CMV infection carries a high risk for the development and progression of CMV disease, allograft dysfunction, and death. Usually we start treatment for CMV infections and disease with ganciclovir, however, many centres have reported a small but rising incidence of ganciclovir resistant CMV infections.
Mechanism of action of ganciclovir:
Ganciclovir is targeting CMV DNA as a competitive inhibitor to CMV DNA polymerase via phosphorylation which is done by the phosphotransferase produced by the gene UL97
Mutations arising in UL97 phosphotransferase lead to ganciclovir resistance. mutations arising in the DNA polymerase gene UL54 also carries resistance to ganciclovir. Different UL97 mutations are associated with different degrees of ganciclovir resistance. Also resistance is increasing with prolonged exposure to ganciclovir Of Note: Foscarnet has cross resistance with ganciclovir as it is also targeting CMV DNA also Diagnosis of ganciclovir resistance:
– Phenotypically :The gold standard plaque reduction assay in which human fibroblasts are cultured with ganciclovir at various defined concentrations. CMV growth can be quantified by counting viral plaque formation or by a DNA hybridization technique. The concentration of ganciclovir required to inhibit 50% of CMV growth is the IC50 value. Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml.5
– Genotypically: genotype analysis to assess for known mutations in the UL54 and UL97 genes Prevalence of ganciclovir resistance in CMV: # The risk of developing ganciclovir resistance varies according to the organ transplanted ,being around 45% in kidney transplant and highest in lung transplant 99%.data from 2 chicago transplant centers in 1994-2001.
# Risk factors for ganciclovir resistance :
1. CMV seronegativity at transplant when receiving a seropositive organ: Seronegative recipients of seropositive organs appear to be at particular risk of both CMV infection and ganciclovir resistance, also decreased survival.
2. Degree of immunosuppression
3. Magnitude of CMV viremia
4. Prolonged exposure to anti-CMV medication.
The FDA approval of the valyl ester prodrug of ganciclovir valganciclovir in 2001, introduced a more potent option for CMV prophylaxis and maintenance therapy of disease in both transplant recipients and AIDS patients. Valganciclovir is approximately ten times more bioavailable than oral ganciclovir. Since ganciclovir resistance is thought to be related to prolonged exposure to subtherapeutic plasma concentrations of ganciclovir.
2 important studies in using valgancyclovir vs ganciclovir regarding resistance:
1-: AIDS patients with CMV retinitis demonstrated equivalence to intravenous ganciclovir in the risk of emergence of ganciclovir resistance, while in the solid organ transplant population, valganciclovir was shown to be superior to oral ganciclovir for the prevention of resistant CMV infection,after 6 months from follow up: ganciclovir resistance mutations in UL97 were found in 9.5% of patients, divided equally between the group induced with valganciclovir and the group induced with intravenous ganciclovir.
2- 301 D+/R– solid organ transplant patients prophylaxed with either valganciclovir 900mg PO qd or ganciclovir 1000mg PO tid for 100 days post-transplant. At the end of 100 days, none of the valganciclovir treated patients had become infected with resistant virus versus 2% of patients in the ganciclovir group. After one year post-transplant, the rate of CMV disease associated with ganciclovir resistant virus remained at zero for the valganciclovir group but had risen to 6% in the ganciclovir group.also there was neutropenia more evident of valgancyclovir group.
Foscarnet:
The primary alternative to ganciclovir for the treatment of CMV viremia and disease . Mech of action:it is a direct competitive inhibitor of DNA polymerase. Unlike ganciclovir, it does not need to be phosphorylated in order to inhibit CMV DNA polymerase. Since it is not dependent on the CMV phosphotransferase UL97 it retains activity against CMV isolates with UL97 mutations that are resistant to ganciclovir.
Mutations in the DNA polymerase gene UL54, however, do confer foscarnet resistance and can sometimes be selected for by prolonged ganciclovir therapy. Like ganciclovir, the risk of resistance increases with the duration of foscarnet therapy. Limitation of use: renal toxicity, electrolyte abnormalities, and seizures Combination therapy with dose reduced ganciclovir and foscarnet:
Data from the AIDS literature showing that combination therapy is superior to monotherapy with the alternative agent alone,27 and that combination therapy has been shown to be effective in pre-emptive therapy of CMV antigenemia in non ganciclovir resistant bone marrow transplant patient ,also it will lead to decreasing the doses of both drugs ,therefore decreasing their toxicity profile. Cidofovir :
Mech of action:
It is a monophosphorylated cytosine analogue which, like ganciclovir, is further phosphorylated intracellularly to form a compound that impedes DNA polymerase activity.
Administration: it has to be given intravenously but need only be administered once or twice per week. Like ganciclovir and foscarnet, resistance to cidofovir is low at baseline but rises Limitation of use: Nephrotoxicity (in some studies it it was irreversible):could be decreased by good hydration and probenecid but this also can decrease tolerability. bone marrow suppression Ocular disease including iritis, uveitis, and vitreous hypotonicity Leflunomide:
Leflunomide is an immunomodulatory drug originally developed for the treatment of rheumatoid arthritis and approved for that indication by the FDA in 1998.
Leflunomide has attracted particular interest from the transplant community because it has immunosuppressive actions as it acts on pyrimidine synthesis and in some kidney transplant cases replaced azathioprinr ,MMF and cNI . Mech of action: acts as a protein kinase inhibitor and as a competitive inhibitor of dihyrdoorotate dehydrogenase, the intracellular enzyme required for pyrimidine synthesis. It specifically inhibits denovo pyrimidine synthesis and hence selectively inhibits activated lymphocytes since resting lymphocytes are able to synthesize pyrimidines via a salvage pathway. Pharmacology: is a prodrug that is rapidly metabolized to the active metabolite, A77 1726. The drug has a long-half life on the order of 15-18 days potentiated by substantial enterohepatic recirculation. Without a loading dose it is estimated that it would take nearly two months to achieve steady-state plasma concentrations. Likewise, after discontinuation of the medication it can take as long as two years for the body to entirely clear the drug. Mech of action in CMV infection: leflunomide inhibits CMV by interfering with final virion assembly rather than with DNA synthesis. As such, the viral target for leflunomide is distinct from that targeted by ganciclovir, foscarnet, and cidofovir. Side effects:increased transaminases,0.02%-0.04% liver necrosis and LCF, diarrhea (17-33%), hypertension (6-12%), reversible alopecia (8-11%), and rash (10-14%) Literature: four renal transplant patients from India with symptomatic gastrointestinal CMV disease who were treated with leflunomide because they could not afford intravenous ganciclovir. All four patients had detectable CMV viremia via quantitative PCR. The patients were treated with a 100mg oral loading dose once daily for three days followed by 20mg/day for three months. All experienced clinical and endoscopic resolution of their disease as well as clearance of serum viremia. No significant adverse effects were reported
Another case of use of leflunomide in an allogeneic bone marrow transplant recipient who developed CMV infection refractory to sequential therapy with ganciclovir, foscarnet, and cidofovir. The patient had multiple comorbidities including severe pre-existing graft-versus-host disease. After starting a combination of leflunomide and foscarnet, the patient’s CMV viral load decreased from 226,000 copies per ml to an undetectable level over the course of six weeks. Leflunomide was stopped after three weeks of therapy due to hyperbilirubinemia. Four weeks after stopping therapy, the patient’s CMV viremia recurred. She expired soon thereafter from bacterial sepsis. So there is both the potential and some of the dilemmas in the use of leflunomide for resistant CMV disease. While the agent was clearly effective in clearing the patient’s CMV viremia, it is possible that it contributed to her death from progressive liver failure.
Regarding our practice , I will write in another box
Cytomegalovirus (CMV) infection is a common and serious complication of immunosuppression in solid organ and bone marrow transplant recipients, and in patients with AIDS.
CMV infection is associated with a high risk for the development and progression of CMV disease,allograft dysfunction, and death.
First line treatment for CMV infections and disease is ganciclovir, many centres have reported a small but rising incidence of ganciclovir resistant CMV infections.
I shall emphasise treatment strategies available to treat ganciclovir-resistant CMV infection including the currently approved alternative agents foscarnet and cidofovir , the use of combination ganciclovir and foscarnet at reduced doses, and the novel immunomodulatory agent, leflunomide. Ganciclovir mechanism of action and drug resistance
Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase.
Mutations arising in the DNA polymerase gene UL54 confer resistance to ganciclovir..
Most patients develop only UL97 mutations, prolonged exposure to ganciclovir can give rise to simultaneous UL54 and UL97 mutations.
The “gold standard” test is the plaque reduction assay in which human fibroblasts are cultured with ganciclovir at various defined concentrations.
The concentration of ganciclovir required to inhibit 50% of CMV growth is the IC50 value.
Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6μg/ml..
Ganciclovir resistance can be detected via genotype analysis to assess for known mutations in the UL54 and UL97 genes.
Detection of resistance via gene mutations is attractive since it is less labour intensive, less time consuming, and is not limited by the need to culture CMV from patient specimens.
The correlation between genotype and phenotype, is imperfect so genotype-based resistance reports need to be interpreted with caution.
Gancicilvir resistentce is uncommon at baseline amongst untreated patients but arises rapidly after prlonged exposure to antiviral agents
In one cohort of AIDS patients newly diagnosed with CMV retinitis, samples of vitreous were assayed for baseline gene mutations associated with ganciclovir resistance.
Blood and urine cultures from 108 AIDS patients newly diagnosed with CMV retinitis were prospectively tested for ganciclovir resistance.
The baseline prevalence of ganciclovir resistance was 0.9% in blood specimens and 2.7% in urine specimens.
After six months of treatment predominantly with intravenous ganciclovir, the prevalence of patients with resistant blood or urine isolates rose to 11.4%.
Identification of a ganciclovir resistant isolate was correlated with the development of CMV retinitis in the contralateral eye..
The risk of developing ganciclovir resistance does seem to vary according to the organ transplanted.
This is felt to reflect different degrees of immunosuppression and different protocols for the prophylaxis of CMV. Organ total number of patients with CMV infection
Risk factors for the acquisition of ganciclovir resistance include CMV seronegativity at transplant when receiving a seropositive organ, degree of immunosuppression, magnitude of CMV viremia, and prolonged exposure to anti-CMV medication.
Seronegative recipients of seropositive organs appear to be at particular risk of both CMV infection and ganciclovir resistance.
In a cohort of 240 liver, kidney, and pancreas recipients who took oral ganciclovir prophylaxis for three months after transplantation, 25 developed invasive CMV disease over the course of one year ofollow-up.
Five of these patients (20%) had isolates with ganciclovir resistance.
All five patients with ganciclovir resistant CMV disease were CMV seronegative recipients of organs from seropositive donors.
The risk of developing ganciclovir resistant CMV among D+/R– patients did not differ if patients were treated for CMV with a prophylactic or preemptive strategy. Prevention of ganciclovir resistant CMV infection
The treatment of ganciclovir resistant CMV infections has not been comprehensively studied.
The FDA approval of the valyl ester prodrug of ganciclovir valganciclovir in 2001, introduced a more potent option for CMV prophylaxis and maintenance therapy of disease in both transplant recipients and AIDS patients.
A study conducted in AIDS patients with CMV retinitis demonstrated equivalence to intravenous ganciclovir in the risk of emergence of ganciclovir resistance, while in the solid organ transplant population, valganciclovir was shown to be superior to oral ganciclovir for the prevention of resistant CMV infection.
In the former study, valganciclovir was compared to intravenous ganciclovir in an open label trial of 148 AIDS patients with CMV retinitis.
Trials comparing ganciclovir and foscarnet in unselected patients give a sense of the relative effectiveness and frequency of adverse effects of these two agents
This information needs to be interpreted with caution as the data were derived from patients with wild type CMV infection rather than ganciclovir resistant isolates.
In the inpatient setting where both these variables can be closely monitored and often pre-empted foscarnet seems to be a reasonable choice but a more challenging option in the management of outpatients. Combination therapy with dose reduction of ganciclovir and foscarnet
A promising avenue for the future treatment of ganciclovir resistant CMV infection has been the use of combination ganciclovir and foscarnet at reduced doses
The rationale for this strategy stems from the recognition that ganciclovir and foscarnet resistance are usually associated with different gene mutations, in vitro demonstration of synergy between the two agents even against ganciclovir resistant isolates, trial data from the AIDS literature showing that combination therapy is superior to monotherapy with the alternative agent alone, and that combination therapy has been shown to be effective in pre-emptive therapy of CMV antigenemia in nonganciclovir resistant bone marrow transplant patients..
The incidence of nephrotoxicity seen with reduced dose foscarnet combination therapy is disappointing relative to the success of the strategy in the ganciclovir resistant CMV trial above
It is probably a more accurate reflection of the adverse effect profile of foscarnet, given the greater number of patients treated in this trial and the well described association of foscarnet with renal dysfunction. Findings
After six months of treatment predominantly with intravenous ganciclovir, the prevalence of patients with resistant blood or urine isolates rose to 11.4%.
When patients were re-evaluated one year post-transplant, the rate of CMV disease associated with ganciclovir resistant virus remained at zero for the valganciclovir group but had risen to 6% in the ganciclovir group..
In AIDS patients with CMV retinitis, for example, the incidence of resistance at 6, 9, and 12 months of therapy rose from 13% to 24% to.
Patients treated with combination therapy were less likely to have PCR negative blood at 14 days.
Among 39 renal transplant patients treated with high-dose leflunomide as an immunosuppressant, the mean hematocrit dropped by an average of 15%. Conclusion
The management of CMV infection remains a substantial challenge for clinicians caring for immunocompromised patients.
While there are a number of agents active against the virus, effective therapy requires prolonged drug use which in turn is associated with emergence of drug resistant virus.
CMV resistance to ganciclovir has been reported with increasing frequency in both AIDS patients treated for CMV retinitis and in recipients of both bone marrow and solid organ transplants.
The alternative therapies foscarnet and cidofovir both appear to have good in vivo activity against CMV but both are limited by their propensity to cause acute renal failure.
Given the often tenuous medical status of immuncompromised patients and the frequent need to simultaneously administer nephrotoxic agents, the risk of renal failure with foscarnet and cidofovir limits their attractiveness as anti-CMV agents.
In our center very few cases was diagnosed with CMV and they responded well with slandered treatment.
Introduction:
Cytomegalovirus (CMV) infection is serious condition in immune compromised patients especially solid organ transplant on immunosuppressive therapy.
Main treatment of CMV is ganciclovir but nowaday some centers shows increase incidence of drug resistance. This review study evidence of foscarnet and cidofovir, or novel immunomodulatory agent, leflunomide in ganciclovir resistance cases.
Mechanism of action of ganciclovir:
It’s inhibit CMV DNA https://s.w.org/images/core/emoji/14.0.0/svg/1f9ec.svg polymerase and ganciclovir resistance arise from defect in Phosphorylation because mutations of UL97 phosphotransferase.
Side effects of ganciclovir is neutropenia.
Prevalence and Risk Factors for Resistance:
Prolong exposure to ganciclovir
CMV seronegativity at transplant when receiving a seropositive organ.
Degree of immunosuppression
Magnitude of CMV viremia.
Prevention of ganciclovir resistance:
valganciclovir is a prodrug of ganciclovir and more potent than ganciclovir and ten times more bioavailability in comparison to ganciclovir.
Foscarnet:
It’s used as alternative to ganciclovir in case of resistance of ganciclovir to treat CMV infection.
It’s competitive inhibitors to CMV DNA polymerase.
Foscarnet resistance occur due to prolonged exposure. Drug resistance was associated with an increased risk of retinitis progression.
Side effects of foscarnet is nephrotoxicity, electrolyte abnormalities, and seizures.
Withdrawal of foscarnet are high because of its toxicity.
Cidofovir:
It’s a monophosphorylated cytosine analogue similar to ganciclovir.
It’s given twice per week and resistance to cidofovir is low.
It’s used to treat CMV retinitis.
Also prolonged treatment of CMV infection with ganciclovir may lead to the development of cross-resistance to cidofovir.
Side effects of cidofovir is nephrotoxic and ocular toxicity.
Leflunomide:
It’s immunomodulatory drug used for treatment of rheumatoid arthritis.
Leflunomide is a prodrug acts as a protein kinase inhibitor and as a competitive inhibitor of dihyrdoorotate dehydrogenase, the intracellular enzyme required for pyrimidine synthesis.
Side effects of Leflunomide is anemia and raised liver enzymes.
Other side effects are alopacia and skin rach , hypertension and pancytopenia.
Treatment of Ganciclovir Resistant CMV infection: Ganciclovir Mechanism of Action and Drug Resistance:
Ganciclovir as an antivirus medication approved by the FDA in 1989, inhibit CMV DNA polymerase.
Act as DNA polymerization competition after phosphorylation.
Resistance to ganciclovir can occur due to mutation in the gene UL97, and mutation in the gene UL54, different mutations in genes UL97 and UL54 can cause different degrees of resistance.
Most mutations develop in gene UL97, but simultaneous mutation can occur in both genes, so it is associated with a higher degree of resistance.
UL54 gene mutation can cause resistance to Foscarnet and cidofovir, as share the same polymerase.
Risk factors for resistance:
CMV R-/D+, at the time of transplantation.
CMV viremia.
Immunosuppressant medication.
Prolong exposure to CMV treatment.
Resistance isolates per type of organ transplant in 2 Chicago transplant centers, 1994-2001:
Lung: among 99 patients with CMV infection; 15% develop CMV resistance.
Heart: among 38 patients with CMV infection; 2% develop CMV resistance.
Liver: among 18 patients with CMV infection; 1% develop CMV resistance.
Kidney: among 45 patients with CMV infection; 1% develop CMV resistance.
Prevention of Ganciclovir-resistant CMV infection:
Use of valyl ester prodrug of ganciclovir valganciclovir, FDA approved in 2002, as it is more potent for prophylaxis and maintenance treatment.
Valganciclovir is 10 times more potent than oral ganciclovir.
Rate of resistance by many studies and severity as well as re-infection of CNV disease, were noted to be more in ganciclovir compared to valganciclovir.
Foscarnet:
1991 FDA approved as a primary alternative treatment to CMV viremia and disease.
A direct competitive inhibitor to DNA polymerase.
Does not need phosphorylation for the active form.
There is some resistance for foscarnet by mutation and is also associated with prolonged exposure, with resistance increasing with treatment time increase.
Limitation to use related to adverse effects of foscarnet, renal toxicity, electrolyte abnormality, and seizure.
Combined therapy: Combined Ganciclovir and Foscarnet offer more promising treatment with less dose and side effects. Other observations show less target treatment response and more side effects as electrolyte abnormality. Cidofovir:
FDA approved in 1996 for treating CMV infection.
Need phosphorylation for the active form.
Administer once or twice per week.
It experienced resistance with the time of treatment.
Adverse effect limited its use: nephrotoxicity, bone marrow suppression.
Leflunomide:
FDA approved in 1998 for treatment of rheumatoid arthritis.
Leflunomide has immunosuppressed medication as well as anti-virus treatment.
A protein kinase inhibitor that inhibit pyrimidine synthesis and hence inhibit activated T-lymphocyte.
It causes transaminase elevation resolved with discontinuation of the drug and acute liver injury, diarrhea, HTN, reversible alopecia, rash, weight loss, and pancytopenia.
Contraindicated in pregnancy as it cause fetal death and teratogenesis.
Used in cases of resistance to ganciclovir, foscarnet, and cidofovir.
Conclusion:
CMV infection treatment is still challengeable in immunocompromised patients.
Although antiviral therapy is effective, but prolong treatment time needed associates with drug resistance, and side effects.
Antiviral other than ganciclovir associated with nephrotoxicity and renal failure.
Combine therapy offer potent antiviral therapy but less nephrotoxicity.
Cidofovir associated with elevated transaminases.
Leflunomide need more study for its use.
In local practice: Adjusted doses of antiviral with balanced reduced doses of IS, with timing of treatment and follow up of kidney function
Please summarise this article Ganciclovir Mechanism of Action and Drug Resistance
-Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase. In order to become active it must first be phosphorylated in three steps to a triphosphorylated form. Once phosphorylated, it acts as a competitive substrate for DNA polymerase and slows the replication of CMV DNA by DNA polymerase.
-Phosphorylation is accomplished by the phosphotransferase produced by the gene UL97. Mutations arising in UL97 phosphotransferase lead to ganciclovir resistance and mutations arising in the DNA polymerase gene UL54 also confer resistance to ganciclovir.
– Prolonged exposure to ganciclovir can give rise to simultaneous UL54 and UL97 mutations. This is associated with higher level resistance to ganciclovir. UL54 mutations can confer cross-resistance to foscarnet and cidofovir .
Definition
-Ganciclovir resistance can be assayed either phenotypically or genotypically. The “gold standard” test is the plaque reduction assay.
– Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6μg/ml.5
-Ganciclovir resistance can also be detected via genotype analysis to assess for known mutations in the UL54 and UL97 genes. Prevalence and Risk Factors for Resistance
-Ganciclovir resistance is uncommon at baseline amongst untreated patients but arises rapidly after prolonged exposure to antiviral agents.
-Among solid organ transplant recipients, the prevalence of CMV resistance ranges between 0 and 15%.
-The risk of developing ganciclovir resistance does seem to vary according to the organ transplanted . This is felt to reflect different degrees of immunosuppression and different protocols for the prophylaxis of CMV. Risk factors for the acquisition of ganciclovir resistance:
– include CMV seronegativity at transplant when receiving a seropositive organ, degree of immunosuppression, magnitude of CMV viremia, and prolonged exposure to anti-CMV medication.
– Patients with ganciclovir resistant disease suffered a statistically significant decrease in survival compared to those with ganciclovir sensitive disease.
-Ganciclovir resistance was common amongst pancreas recipients who receive more potent immunosuppression than other solid organ recipients.
-The risk of developing ganciclovir resistant CMV among D+/R– patients did not differ if patients were treated for CMV with a prophylactic or preemptive strategy. Prevention of Ganciclovir Resistant CMV Infection
-The FDA approval of the valyl ester prodrug of ganciclovir valganciclovir in 2001, introduced a more potent option for CMV prophylaxis and maintenance therapy of disease in both transplant recipients and AIDS patients.
-Valganciclovir is approximately ten times more bioavailable than oral ganciclovir.
-Valganciclovir’s ability to temper ganciclovir resistance has been demonstrated in comparative studies.
-In the solid organ transplant population, valganciclovir was shown to be superior to oral ganciclovir for the prevention of resistant CMV infection.
-The safety profile was generally similar between ganciclovir and valganciclovir except that patients treated with valganciclovir had a higher incidence of neutropenia . Foscarnet
-The primary alternative to ganciclovir for the treatment of CMV viremia and disease is foscarnet.
-It is a direct competitive inhibitor of DNA polymerase.
-The risk of resistance increases with the duration of foscarnet therapy. -Drug resistance was associated with an increased risk of retinitis progression.
– Foscarnet is associated with renal toxicity, electrolyte abnormalities, and seizures. Combination therapy with dose reduced ganciclovir and foscarnet
-The rationale for this strategy stems from the recognition that ganciclovir and foscarnet resistance are usually associated with different gene mutations, in vitro demonstration of synergy between the two agents even against ganciclovir resistant isolates.
Cidofovir
-It is a monophosphorylated cytosine analogue which, like ganciclovir, is further phosphorylated intracellularly to form a compound that impedes DNA polymerase activity.
-Prolonged treatment of CMV infection with ganciclovir can lead to the development of cross-resistance to cidofovir.
-Cidofovir can cause nephrotoxicity in as many as half of all patients ,marrow suppression and ocular disease including iritis, uveitis, and vitreous hypotonicity. Leflunomide
-Leflunomide is an immunomodulatory drug originally developed for the treatment of rheumatoid arthritis .
-Leflunomide has immunosuppressive properties and active against viruses.
– Leflunomide is a prodrug that is rapidly metabolized to the active metabolite.
-It suggested that leflunomide inhibits CMV by interfering with final virion assembly rather than with DNA synthesis. As such, the viral target for leflunomide is distinct from that targeted by ganciclovir, foscarnet, and cidofovir.
-The major toxicity of leflunomide is transaminase elevation.
– Patients with pre-existing liver disease, heavy alcohol intake, or concurrent viral hepatitis should not be given leflunomide.
-Leflunomide is contraindicated in pregnancy due to reports of fetal death and teratogenesis in human subjects. -2.Please reflect on your practice
-We had a few cases of CMV disease and they had a good response to treatment (no CMV resistant case)
CMV infection is a common post transplant complication.
untreated CMV infection in immunocompromised patient associated with increased mortality & graft loss.
Ganciclovir is the first line in CMV infection treatment, but it associated with increased incidence of drug resistant.
Ganciclovir mechanism of action:
It inhibit CMV DNA polymerase
It need to be phosphorylated ( 3 steps) to be an active drug.
Ganciclovir phosphorylation done by phospho-transferase that produced by UL97 gene.
Mutation of UL97 & UL54 genes associated with ganciclovir resistant.
UL97 gene mutation more prevalent mutation, but prolonged ganciclovir exposure can lead to UL97 & UL54 gene mutation together.
Cross-resistant can occur between UL54 mutation & foscarnet & cidofovir
Resistant definition:
Ganciclovir resistant either phenotypic or genotypical.
The gold standard test of ganciclovir resistant is plaque reduction.
Ganciclovir resistant defined as plaque reduction or DNA hybridization IC50 of >6 microgram/ml.
Genotype assay used for UL97 & UL54 gene mutation assessment.
Genotype assay need less time, less lab intensive & not need patient tissue for CMV culture.
Prevalence & risk factors for Ganciclovir resistant:
The prevalence of Ganciclovir resistant before treatment is low (0.9-2.7%), but it increased with prolonged use of the drugs reaching to 27.5% after 9 months of ganciclovir treatment.
Resistant prevalence differ according type of transplanted organ.
Patients with ganciclovir resistant associated with lower survival compared to ganciclovir sensitive patients.
Risk factors of resistance:
D+/R-.
intensity of immunosuppression
prolonged use of antiviral
intensity of CMV viremia.
Prevention of ganciclovir resistant CMV infection:
Bioavailability of valganciclovir (VGC) is 10 times more than oral ganciclovir, so it offered to reduce resistant.
In SOT, VGC is superior to oral ganciclovir in prevention of resistant CMV infection.
Foscarnet:
It is an alternative to ganciclovir in treatment of CMV.
It retain activity against CMV with UL97 mutation ( but not UL54 mutation).
Foscarnet resistant prevalence increased with long term use.
Effective in CMV resistant treatment among AIDS patients & bone marrow transplant recipients.
The main limitation of foscarnet is adverse events as nephrotoxicity, electrolyte disturbance & seizure, so it associated with higher rate of drug withdrawal (4 times more than ganciclovir).
Some studies found that combination of low doses of ganciclovir & foscarnet was superior to mono therapy to alternative agent alone.
Cidofovir:
It interferes with DNA polymerase activity.
It is effective in resistant CMV infection, but resistant increased with prolonged use.
Ganciclovir resistant have cross resistant with cidofovir.
Its use limited by side effects ( nephrotoxicity, bone marrow suppression, & ocular disease.
Leflunomide:
Immuno-modulatory drugs with antiviral activity.
Elevated liver enzyme is the most serious side effects.
It can be used in ganciclovir resistant CMV infection.
In my practice we use oral valganciclovir as prophylaxis (D+/R- for 3-6 months) & treatment of CMV infection.
Introduction
First line treatment for CMV infections and disease is ganciclovir, but there is a small risk ganciclovir resistant CMV infection
Aim of the study: treatment of ganciclovir resistance (foscarnet and cidofovir, combination ganciclovir and foscarnet, and immunomodulatory agent, leflunomide)
Ganciclovir Resistance
Definition
Can be assayed either phenotypically or genotypically
*A plaque reduction or DNA hybridization IC50 of > 6µg/ml (IC50 value is the concentration of ganciclovir required to inhibit 50% of CMV growth)
*Detection via genotype analysis to assess for UL54 and UL97 genes
Mechanism of Action
*Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase
*First phosphorylated to a triphosphorylated form (this acts as a competitive substrate for DNA polymerase and slows the replication of CMV DNA by DNA polymerase)
*Phosphorylation is accomplished by the phosphotransferase produced by the gene UL97
*Mutations in UL97 phosphotransferase lead to ganciclovir resistance (also mutation in UL54)
*UL54 mutations can cause resistance to foscarnet and cidofovir
Prevalence and Risk Factors
Incidence is 0-15% in SOT. Vary according to the organ transplanted (different degrees of immunosuppression and different protocols for the prophylaxis)
Risk factors include:
1. R-/D+
2. Degree of immunosuppression
3. Magnitude of CMV viremia
4. Prolonged exposure to anti-CMV medication
Prevention
*Valganciclovir is approximately ten times more bioavailable than oral ganciclovir
*Ganciclovir resistance maybe related to prolonged exposure to subtherapeutic plasma concentrations of ganciclovir
*Valganciclovir offered a decrease resistance according to many studies
Foscarnet
*Approved by the FDA in 1991
*Direct competitive inhibitor of DNA polymerase (no need for phosphorylation)
*Active against CMV isolates with UL97
*The risk of resistance increases with the duration of foscarnet therapy
The major limitation of foscarnet use is its adverse effect:
1. Renal toxicity
2. Electrolyte abnormalities
3. Seizures
*Less well tolerated for pre-emptive management of CMV viremia (can be used in selected inpatient cases)
*Useful for ganciclovir resistant CMV but treatment will be limited in some patients by nephrotoxicity and/or electrolyte abnormalities
Combination of low dose ganciclovir and foscarnet
*The rationale is that ganciclovir and foscarnet resistance are usually associated with different gene mutations
*Combination would permit lower dosing of each agent and consequent toxicity
show a promising results
Cidofovir
*Approved by the FDA in 1996 for the treatment CMV infection
*A monophosphorylated cytosine analogue (phosphorylated and then impedes DNA polymerase activity)
*Given intravenously (once or twice per week)
*Resistance is low at baseline but rises (Like ganciclovir and foscarnet)
*Prolonged treatment with ganciclovir can also lead to the development of cross-resistance to cidofovir
Its use limited by its adverse effect profile:
1. Nephrotoxicity (half of patients). Rehydration and and use of probenecid can reduce toxicity
2. Bone marrow suppression
3. Ocular disease (iritis, uveitis, and vitreous hypotonicity)
*In the AIDS population using cidofovir to treat CMV retinitis that had recurred or was progressive despite therapy with ganciclovir, foscarnet or both, it delayed progression of retinitis (high nephrotoxicity)
Immunomodulatory therapy (leflunomide)
*Approved for by the FDA in 1998 RA)
*Immunosuppressive and ant-viral
*A protein kinase inhibitor and as a competitive inhibitor of dihyrdoorotate dehydrogenase, the intracellular enzyme required for pyrimidine synthesis
*Specifically inhibits denovo pyrimidine synthesis and hence selectively inhibits activated lymphocytes since resting lymphocytes are able to synthesize pyrimidines via a salvage pathway
*Is a prodrug that is rapidly metabolized to the active metabolite
*Has a long-half life (15-18 days)
*Renal excretion is limited
*Inhibits CMV by interfering with final virion assembly rather than with DNA synthesis (viral target is distinct from that targeted by ganciclovir, foscarnet, and cidofovir)
*Contraindicated in pregnancy (fetal death and teratogenicity)
*Limited use in renal transplant patients and allogeneic bone marrow transplant with sustained reduction or clearance of viremia
Conclusion
*Prolonged drug use is associated with drug resistant virus
*The alternative therapies for ganciclovir resistance are foscarnet and cidofovir both appear to have good in vivo activity against CMV but both are limited by nephrotoxicity
*Risk of renal failure with foscarnet and cidofovir limits use
*The use of reduced dose combination therapy appears to be with less risk of nephrotoxicity (requires further study)
*The immunomodulatory agent leflunomide holds promise for the management of CMV since it both potentiates immunosuppression and suppresses CMV reproduction (not nephrotoxic but can cause transaminase elevation)
Please reflect on your practice
I did not see any case of CMV resistance before. I have no experience with the above medications.
This is anarrative study (level v)
CMV infection is common infection and complications can happen in immunocompromised patients and post solid organ transplant SOT, can be extended to be CMV syndrome include the presence of clinical manifestations with leucopenia or thrombocytopenia with detection of CMV DNA in the blood , and can be extended to be tissue invasive disease which may be life threatening condition, also CMV infection itself is a risk factor for ACR or even humoral rejection, so early detection and treatment by ganciclovir is a crucial step.
Ganciclovir is guanosine analogue that inhibits DNA polymerase of CMV DNA , but to be activated, should be phosphorylated, then will act as a competitive inhibitor to DNA polymerase.
This phosphorylation process is mediated by phosphotransferase enzyme, which is produced by UL97 gene, so any mutation in this gene leads to inactive ganciclovir and resistance to it. In addition, mutation in DNA polymerase gene UL54 will results in the resistance, and prolonged intake of iv ganciclovir will induce mutations of both genes.
Definition of ganciclovir resistance :
Ganciclovir resistance can be assayed either phenotypically or genotypically. The “gold standard” test is the plaque reduction assay in which human fibroblasts are cultured with ganciclovir at various defined concentrations. CMV growth can be quantified by counting viral plaque formation or by a DNA hybridization technique. The concentration of ganciclovir required to inhibit 50% of CMV growth is the IC50 value. Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml.
Ganciclovir resistance can also be detected via genotype analysis to assess for known mutations in the UL54 and UL97 genes. Detection of resistance via gene mutations is attractive since it is less labour intensive, less time consuming, and is not limited by the need to culture CMV from patient specimens. The correlation between genotype and phenotype, however, is imperfect so genotype-based resistance reports need to be interpreted with caution.
Risk factors:
Prevelance of ganciclovir resistance in SOT 0-15%
1- Prolonged exposure to antiviral agents
2- CMV seronegativity at transplant when receiving a seropositive organ
3- degree of immunosuppression
4- magnitude of CMV viremia
Prevention of Ganciclovir Resistant CMV Infection:
No well established protocol yet.
1- valganciclovir is ten times more bioavailable than oral ganciclovir, it decreases resistance while retaining the convenience and safety of an oral agent. It is superior to oral ganciclovir for the prevention of resistant CMV infection.
2- Foscarnet it is direct competitive inhibitor of DNA polymerase, it does not depent on phosphotransferase enzyme as no need for phosphorylation, so it is not affected by mutations in UL97 gene, but can be affected by mutation in UL54 gene, so prolonged exposure to Foscarnet can leads to resistance from that point. This medication has renal toxicity, electrolyte abnormalities, and seizures as adverse effects, these limits its use.
3- foscarnet and ganciclovir are of similar efficacy but that foscarnet is less well tolerated. As such, foscarnet is useful agent to use against ganciclovir resistant CMV but treatment will be limited in some patients by nephrotoxicity and/or electrolyte abnormalities.
4- Combination therapy with dose reduced ganciclovir and foscarnet is superior to monotherapy with the alternative agent alone.
5- Cidofovir it is monophosphorylated cytosine analogue, prolonged treatment of CMV infection with ganciclovir can also lead to the development of cross-resistance to cidofovir, its use is limited because of its adverse effects like nephrotoxicity, ocular diseases and BM suppression.
6- Leflunomide it is immunomodulatory drug used in the treatment of rheumatoid arthritis, it is immunosuppressive medication with anti-infective properties against viruses. major toxicity is transaminase elevation, can be used in multi-drug CMV resistant cases.
in my practice we used valganciclovir (valcyte) in prophylaxis in high risk patient D+/R- or D+/R+ or when using ATG as induction or in the treatment of ACR for 3-6 months.
and we used iv ganciclovir in treating suspected tissue invasive CMV disease
of course renal dose adjustment is needed and requested
I suggest that you use bold or underline for heading or sub-headings that make it easier to read. I like your summary of these guidelines. I like your reflection of current practice in your hospital in relation to these (similar) guidelines
Drugs for treatment of CMV 1. Ganciclovir: is a guanosine analogue that inhibits CMV DNA polymerase. In order to become
active it must first be phosphorylated in three steps to a triphosphorylated form. Once
phosphorylated, it acts as a competitive substrate for DNA polymerase and slows the replication
of CMV DNA by DNA polymerase. Phosphorylation is accomplished by the phosphotransferase
produced by the gene UL97. Mutations arising in UL97 phosphotransferase leads to ganciclovir
resistance. Also, mutations arising in the DNA polymerase gene UL54 leads to resistance to ganciclovir.
2. Valganciclovir: is valyl ester prodrug of ganciclovir and approximately ten times more bioavailable than oral ganciclovir
3. Foscarnet: Foscarnet is a direct competitive inhibitor of DNA polymerase. Unlike ganciclovir, it does not need to be phosphorylated in order to inhibit CMV DNA polymerase. Since it is not dependent on the CMV phosphotransferase foscarnet is effective in UL97 mutations that are resistant to ganciclovir but mutations in the DNA polymerase gene UL54 leads to foscarnet resistance.
4. Cidofovir: It is a monophosphorylated cytosine analogue which, like ganciclovir, is further phosphorylated intracellularly to form a compound that impedes DNA polymerase activity. Its given intravenously once or twice per week.
5. Leflunomide: is immunomodulator and its activity against cytomegalovirus is achieved by inhibition of construction of virions which is dependent upon protein kinase rather than with DNA synthesis. Its protein kinase inhibitor and as a competitive inhibitor of dihydroorotate dehydrogenase, the intracellular enzyme required for pyrimidine synthesis. It specifically inhibits denovo pyrimidine synthesis and hence selectively inhibits activated lymphocytes since resting lymphocytes are able to synthesize pyrimidines via a salvage pathway. Leflunomide is a prodrug that is rapidly metabolized to the active metabolite, A77 1726. The drug has a long-half life on the order of 15-18 days potentiated by substantial enterohepatic recirculation. Without a loading dose it is estimated that it would take nearly two months to achieve steady-state plasma concentrations. Likewise, after discontinuation of the medication it can take as long as two years. for the body to entirely clear the drug. Renal excretion is limited.
Some definitions
· IC50 value is the inhibitory concentration needed by the drug to cause 50% of its therapeutic effect which in ganciclovir equal 6μg/ml.
· Ganciclovir CMV resistance definition either phenotypically or genotypically.
1. Phenotypically means although target level of ganciclovir achieved (IC50 of > 6μg/ml) and no CMV reduction by counting plaque formation or by PCR.
2. Genotype analysis to assess for known mutations in the UL54 and UL97 genes.
3. The “gold standard” test still is viral culture with ganciclovir at various defined concentrations. Risk factors
1. CMV seronegative at transplant when receiving a seropositive organ.
2. degree of immunosuppression.
3. magnitude of CMV viremia.
4. prolonged exposure to anti-CMV medication especially to subtherapeutic plasma concentrations of ganciclovir. Prevention and treatment of Ganciclovir Resistant CMV Infection: Usage of valganciclovir: valganciclovir afford more stable therapeutic level in long term use and prevent resistance. Foscarnet use: still its use limited for CMV resistant cases either as monotherapy of as combination with ganciclovir with reduced dose (half-dose ganciclovir (5mg/kg IV q24h) and half-dose foscarnet (90mg/kg
IV q24h) because of its side effects and availability.
It’s usually cause nephrotoxicity and electrolytes disturbance in the form of sever hypomagnesaemia, hypocalcemia, hypokalemia. Studies evaluated foscarnet for newly diagnosed CMV cases as monotherapy of as combination with ganciclovir with reduced dose showed inferiority in comparison to ganciclovir monotherapy and more side effects. Cidofovir: its use still limited to limited cases because of adverse effect in the form of nephrotoxicity This can be attenuated by pre-hydration and the use of probenecid but these two interventions can also limit tolerance. In addition, cidofovir has been noted in case reports to cause bone marrow suppression and ocular disease including iritis, uveitis, and vitreous hypotonicity. Leflunomide: still also limited to ganciclovir resistant cases and the major toxicity of leflunomide is transaminase elevation, hepatic necrosis and death from liver failure have been reported but are rare, diarrhea , hypertension , reversible alopecia, and rash. In my transplant center we used to divide cases into
1. High risk patients (D+ to R-): for such patients we used to give ganciclovir therapeutic dose for 5-7 days post-transplant then switch to valganciclovir therapeutic for 3weaks then prophylactic for 3-6m.
2. Medium risk patient (D+ to R+) who received depleting induction or desensitization we used to give them valganciclovir prophylactic dose for 3-6m post-transplant
3. Low risk patients (D+ to R+) with low immunological risk who didn’t receive depleting induction we follow frequent monitoring of CMV PCR and preemptive treatment.
CMV infection used to treat with ganciclovir in severe cases and valganciclovir in mild cases.
Therapeutic dose continued for at least 2 PCR -ve then switch to prophylactic dose beside decrease immunosuppression to accepted levels according to duration of transplant and severity of infection then switched to prophylactic dose for 6-9m by valganciclovir.
CMV resistance diagnosed by PCR quantitive titer which not responding or increasing although therapeutic optimum ganciclovir dose obtained according to eGFR for such cases we used to give CMV specific IVIG with stop MMF and CNI on the lower level.
We have no experience in use of cidofovir for CMV and we used only leflunomide for BK nephropathy.
I like your summary of these guidelines. I like your reflection of current practice in your hospital in relation to these (similar) guidelines. I note your mention about challenges of resistance.
-Summary Ganciclovir Mechanism of Action and it’s Resistance
Ganciclovir active forum is triphosphorylated forum done by the phosphotransferase
produced by the gene UL97,it acts by inhibiting CMV DNA polymerase decreasing CMV replication.
Mutations in UL97 phosphotransferase and DNA polymerase gene UL54can cause the resistance, the mutations can occur separately or simultaneously.
UL54 mutations can lead to cross resistance to foscarnet and cidofovir . Definition
Ganciclovir resistance phenotypic assay which is the gold standard test is the reduction assay of the plaques where human fibroblasts are cultured with ganciclovir .
Ganciclovir resistance represents plaque reduction or DNA hybridization IC50 of > 6µg/ml.
Ganciclovir resistance genotypic assay includes detection of the gene mutation
Correlation between both assays is not well established Prevalence and resistance risk factors
It is uncommon for untreated cases but develops rapidly after extended courses of antiviral medications.
CMV resistance ranges from 0-15% in SOT cases varies according to immunosuppression and organ transplanted with highest prevalence in lung transplants and the least is the kidney transplants
Ganciclovir resistance risk factors are CMV D+/R-, immunosuppression regimen and doses, CMV viral load and prolonged exposure to anti-CMV medication. Ganciclovir Resistant CMV Infection prevention Valganciclovir was introduced in 2001, it is nearly 10 times more bioavailable than oral ganciclovir. Valganciclovir can decrease ganciclovir resistance caused by prolonged subtherapeutic doses of ganciclovir while keeping the advantages of an oral agent.
Valganciclovir is better than oral ganciclovir for the prevention of resistant CMV infection in SOT but it can increase neutropenia risk.
Foscarnet
It is a direct inhibitor of DNA polymerase without needing to be phosphorylated therefore it can maintain it’s effect against CMV isolates with UL97 mutations resistant to ganciclovir.
Meanwhile DNA polymerase gene UL54 mutations and prolonged foscarnet treatment can lead to foscarnet resistance.
Foscarnet side effects that limited it’s use are renal toxicity, electrolyte abnormalities, and seizures.
A study concluded that both ganciclovir and foscarnet have the same efficacy.
Combination therapy of ganciclovir and foscarnet with dose reduction
This was an acceptable protocol of ganciclovir resistant CMV infection treatment as ganciclovir and foscarnet resistance can occur with different gene mutations.
Data suggested that combination therapy can be efficient in pre-emptive therapy of CMV antigenemia in non ganciclovir resistant bone marrow transplant patients as well as dose reduction can decrease toxic side effects .
A study tested the combination therapy with acceptable results apart from hypomagnesemia that was treated
A study evaluated combination therapy and isolated ganciclovir in preemptive therapy for recipients with CMV viremia revealing that cases receiving isolated ganciclovir were more likely to have negative PCR after 14 days and less adverse events compared to combination therapy. Cidofovir
It has to be phosphorylated as ganciclovir to inhibit DNA polymerase.
It has low resistance risk at baseline but can increase with prolonged usage also it has cross resistance with ganciclovir.
Cidofovir use is limited due to it’s toxicity in the forum of nephrotoxicity and bone marrow suppression and ocular diseases. Leflunomide
It is an immunomodulatory drug with immunosuppressive anti -infective properties,it has a long half life due to enterohepatic circulation ,with limited renal excretion ,it can be totally cleared from the body after years .
It can inhibit multidrug-resistant CMV isolate as confirmed by plaque reduction assays , it acts through interfering with final virion assembly.
It’s side effect include elevated liver enzymes that resolve after stopping the drug as well as diarrhea ,hypertension and rashes. Conclusion
CMV infection therapy is challenging in immunocompromised cases ,as Ganciclovir resistance is detected in SOT recipients treated with prolonged courses , Foscarnet and Cidofovir are alternativies but carry high risk of nephrotoxicity thereby limiting their use.
Combination therapy with reduced doses to lesson side effects needs further evaluation
Leflunomide as an immunomodulator with antiviral effect is under further studies ,it causes elevation of liver enzymes.
-My practice
Ganciclovir resistance is challenging so it can be treated with Foscarnet but with caution due to it’s nephrotoxicity
I like your summary of these guidelines. I like your reflection of current practice in your hospital in relation to these (similar) guidelines. I like your summary of these guidelines. I note your mention about challenges of ganciclovir resistance.
Drug Resistance to Ganciclovir
Guanosine analog ganciclovir inhibits CMV DNA polymerase. It must be phosphorylated three times to become active. Phosphorylated, it competes with DNA polymerase and reduces CMV DNA replication. UL97 phosphotransferase phosphorylates. UL97 phosphotransferase mutations cause ganciclovir resistance. UL54 DNA polymerase gene mutations also provide ganciclovir resistance.
Definition
Ganciclovir resistance may be tested phenotypically or genotypically. Ganciclovir-cultured human fibroblasts are the “gold standard” test. Viral plaque development or DNA hybridization may measure CMV growth. Ganciclovir’s IC50 inhibits 50% of CMV growth. Plaque reduction or DNA hybridization IC50 > 6 g/mL indicates ganciclovir resistance.
Risk factors for drug resistance:
Ganciclovir resistance is associated with CMV seronegativity upon transplant when receiving a seropositive organ, immunosuppression, CMV viremia, and chronic anti-CMV drug use. Seronegative recipients of seropositive organs are at risk of CMV infection and ganciclovir resistance.
Preventing Ganciclovir-Resistant CMV
Ganciclovir-resistant CMV infections are unstudied.
Only case reports and case series on resistant infection treatment results exist. Controlled trials evaluating alternate techniques have not been reported. Preventing ganciclovir resistance is important because it can cause a lot of illnesses, and there isn’t a good second-line treatment for it.
Foscarnet
Foscarnet is the most important medication that may be used instead of ganciclovir for the treatment of CMV viremia and illness.
Dose-reduced ganciclovir with foscarnet treatment
A combination of ganciclovir and foscarnet at decreased dosages may treat CMV infections resistant to ganciclovir. Ganciclovir and foscarnet resistance are frequently caused by separate gene mutations, which justifies this technique.
Cidofovir
Cytomegalovirus therapy with cidofovir was FDA-approved in 1996. Like ganciclovir, it is an analog of monophosphorylated cytosine that is phosphorylated inside cells to make a DNA polymerase inhibitor. Cidofovir must be taken intravenously, but only once or twice a week. Like ganciclovir and foscarnet, cidofovir resistance starts low but builds.
Leflunomide
The FDA authorized leflunomide in 1998 to treat rheumatoid arthritis. Leflunomide’s antiviral qualities make it appealing to transplant patients. Researchers found that leflunomide was effective against cytomegalovirus when they thought that the high number of phosphoproteins in CMV would show that intracellular virions depend on protein kinase.
Please reflect on your practice
I did not face any cases of CMV resistant to gancyclovir. I did not use Foscarnet or Cidofovir.
I used leflunomide for BK nephropathy.
I like your summary of these guidelines. I like that your reflection of current practice in your hospital in relation to these (similar) guidelines. I note your mention about your experience in using leflunomide for BKV.
Gancyclovir acts by inhibiting CMV DNA polymerase, and in order to be activated it needs phosphorylation by phosphotransferase produced by the gene UL97.
Valgancyclovir is 10 times more bioavailable than oral gancyclocir
UL97 and UL54 gene mutations are responsible for gancyclovir resistance
Diagnosis of gancyclovir resistance
Plaque reduction assay (gold standard test) in which human fibroblasts are cultured with ganciclovir at different concentrations, and CMV growth is assesned by counting the viral plaques or DNA hybridization technique. Gancyclovir resistance is defined as plaque reduction or DNA hybridization IC 50 of > 6µg/ml
Detection of UL97 and UL54 gene mutations
Risk factors for gancyclovir resistance
Type of organ transplant: the prevalence of gancyclovir resistance is ranging from 0 up to 15% with the highest prevalence occur with lung and pancreas and the lowest prevalence occurring with liver and renal transplantation
Patients receiving long or suboptimal courses of treatment
Very high viral load
(D+/R-) transplantation
Patients receiving aggressive ATG for acute rejection
Treatment of Ganciclovir Resistant CMV Infection
1- Foscarent
It is a direct competitive inhibitor of DNA polymerase but it needs no phosphorylation to be active so not affected by UL97 mutation but may be affected by UL54 gene mutations
It is given in a dose of 60mg/kg IV every 8h for 2 weeks followed by 90mg/kg/day
·
Its effect is comparable to IV gancyclovir
Associated with renal and GIT toxcicity and electrolyte imbalance and seizures, genital ulcers and infusion related symptoms
Neutropenia is less common with Foscarent than with gancyclovir
Prolonged use of gancyclovir can cause cross resistance
2- Combination therapy with reduced doses of ganciclovir and foscarnet
The regimen include the use of half the dose of IV gancyclovir (5mg/kg IV q24h) and 2/3 the dose of foscarnet (125mg/kg IV q24h)
Associated with comparable efficacy and less side effects
3- Cidofovir
Effective
Given IV twice weekly
Associated with high incidence of nephrotoxicity (50% of cases), myelosuppression and ocular disease( iritis, uveitis, and vitreous hypotonicity).
Prolonged use of gancyclovir can cause cross resistance
4- Leflunamide
It has immunosuppressive and antiviral activity at the same time, so it may provide the balance between treating virus and avoid reduction of immunosuppression
It is given in a loading dose then maintance dose
Persist in the blood for very long time after stopping the mnedication (up to 2 years)
Side effects includes, hepatitis, myelosupression, hypertension, GI side effects, alopecia and skin rash
In my practice
I did not see any case of gancyclovir resistance and I did not use any of the previous drugs except leflunamide in treatment of rheumatoid artheritis
I like your summary of these guidelines. I like your reflection of current practice in your hospital in relation to these (similar) guidelines. I note your mention about challenges of ganciclovir resistance.
Treatment of Ganciclovir Resistant Cytomegalovirus Infection 1-Please summarise this article; Ganciclovir; Mechanism of Action and Drug Resistance; -Ganciclovir was approved by the FDA in 1989. -Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase. In order to become active it must first be phosphorylated in three steps to a triphosphorylated form. -Mutations arising in UL97 phosphotransferase lead to ganciclovir resistance. Similarly, mutations arising in the DNA polymerase gene UL54 also confer resistance to ganciclovir. -The “gold standard” test is the plaque reduction assay in which human fibroblasts are cultured with ganciclovir at various defined concentrations. CMV growth can be quantified by counting viral plaque formation or by a DNA hybridization technique. -Ganciclovir resistance is uncommon at baseline amongst untreated patients but arises rapidly after prolonged exposure to antiviral agents. -Among solid organ transplant recipients, the prevalence of CMV resistance ranges between 0 and 15%. Risk factors; -Seronegative recipients of seropositive organs appear to be at particular risk of both CMV infection and ganciclovir resistance. -Degree of immunosuppression, -Magnitude of CMV viremia, -Prolonged exposure to anti-CMV medication, Prevention of Ganciclovir Resistant CMV Infection; -The treatment of ganciclovir resistant CMV infections has not been comprehensively studied. -The FDA approval of the valyl ester prodrug of ganciclovir valganciclovir in 2001, introduced a more potent option for CMV prophylaxis and maintenance therapy of disease in both transplant recipients and AIDS patients. -Valganciclovir is approximately ten times more bioavailable than oral ganciclovir. -In some studies valganciclovir was shown to be superior to oral ganciclovir for the prevention of resistant CMV infection. -The safety profile was generally similar between the two groups except that patients treated with valganciclovir had a higher incidence of neutropenia (8.2%, vs 3.2%). Foscarnet; -The primary alternative to ganciclovir for the treatment of CMV viremia and disease is foscarnet. -Foscarnet was approved by the FDA in 1991. Foscarnet is a direct competitive inhibitor of DNA polymerase.Unlike ganciclovir, it does not need to be phosphorylated in order to inhibit CMV DNA polymerase. -Since it is not dependent on the CMV phosphotransferase UL97 it retains activity against CMV isolates with UL97 mutations that are resistant to ganciclovir. -Mutations in the DNA polymerase gene UL54. -The risk of resistance increases with the duration of foscarnet therapy. -The major limitation to greater use of foscarnet has been its adverse effect profile; Nephrotoxicity, Electrolytes Disturbances (Hypocalcemia , Hypomagnesemia , Hypokalemia, Hypophosphatemia), Seizures, Genital ulcers, Infusion-related symptoms (fatigue, anxiety, nausea, numbness/tingling). Combination therapy with dose reduced ganciclovir and foscarnet; -Combination therapy has been shown to be effective in pre-emptive therapy of CMV antigenemia in non-ganciclovir resistant bone marrow transplant patients. -Moreover, investigators reasoned that synergy between the two agents would permit lower dosing of each agent and consequent mitigation of their different toxicity profiles. -Combination therapy was also more likely to cause renal dysfunction and electrolyte abnormalities (seen in 25% of combination patients versus 0% of monotherapy patients, -The relative inferiority of reduced dose combination therapy in this trial perhaps reflects the obvious advantage in treating ganciclovir sensitive isolates with full dose ganciclovir. Cidofovir; -Cidofovir was approved by the FDA in 1996 for the treatment of cytomegalovirus infection. -It is a monophosphorylated cytosine analogue which, like ganciclovir, is further phosphorylated intracellularly to form a compound that impedes DNA polymerase activity. -The pharmacology of cidofovir is such that it has to be given intravenously but need only be administered once or twice per week. -Like ganciclovir and foscarnet, resistance to cidofovir is low at baseline but rises. -Notably, prolonged treatment of CMV infection with ganciclovir can also lead to the development of cross-resistance to cidofovir. -The popularity of cidofovir therapy has been limited by its adverse effect profile. -Cidofovir can cause nephrotoxicity in as many as half of all patients.This can be attenuated by pre-hydration and the use of probenecid but these two interventions can also limit tolerance. -In addition, cidofovir has been noted in case reports to cause bone marrow suppression and ocular disease including iritis, uveitis, and vitreous hypotonicity. Leflunomide; -Leflunomide is an immunomodulatory drug originally developed for the treatment of rheumatoid arthritis and approved for that indication by the FDA in 1998. -Leflunomide has attracted particular interest from the transplant community because in addition to immunosuppressive properties it is active against viruses. -It specifically inhibits denovo pyrimidine synthesis and hence selectively inhibits activated lymphocytes since resting lymphocytes are able to synthesize pyrimidines via a salvage pathway. -The drug has a long-half life on the order of 15-18 days potentiated by substantial enterohepatic recirculation. -Without a loading dose it is estimated that it would take nearly two months to achieve steady-state plasma concentrations. -The major toxicity of leflunomide is transaminase elevation. Cases of hepatic necrosis and death from liver failure have been reported but are rare. -The FDA has estimated the incidence of hepatic necrosis to be 0.02 to 0.04%. -Patients with pre-existing liver disease, heavy alcohol intake, or concurrent viral hepatitis should not be given leflunomide. -Leflunomide is contraindicated in pregnancy due to reports of fetal death and teratogenesis in human subjects. -Other averse effects; diarrhea (17-33%), hypertension (6-12%), reversible alopecia (8-11%), and rash (10-14%). -In addition, there have been case reports of weight loss and pancytopenia.
–This article considered a narrative review; (level V) 2-Please reflect on your practice; -In our practice; we have oral valganciclovir for treatment of CMV and for Prophylaxis protocol. -We have experience with the use iv ganciclovir in treatment (tissue invasive CMV). -We use (foscarnet) in case (post kidney transplant with CMV colitis) with ganciclovir resistence,but unfortunately developed deterioration of graft function and lost graft and starting haemodialysis. -We have no experience in our service with the use of Leflunomide. –The novel immunomodulatory agent leflunomide holds promise as a future agent for the management of CMV since it both potentiates immunosuppression and suppresses CMV reproduction. -Management of CMV resistance is challenging due to difficulty of getting the viral genotype testing and availability of the second line therapy.
I like your summary of these guidelines. I like your reflection of current practice in your hospital in relation to these (similar) guidelines. I note your mention about challenges of genotyping.
Ganciclovir Mechanism of Action and Drug Resistance;
——————————————————————————————–
Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase. The active triphosphorylated form acts as a competitive substrate for DNA polymerase and slows the replication of CMV DNA by DNA polymerase. Phosphorylation is accomplished by the phosphotransferase produced by the gene UL97. Mutations arising in UL97 phosphotransferase lead to ganciclovir resistance. Similarly, mutations arising in the DNA polymerase gene UL54 also confer resistance to ganciclovir.
Definition ;
————————————————
Ganciclovir resistance can be assayed either;
1-Phenotypically ;
The “gold standard” test is the plaque reduction assay in which human fibroblasts are cultured with ganciclovir at various defined concentrations. CMV growth can be quantified by counting viral plaque formation or by a DNA hybridization technique.
Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6μg/ml.
2-Genotypically.
Ganciclovir resistance can also be detected via genotype analysis to assess for known mutations in the UL54 and UL97 genes. Detection of resistance via gene mutations is attractive since it is less labour intensive, less time consuming, and is not limited by the need to culture CMV from patient specimens. The correlation between genotype and phenotype, however, is imperfect so genotype-based resistance reports need to be interpreted with caution.
Prevalence and Risk Factors for Resistance; —————————————————————————
Among solid organ transplant recipients, the prevalence of CMV resistance ranges between 0 and 15%.
Risk factors for the acquisition of ganciclovir resistance include;
1- CMV seronegativity at transplant when receiving a seropositive organ 2- degree of immunosuppression 3- magnitude of CMV viremia 4- prolonged exposure to anti-CMV medication.
Patients with ganciclovir resistant disease suffered a statistically significant decrease in survival compared to those with ganciclovir sensitive disease.
Prevention of Ganciclovir Resistant CMV Infection; ————————————————————————-
1-introduction of more potent option for CMV prophylaxis and maintenance therapy of disease in both transplant recipients and AIDS patients .
a-Valganciclovir;
is approximately ten times more bioavailable than oral ganciclovir. Since ganciclovir resistance is thought to be related to prolonged exposure to subtherapeutic plasma concentrations of ganciclovir, valganciclovir offered a potential means to decrease resistance while retaining the convenience and safety of an oral agent.
b-Foscarnet;
Unlike ganciclovir, it does not need to be phosphorylated in order to inhibit CMV DNA polymerase.
Since it is not dependent on the CMV phosphotransferase UL97 it retains activity against CMV isolates with UL97 mutations that are resistant to ganciclovir. Mutations in the DNA polymerase gene UL54, however, do confer foscarnet resistance and can sometimes be selected for by prolonged ganciclovir therapy.
Like ganciclovir, the risk of resistance increases with the duration of foscarnet therapy. Drug resistance was associated with an increased risk of retinitis progression.
Foscarnet is associated with renal toxicity, electrolyte abnormalities, and seizures .
c-Combination therapy with dose reduced ganciclovir and foscarnet;
1-The rationale for this strategy stems from the recognition that ganciclovir and foscarnet resistance are usually associated with different gene mutations .
2-In vitro demonstration of synergy between the two agents even against ganciclovir resistant isolates.
3-Trial data from the AIDS literature showing that combination therapy is superior to monotherapy with the alternative agent alone.
4-The combination therapy has been shown to be effective in pre-emptive therapy of CMV antigenemia in non- ganciclovir resistant bone marrow transplant patients.
5-Investigators reasoned that synergy between the two agents would permit lower dosing of each agent and consequent mitigation of their different toxicity profiles.
d -Cidofovir;
It is a monophosphorylated cytosine analogue which, like ganciclovir, is further phosphorylated intracellularly to form a compound that impedes DNA polymerase activity.
The pharmacology of cidofovir is such that it has to be given intravenously but need only be administered once or twice per week. Like ganciclovir and foscarnet, resistance to cidofovir is low at baseline but rises under sustained drug pressure.
Prolonged treatment of CMV infection with ganciclovir can also lead to the development of cross-resistance to cidofovir. Treatment with cidofovir alone can confer resistance to ganciclovir .
Cidofovir can cause nephrotoxicity in as many as half of all patients. In addition, cidofovir has been noted in case reports to cause bone marrow suppression and ocular disease including iritis, uveitis, and vitreous hypotonicity.
Clinical reports of the use of cidofovir in ganciclovir-resistant infection are scarce.
Leflunomide ;
Leflunomide is an immunomodulatory drug . Leflunomide acts as a protein kinase inhibitor and as a competitive inhibitor of dihyrdoorotate dehydrogenase, the intracellular enzyme required for pyrimidine synthesis.
Leflunomide’s activity against cytomegalovirus was discovered when investigators hypothesized that the predominance of phosphoproteins within CMV might imply that intracellular construction of virions is dependent upon protein kinase.
The major toxicity of leflunomide is transaminase elevation. Patients with pre-existing liver disease, heavy alcohol intake, or concurrent viral hepatitis should not be given leflunomide.
Other adverse effects reported in the major trials of leflunomide for the treatment of rheumatoid arthritis include diarrhea , hypertension , reversible alopecia , and rash .In addition, there have been case reports of weight loss and pancytopenia.
Conclusion;
——————————————
The management of CMV infection remains a substantial challenge for clinicians caring for immunocompromised patients. While there are a number of agents active against the virus, effective therapy requires prolonged drug use which in turn is associated with emergence of drug resistant virus.
CMV resistance to ganciclovir has been reported with increasing frequency in both AIDS patients treated for CMV retinitis and in recipients of both bone marrow and solid organ transplants.
The alternative therapies foscarnet and cidofovir both appear to have good in vivo activity against cytomegalovirus but both are limited by their propensity to cause acute renal failure.
The use of reduced dose combination therapy appears to deliver potent antiviral therapy with less risk of nephrotoxicity but this approach requires further study.
The novel immunomodulatory agent leflunomide holds promise as a future agent for the management of CMV since it both potentiates immunosuppression and suppresses CMV reproduction..
Please reflect on your practice; ———————————————————- I have no previous experience in treating Ganciclovir resistant CMV infection . No other available options of therapy rather than valganciclovir and Ganciclovir .We depend upon the clinical index of suspicion in the diagnosis of Ganciclovir resistant .
What is your analysis regarding the level of evidence, limitations and strengths of this publication? I like your reflection of your own practice mentioning challenges of genotyping.
Typing the whole sentence in bold or capitals amounts to ‘shouting’.
limitation ;
———————- 1-almost of trials are small in sample size. 2- Experimental data on the use of leflunomide in human beings is extremely limited and remains on the case report level.
I like your summary of these guidelines. Typing the whole sentences as the past paragraph amounts to shouting. I like your reflection of current practice in your hospital in relation to these (similar) guidelines. I note your mention about challenges of genotyping.
Ganciclovir resistance:
CMV infection is commonly encountered in the context of transplantation. It might lead to progressive disease with excessive morbidity and mortality.
Ganciclovir is first line therapy for CMV infection. However, it was increasingly noticed that Ganciclovir resistance is increasing among transplant patients . Mechanism of Ganciclovir resistance :
Ganciclovir is guanosine analogue that impair proliferation of CMV virus resultant in remission of CMV disease.
its usually activated by triple phosphorylation mediated by phosphotransferase enzyme.
Phosphotransferase enzyme is encoded by UL97 gene, therefore any mutation in that gene would result in Ganciclovir resistant.
after phosphorylation , ganciclovir utilized as a substrate for DNA polymerase enzyme competing with CMV DNA , resultant in inhibition of CMV proliferation. DNA polymerase enzyme: is encoded by UL54 gene, therefore any mutation in that gene lead to abnormal enzyme DNA polymerase with resistance to Ganciclovir therapy.
UL54 mutation might result in resistance to foscarnet and cidofovir medicines as both of them are utilizing same enzyme DNA polymerase . Risk factors for CMV resistance:
1] Primary ganciclovir resistance is uncommon, however, after extended administration of the medicine , an increased prevalence is observed , mediated via mutation of UL97 gene and UL54 gene.
2] Its higher with lung transplant reaching to 15%.
3] Seronegative recipient of a seronegative donor.
4] Intensity of immune suppression, with lymphocye depleting agent at induction time.
5] volume of CMV virus. Reducing incidence of ganciclovir resistance:
prescribing valganciclovir is associated with less incidence of resistance in comparison to ganciclovir. Alternatively, using foscarnet was linked to less risk of resistance. Its side effects limit its use , which include renal toxicity, seizure and electrolytes disturbance. Combined Ganciclovir and foscarnet protocol:
Owing to different enzymes mutation reported with each of ganciclovir and Foscarnet , a combination protocol was advocated to overcome the resistance risk related to each one. Cidofovir :
Similar to other medication, resistance to Cidofovir might emerge from cross-resistance to Foscarnet and Ganciclovir, in particular , after prolonged courses of the latter. Leflunomide:
is a promising immunomodulating therapy less reported to be associated with resistance.
IntroductionCMV infection and disease is very common among the solid organ transplantation patient due to partly the effect of the immunosuppressive state and the CMV status either the donors or the recipients. Moreso, some degree of resistance have been noticed among patient that received ganciclovir for treatmentof the CMV disease.
Ganciclovir mechanism of action and drug resistance.
ganciclovir is first phosphorylated in three steps to a triphosphorylated
the phosphorylated form slow down the replication of CMV DNA by acting as competitive substrates to DNA polymerase
Phosphorylation is accomplished by phosphotransferase produced by UL97 gene
Mutation arising from UL54 and UL97 leads to Ganciclovir resistance
Ganciclovir resistance can be efined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml. Tis could be asseyed phenotypically or genetically
Prevalence and risk factors for resistance
prevalence is between 0-15% among solid organ recipients transplant
the risk vary according to the type of the organ transplanted, highest among lung transplant and lowest among kidney transplant.
risk factors are:
-CMV D+/R-
-degree of immunosuppression
-magnitude of CMV viraemia
-prolong exposure to anti-CMV medication
Prevention of Ganciclovir Resistant CMV Infection
treatment of CMV resistance has not been well studied
the following drugs had been used as an alternative to the treatment of resistance
-Valganciclovir, Foscarnate, Cidofovir, and Leflunomide
Conclusion
One of the fall outs of solid organ transplantation is the occurrence of CMV infection or disease which can cause graft failure if not detected early. Also the prolong use of antiviral agent like ganciclovir has resulted in resistance and paving way for others like valganciclovir, foscarnate, cidofovir, and leflunomide.
In my country of practice then, the available drugs are ganciclovir and Valganciclovir. Unfortunately, for most patients that might have developed resistance are likely to lose their kidney allograft as the facility to even test the CMV genotype variant is scarce and out of the reach of the majority to pay for such an investigation
What is your analysis regarding the level of evidence, limitations and strengths of this publication? I like your reflection of your own practice mentioning challenges of genotyping.
I like your summary of these guidelines. I like your reflection of current practice in your hospital in relation to these (similar) guidelines. I note your mention about challenges of genotyping.
This study is a narrative review evaluating alternatives for Cytomegalovirus treatment for immunosuppressed patients (either by AIDS, solid organ transplantation, or bone marrow transplantation) who develop resistance to standard Ganciclovir treatment.
Resistance
CMV infection can lead to graft loss and death if not properly treated. Ganciclovir works on two key genes, UL97 and UL54, decreasing the ability of the virus to multiply. Mutation at these loci leads to drug resistance. Mutations in UL54 can cause cross-resistance to cidofovir and Foscarnet.
Two tests can be used. Detection of UL97 and UL54 mutations (genotypically) or increase in a minimum inhibitory concentration greater than 6microgamma/mL (phenotypically).
Risk factors for resistance
– Prolonged use of antivirals
– Degree of immunosuppression
– Magnitude of viral load
– Giver+/Recipient-
Valganciclovir was released as therapy and prophylaxis. After six months of use, an increase in resistance was found, but smaller when compared to the group that used ganciclovir.
foscarnet
It does not use the UL97 gene, but it can interfere with resistance with the UL54 gene. Associated with nephrotoxicity, electrolyte disturbances, and convulsions. It can be used in combination with Ganciclovir in an attempt to reduce the dose of both and, consequently, their toxicity.
Cidofovir
It can also be mutated by UL54. It presents greater resistance throughout its duration when compared to the previous drugs. Significant nephrotoxicity, which is why its use is sometimes added with dilution and probenecid.
Leflunomide
It is an immunomodulator that has an indirect action on CMV, impacting at the same time as an immunosuppressant and antiviral. Its side effects include the elevation of liver transaminases.
Conclusion
In Brazil, we do not have Cidofovir. We had no experience in our service with the use of Leflunomide. Due to the difficulty in importing Foscarnet, there is a tendency to raise the dose of Ganciclovir to 15mg/kg/day and titrate it depending on the side effects of the drug.
We do not have Valganciclovir, which also limits the therapy.
Recently, Letermovir was approved for the prophylaxis of Bone Marrow Transplantation and the use of Maribavir and Enriched Immunoglobulin for CMV is currently in the process of being validated.
What is your analysis regarding the level of evidence, limitations and strengths of this publication? Please type headings and subheadings in bold or underline to make it easy to read. I like your reflection of your own practice.
I suggest that you use bold or underline for heading or sub-headings that make it easier to read. I like your summary of these guidelines. I like your reflection of current practice in your hospital in relation to these (similar) guidelines
Gancyclovir mechanism of action & drug resistance:
Mecahism of action: inhibit CMV DNA polymerase
Mechanism of resistance: UL 97 or UL 54 mutation
Definition:
Plaque reduction assay; fibroblast are culture with ganciclovir at different concentration
Plaque reduction or DNA hybridization IC > 6 micro-gram/ml
Prevalence and risk factors for resistance:
Prevalence: between 0 to 15% according to the type organ transplanted (highest in lung transplantation)
Risk factors: D+/ R- status, amount of immune-suppression, degree of CMV viremia, prolonged anti-viral therapy
Prevention of Ganciclovir Resistance CMV infection:
-Oral valganciclovir (higher bioavailability):
May be better than oral gancyclovir and it is equivalent to IV gancyclovir
-Foscarnt:
Direct inhibitor of CMV DNA polymerase ( no need for viral phosphorylation)
UL54 mutation may cause foscarnet resistance
Associated with nephrotoxicity, electrolytes disturbance , and convulsions
-Combination therapy with dose reduced ganciclovir and foscarnet:
This may be superior to use of drug alone (AIDS trial)
Synergistic because both drugs are associated with different mutations
Less side effect due to smaller doses of both drugs
-Cidofovir:
Monophosphorlyated cytosine analogue,inhibit CMV DNA polymerase
Given IV once or twice weekly
Low base line drug resistance bu goes up with time
May confer resistance to gancylovir
Associated with nephrotoxicity, myelosuppreesion, and occular abnormalities such as iritis,uveitis, and vitreous hyotonicity.
-Leflunomide:
Immunesuppressive drug with anti-viral activity (confirmed in vitro by plaque reduction assay using a virus recovered from heart transplant patient with CMV pneumonia)
Protein kinase inhibitor, de novo pyridimdine synthesis inhibitor (activated lymphocytes)
Requires a loading dose (half-life is 15 to 18 days)
slow clearance from the body up to 2 years
Interfering virion assembly and not CMV DNA polymerase
Side effect; transaminitis due to hepatic necrosis and therefore contraindicated in those with pre-existing liver disease. other side effects are diarrhea, hypertension, reversible alopecia , rash and pancytopenia. It is not advice in pregnancy
Conclusion;
Prevention of CMV infection is essential
Treatment of CMV may be associated with drug resistance
Management of drug resistance may include forcarnet, cidofovir, leflonaminde and most of these drug as are associated with significant side effect profiles
B.My practice:
We screen for CMV status by Ig G
Most of our patients are of D+/R+
We do have oral valganciclovir for treatment of CMV but not prophylaxis due to cost implications
Management of CMV resistance is challenging due to difficulty of getting the viral genotype testing and availability of the second line therapy
I like your analysis regarding the level of evidence. You need not to type the whole sentence in bold or capitals. That amounts to ‘shouting.’ I like your reflection of your own practice.
Ganciclovir Drug Resistance
Mutations can occur as followings:
· Arising in UL97 phosphotransferase. Different UL97 mutations are associated with different degrees of ganciclovir resistance. Most patients develop only UL97 mutations.
· Arising in the DNA polymerase gene UL54 also confer resistance to ganciclovir.
· Prolonged exposure to ganciclovir can give rise to simultaneous UL54 and UL97 mutations. This is associated with higher level resistance to ganciclovir.
Definition of Ganciclovir resistance:
Can be assayed either phenotypically or genotypically. The “gold standard” test is the plaque reduction assay in which human fibroblasts are cultured with ganciclovir at various defined concentrations. CMV growth can be quantified by counting viral plaque formation or by a DNA hybridization technique. The concentration of ganciclovir required to inhibit 50% of CMV growth is the IC50 value.
Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml.
Risk factors for the acquisition of ganciclovir resistance include:
· CMV seronegativity at transplant when receiving a seropositive organ,
· Degree of immunosuppression,
· Magnitude of CMV viremia, and
· Prolonged exposure to anti-CMV medication.
The primary alternative to ganciclovir for the treatment of CMV viremia and disease:
1. Foscarnet. Like ganciclovir, the risk of resistance increases with the duration of foscarnet therapy. Foscarnet and ganciclovir are of similar efficacy but that foscarnet is less well tolerated. The major limitation to greater use of foscarnet has been its adverse effect profile. Foscarnet is associated with renal toxicity, electrolyte abnormalities, and seizures.
2. Combination therapy with dose-reduced ganciclovir and foscarnet.
3. Cidofovir. The popularity of cidofovir therapy has been limited by its adverse effect profile. Cidofovir can cause nephrotoxicity in as many as half of all patients.
4. Leflunomide. Electron micrographic evaluation suggested that leflunomide inhibits CMV by interfering with final virion assembly rather than with DNA synthesis. The major toxicity of leflunomide is transaminase elevation. Other adverse effects reported include diarrhea (17-33%), hypertension (6-12%), reversible alopecia (8-11%), rash (10-14%), and pancytopenia. In an experience from India, 4 patients were treated with a 100mg oral loading dose once daily for three days followed by 20mg/day for three months. All experienced clinical and endoscopic resolution of their disease as well as clearance of serum viremia. No significant adverse effects were reported.
Reflection on our practice: till date, we never came across cases resistant to ganciclovir therapy, however, if it happened probably we can try Leflunomide and observe its effects, it’s less toxic compared to another Rx.
What is your analysis regarding the level of evidence, limitations and strengths of this publication? I like your attempt at reflection of your own practice.
II. Treatment of Ganciclovir Resistant Cytomegalovirus Infection
Please summarise this article
Cytomegalovirus infection is a common complication of immunosuppression in solid organ and bone marrow transplant recipients, and in patients with AIDS.
Untreated CMV infection is associated with a high risk for the development and progression of CMV disease, allograft dysfunction, and death.
Many centres have reported a small but rising incidence of ganciclovir resistant CMV infections.
Ganciclovir Mechanism of Action and Drug Resistance
Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase. In order to become active it must first be phosphorylated in three steps to a triphosphorylated form.
Mutations arising in the phosphotransferase gene UL97 lead to gancicludir resistance.
Ganciclovir resistance is uncommon at baseline amongst untreated patients but arises rapidly after prolonged exposure to antiviral agents. In one cohort of AIDS patients newly diagnosed with CMV retinitis, samples of vitreous were assayed for baseline gene mutations and found only 1 out of 195 eyes tested.
Among solid organ transplant recipients, the prevalence of resistance ranges between 0 and 15%.
Patients with resistant isolates of ganciclovir are more likely to have experienced a greater number of CMV episodes in the past, to be D+/R– and to have prior exposure to intravenous ganciliclovir.
These risk factors were borne out in a retrospective review of 212 lung transplant recipients.
Ganciclovir resistance is more common among pancreas recipients who receive more potent immunosuppression than other solid organ recipients, according to a study published in the Journal of Clinical Virology.
The risk of developing ganciclovir resistant CMV among D+/R– patients did not differ from those who were treated for CMV with a prophylactic or preemptive strategy, according to a study published in the journal Clinical Infectious Diseases.
The treatment of ganciclovir resistant CMV infections has not been comprehensively studied.
Controlled trials comparing various alternative strategies have yet to be published.
In light of the serious morbidity associated with this infection and the lack of a clearly efficacious second line therapy, efforts to prevent the emergence of resistance are warranted.
Valganciclovir is a more potent option for CMV prophylaxis and maintenance therapy of disease in both transplant recipients and AIDS patients.
It is approximately ten times more bioavailable than oral gancicludir and has potential to decrease resistance while retaining the convenience and safety of an oral agent.
After six months of therapy, resistance mutations in UL97 were found in 9.5% of patients treated with valganciliclovir compared to those treated with intravenous ganciclovar.
The rate of CMV disease associated with ganciclovir resistant virus rose from zero to 6% in patients treated with the drug one year after transplant.
The safety profile was generally similar between the two groups except for a higher incidence of neutropenia (8.2%, vs 3.2%).
Foscarnet is a direct competitive inhibitor of DNA polymerase.
Unlike ganciclovir, it does not need to be phosphorylated in order to inhibit CMV DNA polyphosphate.
Mutations in the DNA Polyphosphatase gene UL54 confer foscarnets resistance and can sometimes be selected for by prolonged ganciliclovir therapy.
The AIDS literature reports upon two patients with progressive CMV retinitis despite longterm ganciclovir therapy.
In both patients, CMV isolates cultured from blood and urine were shown to have phenotypic resistance to foscarnet.
Analysis of the study did not reveal any impact on time to progression of retinaitis amongst patients who were previously treated with ganciliclovir.
A study of 23 patients with suspected resistance to ganciclovir-resistant CMV has shown that out of 15 patients treated with foscarnet, 13 (87%) showed virologic and/or clinical improvement.
Foscarnet is associated with renal toxicity, electrolyte abnormalities, and seizures.
Trials comparing ganciclovir and foscarin give a sense of the relative effectiveness and frequency of adverse effects of these two agents.
This information needs to be interpreted with caution as the data were derived from patients with wild type CMV infection rather than ganciliclovir resistant isolates.
Patients treated with ganciclovir were significantly more likely to suffer neutropenia while those treated with foscarnet had a greater incidence of nephrotoxicity and electrolyte abnormalities.
88% of the people who switched from foscarnet to gancicclovir because of toxic reactions did so because of side effects.
A clinical trial comparing foscarnet and ganciclovir for pre-emptive management of CMV viremia in patients undergoing bone marrow transplantation (BMT) found that 5% of patients in each treatment arm developed CMV disease.
The probability of event-free survival (defined as the probability of death from CMV or CMV-related causes) was identical in each group.
Severe neutropenia or thrombocytopenia required discontinuation of ganciclovir treatment in 6 (6%) patients but in no foscarnet-treated patient.
Serum electrolyte abnormalities were siginificantly more frequent in the foscaranet grou.
Renal impairment did occur more than twice as often in the fosarnet arm but was not statistically significant.
Foscarnet is of similar efficacy to ganciclovir but less well tolerated and treatment will be limited in some patients by nephrotoxicity and/or electrolyte abnormalities.
In the inpatient setting this may be a reasonable choice but a more challenging option in the management of outpatients.
Combination therapy with dose reduced ganciclovir and foscarnet
Combination therapy with dose reduced ganciclovir and foscarnet is a promising avenue for the future treatment of CMV infection.
In vitro studies have shown synergy between the two agents, which would permit lower dosing of each agent and consequent mitigation of their different toxicity profiles.
Intravenous ganciclovir combined with foscarnet to treat CMV infection that was refractory to three or more weeks of treatment.
Patients had a clinical response within 72-96 hours and completely cleared their antigenemia within 4-8 weeks. No relapses were seen after 12-36 months of follow-up.
Combination therapy was found to be more likely to cause renal dysfunction and electrolyte abnormalities in patients with CMV viremia compared to monotherapy.
Patients treated with combination therapy were less likely to have PCR negative blood at 14 days, although the difference was not statistically significant.
The incidence of nephrotoxicity seen with reduced dose combination therapy is disappointing relative to the success of the strategy in the ganciclovir resistant CMV trial.
It is probably a more accurate reflection of the adverse effect profile of foscarnet, given the greater number of patients treated in this trial.
Cidofovir was approved by the FDA in 1996 for the treatment of cytomegalovirus infection.
It is a monophosphorylated cytosine analogue which, like ganciclovir, is further phosphorylated intracellularly to form a compound that impedes DNA polymerase activity.
In a series of 122 treatment naïve AIDS patients with CMV retinitis, resistance was identified in 4.1 and 6.6% of blood and urine culture specimens respectively.
Extensive treatment of CMV infection with ganciclovir can also lead to the development of cross-resistance to cidofovir.
In the Seattle series of 240 liver, kidney, and pancreas transplant recipients prophylaxed with oral ganciliclovir, five patients developed resistance to this drug.
It can also cause bone marrow suppression and ocular disease including iritis, uveitis and vitreous hypotonicity.
Cidofovir has been used to treat CMV retinitis that had recurred or was progressive despite treatment with ganciclovir, foscarnet or both.
In a study, high dose treatment significantly delayed progression beyond the 115 day duration of the study.
Nephrotoxicity occurred in 24% of patients and proteinuria was detected in 39%.
The majority of patients treated with cidofovir for invasive CMV disease (57%) had received prior therapy with ganciclovir, foscarnet, or both.
38 patients who received secondary pre-emptive therapy had by definition failed or relapsed after prior preemptive therapy with another agent.
Leflunomide is an immunomodulatory drug originally developed for the treatment of rheumatoid arthritis.
It has attracted particular interest from the transplant community because in addition to immunosuppressive properties it is active against viruses.
The medical management of transplant patients is often a fine balance between maximising immune suppression and minimizing infection.
Leflunomide acts as a protein kinase inhibitor and as a competitive inhibitor of dihyrdoorotate dehydrogenase.
It inhibits denovo pyrimidine synthesis and hence selectively inhibits activated lymphocytes.
The drug has a long-half life on the order of 15-18 days potentiated by substantial enterohepatic recirculation.
In a single center, retrospective review, 53 liver and kidney transplant patients who were failing conventional immunosuppressive therapy were treated with leflunomide.
Two thirds of renal patients were able to reduce their dose of cyclosporine and prednisone by about a third.
Four out of five patients with liver transplants who tolerated leflunomide were able to stop cyclosporine or FK-506 entirely, while the fifth reduced his dose by 65%.
There were no cases of allograft rejection. Lefluomide was discontinued in 8 of the 53 patients due to adverse effects.
Leflunomide inhibits CMV by interfering with final virion assembly rather than with DNA synthesis.
As such, it is distinct from that targeted by ganciclovir, foscarnet, and cidofovir.
Its potential to inhibit a multidrug-resistant CMV isolate was confirmed in vitro by plaque reduction assays.
The major toxicity of leflunomide is transaminase elevation(Patients with pre-existing liver disease, heavy alcohol intake, or concurrent viral hepatitis should not be given the drug and cases of hepatic necrosis and death from liver failure have been reported but are rare).
Adverse effects of leflunomide for the treatment of rheumatoid arthritis include diarrhea (17-33%), hypertension (6-12%), reversible alopecia (8-11), and rash (10-14%).
The drug is contraindicated in pregnancy due to reports of fetal death and teratogenesis in human subjects.
The use of leflunomide to treat CMV in humans is still very limited and remains on the case report level.
The largest series published to date describes the experiences of four renal transplant patients from India with symptomatic gastrointestinal CMV disease who were treated with 100mg/day oral loading doses.
The use of leflunomide in an allogeneic bone marrow transplant recipient who developed CMV infection refractory to sequential therapy with ganciclovir, foscarnet, and cidofovir has been reported.
While the agent was clearly effective in clearing the patient’s CMV viremia, it is possible that it contributed to her death from progressive liver failure.
Evidence exists on the use of leflunomide to treat CMV viremia in solid organ transplant patients at the Cleveland Clinic.
It has also been used in two patients at Massachusetts General Hospital.
The first patient died from underlying comorbidities the day after starting treatment.
The management of CMV infection remains a substantial challenge for clinicians caring for immunocompromised patients.
Effective therapy requires prolonged drug use which in turn is associated with emergence of drug-resistant virus.
CMV resistance to ganciclovir has been reported with increasing frequency in both AIDS patients treated for CMV retinitis and recipients of bone marrow and solid organ transplants.
The risk of renal failure with foscarnet and cidofovir limits their attractiveness as anti-CMV agents.
The use of reduced dose combination therapy appears to deliver potent antiviral therapy with less risk of nephrotoxicity.
The novel immunomodulatory agent leflunomide holds promise as a future agent for the management of CMV.
Yes of course
I’m going to learn more about the treatment plan and examine the perceived advantages of the therapy. I’ll also learn more about how frequently hospitals provide clinical trials that patients can take advantage of.
I like that you use bold for heading or sub-headings that make it easier to read. I like your summary of this article. What is the level of evidence that this publication provides?
What is your analysis regarding the level of evidence, limitations and strengths of this publication? I like your attempt at reflection of your own practice, but it is very fuzzy. I am not sure what your current practice is
Solid organ and bone marrow transplant recipient patients are prone to develop infections particularly Cytomegalovirus (CMV) infection which is associated with the development of CMV disease,allograft dysfunction, and death. First line treatment is ganciclovir but these days patients have developed resistance to ganciclovir.
Mechanism of action of ganciclovir:
Ganciclovir –an antiviral agent ,inhibit CMV DNA polymerase, first approved by the FDA in 1989.Various different gene mutations are responsible for resistance. Gene UL97, and gene UL54, both causes resistance individually and in combination if it occurs, then very high level of resistance.Risk factors which increase the resistance to ganciclovir include: CMV D+/R-,Prolong exposure to ganciclovir ,intense immunosuppression, and heavy viral load.
According to the data of two Chicago transplant centers,from 1994-2001,Lung transplant represent highest level of resistance comprising about 15%.
Prevention of Ganciclovir-resistant CMV infection:
Drugs which can be used for ganciclovir resistance include : valganciclovir, foscarnet, cidofovir or Leflunomide
Valganciclovir (VGC): 10 times more potent than ganciclovir
Foscarnet: Inhibit CMV DNA polymerase-competitive.
Side effects-nephrotoxicity, electrolyte abnormalities, and seizures.
Cidofovir: FDA approved in 1996, monophosphorylated cytosine analogue that needs phosphorylation to inhibit DNA polymerase activity.
Side effects of cidofovir is nephrotoxic and ocular toxicity
Leflunomide-immunomodulatory drug, and is a protein kinase inhibitor and also competitive inhibitor of dihyrdoorotate dehydrogenase
Side effects: raised liver enzymes,alopecia , skin rash , hypertension and pancytopenia.
In my practice,valganciclovir is used for prophylaxis ,however, for mild –moderate disease valganciclovir and ganciclovir for severe infection. Unfortunately we don’t have facility of drug resistance testing and non availability of drugs like cidofovir ,foscarnet so no experience ,But leflunomide is available,have used this drug in BK nephropathy.
This review is discussing the treatment strategies available to treat ganciclovir-resistant CMV infection. Ganciclovir resistance can be assayed either phenotypically or genotypically. The “gold standard” test is the plaque reduction assay in which human fibroblasts are cultured with ganciclovir at various defined concentrations. The concentration of ganciclovir required to inhibit 50% of CMV growth is the IC50 value. Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml.
Valganciclovir has offered a potential means to decrease ganciclovir resistance. valganciclovir was shown to be superior to oral ganciclovir for the prevention of resistant CMV infection.
Foscarnet can lead to clearance of blood and urine cultures as well as stabilization of retinitis.The major limitation to greater use of foscarnet has been its adverse effect profile. Foscarnet is associated with renal toxicity, electrolyte abnormalities, and seizures.
combined ganciclovir and foscarnet at reduced doses as ganciclovir and foscarnet resistance are usually associated with different gene mutations. combination therapy has been shown to be effective in pre-emptive therapy of CMV antigenemia in non-ganciclovir resistant bone marrow transplant patients, permit lower dosing of each agent and consequent mitigation of their different toxicity profiles.
Cidofovir was approved by the FDA in 1996 for the treatment of cytomegalovirus infection. The pharmacology of cidofovir is such that it has to be given intravenously but need only be administered once or twice per week. Like ganciclovir and foscarnet, resistance to cidofovir is low at baseline but rises under sustained drug pressure. it has been noted in case reports to cause bone marrow suppression and ocular disease including iritis, uveitis, and vitreous hypotonicity.
Leflunomide has attracted particular interest from the transplant community because in addition to immunosuppressive properties it is active against viruses. It has a long-half life on the order of 15-18 days potentiated by substantial enterohepatic recirculation. Without a loading dose it is estimated that it would take nearly two months to achieve steady-state plasma concentrations. Likewise, after discontinuation of the medication it can take as long as two years for the body to entirely clear the drug. Renal excretion is limited. Its potential to inhibit a multidrug-resistant CMV isolate was confirmed in vitro by plaque reduction assays using a virus recovered from a heart transplant patient with CMV pneumonitis. Cases of hepatic necrosis and death from liver failure have been reported but are rare.
Our local practice is limited by the un-accessible alternative medications
1. Please summarise this article
Cytomegalovirus (CMV) infection is a common and serious complication of immunosuppression in solid organ transplantation and in AIDs. If not treated it is associated with a high risk for the development and progression of CMV disease, allograft dysfunction, and death.
First line treatment for CMV infections and disease is ganciclovir, but some centres have reported a small but rising incidence of ganciclovir resistant CMV infections.
Strategies available to treat ganciclovir-resistant CMV infection include approved alternative agents foscarnet and cidofovir, the use of combination ganciclovir and foscarnet at reduced doses, and the novel immunomodulatory agent, leflunomide.
Mutations arising in UL97 phosphotransferase lead to ganciclovir resistance. Similarly, mutations arising in the DNA polymerase gene UL54 also confer resistance to ganciclovir. Different UL97 mutations are associated with different degrees of ganciclovir resistance.
Definition
Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml.
Options for treatment of ganciclovir resistant CMV:
Foscanet
Cidofovir
Lefluconamide.
Foscarnet and cidofovir limits their attractiveness as anti-CMV agents. The use of reduced dose combination therapy appears to deliver potent antiviral therapy with less risk of nephrotoxicity but this approach requires further study.
The novel immunomodulatory agent leflunomide holds promise as a future agent for the management of CMV since it both potentiates immunosuppression and suppresses CMV reproduction.
2. Please reflect on your practice:
We use gancicolovir/valganciclovir for treatment of CMV infection. We did not face a case ganciclovir resistance. We do not have tests for ganciclovir resistance. If we face such case we need to ask for referral to higher center for treatment.
Treatment of Ganciclovir Resistant Cytomegalovirus Infection
Cytomegalovirus (CMV) infection is a common and serious complication of immunosuppression
in solid organ and bone marrow transplant recipients, and in patients with AIDS.
Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase.
Ganciclovir resistance can be assayed either phenotypically or genotypically.
Ganciclovir resistance has been
defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml.5
Ganciclovir resistance is uncommon at baseline amongst untreated patients but arises rapidly after prolonged exposure to antiviral agents
Risk factors for the acquisition of ganciclovir resistance include CMV seronegativity at
transplant when receiving a seropositive organ, degree of immunosuppression, magnitude of
CMV viremia, and prolonged exposure to anti-CMV medication.
The alternative therapies foscarnet and cidofovir both appear to have good in
vivo activity against cytomegalovirus but both are limited by their propensity to cause acute renal failure.
Ganciclovir resistance is uncommon but can arises rapidly after prolonged exposure to antiviral agents.
The prevalence of CMV resistance in solid organ transplant recipients, ranges between 0 and 15%. The risk of developing ganciclovir resistance differs according to organ transplanted .
Definition
Ganciclovir resistance can be assayed either phenotypically or genotypically. The standard test is the plaque reduction assay. The human fibroblasts are cultured with ganciclovir at various defined concentrations. CMV growth can be quantified by counting viral plaque formation or by a DNA hybridization technique. The concentration of ganciclovir required to inhibit 50% of CMV growth is the IC50 value. Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6μg/ml.
Ganciclovir resistance can also be detected by genotype analysis.
Prevalence and Risk Factors for Resistance :
Risk factors for ganciclovir resistance include :
1- CMV seronegativity at transplant when receiving a seropositive organ
2- degree of immunosuppression
3- magnitude of CMV viremia
4- prolonged exposure to anti-CMV medication.
Prevention of Ganciclovir Resistant CMV Infection :
1- Valganciclovir which is valyl ester prodrug of ganciclovir
2- Foscarnet
The side effect include renal toxicity, electrolyte abnormalities and seizures
3- Combination therapy with low dose ganciclovir and foscarnet
4- Cidofovir
5- Leflunomide
the main side effect is transaminase elevation
Please summarize this article
Ganciclovir resistant CMV is suspected if CMV PCR is not falling by >1copies/ml after 2 weeks or if there is no clinical improvement.
Risk factors for ganciclovir resistant CMV:
CMV D+/R-, prolonged exposure, UL97 gene mutation and lung transplantation.
Treatment of ganciclovir resistant CMV:
1-Foscarnet: side effects include nephrotoxicity, metabolic changes, cardiac arrhythmias, and genital ulceration.
2-Cidofovir: side effects include nephrotoxicity, neutropenia, metabolic acidosis and ocular hypotony.
3-Letemovir: can be used with other anti-CMV drugs, its dose should be adjusted in renal and hepatic impairment, it can interact with other immune-suppressive medications.
4-Maribavir: is effective against viral UL97 kinase, less hepatotoxic and nephrotoxic compared to ganciclovir and valganciclovir.
5-CMV IVIG: especially in cmv pneumonitis.
Untreated CMV is associated with CMV progression, allograft dysfunction and death.
First line of treatment for CMV infection is Ganciclovir, but there is small increasing incidence of Ganciclovir resistant CMV infection reported by many centers.
Mechanism of action and drug resistance of Ganciclovir
Ganciclovir is a guanosine analog that inhibits CMV DNA polymerase. The drug to be active need to be phoshorylated by the gene UL97. Mutation of this gene leads to Ganciclovir resistance. Also Mutation of the DNA polymerase gene UL54 leads to Ganciclovir resistance.
Ganciclovir resistance can be detected either phenotypically or genotypically
Ganciclovir resistance is defined as a plaque reduction DNA hybridization IC50 of > 6ug/ml.
Also can be detected via genotype analysis to assess for mutation in the UL54 and UL97 genes.
The prevelance of CMV resistance ranges between 0 to 15 %.
Risk factors for Ganciclovir resistance: CMV seronegativity at transplant when receiving a seropositive organ, degree of immunosuppression, magnitude of CMV viremia and prolonged exposure to anti CMV medication.
Prevention and treatment of Ganciclovir resistant CMV infection
1. Valganciclovir is more potent option for CMV prophylaxis and maintenance therapy compared to Ganciclovir. Valganciclovir is ten times more bioavialable than Ganciclovir. So it can decrease resistance.
2. Foscarnet
Foscarnet is a direct competitive inhibitor of DNA polymerase. Unlike Ganciclovir, it doesn’t need to be phoshorylated to become active, so it doesn’t affected by mutation in the UL97 gene.
The risk of resistance increases with the duration of drug and drug resistance is associated with an increased risk of retinitis progression.
The main limitation to the use of foscarnet is its side effect as it is associated with renal toxicity, electrolyte abnormalities and seizures.
The efficacy of foscarnet is similar to Ganciclovir, so it is a useful agent can be used in Ganciclovir resistance, but its side effects especially nephrotoxicity and electrolyte disturbance limit its use .
3. Combination therapy with dose reduced Ganciclovir and Foscarnet
4. Cidofovir
It is a monophosphorylated cytosine analogu and inhibits DNA polymerase activity .
It is given intravenously once or twice per week.
5. Leflunomide
It is immunomodulatory drug and it is active against viruses, it is protein kinase inhibitor and inhibits activated lymphocytes.
cmv resistant is in the range of 0-15, usually GCV resistant due to genetic mutation in UL97, UL54, carry high morbidity and mortality risk and is associated with graft loss and many risk factors related to the CMV serostatus of the recipient and donor (D+ve /R-ve, the immunosuppression type and intensity, duration of antiviral use and the subtherapeutic dosing, types of organ transplantation like higher risk in lung and heart transplantation while kidney transplantation have a lower risk
treatment for GCV-resistant CMV includes second-line traditional therapy with a wide range of side effects like foscarnet and cidofovir, leflunomide.
new novel oral treatment and is FDA-approved and recommended for treatment of R/R CMV disease after SOT, HSCT including the nice guideline 2023, can be given as oral medication with fewer side effects and cost-effective compared to early preemptive therapy in prevention and treatment for R/R CMV
screening for UL97 genetic mutation should be considered in suspected cases of CMV resistance.
narrative review level 5
My experience with resistant CMV infection was two cases from hematology after HSCT , and a second case of resistant PNH was on regular eculizumab both died with massive GI bleeding from confirmed CMV invasive colitis resistant to first-line treatment which is IV GCV and even second-line treatment
we use GCV IV as the standard of care for the treatment of CMV disease alternative oral valganciclovir 900mg BID for 3 weeks followed by 900mg OD for another 28 days or till two CMV PCR tests turned negative
we don’t have reported resistant CMV disease after kidney transplantation
Ganciclovir resistance should be suspected in patients who have rising or persistently elevated viral loads despite treatment with appropriately dosed ganciclovir for more than two weeks .
Ganciclovir Mechanism of Action and Drug Resistance-
Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase.In order to become active it must first be phosphorylated in three steps to a triphosphorylated form. Once phosphorylated, it acts as a competitive substrate for DNA polymerase and slows the replication of CMV DNA by DNA polymerase. Phosphorylation is accomplished by the phosphotransferase produced by the gene UL97. Mutations arising in UL97 phosphotransferase lead to ganciclovir resistance. Similarly, mutations arising in the DNA polymerase gene UL54 also confer resistance to ganciclovir
UL54 mutations are much less common and confer various patterns of cross-resistance depending on the specific mutation .UL54 mutations confer dual ganciclovir-cidofovir resistance. A significant number of patients with clinically ganciclovir-resistant CMV disease have no detectable mutation.
Definition-
Ganciclovir resistance can be assayed either phenotypically or genotypically. The “gold standard” test is the plaque reduction assay in which human fibroblasts are cultured with ganciclovir at various defined concentrations. Ganciclovir resistance can also be detected via genotype analysis to assess for known mutations in the UL54 and UL97 genes. Detection of resistance via gene mutations is attractive since it is less labour intensive, less time consuming.
Prevalence and Risk Factors for Resistance
Ganciclovir resistance is uncommon at baseline amongst untreated patients but arises rapidly after prolonged exposure to antiviral agents.The risk of developing ganciclovir resistance does seem to vary according to the organ transplanted (Lung most common,kidney least common).Risk factors for the acquisition of ganciclovir resistance include CMV seronegativity at transplant when receiving a seropositive organ, degree of immunosuppression, magnitude of CMV viremia, and prolonged exposure to anti-CMV medication.
Prevention of Ganciclovir Resistant CMV Infection
Valganciclovir is approximately ten times more bioavailable than oral ganciclovir. Since ganciclovir resistance is thought to be related to prolonged exposure to subtherapeutic plasma concentrations of ganciclovir, valganciclovir offered a potential means to decrease resistance while retaining the convenience and safety of an oral agent.
Treatment–
Foscarnet -A pyrophosphate analog that inhibits viral replication by selectively binding to viral DNA polymerase and requires IV administration. it is active against CMV with UL97 and UL54 mutations.Foscarnet is dosed at 60 mg/kg IV every 8 hours or 90 mg/kg every 12 hours, with dose adjustment for kidney function impairment. Foscarnet is highly nephrotoxic and patients should receive pre- and postinfusion hydration, and close monitoring of electrolytes, creatinine, magnesium, and phosphorus is essential given that acute kidney injury is common with foscarnet.
Cidofovir –t is active against CMV with UL97 mutations but not against CMV with UL54 mutations. It is also highly nephrotoxic. it can also cause uveitis .Cidofovir can be dosed at 1 mg/kg IV three times a week. Cidofovir should be given with aggressive hydration.
Leflunomide-Leflunomide has attracted particular interest from the transplant community because in addition to immunosuppressive properties it is active against viruses.Experimental data on the use of leflunomide in human beings is extremely limited and remains on the case report level. The largest series published to date describes the experiences of four renal transplant patients from India with symptomatic gastrointestinal CMV disease who were treated with leflunomide because they could not afford intravenous ganciclovir. All four patients had detectable CMV viremia via quantitative PCR. The patients were treated with a 100mg oral loading dose once daily for three days followed by 20mg/day for three months. All experienced clinical and endoscopic resolution of their disease as well as clearance of serum viremia. No significant adverse effects were reported.The major toxicity of leflunomide is transaminase elevation.
Conclusion–
The risk of renal failure with foscarnet and cidofovir limits their attractiveness as anti-CMV agent. The novel immunomodulatory agent leflunomide holds promise as a future agent for the management of CMV since it both potentiates immunosuppression and suppresses CMV reproduction.Unlike foscarnet and cidofovir it does not appear to be nephrotoxic but can cause transaminase elevation.But it has limited experience in human subjects.
Newer agent to treat drug-resistant CMV–
Maribavir – An oral drug that inhibits UL97 phosphotransferase and stops viral maturation and egress. Maribavir is active against CMV with UL97 and UL54 mutations. Maribavir is dosed at 400 mg orally twice daily for eight weeks. Dysgeusia is a frequent side effect, and maribavir cannot be coadministered with ganciclovir or valganciclovir.Key advantages of maribavir over other agents are lack of bone marrow and kidney toxicity. Due to a drug interaction with calcineurin inhibitors and mammalian (mechanistic) target of rapamycin (mTOR) inhibitors, close monitoring of these immunosuppressive agents is required.
Our institute protocol–
Since we lack the facility to test cmv resistance,we refer them to higher center.We dont have experience of treating resistant cmv cases.
Treatment of Ganciclovir Resistant Cytomegalovirus Infection:
Ganciclovir Resistant:
it is suspected when no clinical improvement despite treatment or CMV PCR failed to decrease by at least >1copies /ml after 2 weeks of treatment
Mechanism of ganciclovir resistance:
mutation in UL97 phosphotransferase
Risk factors:
– D+/R-
– excessive using antiviral agent
– Lung transplantation
Treatment:
second line of treatment:
-Foscarnet but it is nephrotoxic.
-Cidovir: also nephrotoxic
-letemovir
-Maribavir
CMV IVIG can be used
Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase. In order to become active, it must first be phosphorylated in three steps to a triphosphorylated form. Once phosphorylated, it acts as a competitive substrate for DNA polymerase and slows the replication of CMV DNA by DNA polymerase.
Ganciclovir resistance can be assayed either phenotypically or genotypically. The “gold standard” test is the plaque reduction assay in which human fibroblasts are cultured with ganciclovir at various defined concentrations. CMV growth can be quantified by counting viral plaque formation or by a DNA hybridization technique. The concentration of ganciclovir required to inhibit 50% of CMV growth is the IC50 value. Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6μg/ml.
Ganciclovir resistance is uncommon at baseline amongst untreated patients but arises rapidly after prolonged exposure to antiviral agents. In one cohort of AIDS patients newly diagnosed with CMV retinitis, samples of vitreous were assayed for baseline gene mutations associated with ganciclovir resistance. A UL97 mutation was found in only 1 out of 195 eyes tested.
Prevention of Ganciclovir Resistant CMV Infection
The treatment of ganciclovir resistant CMV infections has not been comprehensively studied. The existing literature consists exclusively of case reports and case series describing the outcomes of treatment for patients with resistant infections. Controlled trials comparing various alternative strategies have yet to be published. In light of the serious morbidity associated with ganciclovir resistant infection and the lack of a clearly efficacious second line therapy, efforts to prevent the emergence of ganciclovir resistance are warranted.
Foscarnet
The primary alternative to ganciclovir for the treatment of CMV viremia and disease is foscarnet. Foscarnet was approved by the FDA in 1991. Foscarnet is a direct competitive inhibitor of DNA polymerase. Unlike ganciclovir, it does not need to be phosphorylated in order to inhibit CMV DNA polymerase. Since it is not dependent on the CMV phosphotransferase UL97 it retains activity against CMV isolates with UL97 mutations that are resistant to ganciclovir.
Cidofovir
Cidofovir was approved by the FDA in 1996 for the treatment of cytomegalovirus infection. It is a monophosphorylated cytosine analogue which, like ganciclovir, is further phosphorylated intracellularly to form a compound that impedes DNA polymerase activity. The pharmacology of cidofovir is such that it has to be given intravenously but need only be administered once or twice per week. Like ganciclovir and foscarnet, resistance to cidofovir is low at baseline but rises.
under sustained drug pressure. In a series of 122 treatment naïve AIDS patients with CMV retinitis, cidofovir resistance was identified in 4.1 and 6.6% of blood and urine culture specimens respectively. After three months of cidofovir therapy, 29% of patients had a resistant blood or urine isolate.
Leflunomide
Leflunomide is an immunomodulatory drug originally developed for the treatment of rheumatoid arthritis and approved for that indication by the FDA in 1998. Leflunomide has attracted particular interest from the transplant community because in addition to immunosuppressive properties it is active against viruses. Since the medical management of transplant patients is often a fine balance between maximising immunosuppression to prevent allograft rejection and minimizing immunosuppression to prevent infection, an agent with simultaneous immunosuppressive and anti-infective properties is particularly alluring.
Conclusion
The management of CMV infection remains a substantial challenge for clinicians caring for immunocompromised patients. While there are a number of agents active against the virus, effective therapy requires prolonged drug use which in turn is associated with emergence of drug resistant virus. CMV resistance to ganciclovir has been reported with increasing frequency in both AIDS patients treated for CMV retinitis and in recipients of both bone marrow and solid organ transplants.
Protocol for prophylaxis, surveillance, and treatment of CMV after renal transplantation:
Principles:
§ The risk of disease determined by serological status of the donor and recipient and intensity of immunosuppression.
§ Valganciclovir is licensed for prophylaxis but is often also used for the treatment of disease.
§ High-risk patients (D+R-) remain at risk of CMV viraemia and disease after they complete the prophylaxis.
Prophylaxis:
1) D+/R- 200 days of valganciclovir.
2) D-/R+ and D+/R+ 100 days of valganciclovir, 200 days after ATG or Alemtuzumab.
3) D-/R- No valganciclovir.
4) Any patient receiving intensified immunosuppression at any time point beyond 100 days consider prophylaxis.
5) Prophylaxis dose is 900mg od adjusted in renal impairment.
Surveillance and testing by indication in suspected CMV viraemia or disease:
1. Routine surveillance for viraemia is not required during prophylaxis.
2. D+/R- patients should have their serostatus (CMV IgG) checked at or around 200 days.
3. D+/R- patients should start surveillance with CMV PCR once they finish prophylaxis.
This may be more frequent than clinic visits and can be achieved with extra “Bloods and Go” visits to RAU if required as per the following schedule:
– 2 weeks
– 4 weeks
– 8 weeks
– 12 weeks
The recipient team will coordinate this.
4. CMV PCR on blood is the standard test for all transplant patients where CMV viraemia or disease is suspected or a possibility in outpatients or inpatients, irrespective of whether on prophylaxis or not.
Thresholds for treatment:
A. Patients that develop viraemia or disease whilst not on prophylaxis
1. Treatment is mandatory in all cases of suspected tissue-invasive CMV disease, irrespective of viral load.
2. Consider appropriate reduction in immunosuppression in R+ patients with a viral load of fewer than 3 logs 10. Page 3 of 3
3. Consider treatment with valganciclovir when the viral load exceeds 3 logs 10 if symptomatic or rapidly rising titre in high-risk patients.
4. Treatment with valganciclovir or IV ganciclovir is mandatory when the viral load exceeds 4 logs 10.
5. IV ganciclovir is indicated where enteric absorption is likely to be compromised (proven GI involvement, diarrhea or vomiting).
6. IV ganciclovir is indicated in any patient with severe organ involvement (e.g. pneumonitis, encephalitis) – Consultant decision.
B. Patients that develop viraemia or disease whilst on prophylaxis
1. Discuss all such cases with a consultant virologist to agree best treatment regime and discuss resistance testing.
Treatment:
The choice of oral versus IV therapy is determined by the abovementioned thresholds and criteria. There are three options:
1. Oral valganciclovir 900mg bd* for 21 days, then 900mg od* for 28 days or until 2 x PCR negative, whichever occurs first (off-label drug use).
2. IV ganciclovir 5mg/kg bd* for 5 days followed by oral valganciclovir 900mg od* until 2 x PCR negative.
3. IV ganciclovir 5mg/kg bd* for 14-21 days, stop date determined by 2 x PCR negative.
Please note dose reductions for renal impairment are commonly needed with valganciclovir and ganciclovir therapy; please consult the Renal Drug Handbook or pharmacist for an appropriate regime and revise in the event of changing renal function.
Virological, pharmacy and other specialist advice should be sought in less straightforward cases. Additional therapy may be appropriate following the discussion.
Treatment of Ganciclovir Resistant Cytomegalovirus Infection:
Ganciclovir Resistant: should be suspected if CMV PCR count has not fallen by >1copies/ml after two weeks of therapy or if there is no clinical improvement despite treatment.
Mechanism of ganciclovir resistance:
After phosphorylation it acts as a competitive substrate for DNA polymerase. Phosphorylation is accomplished by the phosphotransferase produced by the gene UL97. Mutation in UL97 phosphotransferase leading to ganciclovir resistance.
Risk factors:
1) Serostatus- D+/R-
2) Prolong exposure to antiviral agent
3) UL97 gene mutation
4) Lung transplantation
Prevention:
By prophylaxis oral valganciclovir
Treatment:
§ Exclude other causes of symptoms.
§ Switch to second line:
1) Foscarnet: nephrotoxic, it can result in metabolic changes as well as cardiac arrythmias and genital ulceration.
2) Cidovir: nephrotoxic and causes neutropenia, metabolic acidosis, and ocular hypotony.
3) Letemovir: is newly approved anti-CMV antiviral which inhibits the viral terminase complex. It interacts with immunosuppression, require dose adjustment in renal and hepatic impairment and can be used with other anti-CMV medication.
4) Maribavir: is a promising new antiviral against the viral UL97 kinase. Reduced haematotoxicity and nephrotoxicity compared to GCV and VGCV and so could eventually replace these older compounds.co-administration of with GCV is not advised as maribovir is an inhibitor of the UL97enzyme required for anabolism of the later.
§ Consider further reduction in immunosuppression.
§ Consider immunoglobulins (especially if pneumonitis). CMVIG can be used to induce a passive immune resistant infection and side effects of VGC.
§ Request for genotypic resistance.
Introduction :
Cytomegalovirus (CMV) infection is a common and serious complication of immunosuppression in solid organ and bone marrow transplant recipients, and in patients with AIDS. Untreated CMV infection is associated with a high risk for the development and progression of CMV disease, allograft dysfunction, and death
Recently we started to see cases of Ganciclovir Resistant Cytomegalovirus Infection due to mutation arising in UL97 phosphotransferase or UL54 lead to ganciclovir resistance.
Ganciclovir resistance can be assayed either phenotypically or genotypically.
Risk factors for resistant CMV infection .
1- prolonged exposure to antiviral agents
2- which organ is transplanted ( most common in Lung )
3- CMV seronegativity at transplant when receiving a seropositive organ degree of immunosuppression, magnitude of CMV viremia, and prolonged exposure to anti-CMV medication
Prevention of Ganciclovir Resistant CMV Infection
Foscarnet
it is not dependent on the CMV phosphotransferase UL97 so it retains activity against CMV isolates with UL97 mutations that are resistant to ganciclovir but Mutations in the DNA polymerase gene UL54, however, do confer foscarnet resistance and can sometimes be selected for by prolonged ganciclovir therapy .
The major limitation to greater use of foscarnet has been its adverse effect profile. Foscarnet is associated with renal toxicity, electrolyte abnormalities, toxic reactions and seizures .
Overall, it seems that foscarnet and ganciclovir are of similar efficacy but that foscarnet is less well tolerated. As such, foscarnet is useful agent to use against ganciclovir resistant CMV but treatment will be limited in some patients by nephrotoxicity and/or electrolyte abnormalities. In the inpatient setting where both these variables can be closely monitored and often pre-empted foscarnet seems to be a reasonable choice but a more challenging option in the management of outpatients.
Combination therapy with dose reduced ganciclovir and foscarnet
Cidofovir
Leflunomide
The novel immunomodulatory agent leflunomide holds promise as a future agent for the management of CMV since it both potentiates immunosuppression and suppresses CMV reproduction. Unlike foscarnet and cidofovir it does not appear to be nephrotoxic but can cause transaminase elevation. The longterm effectiveness, tolerability, and ideal settings for the use of leflunomide remain to be defined by ongoing and future studies.
1- summarise the article:
Treatment of Ganciclovir Resistant Cytomegalovirus Infection
Cytomegalovirus (CMV) infection is a common and serious complication, If untreated , can result in allograft dysfunction and might cause death as well.
Some time the patient is resistant to the standard treatment hence another line of treatment being proposed and approved for such patients.
Ganciclovir Mechanism of Action and Drug Resistance
Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase
first be phosphorylated in three steps to a triphosphorylated form. then, it acts as a competitive substrate for DNA polymerase and slows the replication of CMV DNA by DNA polymerase.
Phosphorylation is accomplished by the phosphotransferase produced by the gene UL97.
· Mutations arising in UL97 phosphotransferase lead to ganciclovir resistance
· mutations arising in the DNA polymerase gene UL54 also confer resistance to ganciclovir.
· prolonged exposure to ganciclovir can give rise to simultaneous UL54 and UL97 mutations. This is associated with higher level resistance to ganciclovir.
· UL54 mutations can confer cross resistance to foscarnet and cidofovir since these agents also target CMV DNA polymerase.
Definition
Ganciclovir resistance can be assayed either phenotypically or genotypically.
The “gold standard” test is the plaque reduction assay in which human fibroblasts are cultured with ganciclovir at various defined concentrations.
CMV growth can be quantified by
· counting viral plaque formation
· or by a DNA hybridization technique.
The concentration of ganciclovir required to inhibit 50% of CMV growth is the IC50 value.
Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml
Ganciclovir resistance can also be detected via genotype analysis to assess for known mutations in the UL54 and UL97 genes.
Detection of resistance via gene mutations is attractive since it is less labour intensive, less time consuming, and is not limited by the need to culture CMV from patient specimens.
The correlation between genotype and phenotype, however, is imperfect so genotype-based resistance reports need to be interpreted with caution.
Prevalence and Risk Factors for Resistance
· Ganciclovir resistance is uncommon at baseline amongst untreated patients but arises rapidly after prolonged exposure to antiviral agents.
· Among solid organ transplant recipients, the prevalence of CMV resistance ranges between 0 and 15%. The risk of developing ganciclovir resistance does seem to vary according to the organ transplanted
· This is felt to reflect different degrees of immunosuppression and different protocols for the prophylaxis of CMV.
Risk factors for the acquisition of ganciclovir resistance include
1. CMV sero-negativity at transplant when receiving a sero-positive organ
2. degree of immunosuppression
3. magnitude of CMV viremia
4. prolonged exposure to anti-CMV medication.
· Patients with ganciclovir resistant disease suffered a statistically significant decrease in survival compared to those with ganciclovir sensitive disease.
· Ganciclovir resistant CMV disease was diagnosed a median of 10 months after transplant (range 7-12 months) suggesting an association with prolonged ganciclovir exposure.
· It is reported that outcomes for patients with ganciclovir resistance were poor.
· The patient usually treated with reduced immunosuppression and CMV immunoglobulin.
Prevention of Ganciclovir Resistant CMV Infection
· The treatment of ganciclovir resistant CMV infections has not been comprehensively studied.
· It is based on case reports and case series
· Valganciclovir is approximately ten times more bioavailable than oral ganciclovir.
· valganciclovir offered a potential means to decrease resistance while retaining the convenience and safety of an oral agent.
· valganciclovir was shown to be superior to oral ganciclovir for the prevention of resistant CMV infection.
· Another report noted that CMV viremia was less frequent during the prophylactic period
· valganciclovir had a higher incidence of neutropenia
Foscarnet
· The primary alternative to ganciclovir for the treatment of CMV viremia and disease is foscarnet.
· Foscarnet is a direct competitive inhibitor of DNA polymerase.
· Unlike ganciclovir, it does not need to be phosphorylated in order to inhibit CMV DNA polymerase. Since it is not dependent on the CMV phosphotransferase UL97 it retains activity against CMV isolates with UL97 mutations that are resistant to ganciclovir.
· Like ganciclovir, the risk of resistance increases with the duration of foscarnet therapy.
· Treatment with foscarnet led to clearance of blood and urine cultures as well as stabilization of retinitis for 12-25 weeks in a large trial.
· The major limitation to greater use of foscarnet has been its adverse effect profile. Foscarnet is associated with renal toxicity, electrolyte abnormalities, and seizures.
· Nephrotoxicity was more likely to occur in patients assigned to foscarnet who were taking additional nephrotoxic agents.
· In the inpatient setting where both these variables can be closely monitored and often pre-empted foscarnet seems to be a reasonable choice but a more challenging option in the management of outpatients.
Combination therapy with dose reduced ganciclovir and foscarnet
· A promising avenue for the future treatment of ganciclovir resistant CMV infection has been the use of combination ganciclovir and foscarnet at reduced doses.
· The rationale for this strategy stems from the recognition that ganciclovir and foscarnet resistance are usually associated with different gene mutations, in vitro demonstration of synergy between the two agents even against ganciclovir resistant isolates.
· trial data from the AIDS literature showing that combination therapy is superior to monotherapy with the alternative agent alone.
· Moreover, investigators reasoned that synergy between the two agents would permit lower dosing of each agent and consequent mitigation of their different toxicity profiles.
· In a trial, Patients were treated with ganciclovir at half the usual therapeutic dose (5mg/kg IV q24h) combined with foscarnet at two-thirds the usual induction dose (125mg/kg IV q24h).
· Dosages were adjusted for renal dysfunction and foscarnet was titrated to a therapeutic dose over a few days.
· All patients also received CMV hyperimmunoglobulin.
· All patients had a clinical response within 72-96 hours and completely cleared their antigenemia within 4-8 weeks.
· No relapses were seen after 12-36 months of follow-up.
Treatment of Ganciclovir Resistant CMV
significant hypomagnesemia requiring 10-24g of magnesium replenishment per day was noted.
No other adverse effects were reported.
Cidofovir
· Cidofovir was approved by the FDA in 1996 for the treatment of cytomegalovirus infection.
· It is a monophosphorylated cytosine analogue which, like ganciclovir, is further phosphorylated intracellularly to form a compound that impedes DNA polymerase activity.
· it has to be given intravenously, to be administered once or twice per week.
· Like ganciclovir and foscarnet, resistance to cidofovir is low at baseline but rises under sustained drug pressure.
· prolonged treatment of CMV infection with ganciclovir can also lead to the development of cross-resistance to cidofovir.
· Cross-resistance to cidofovir in transplant patients treated with ganciclovir alone has also been reported Likewise, treatment with cidofovir alone can confer resistance to ganciclovir.
· The popularity of cidofovir therapy has been limited by its adverse effect profile.
· Cidofovir can cause nephrotoxicity in as many as half of all patients. This can be attenuated by pre-hydration
Treatment of Ganciclovir Resistant CMV Klompas
· cidofovir has been noted in case reports to cause bone marrow suppression and ocular disease including iritis, uveitis, and vitreous hypotonicity.
· Clinical reports of the use of cidofovir in ganciclovir-resistant infection are scarce.
· Cidofovir at high dose significantly delayed progression of however, nephrotoxicity occurred in 24% of patients and proteinuria was detected in 39%.34 in a study with AID patients.
Leflunomide
· Leflunomide is an immunomodulatory drug originally developed for the treatment of Rheumatoid arthritis and approved for that indication by the FDA in 1998.
· Leflunomide has attracted particular interest from the transplant community because in addition to immunosuppressive properties it is active against viruses.
· It is an an agent with simultaneous immunosuppressive and anti-infective properties .
· Leflunomide acts as a protein kinase inhibitor and as a competitive inhibitor of dihydroorotate
· Leflunomide is a prodrug that is rapidly metabolized to the active metabolite, A77 1726. With long-half life 15-18 days, potentiated by substantial enterohepatic recirculation.
· Without a loading dose it is estimated that it would take nearly two months to achieve steady-state plasma concentrations.
· Likewise, after discontinuation of the medication it can take as long as two years for the body to entirely clear the drug.
· Renal excretion is limited.
· Leflunomide’s immunomodulatory properties were the first aspect of the drug to be probed. In a single center, retrospective review, 53 liver and kidney transplant patients who were failing conventional immunosuppressive therapy were treated with leflunomide. Two thirds of renal patients were able to reduce their dose of cyclosporine and prednisone by about a third.
Treatment of Ganciclovir Resistant CMV Klompas
· four out of five patients with liver transplants who tolerated leflunomide were able to stop cyclosporine or FK-506 entirely, while the fifth reduced his dose by 65%.
· There were no cases of allograft rejection.
· adverse effects includes (predominantly anemia, one case of liver enzyme elevation).
· Human CMV isolates were tested for susceptibility to leflunomide using a plaque reduction assay and proved vulnerable.
· the viral target for leflunomide is distinct from that targeted by ganciclovir, foscarnet, and cidofovir.
· The major toxicity of leflunomide is transaminase elevation (less than three times the upper limit of normal) that generally resolve with discontinuation of the drug.
· Cases of hepatic necrosis and death from liver failure have been reported but are rare. (0.02 to 0.04%)
· Patients with pre-existing liver disease, heavy alcohol intake, or concurrent viral hepatitis should not be given leflunomide.
· Other adverse effects reported diarrhea (17-33%), hypertension (6-12%), reversible alopecia (8-11%), and rash (10-14%).
· In addition, there have been case reports of weight loss and pancytopenia.
· Leflunomide is contraindicated in pregnancy due to reports of fetal death and teratogenesis in human subjects.
Treatment of Ganciclovir Resistant CMV Klompas
Leflunomide caused hyperbilirubemia in patient with allogeneic bone marrow transplant necessitate stopping treatment. Four weeks after stopping therapy, the patient’s CMV viremia recurred.
Anecdotal evidence also exists on the use of leflunomide to treat CMV viremia in solid organ transplant patients at the Cleveland Clinic. Patients treated with leflunomide in combination with ganciclovir or valganciclovir. All had sustained reduction or clearance of viremia but CMV viremia recurred at a low level when the ganciclovir was discontinued. There is speculation that this is related to underdosing of leflunomide. None of these patients suffered any hepatotoxicity .
2- reflect on your practice
among our transplant patient , positive CMV infection being treated with valgancyclovir orally treatment dose 900mg bd until we get 2 negative PCR, no resistance cases were observed.
Summary:
Cytomegalovirus (CMV) infection is a common and serious complication of immunosuppression
in solid organ and bone marrow transplant recipients, and in patients with AIDS. Untreated
CMV infection is associated with a high risk for the development and progression of CMV
disease, allograft dysfunction, and death. First line treatment is
ganciclovir, but , a lot off centres have reported a little but rising incidence of ganciclovir
resistant .
Ganciclovir Mechanism of Action and Drug Resistance:
Ganciclovir is a guanosine analogue that inhibits DNA polymerase. Mutations arising in UL97 phosphotransferase lead to ganciclovir resistance. mutations arising in the DNA polymerase gene UL54 also confer resistance to ganciclovir. Different UL97 mutations are associated with different degrees of ganciclovir resistance .
Definition:
Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml.
Ganciclovir resistance can also be detected via genotype analysis to assess for known mutations in the UL54 and UL97 genes. Ganciclovir resistance is uncommon at baseline amongst untreated patients but arises rapidly after prolonged exposure to antiviral agents
Among solid organ transplant recipients, the prevalence of CMV resistance ranges between 0
and 15%.
Risk factors for ganciclovir resistance include
1- CMV seronegativity at transplant when receiving a seropositive organ .
2- degree of immunosuppression .
3- magnitude of CMV viremia .
4- prolonged exposure to anti-CMV medication.
Note: D-VE TO R –VE appear to be at particular risk of both CMV infection and ganciclovir Resistance.
In one study Patients with ganciclovir resistant disease suffered a statistically significant decrease in survival compared to those with ganciclovir sensitive disease.
Prevention of Ganciclovir Resistant CMV Infection:
In light of the serious morbidity associated with ganciclovir resistant infection and the lack of a clearly efficacious second line therapy, efforts to prevent the emergence of ganciclovir resistance are warranted.
The FDA approval of the valyl ester prodrug of ganciclovir valganciclovir in 2001, introduced a
more potent option for CMV prophylaxis and maintenance therapy of disease in both transplant
recipients and AIDS patients. Valganciclovir is approximately ten times more bioavailable than
oral ganciclovir. Since ganciclovir resistance is thought to be related to prolonged exposure to
sub therapeutic plasma concentrations of ganciclovir, valganciclovir offered a potential means to
in solid organ transplant population, valganciclovir was shown to be superior to oral ganciclovir for the
prevention of resistant CMV infection decrease resistance while retaining the convenience and safety of an oral agent.
Foscarnet :
The primary alternative to ganciclovir for the treatment of CMV viremia and disease is foscarnet.
Foscarnet was approved by the FDA in 1991. Foscarnet is a direct competitive inhibitor of DNA
polymerase.
The major limitation to greater use of foscarnet has been its adverse effect profile. Foscarnet is
associated with renal toxicity, electrolyte abnormalities, and seizures.
Patients treated with ganciclovir were significantly more likely to suffer neutropenia while those
treated with foscarnet had a greater incidence of nephrotoxicity and electrolyte abnormalities.
The toxic reactions usually resolved after discontinuing foscarnet. No permanent disability or death resulted from toxic reactions was reported .
Overall, foscarnet and ganciclovir are of similar efficacy but that foscarnet is less well tolerated. foscarnet is useful agent to use against ganciclovir resistant CMV but treatment will be limited in some patients by nephrotoxicity and/or electrolyte abnormalities.
Combination therapy with dose reduced ganciclovir and foscarnet :
The investigators reasoned that synergy between the two agents would permit lower dosing of each agent and consequent mitigation of their different toxicity profiles.
Cidofovir:
Cidofovir was approved by the FDA in 1996 for the treatment of cytomegalovirus infection. it inhibits DNA polymerase activity.
it should given intravenously but need only be administered once or twice per week. Like ganciclovir and foscarnet, resistance to cidofovir is low at baseline but rises .
in one study cidofovir resistance was identified in 4.1 and 6.6% of blood and urine culture specimens
respectively. After three months of cidofovir therapy, 29% of patients had a resistant blood or
urine isolate. Notably, prolonged treatment of CMV infection with ganciclovir can also lead to the
development of cross-resistance to cidofovir.
The popularity of cidofovir therapy has been limited by its adverse effect profile. Cidofovir can
cause nephrotoxicity in as many as half of all patients. Clinical reports of the use of cidofovir in ganciclovir-resistant infection are scarce.
Leflunomide:
Leflunomide is an immunomodulatory drug originally developed for rheumatoid
arthritis and approved by the FDA in 1998. Leflunomide has attracted particular interest from the transplant community because in addition to immunosuppressive properties it is active against viruses.
Leflunomide acts as a protein kinase inhibitor and as a competitive inhibitor of dihyrdoorotate
dehydrogenase, the intracellular enzyme required for pyrimidine synthesis. It specifically
inhibits denovo pyrimidine synthesis and hence selectively inhibits activated lymphocytes since
resting lymphocytes are able to synthesize pyrimidines via a salvage pathway. Leflunomide is a
prodrug that is rapidly metabolized to the active metabolite, A77 1726. The drug has a long-half
life on the order of 15-18 days potentiated by substantial enterohepatic recirculation. Without a
loading dose it is estimated that it would take nearly two months to achieve steady-state plasma
concentrations. Likewise, after discontinuation of the medication it can take as long as two year
for the body to entirely clear the drug. Renal excretion is limited.
The major toxicity of leflunomide is transaminase elevation. Patients with pre-existing liver disease, heavy alcohol intake, or concurrent viral hepatitis should not be given leflunomide
Other adverse effects reported include diarrhea, hypertension ,reversible alopecia , rash and case reports of weight loss and pancytopenia .
Leflunomide is contraindicated in pregnancy due to fetal death and teratogenesis in human .
Experimental data on the use of leflunomide in human beings is extremely limited and remains
Conclusion:
The management of CMV infection remains a substantial challenge for clinicians caring for
immunocompromised patients. While there are a number of agents active against the virus,
effective therapy requires prolonged drug use which in turn is associated with emergence of drug
resistant virus. CMV resistance to ganciclovir has been reported with increasing frequency in
both AIDS patients treated for CMV retinitis and in recipients of both bone marrow and solid
organ transplants. The alternative therapies foscarnet and cidofovir both appear to have good in
vivo activity against cytomegalovirus but both are limited by their propensity to cause acute
renal failure. Given the often tenuous medical status of immuncompromised patients and the
frequent need to simultaneously administer nephrotoxic agents, the risk of renal failure with foscarnet and cidofovir limits their attractiveness as anti-CMV agents. The use of reduced dose
combination therapy appears to deliver potent antiviral therapy with less risk of nephrotoxicity
but this approach requires further study. The novel immunomodulatory agent leflunomide holds
promise as a future agent for the management of CMV since it both potentiates
immunosuppression and suppresses CMV reproduction. Unlike foscarnet and cidofovir it does
not appear to be nephrotoxic but can cause transaminase elevation. The longterm effectiveness,
tolerability, and ideal settings for the use of leflunomide remain to be defined by ongoing and
future studies.
Q2 – reflect on your practice .
In our center
1- We have no facility to prove CMV drug resistance .
2- Clinically we did not face drug resistant CMV .
3- We never used second line anti CMV drug .
4- We have no facility to diagnose the UL97 and UL 54 gen mutation.
5- We have no experience with foscarnet and cidofovir drug use .
6- We never use combined anti viral drug therapy.
7- We never use leflonmide in the treatment of CMV .
-Definition of ganciclovir resistance
It can be tested either phenotypically or genotypically. The gold standard test is plaque reduction assay( plaque reduction or DNA hybridization IC50 of> 6 ug/ ml). It can also be tested via genotype analysis ( mutation in UL54 and UL97 gene)
–Mechanism of gancyclovir resistance
Activation of ganciclovir require phospho
rylation. After phosphorylation it acts as a competitive substrate for DNA polymerase. Phosphorylaion is accomplished by the phosphotransferase produced by the gene UL97. Mutation in UL97 phosphotransferase leading to ganciclovir resistance.
–Risk factors for ganciclovir resistance
1. Serostatus- D+/R-
2. Prolong exposure to antiviral agent
3. UL97 gene mutation
4. Lung transplantation
-Prevention of ganciclovir resistance
Oral valganciclovir prophylaxis with adequate dose and duration.
–Treatment of ganciclovir resistance
Ganciclovir resistant CMV infections has not been comprehensively studied. The existing literature consists exclusively of case reports & case series describing the outcomes of treatment for patients with resistant infection.
-Foscarnet
The primary alternative to ganciclovir for the treatment of CMV viremia and disease is foscarnet.
Foscarnet was approved by the FDA in 1991. Foscarnet is a direct competitive inhibitor of DNA polymerase.Unlike ganciclovir, it does not need to be phosphorylated in order to inhibit CMV DNA polymerase.
Since it is not dependent on the CMV phosphotransferase UL97 it retains activity against CMV isolates with UL97 mutations that are resistant to ganciclovir.
Mutations in the DNA polymerase gene UL54.
The risk of resistance increases with the duration of foscarnet therapy.
The major limitation to greater use of foscarnet has been its adverse effect profile:
Nephrotoxicity,
Electrolytes Disturbances (Hypocalcemia , Hypomagnesemia , Hypokalemia, Hypophosphatemia),
Seizures,
Genital ulcers,
Infusion-related symptoms (fatigue, anxiety, nausea, numbness/tingling).
-Dose reduced ganciclovir and foscarnet combination
Combined Ganciclovir and Foscarnet offer more promising treatment with less dose and side effects.
Other observations show less target treatment response and more side effects as electrolyte abnormality.
–Cidofovir
It is a monophosphorylated cytosine analogue, require phosphorylation to impedes DNA polymerase activity.
Given IV once or twice per week.
Prolonged treatment with ganciclovir can also lead to cross-resistance to cidofovir. Likewise, treatment with cidofovir alone can confer resistance to ganciclovir
Adverse effect profile; nephrotoxicity reduced by (pre-hydration and the use of probenecid), bone marrow suppression and ocular disease.
-Leflunomide
It specifically inhibits activated lymphocytes as a protein kinase inhibitor and competitive inhibitor of dihyrdoorotate dehydrogenase, the intracellular enzyme needed for pyrimidine production. It has immunomodulatory, immunosuppressive, and anti-viral effects. Inhibits CMV via final virion assembly rather than DNA synthesis. It lasts 15–18 days. It has the potential to inhibit a multidrug-resistant CMV. Side effects include in Transaminases, diarrhea, hypertension, reversible alopecia, dermatitis, weight loss, and pancytopenia.
Treatment of Ganciclovir Resistant Cytomegalovirus Infection :
Summary:
Ganciclovir Mechanism of Action and Drug Resistance:
Once active it is a competitive substrate for DNA polymerase and slows the replication of CMV DNA by DNA polymerase. UL54 and UL97 genes mutations lead to resistance
Definition:
Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml. Where the IC50 is the concentration value required to inhibit 50% of CMV growth. Genotype analysis helps to assess known mutations in the UL54 and UL97 genes.
Prevalence:
Prevalence ranges from 0-15 % and it is higher with the lung transplant. Renal is around 2%.
Risk Factors for Resistance :
D+ / R-
Lymphocyte depleting agent at induction time.
CMV viral load
Prolonged antiviral treatment
Other agents for Ganciclovir Resistant CMV Infection :
Reflection:
It looks like very old article as the most recent evidence was 2004 and they accessed FDA webpage Oct 2004 (Ref 40).
No information about the article, where and when it was published and if it peer reviewed or not therefore it is hard to assess the accuracy of the information given.
We haven’t seen such case in our center
Introduction
Mechanism of Action of Ganciclovir and Drug Resistance
Definition of resistance to ganciclovir
Prevalence and Risk Factors for Resistance
Treatment of Ganciclovir Resistant CMV Infection
—————————————————————————————————
Foscarnet
Combination therapy with dose reduced ganciclovir and foscarnet
Cidofovir
Leflunomide:
Reflection in practice:
We have used oral valganciclovir for routine CMV prophylaxis. We did not encounter any CMV disease or resistance to this agent.
1. Please summarise this article.
Introduction
Gancyclovir and Valagancyclovir has been recommended as the first line of treatment and prophylaxes for CMV infection post-transplant.
Many centres have reported rising incidence of ganciclovir resistant CMV infections.
Ganciclovir Mechanism of Action and Drug Resistance
Definition of resistance:
– CMV growth can be quantified by counting viral plaque formation or by a DNA hybridization technique.
– The concentration of ganciclovir required to inhibit 50% of CMV growth is the IC50 value.
– Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml.
· Genotype analysis to detect mutations on UL97 and UL54 genes can also assess Ganciclovir resistance.
– It takes less time and labour, and is not limited by the need to culture CMV
Prevalence and Risk Factors for Resistance
Around 2 % for Gancyclovir, around 4% cross resistance to Foscarnet
Risk factors:
· CMV seronegativity at transplant (D+/R-)
· degree of immunosuppression,
· magnitude of CMV viremia,
· prolonged exposure to anti-CMV medication.
Prevention and treatment of Ganciclovir Resistant CMV Infection
Valganciclovir – valyl ester prodrug of ganciclovir
· Ten times more bioavailable and more potent than Gancyclovir for CMV prophylaxis and treatment of CMV disease in both transplant recipients and AIDS patients.
Foscarnet
· direct competitive inhibitor of DNA polymerase.
– Because of different mechanisms of action and gene mutations, synergistic action demonstrated in vitro by the two agents even against ganciclovir resistant isolates.
– Result of Reduced dose ganciclovir and foscarnet Combination therapy was good in a study, while clinically not translated in the other.
Cidofovir
Leflunomide
Conclusions:
2. Reflect on Practice
In India, due to less use of Induction ATG, we don’t see much of CMV infection, although we don’t routinely monitor CMV viremia due to cost.
Many years back, I have seen 3 patients in my practice in India –
2005 and 2010- 2 patients with CMV disease involving Renal allograft dysfunction – responded to IV Gancyclovir for 1 week followed by oral Valgancyclovir – responded well.
2014 – 1 patient with extensive CMV disease, encephalitis, colitis, graft dysfunction associated with rejection (ACR + ABMR), flared up very fast, and in spite of IV antiviral therapy succumbed to the illness.
In my current practice in Kenya, we don’t see symptomatic CMV disease, although we don’t routinely monitor CMV DNA on follow up.
1. Please summarise this article.
CMV infection is prevelant in immunocompromised recipient in solid organ transplantation.
Valagancyclovir, Gancyclovir has been recommended as the first line of treatment and prophylaxes.
The incidence of resistance has been reported increasing. Also it has association with prolong exposure to genciclovir.
Mechanism of action,
The drug gancyclovir is a guanosine analogue when phosphorelated it competitively inhibits viral DNA polymerase and inhibit CMV replication.
It became active in three steps, it has association with prolong exposure to genciclovir.
Mutations are firstly, UL97 in which enzyme will affect active drug generation adherence resistance development, second, UL54 it makes mutation in DNA polymerase and resistance.
The risk of developing ganciclovir resistance looks to very according to the organ transplantation, immunosuppression load and protocol.
Risk and prevalence.
The prevalence of resistance in solid organ transplant is around <15%.
Risk increases with immunosuppression load and protocol,
Seropositivity and negativity,
Magnitude of CMV load,
Prolong exposure to gencyclovir.
Prevention of Resistance.
Valganciclovir is 10 times more potent than ganciclovir.
Incidence of resistance is more in ganciclovir than valganciclvir.
Foscarnet;
It’s a competitive inhibitor of DNA polymerase.
It was approved by FDA at 1991 for second line treatment of resistant vs alternate treatment of CMV.
Side effects are nephrotoxicity, electrolyte misbalance, and fits.
It can be used combined with ganciclovir with better effect with low dose and less side effect.
Other second line drugs are Cidofovir, and Leflonamide,
2. Please reflect on your practice;
We have treated patients with CMV disease and syndrome, firtunatly they had responded to ganciclovir very well.
Introduction:
Definition of resistance:
Prevalence and Risk Factors for Resistance
Prevention of Ganciclovir Resistant CMV Infection
Valganciclovir
Foscarnet
Combination therapy with dose reduced ganciclovir and foscarnet
Cidofovir
Leflunomide
Conclusion:
Ganciclovir Mechanism of Action and Drug Resistance:
Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase.
Mutations arising in UL97 phosphotransferase lead to ganciclovir resistance.
Also mutation in the DNA polymerase gene UL54 also confer ganciclovir resistance.
Most patients develop only UL97 mutations, however, prolonged exposure to ganciclovir can give rise to simultaneous UL54 and UL97 mutations.
UL54 mutations can confer cross resistance to Foscarnet and cidofovir since these agents also target CMV DNA polymerase.
Ganciclovir resistance:
Can be assayed either phenotypically or Geno typically.
The “gold standard” test is the plaque reduction assay:
In which human fibroblasts are cultured with ganciclovir at various defined concentrations.
Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml.
Genotype analysis mutations in the UL54 and UL97 genes.
Prevalence and Risk Factors for Resistance:
The prevalence of CMV resistance ranges between 0 and 15%.
Arises rapidly after prolonged exposure to antiviral agents.
The risk of developing ganciclovir resistance does seem to vary according to the organ transplanted, highest in lung transplant lower in renal and liver transplant.
CMV seronegativity at transplant when receiving a seropositive organ,
Degree of immunosuppression,
Magnitude of CMV viremia,
And Prevention of Ganciclovir Resistant CMV Infection prolonged exposure to anti-
CMV medication.
Valganciclovir:
Ability to temper ganciclovir resistance has been demonstrated in comparative studies.
Valganciclovir shown to be superior to oral ganciclovir for the prevention of resistant CMV infection.
Foscarnet:
Foscarnet is a direct competitive inhibitor of DNA polymerase.
Unlike ganciclovir, it does not need to be phosphorylated in order to inhibit CMV DNA polymerase. Since it is not dependent on the CMV phosphotransferase UL97 it retains activity against CMV isolates with UL97 mutations that are resistant to ganciclovir.
Mutations in the DNA polymerase gene UL54, however, do confer Foscarnet resistance and can sometimes be selected for by prolonged ganciclovir therapy.
Adverse effect profile:
Renal toxicity, electrolyte abnormalities ( Hypocalcemia, Hypomagnesemia Hypophosphatemia, hypokalemia) and seizures.
Infusion-related symptoms (fatigue, anxiety, nausea, numbness/tingling).
Combination therapy with dose reduced ganciclovir and Foscarnet:
A promising avenue for the future treatment of ganciclovir resistant CMV infection has been the use of combination ganciclovir and Foscarnet at reduced doses.
Cidofovir:
A monophosphorylated cytosine analogue which, like ganciclovir, is further phosphorylated intracellularly to form a compound that impedes DNA polymerase activity.
Cross-resistance to cidofovir in transplant patients treated with ganciclovir alone has also been reported in other series. Likewise, treatment with cidofovir alone can confer resistance to ganciclovir.
Cidofovir therapy has been limited by its adverse effect profile, nephrotoxicity.
Case reports to cause bone marrow suppression and ocular disease including iritis, uveitis, and vitreous hypotonicity.
Leflunomide:
Acts as a protein kinase inhibitor and as a competitive inhibitor of dihydroorotate dehydrogenase, the intracellular enzyme required for pyrimidine synthesis.
Its potential to inhibit a multidrug-resistant CMV isolate was confirmed in vitro by plaque redز
Major toxicity
of Leflunomide is transaminase elevation,
Diarrhea (17-33%), hypertension (6-12%), reversible alopecia (8-11%), and rash (10-14%).
Weight loss44 and pancytopenia.45 Among 39 renal transplant patients treated with high-dose Leflunomide as an immunosuppressant, the mean hematocrit dropped by an average of 15%
Contraindication in pregnancy due to reports of fetal death and teratogenesis in human
Conclusion:
The use of reduced dose combination therapy appears to deliver potent antiviral therapy with less risk of nephrotoxicity but this approach requires further study. The novel immunomodulatory agent Leflunomide holds promise as a future agent for the management of CMV .
Fortunately we don’t encountered resistance in our practice.
In this article Michael Kloamps has tried to look into treatment strategies for Ganciclovir resistant CMV.
Ganciclovir Mechanism of Action and Drug Resistance
Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase. In order to become active it must first be phosphorylated in three steps to a triphosphorylated form. Once phosphorylated, it acts as a competitive substrate for DNA polymerase and slows the replication of CMV DNA by DNA polymerase. Phosphorylation is accomplished by the phosphotransferase produced by the gene UL97. Mutations arising in UL97 phosphotransferase lead to ganciclovir resistance. Similarly, mutations arising in the DNA polymerase gene UL54 also confer resistance to ganciclovir. Different UL97 mutations are associated with different degrees of ganciclovir resistance.
UL54 mutations can confer cross- resistance to foscarnet and cidofovir since these agents also target CMV DNA polymerase. Ganciclovir resistance does not appear to impair viral virulence.
Ganciclovir resistance can be assayed either phenotypically or genotypically.
Prevention of Ganciclovir Resistant CMV Infection
The treatment of ganciclovir resistant CMV infections has not been comprehensively studied. The existing literature consists exclusively of case reports and case series describing the outcomes of treatment for patients with resistant infections. Controlled trials comparing various alternative strategies have yet to be published. In light of the serious morbidity associated with ganciclovir resistant infection and the lack of a clearly efficacious second line therapy, efforts to prevent the emergence of ganciclovir resistance are warranted.
The FDA approval of the valyl ester prodrug of ganciclovir valganciclovir in 2001, introduced a more potent option for CMV prophylaxis and maintenance therapy of disease in both transplant recipients and AIDS patients. Valganciclovir is approximately ten times more bioavailable than oral ganciclovir. Since ganciclovir resistance is thought to be related to prolonged exposure to subtherapeutic plasma concentrations of ganciclovir, valganciclovir offered a potential means to decrease resistance while retaining the convenience and safety of an oral agent.
Treatment of Ganciclovir Resistant CMV
Foscarnet
The primary alternative to ganciclovir for the treatment of CMV viremia and disease is foscarnet. Foscarnet was approved by the FDA in 1991. Foscarnet is a direct competitive inhibitor of DNA polymerase. Unlike ganciclovir, it does not need to be phosphorylated in order to inhibit CMV DNA polymerase. Since it is not dependent on the CMV phosphotransferase UL97 it retains activity against CMV isolates with UL97 mutations that are resistant to ganciclovir. Mutations in the DNA polymerase gene UL54, however, do confer foscarnet resistance and can sometimes be selected for by prolonged ganciclovir therapy. Like ganciclovir, the risk of resistance increases with the duration of foscarnet therapy.
The major limitation to greater use of foscarnet has been its adverse effect profile. Foscarnet is associated with renal toxicity, electrolyte abnormalities, and seizures.
Combination therapy with dose reduced ganciclovir and foscarnet
A promising avenue for the future treatment of ganciclovir resistant CMV infection has been the use of combination ganciclovir and foscarnet at reduced doses.
Cidofovir
Cidofovir was approved by the FDA in 1996 for the treatment of cytomegalovirus infection. It is a monophosphorylated cytosine analogue which, like ganciclovir, is further phosphorylated intracellularly to form a compound that impedes DNA polymerase activity. The pharmacology of cidofovir is such that it has to be given intravenously but need only be administered once or twice per week.
Anecdotal evidence also exists on the use of leflunomide to treat CMV viremia in solid organ transplant patients at the Cleveland Clinic.
We at our center have never observed any Ganciclovir resistance so have no real experience of dealing with such patients
Dear All
I’m very pleased with your summary and the feedback of some of you suggesting the article might be old in view of the emergence of new treatments for CMV resistant cases. Most of the alternatives for Gancyclvir/valgancyclovir have untoward side effects. Hence the emergence of other alternatives such as maribavir which is unfortunately very expensive.
Please read the attached NICE guidance published few days ago for Maribavir as an alternative treatment for CMV resistant cases.
https://www.nice.org.uk/guidance/ta860/resources/maribavir-for-treating-refractory-cytomegalovirus-infection-after-transplant-pdf-82613605967557
Treatment of Ganciclovir Resistant Cytomegalovirus Infection
Summary:
Ganciclovir Mechanism of Action and Drug Resistance: Once active it is a competitive substrate for DNA polymerase and slows the replication of CMV DNA by DNA polymerase. UL54 and UL97 genes mutations lead to resistance
Definition: Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml. Where the IC50 is the concentration value required to inhibit 50% of CMV growth. Genotype analysis helps to assess known mutations in the UL54 and UL97 genes.
Prevalence: ranges from 0-15 % and it is higher with the lung transplant. Renal is around 2%.
Risk Factors for Resistance
D+ / R-
Lymphocyte depleting agent at induction time.
CMV viral load
Prolonged antiviral ttt
Other agents for Ganciclovir Resistant CMV Infection
Reflection:
It looks like very old article as the most recent evidence was 2004 and they accessed FDA webpage Oct 2004 (Ref 40).
No information about the article, where and when it was published and if it peer reviewed or not therefore it is hard to assess the accuracy of the information given.
Personally I have not encounter a case before.
Well done. It’s too old. Are you aware of NICE guidance Jan 2023?
Thanks professor. I was not aware and I looked it now.
“Maribavir for treating refractory cytomegalovirus infection after transplant”
https://www.nice.org.uk/guidance/ta860/chapter/1-Recommendations
Summary
· Definition of ganciclovir resistance: detected by either human fibroblasts culture with ganciclovir at various defined concentrations. (The concentration of ganciclovir required to inhibit 50% of CMV growth is the IC50 value) . Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6μg/ml.5 Or by genotype analysis to assess for known mutations in the UL54 and UL97 genes.
· Prevalence in SOT: varies from 0-15 %.
· Risk factors: prolonged use of antiviral prophylaxis as in high risk recipients for CMV infection as heart-lung transplantation, use of induction therapy, intensive IS or repeated courses of anti rejection therapy.
· The higher bioavailability of valganciclovir contributed to decrease in ganciclovir resistance.
· Lines of ttt of ganciclovir resistant CMV:
o Foscarnet: but it causes nephrotoxicity, electrolyte disturbance.
o Cidofovir: needs hepatic and renal adjustment.
o Although foscarnet and cidofovir are potent, but their side effects limit their use.
o Combination ganciclovir and foscarnet at reduced doses is better than monotherapy due to synergistic effect, also decrease side effects of both.
o Novel immunomodulatory agent, leflunomide: better safety profile but can cause mild transaminitis, but not used in combination with ganciclovir.
Reflect on our practice”
I don’t have experience on ganciclovir resistant CMV, but we use oral valganiclovir in prophylaxis and IV ganciclovir for ttt of tissue invasive disease .
Treatment of Ganciclovir Resistant Cytomegalovirus Infection
Mechanism of Action and Drug Resistance
Prevalence and Risk Factors for Resistance
Resistance – uncommon at baseline amongst untreated patients but arises rapidly after prolonged exposure to antiviral agents
one cohort of AIDS patients newly diagnosed with CMV retinitis-UL97 mutation was found in only 1 out of 195 eyes tested
similar cohort of untreated patients-CMV cultured from blood or urine was resistant to ganciclovir in 2% of patients and resistant to foscarnet in 4% of patients
Another study- baseline prevalence of ganciclovir resistance was 0.9% in blood specimens and 2.7% in urine specimens
-After six months of treatment predominantly with intravenous ganciclovir, the prevalence of patients with resistant blood or urine isolates rose to 11.4%. By nine months of therapy, resistant virus was cultured from 27.5% of patients
Risk factors
Foscarnet
Combination therapy with dose reduced ganciclovir and foscarnet
Cidofovir
Leflunomide
1. Please summarise this article
Cytomegalovirus (CMV) is a serious infection, seen in immunosuppressed patients, and if untreated, is associated with increased risk of CMV disease, graft dysfunction and mortality. Injection Ganciclovir is first-line treatment for CMV infection and disease.
Ganciclovir mechanism of action and drug resistance:
UL97 phosphotransferase phosphorylates Ganciclovir, which inhibits CMV DNA polymerase. Ganciclovir resistance can be assayed genotypically by mutations in UL97 and UL54 genes , and phenotypically by plaque reduction or DNA hybridization IC50 (concentration of ganciclovir required to inhibit 50% of CMV growth) value of >6 microgram/ml.
Risk factors for ganciclovir resistance include CMV seronegativity of recipient with donor being seropositive, degree of immunosuppression, magnitude of CMV viremia, and prolonged exposure to anti-CMV medications. All these risk factors lead to reduced survival. Ganciclovir resistance prevalence rages from 0-15% in solid organ transplants (SOT), with increased prevalence in lung transplant and least among kidney transplant recipients.
Prevention: Valganciclovir use, in convenient oral formulation, has helped in reducing ganciclovir resistance and has been shown to be superior to oral ganciclovir to reduce ganciclovir resistance in SOT. Valganciclovir has been associated with neutropenia.
Treatment: Foscarnet inhibits CMV polymerase and UL54 mutations (but not UL97 mutations) confer foscarnet resistance. Foscarnet has efficacy similar to ganciclovir, but is associated with increased incidence of seizures, infusion-related symptoms, genital ulcers, nephrotoxicity, hypocalcemia, hypomagnesemia, hypophosphatemia, and hypokalemia, and, hence, is less well tolerated. Combination of low dose ganciclovir and foscarnet has not been shown to be superior to full dose ganciclovir. Cidofovir can be given intravenously once or twice a week, but a prolonged use of ganciclovir leads to cross-resistance to cidofovir. Cidofovir is associated with nephrotoxicity in 50% cases, bone marrow suppression, and ocular disease. Leflunomide inhibits pyrimidine synthesis (inhibiting activated lymphocytes), and has anti-viral properties in addition to immunosuppressive effects. It inhibits CMV by interfering with final virion assembly, and is associated with anemia, diarrhea, hypertension, alopecia, rash, loss of weight, and elevated liver enzymes. When used in combination with ganciclovir, CMV viremia improved, but recurred on stopping ganciclovir.
Conclusion: CMV treatment is challenging, especially once ganciclovir resistance develops. Foscarnet and cidofovir have been used in such a scenario, but are associated with nephrotoxicity. Reduced ganciclovir dose with other agents in combination needs further evaluation. Leflunomide use has potential due to lack of nephrotoxicity, but needs further evaluation.
2. Please reflect on your practice
Tablet Valganciclovir is used as CMV prophylaxis in transplant patients in our unit. CMV infection is very rarely seen in our unit. In a scenario with CMV infection, we use Injection Ganciclovir and have not come across any patient with Ganciclovir resistance till now.
TREATMENT OF GANCICLOVIR RESISITANT CMV.
DEFINITION.
-Its plaque reduction or DNA hybridization IC50 of >6 microgram/mls. Plaque reduction is the gold standard for testing resistance.
-Can also be assessed genotypically using UL54 & UL 97 mutation. This is cheap and needs less time to get results.
PREVALENCE & RISK FACTORS.
-In SOT,CMV Resistance it is varied between 0-15% irrespective of organ transplanted.
-Risk factors;
-Prolonged exposure to antivirals esp anti CMV therapy, most infection occur after a median of 10/12 after treatment.
PREVENTION OF GANCICLOVIR RESISTANT CMV INFECTION.
1.VALGANCICLOVIR.
-Valganciclovir is x10 more bioavailable than PO ganciclovir and thus decreased resistance with same efficacy orally. It has also demonstrated superiority to PO valganciclovir for prevention of resistant CMV infection.
2.FOSCARNET.
-Main alternative for treatment of CMV infection and disease,
-Direct competitive inhibitor of DNA polymerase and doesn’t need to be phosphorylated to block CMV DNA polymerase.
-Effective against UL97 but not UL54 mutation.
-Risk for foscarnet resistance increases with prolonged foscarnet therapy .
-Has an extensive SE compared to ganciclovir; Neutropenia ,seizures, genital ulcers and infusion related symptoms(More nephrotoxicity and les neutropenia compared to ganciclovir with a x4 probability of switching to alternative treatment compared to foscarnet)
3.COMBINED THERAPY.- DECREASED DOSE GANCICLOVIR +FOSCARNET.
-In HIV studies and BM transplant recipients, combined therapy has so far shown some superiority to monotherapy. This is an option but more studies are needed in ganciclovir resistance cohort to get more evidence for this to be applied in clinical practice beyond studies.
4.CIDOFOVIR.
-Given parenterally x1/x2 per week.
-Resistance increases with more drug exposure.
-Its resistance has also been associated with ganciclovir resistance.
-Associated with nephrotoxicity in up to 50% of patients on it which can be decreased with proper rehydration.
5.LEFLUNOMIDE.
-Its a protein kinase inhibitor and a competitive inhibitor of dihydoorotate dehydrogenase.
-Has been found to be able to inhibit multidrug resistant CMV but with a major side effect of transaminase elevation.
-Cheaper and effective but more studies needed in various SOT.
CONCLUSION.
-Ganciclovir resistant CMV treatment is challenging. It is mostly associated with prolonged use ,Cidofovir and foscarnet are good alternatives but associated with renal toxicities. Use of reduced dose combination therapy is a potential option with less nephrotoxicity but needs more studies before application in clinical studies.
REFLECTION ON PRACTICE.
Limited resources has limited my exposure to this and as such I haven’t been able to work up a pt fully, appropriately manage and follow up as required by protocol. I will definitely put into practice the above going forward.
Treatment of Ganciclovir Resistant Cytomegalovirus Infection
Introduction
Cytomegalovirus (CMV) infection is a common and serious complication of immunosuppression in solid organ and bone marrow transplant recipients, and in patients with AIDS.
Untreated CMV infection is associated with a high risk for the development and progression of CMV disease, allograft dysfunction, and death.
Ganciclovir is the first line treatment for CMV infections in transplanted patients
However, resistance to this agent is manifesting Alternative therapies have been discussed in this article
Mechanism of Action of Ganciclovir and Drug Resistance
Ganciclovir enters the virus and is activated by phosphotransferase
The UL97 gene codes for this phosphotransferase enzyme
Activated Ganciclovir inhibits viral DNA polymerase to prevent replication
Mutations of the UL97 and UL54 gene result in resistance to ganciclovir
Definition of resistance to ganciclovir
Genetic test is positive for presence of mutations of the UL97 and UL54 gene
Culture of CMV within human fibroblasts produce viral plaques which can be inhibited by Ganciclovir. CMV is deemed resistant if plaque reduction (gold standard test) is sub-optimal despite using higher concentrations of ganciclovir.
Prevalence and Risk Factors for Resistance
Prevalence of CMV resistance ranges from 0 to 15% among solid organ transplant recipients
At baseline, ganciclovir resistance is uncommon amongst untreated patients but after prolonged sub-optimal dose exposure to this agent it rises rapidly
CMV Positive organ transplanted into CMV negative patient
Higher magnitude of CMV viremia also leads to prolonged dosing and resistance
Treatment of Ganciclovir Resistant CMV Infection
Foscarnet:
Direct competitive inhibitor of DNA polymerase requiring no phosphorylation (thus unaffected by UL97 mutation)
Associated with electrolyte abnormalities and renal toxicity as well as seizures.
Neutropenia is less common with Foscarent than with Ganciclovir
Combination therapy with dose reduced ganciclovir and foscarnet
Combination therapy is superior to monotherapy with the alternative agent alone
Dosage guideline: Half the dose of gancyclovir and two-thirds of the dose of foscarnet
Results in better efficacy and reduced side effects than either agent alone
Cidofovir:
Monophosphorylated cytosine analogue which requires further phosphorylation like ganciclovir leading to DNA polymerase inhibition
Given IV once or twice weekly
Causes nephrotoxicity (50% of cases), myelosuppression and ocular disease – hence not widely used
Leflunomide:
Leflunomide is an immunomodulatory drug originally developed for the treatment of rheumatoid arthritis. In addition to immunosuppressive properties, it is active against viruses.
Leflunomide acts as a protein kinase inhibitor and as a competitive inhibitor of dihydroorotate dehydrogenase, the intracellular enzyme required for pyrimidine synthesis.
It has the potential to inhibit a multidrug-resistant CMV isolate.
There were reported clinical and endoscopic resolution of GI CMV after using leflunomide in 4 renal transplant patients from India.
Adverse effects; hepatic necrosis, death from liver failure, diarrhea, hypertension, reversible alopecia, and rash.
Leflunomide is contraindicated in pregnancy due to reports of fetal death and teratogenesis in human subjects.
Causes transaminase elevation, diarrhoea, rash, and hypertension
Dose: a 100mg oral loading dose once daily for three days followed by 20mg/day for three months
Reflection in practice:
I Have one patient Resistant to PO valganciclovir and IV Ganciclovir and we started on Fosacarnet waiting for Genetic tests for Mutations of the UL97 and UL54 gene
Treatment of Ganciclovir Resistant Cytomegalovirus Infection.
Definition
Ganciclovir resistance can be assayed either phenotypically or genotypically which is defined as a plaque reduction or DNA hybridization IC50 of > 6μg/ml and also can be detected by genotype analysis to assess for known mutations in the UL54 and UL97 genes.
Among solid organ transplant recipients, the prevalence of CMV resistance ranges between 0 and 15%.
Risk factors of ganciclovir resistance :
=CMV seronegativity at transplant when receiving a seropositive organ, =Degree of immunosuppression.
=Magnitude of CMV viremia.
=Prolonged exposure to anti-CMV medication.
Ganciclovir Mechanism of Action and Drug Resistance.
Ganciclovir is a competitive substrate for DNA polymerase that inhibit CMV DNA replications but it become activated when be phosphorylated by the phosphotransferase produced by the gene UL97 and so mutations arising in the DNA polymerase gene UL54 also confer resistance to ganciclovir.
Prevention of Ganciclovir Resistant CMV Infection.
=Val ganciclovir offered a potential means to decrease resistance while retaining the convenience and safety of an oral agent.
=Foscarnet: is considered an alternative to ganciclovir for the treatment of CMV viremia and disease and it does not need to be phosphorylated. Like ganciclovir, the risk of resistance increases with the duration of Foscarnet therapy. in AIDS patients with CMV retinitis, for example, the incidence of resistance at 6, 9, and 12 months of therapy rose from 13% to 24% to 37% respectively.
Foscarnet is as effective as Val ganciclovir but had a greater incidence of nephrotoxicity and electrolyte abnormalities and less well tolerated but is considered an option for resistance.
=Combination therapy with dose reduced ganciclovir and Foscarnet.
Combination therapy is superior to monotherapy with the alternative agent alone, and also shown less side effects revealed by many studies.
=Cidofovir.
Cidofovir is a monophosphorylated cytosine analogue which, like ganciclovir impedes DNA polymerase activity, given intravenously but need only be administered once or twice per week. Also, prolonged treatment of CMV infection with ganciclovir can also lead to the development of cross-resistance to Cidofovir and Cidofovir can cause nephrotoxicity in as many as half of all patients.
Leflunomide.
Leflunomide’s immunomodulatory properties and considered prodrug that is rapidly metabolized to the active metabolite, A77 1726. The drug has a long-half life on the order of 15-18 day. It has a good role as antiviral and can discontinue CNI or substituted by MMF to avoid the risk of rejection and the major toxicity of leflunomide is transaminase elevation and anemia .
It is considered an option for CMV viremia treatment in VGC resistance with good outcome but bear in mind the side effects.
Conclusion .
CMV is one of the most common infection in immunocompromised patient such as AIDS and in solid organ transplant recipients, VGC resistance is a rare condition but it is still challenges and many alternative medications can be used such as Foscarnet, Cidofovir, Leflunomide and combinations of small doses of these medications.
Please reflect on your practice.
CMV screening post kidney transplant and importance of prophylactic treatment is better than treatment.
VGC is the most common drug used in CMV treatment and VGC resistance is uncommon and I had never met it before, but keeping the other option in mind is important and to be familiar with these medications and their side effects.
I note your personal experience of no resistant cases
Introduction :
Immunosuppressive status in solid organ and bone marrow transplant recipients, and in patients with AIDS will lead to many complications including opportunistic infections , CMV is one of the common and serious infections which if left untreated is associated with a high risk for the development serious complication can lead to graft loss and even death . ganciclovir is the mainstay of treatment but unfortunately many centres reported increasing incidence of resistance .
Ganciclovir Mechanism of Action and Drug Resistance
Ganciclovir is a guanosine analogue which acts by inhibition of CMV DNA polymerase that slows the replication of CMV DNA,this occur by phosphorylation of ganciclovir with the enzyme phosphotransferase which is produced by the gene UL97,mutation of this gene will lead to ganciclovir resistance . Similarly, mutations arising in the DNA polymerase gene UL54 also confer resistance to ganciclovir which also causes cross resistance to foscarnet and cidofovir since these agents also target CMV DNA polymerase.
Definition:
Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml (plaque reduction assay is the gold standard test, ). Ganciclovir resistance can also be detected via genotype analysis to assess for known mutations in the UL54 and UL97 genes.
Prevalence and Risk Factors for Resistance :
Ganciclovir resistance arises rapidly after prolonged exposure to antiviral agents . In a prospective study done to illustrate the impact of treatment upon the prevalence of ganciclovir resistance,blood and urine cultures from 108 AIDS patients newly diagnosed with CMV retinitis were tested for ganciclovir resistance .After six months of treatment predominantly with intravenous ganciclovir, the prevalence of patients with resistant blood or urine isolates rose to 11.4%. By nine months of therapy, resistant virus was cultured from 27.5% of patients.
Risk factors for the acquisition of ganciclovir resistance include : CMV seronegativity at transplant when receiving a seropositive organ, degree of immunosuppression, magnitude of CMV viremia, and prolonged exposure to anti-CMV medication. Seronegative recipients of seropositive organs appear to be at particular risk of both CMV infection and ganciclovir resistance.
Prevention of Ganciclovir Resistant CMV Infection
The treatment of ganciclovir resistant CMV infections has not been comprehensively studied. Because of serious morbidities associated with emergence of ganciclovir resistance every effort to prevent it is warranted . When compared to oral ganciclovir valganciclovir is approximately ten times more bioavailable this why valganciclovir is more effective in prophylaxis than oral ganciclovir
.
Foscarnet :
Foscarnet is a direct competitive inhibitor of DNA polymerase.It does not need to be phosphorylated in order to inhibit CMV DNA polymerase so it is not affected by mutation in UL97 gene however prolog ganciclovir therapy can cause UL54 gene mutation that lead to foscarnet resistant .
Combination therapy with dose reduced ganciclovir and foscarnet :
Ganciclovir and foscarnet resistance are usually associated with different gene mutations which promising avenue for the future treatment of ganciclovir resistant CMV infection , Moreover, investigators reasoned that synergy between the two agents would permit lower dosing of each agent and consequent mitigation of their different toxicity profiles.
Cidofovir :
Is a monophosphorylated cytosine analogue which, like ganciclovir, is further phosphorylated intracellularly to form a compound that impedes DNA polymerase activity .Resistance to cidofovir is low at baseline but unfortunately rises.
Leflunomide:
It is an immunomodulatory drug but also has antiviral activity .It act as a protein kinase inhibitor and as a competitive inhibitor of dihydroorotate dehydrogenase, the intracellular enzyme required for pyrimidine synthesis , leflunomide inhibits CMV by interfering with final virion assembly rather than with DNA synthesis evident by electron microscopy . As such, the viral target for leflunomide is distinct from that targeted by ganciclovir, foscarnet, and cidofovir,,
Conclusion :
The management af CMV is still challenging especially with rising resistant to ganciclovir and toxicity of other medications hence the novel immunomodulatory agent leflunomide holds promise as a future agent for the management of CMV since it both potentiates immunosuppression and suppresses CMV reproduction.
in our centre we used to give valganciclovir as prophylaxis to CMV post kidney transplant we didn’t encounter any resistance of valganciclovir or even iv ganciclovir .
I note your personal experience of no resistant cases
II. Treatment of Ganciclovir Resistant Cytomegalovirus Infection
Summarise this article
Introduction
– CMV is a common infection among immunosuppressed individuals. It is associated with graft dysfunction, graft loss and even death in severe cases.
– Ganciclovir is the drug of choice but there is associated drug resistance hence the need for alternative regimens.
Ganciclovir mechanism of action
– Ganciclovir is a guanosine analogue which inhibits CMV DNA polymerase. It has to undergo phosphorylation for it to become active.
Ganciclovir mechanism of drug resistance
– Mutation in the UL97 gene which is responsible for phosphorylation
– Mutations in the DNA polymerase gene UL54. This mutation can also confer cross-resistance to foscarnet and cidofovir since they also target CMV DNA polymerase
– Prolonged exposure to subtherapeutic plasma concentrations of ganciclovir can cause simultaneous UL54 and UL97 mutation which is associated with a higher level of resistance to ganciclovir.
Definition of ganciclovir resistance
– Ganciclovir resistance can be determined phenotypically or genotypically.
– The plaque reduction assay in which human fibroblasts are cultured with ganciclovir at different concentrations is the gold standard test.
– Ganciclovir resistance is defined as a plaque reduction or DNA hybridisation IC50 of > 6µg/ml.
– Genotypic analysis involves assessment for mutations in the UL54 and UL97 genes. This method is faster, less labour intensive and there is no need for cultured specimens.
Prevalence of ganciclovir resistance
0-15% among SOT recipients
Risk factors for ganciclovir resistance
– Prolonged exposure to subtherapeutic plasma concentrations of ganciclovir
– Degree of immunosuppression
– Donor/ recipient CMV serostatus (D+/ R-)
– Magnitude of CMV viremia
Prevention of ganciclovir resistant CMV infection
– Use of valganciclovir which is a prodrug of ganciclovir and is almost 10 times more bioavailable than oral ganciclovir.
Treatment for ganciclovir resistant CMV
Options available include: –
– It is a direct competitive inhibitor of DNA polymerase. It does not require phosphorylation for it to be active hence is not affected by UL97 gene mutation.
– However, UL54 gene mutation confers foscarnet resistance. Risk of resistance increases with the duration of foscarnet therapy.
– Side effects include: – nephrotoxicity, seizure, electrolyte abnormalities
– Ganciclovir and foscarnet resistance are associated with different gene mutations.
– Effective in pre-emptive treatment of CMV.
– It is a monophosphorylated cytosine analogue, it requires further phosphorylation.
– It is given intravenously once or twice per week.
– Prolonged ganciclovir use can result in the development of cidofovir cross-resistance.
– Side effects – nephrotoxicity, bone marrow suppression, ocular disease
– It is an immunomodulatory drug with immunosuppressive and antiviral properties.
– It acts as a protein kinase inhibitor with limited renal excretion
– Side effects – anaemia, elevated transaminases, diarrhoea, hypertension
– Avoid leflunomide in pregnancy, in patients with heavy alcohol intake, pre-existing liver disease, concurrent viral hepatitis
Conclusion
Ganciclovir resistant CMV is more prevalent among AIDs patients managed for CMV retinitis and recipients of SOTs and BMTs.
Foscarnet and cidofovir are the alternative therapies but are nephrotoxic making the risks greater than the benefits involved.
Although studies are still ongoing, leflunomide seems to be a promising agent since it potentiates immunosuppression as well as suppresses CMV replication. It is not nephrotoxic but it can cause an elevation in the transaminases.
Reflect on your practice
Unfortunately, we do not have the expertise to assess for ganciclovir resistance at our transplant center. And again, we do not routinely use ganciclovir due to the cost implications.
Generally, we offer valganciclovir as treatment for CMV disease.
I appreciate sharing your experience and challenges of treating CMV
Thank you Prof.
Treatment of Ganciclovir Resistant Cytomegalovirus Infection
Michael Klompas in this review article explained the diagnosis and mechanism of ganciclovir resistance, prevalence of risk factors, and the strategies of treatment and prevention.
Mechanism of action of ganciclovir and resistance to ganciclovir
Ganciclovir is an analogue of guanosine and inhibits DNA polymerase by competitive inhibition. Before the formation of the nucleoside analogue, it undergoes phosphorylation by viral and cellular kinases mediated by UL97 gene, hence mutation of this gene can lead to drug resistance. Prolonged exposure to ganciclovir can lead to simultaneous UL54 and UL97 mutations which leads to cross resistance of the virus to other inhibitors of DNA polymerase like cidofovir and foscarnet.
Definition of ganciclovir resistance
Phenotypic definition: Ganciclovir resistance is defined as a plaque reduction or DNA hybridization IC50 (the concentration of ganciclovir required to inhibit 50% of CMV growth) value of > 6µg/ml.
Genotypic definition: Detection of UL54 and UL97 genetic mutation.
Prevalence and risk factors for ganciclovir resistance
The prevalence of CMV resistance among recipients of solid organ transplant ranges between 0 and 15%. Ganciclovir resistance is uncommon, but risk tend to rise following a prolonged exposure to antiviral agents.
In a study of 108 patients with AID having CMV retinitis, baseline prevalence of ganciclovir resistance was 0.9% and 2.7% from blood and urine respectively. At 6 months of treatment with ganciclovir, 11.4% had resistance with both urine and blood isolates and this rose to 27.5% at 9 months (OR -9.06; P =0.003).
According to a study of prevalence of drug resistant isolates among transplant recipients infected with CMV at two Chicago transplant centres, between 1994-2001.The risk of developing ganciclovir resistance is highest with lung transplant and least with kidney transplant recipients. Heart and liver transplantation is in between but the risk is higher in heart compared with liver transplant recipients.
Risk factors for development of ganciclovir resistance include CMV seronegative recipient transplanted with a CMV positive donor, intense immunosuppression, magnitude of CMV viremia, and prolonged use of anti-CMV medication.
Prevention of Ganciclovir Resistant CMV Infection
Use of valganciclovir, valyl ester prodrug of ganciclovir valganciclovir with 10 times better bioavailability. In an open label trial comparing valganciclovir to intravenous ganciclovir in 148 AIDS patients with CMV retinitis, valganciclovir was superior to oral ganciclovir for the prevention of resistant CMV infection. Other studies also demonstrate similar results.
Other treatment options are foscarnet, ganciclovir and foscarnet combination, Cidofovir, Leflunomide.
Conclusion
Treatment of ganciclovir resistance is still a difficult job for clinicians as the available options such as foscarnet and cidofovir are nephrotoxic. However, leflunomide is promising but will require long term studies.
Reflecting on my own practice
Honestly, I have never treated a patient with CMV disease before and never had to treat a resistant case. But this definitely has enriched my knowledge on the approach when confronted with such.
I note your personal experience of no resistant cases
Please summarise this article
# Introduction:
* (CMV) infection is frequent and severs complication of immunosuppression post SOT, BMT as well as patients with AIDS.
*The first line for treatment of CMV infections and disease is ganciclovir, but, drug resistant may develop.
*The objective of this review to emphasise treatment strategies available to treat ganciclovir-resistant CMV infection including the currently approved alternative agents foscarnet and cidofovir, the use of combination ganciclovir and foscarnet at reduced doses, and the novel immunomodulatory agent, leflunomide.
# Ganciclovir Mechanism of Action and Drug Resistance
*Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase.
*For activation it should be first be phosphorylated in three steps to a triphosphorylated.
*Phosphorylation is associated with phosphotransferase produced by the gene UL97.
* Mutations arising in UL97 phosphotransferase lead to ganciclovir resistance.
* Also mutations arising in the DNA polymerase gene UL54 also confer resistance to ganciclovir.
# Definition:
*Ganciclovir resistance can be assayed either phenotypically or genotypically.
* The “gold standard” test is the plaque reduction assay.
*The concentration of ganciclovir required to inhibit 50% of CMV growth is the IC50 value. Resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6μg/ml.5
*Genotype analysis when there is a mutation in the UL54 and UL97 genes.
# Prevalence and Risk Factors for Resistance:
*Ganciclovir resistance is not frequent at baseline between untreated patients but arises rapidly following prolonged exposure to antiviral agents.
*In SOT, the prevalence of CMV resistance ranges between 0 and 15%.
*The risk of developing ganciclovir resistance does seem to vary according to the organ transplanted.
# The risk factors include:
* CMVseostutus (D+ /R-).
*The degree of immunosuppression.
*Magnitude of CMV viremia.
*Prolonged exposure to anti-CMV medication.
# Prevention of Ganciclovir Resistant CMV Infection:
* The FDA approval of the valyl ester prodrug of ganciclovir valganciclovir in 2001.
# Valganciclovir:
Is approximately ten times more bioavailable than oral ganciclovir.
*Valganciclovir offered a potential means to decrease resistance while retaining the convenience and safety of an oral agent.
# Foscarnet:
*Is a primary alternative to ganciclovir for the treatment of CMV viremia and disease.
*It is a direct competitive inhibitor of DNA polymerase, and does not need to be phosphorylated, so UL97 it retains activity against CMV isolates with UL97 mutations that are resistant to ganciclovir.
* Mutations in the DNA polymerase gene UL54, however, do confer foscarnet resistance
*The risk of resistance increases with the duration of foscarnet therapy.
*The major limitation to greater use of foscarnet has been its adverse effect profile (associated with renal toxicity, electrolyte abnormalities, and seizures).
*Patients treated with ganciclovir were suffer from neutropenia.
*Foscarnet is useful agent against ganciclovir resistant CMV but treatment will be limited in some patients by nephrotoxicity and/or electrolyte abnormalities.
# Combination therapy with dose reduced ganciclovir and foscarnet:
*The rationale for this strategy stems from the recognition that ganciclovir and foscarnet resistance are usually associated with different gene mutations.
*Trial data from the AIDS literature showing that combination therapy is superior to monotherapy with the alternative agent alone.
* synergy between the two agents would permit lower dosing of each agent and consequent mitigation of their different toxicity profiles.
# Cidofovir:
*It is a monophosphorylated cytosine analogue which need further phosphorylated to impedes DNA polymerase activity.
*Given I/V once or twice per week.
*Like ganciclovir and foscarnet, resistance to cidofovir is low at baseline but rises under sustained drug pressure.
*The use of cidofovir has been limited due to its adverse effect profile, it lead to nephrotoxicity in half of all patients. This can be degraded by pre-hydration and use of probenecid.
*Also it causes bone marrow suppression, iritis, uveitis, and vitreous hypotonicity.
# Leflunomide:
*Is an immunomodulatory drug, in addition to immunosuppressive properties it is active against viruses.
*It inhibits denovo pyrimidine synthesis and inhibits activated lymphocytes.
* Leflunomide is a prodrug that is rapidly metabolized to the active metabolite, A77 1726.
*Has a long-half life on the order of 15-18 days potentiated by substantial enterohepatic recirculation.
*It is potential to inhibit a multidrug-resistant CMV isolate was confirmed in vitro by plaque reduction assays using a virus recovered from a heart transplant patient with CMV pneumonitis.
*The major toxicity of leflunomide is transaminase elevation, diarrhea, hypertension, reversible alopecia, rash, weight loss and pancytopenia, and the effect appeared to be dose related.
*It is contraindicated in pregnancy due to reports of fetal death and teratogenesis.
* The novel immunomodulatory agent leflunomide holds promise as a future agent for the management of CMV since it both potentiates immunosuppression and suppresses CMV reproduction.
* Unlike foscarnet and cidofovir it does not appear to be nephrotoxic but can cause transaminase elevation.
*The longterm effectiveness, tolerability, and ideal settings for the use of leflunomide remain to be defined by ongoing and future studies.
# Please reflect on your practice:
I have not seen gancyclovir resistance case in my center, we use valgancyclovir and gancyclovir. I think this article will help us in the future to deal with such case.
I note your personal experience of no resistance to ganciclovir
Introduction:
Ganciclovir:
Mechanism of Action and Drug Resistance:
Prevention of Ganciclovir Resistant CMV Infection
Options for treatment of ganciclovir resistant CMV:
1. Foscarnet:
2. Combination therapy with dose reduced ganciclovir and foscarnet:
3. Cidofovir:
4. Leflunomide:
.
We have good experience with the use oral valganciclovir for the treatment of CMV infection (combined with the reduction of antimetabolite dose). Followed by Prophylactic dose of valganciclovir for 3 months. Probably we don’t see resistant cases because we usually use oral valganciclovir rather than ganciclovir.
I note your personal experience of no resistance to Valganciclovir
Summary of the article
Treatment of Ganciclovir Resistant Cytomegalovirus Infection
Ganciclovir is the first line treatment for CMV infections and disease, however, many centres have reported a small but rising incidence of ganciclovir resistant CMV infections.
Ganciclovir Mechanism of Action and Drug Resistance
a) Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase.
· The active substance is the triphosphorylated form.
· Phosphorylation is accomplished by the phosphotransferase produced by the gene UL97.
· Prolonged exposure to ganciclovir can give rise to simultaneous UL54 and UL97 mutations.
· The concentration of ganciclovir required to inhibit 50% of CMV growth is the IC50 value.
b) Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6μg/ml.
c) Ganciclovir resistance can be detected via genotype analysis for mutations in the UL54 and UL97 genes.
d) Identification of a ganciclovir resistant isolate was correlated with the development of CMV retinitis in the contralateral eye.
Prevalence of Ganciclovir resistance
According to Chicago transplant centres, 1994-2001, the prevalence of CMV resistance ranges between 0 and 15%. With highest resistance in lung transplants and lowest one in kidney and liver transplants.
Risk Factors for Ganciclovir Resistance
a) CMV seronegativity at transplant when receiving a seropositive organ.
b) Degree of immunosuppression.
c) Magnitude of CMV viremia.
d) Prolonged exposure to anti-CMV medication.
Prevention of Ganciclovir Resistant CMV Infection
a) Valganciclovir is approximately ten times more bioavailable than oral ganciclovir. It offered a potential means to decrease resistance while retaining the convenience and safety of an oral agent.
b) valganciclovir was shown to be superior to oral ganciclovir for the prevention of resistant CMV infection.
Treatment of ganciclovir resistant CMV infection
1. Foscarnet
a) Foscarnet is the primary alternative to ganciclovir for the treatment of CMV viremia and disease.
b) Foscarnet is a direct competitive inhibitor of DNA polymerase, it does not need to be phosphorylated in order to inhibit CMV DNA polymerase.
c) It retains activity against CMV isolates with UL97 mutations.
d) Like ganciclovir, the risk of resistance increases with the duration of foscarnet therapy.
e) Foscarnet is associated with renal toxicity, electrolyte abnormalities, seizures and infusion related symptoms(fatigue, anxiety, nausea, numbness/tingling).
2. Combination therapy with dose reduced ganciclovir and foscarnet
a) combination therapy is superior to monotherapy with the alternative agent alone.
b) Combination therapy has been shown to be effective in pre-emptive therapy of CMV antigenemia in non- ganciclovir resistant bone marrow transplant patients.
c) Synergy between the two agents would permit lower dosing of each agent and consequent mitigation of their different toxicity profiles.
d) Ganciclovir at half the usual therapeutic dose (5mg/kg IV q24h) combined with Foscarnet at two-thirds the usual induction dose (125mg/kg IV q24h).
e) According to British investigators:
· Combination therapy were less likely to have PCR negative blood at 14 days(the difference wasn’t statistically significant).
· Combination therapy was also more likely to cause renal dysfunction and electrolyte abnormalities.
3. Cidofovir
a) It is a monophosphorylated cytosine analogue, to be given intravenously once or twice per week.
b) Prolonged treatment of CMV infection with ganciclovir can also lead to the development of cross-resistance to cidofovir.
c) Cidofovir can cause nephrotoxicity in as many as half of all patients, bone marrow suppression and ocular disease including iritis, uveitis, and vitreous hypotonicity.
4. Leflunomide
a) Leflunomide is an immunomodulatory drug originally developed for the treatment of rheumatoid arthritis. In addition to immunosuppressive properties it is active against viruses.
b) Leflunomide acts as a protein kinase inhibitor and as a competitive inhibitor of dihyrdoorotate dehydrogenase, the intracellular enzyme required for pyrimidine synthesis.
c) It has the potential to inhibit a multidrug-resistant CMV isolate.
d) There were reported clinical and endoscopic resolution of GI CMV after using leflunomide in 4 renal transplant patients from India.
e) Adverse effects; hepatic necrosis, death from liver failure, diarrhea, hypertension, reversible alopecia, and rash.
f) Leflunomide is contraindicated in pregnancy due to reports of fetal death and teratogenesis in human subjects.
5. Combination of leflunomide and foscarnet
a) After starting a combination of leflunomide and foscarnet,for patient with BM transplant, the patient’s CMV viral load decreased from 226,000 copies per ml to an undetectable level over the course of six weeks.
b) Leflunomide was stopped after three weeks of therapy due to hyperbilirubinemia.
c) While the agent was clearly effective in clearing the patient’s CMV viremia, it is possible that it contributed to her death from progressive liver failure.
Please reflect on your practice
Encountered cases of CMV infection were responding well to Valganciclovir and no noticed resistance to the drug.
I note your personal experience of no resistance to Valganciclovir
Treatment of Ganciclovir Resistant Cytomegalovirus Infection:
Introduction
Cytomegalovirus (CMV) infection is a common and serious complication of immunosuppression in solid organ and bone marrow transplant recipients, and in patients with AIDS.
Ganciclovir Mechanism of Action and Drug Resistance:
Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase Once phosphorylated, it acts as a competitive substrate for DNA polymerase and slows the replication of CMV DNA by DNA polymerase. Phosphorylation is accomplished by the phosphotransferase produced by the gene UL97.
Mutations arising in UL97 phosphotransferase lead to ganciclovir resistance.
Definition:
Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml.5
Prevalence and Risk Factors for Resistance:
Risk factors for the acquisition of ganciclovir resistance include CMV sero negativity at transplant when receiving a sero positive organ, degree of immunosuppression, magnitude of CMV viremia, and prolonged exposure to anti-CMV medication.
Seronegative recipients of seropositive organs appear to be at particular risk of both CMV infection and ganciclovir resistance.
Ganciclovir resistant CMV disease was diagnosed a median of 10 months after transplant (range 7-12 months) suggesting an association with prolonged ganciclovir exposure. The outcomes for patients with ganciclovir resistance in this study were poor
Prevention of Ganciclovir Resistant CMV Infection:
The treatment of ganciclovir resistant CMV infections has not been comprehensively studied. The existing literature consists exclusively of case reports and case series describing the outcomes of treatment for patients with resistant infections
Valganciclovir:
Valganciclovir’s ability to temper ganciclovir resistance has been demonstrated in comparative studies
Foscarnet :
The primary alternative to ganciclovir for the treatment of CMV viremia and disease
Combination therapy with dose reduced ganciclovir and foscarnet
A promising avenue for the future treatment of ganciclovir resistant CMV infection has been the use of combination ganciclovir and foscarnet at reduced doses
Cidofovir :
Cidofovir was approved by the FDA in 1996 for the treatment of cytomegalovirus infection. It is a monophosphorylated cytosine analogue which, like ganciclovir, is further phosphorylated intracellularly to form a compound that impedes DNA polymerase activity
Leflunomide
Leflunomide’s activity against cytomegalovirus was discovered when investigators hypothesized that the predominance of phosphoproteins within CMV might imply that intracellular construction of virions is dependent upon protein kinase
Conclusion :
The novel immunomodulatory agent leflunomide holds promise as a future agent for the management of CMV since it both potentiates immunosuppression and suppresses CMV reproduction Unlike foscarnet and cidofovir it does not appear to be nephrotoxic but can cause transaminase elevation
Thank you
In solid organ and bone marrow transplant recipients and AIDS patients, cytomegalovirus (CMV) infection is a common and significant immunosuppressive consequence. CMV illness, allograft malfunction, and death are more likely with an untreated CMV infection.
Ganciclovir Mechanism of Action and Drug Resistance
Guanosine analogue ganciclovir inhibits CMV DNA polymerase. It must be phosphorylated three times to become active. Phosphorylated, it competes with DNA polymerase and reduces CMV DNA replication. UL97 phosphotransferase phosphorylates. UL97 phosphotransferase mutations cause ganciclovir resistance. Similarly, DNA polymerase gene UL54 mutations cause ganciclovir resistance.
Definition
Ganciclovir resistance can be tested phenotypically or genotypically. Ganciclovir-cultured human fibroblasts are the “gold standard” test. Plaque formation or DNA hybridization can measure CMV growth. Ganciclovir’s IC50 inhibits 50% of CMV growth. Plaque reduction or DNA hybridization IC50 > 6μg/ml indicates ganciclovir resistance.
Resistance Risk and Prevalence
Solid organ transplant recipients have up to 15% CMV resistance. Ganciclovir resistance is rare in untreated patients, although it rapidly builds after sustained sub-optimal dosage exposure. Higher CMV viremia prolongs dosing and resistance.
Prevention of Ganciclovir Resistant CMV Infection
In 2001, the FDA approved valganciclovir, a strong valyl ester prodrug of ganciclovir, for CMV prevention and disease maintenance in transplant recipients and AIDS patients. Valganciclovir is ten times bioavailable. Valganciclovir may reduce ganciclovir resistance by reducing prolonged exposure to subtherapeutic plasma concentrations.
In solid organ transplant patients, valganciclovir reduced resistant CMV infection better than oral ganciclovir, whereas in AIDS patients with CMV retinitis, it was equivalent to intravenous ganciclovir.
Foscarnet
Foscarnet, an alternative to ganciclovir, inhibits DNA polymerase directly without phosphorylation. -Active against UL97 but not UL54 CMV isolates. Foscarnet treatment lengthens resistance risk. Renal toxicity, electrolyte imbalances, and convulsions are all adverve effects of Foscarnet use. Foscarnet withdrawal eliminated all adverse affects.
Combination therapy with dose reduced ganciclovir and foscarnet
In vitro synergy between dose-reduced ganciclovir and foscarnet against ganciclovir-resistant isolates supports combination therapy. Combination therapy outperformed alternative agent monotherapy in trials. Reduce agent dose and toxicity.
Cidofovir
Monophosphorylated cytosine analogues inhibit DNA polymerase activity through phosphorylation. It is given IV twice weekly. Long-term ganciclovir treatment can also cause cidofovir resistance. Cidofovir alone can make ganciclovir resistant. Pre-hydration and probenecid minimize nephrotoxicity, bone marrow suppression, and eye disease.
Leflunomide
It specifically inhibits activated lymphocytes as a protein kinase inhibitor and competitive inhibitor of dihyrdoorotate dehydrogenase, the intracellular enzyme needed for pyrimidine production. It has immunomodulatory, immunosuppressive, and anti-viral effects. Inhibits CMV via final virion assembly rather than DNA synthesis. It lasts 15–18 days. It has the potential to inhibit a multidrug-resistant CMV. Side effects include in Transaminases, diarrhea, hypertension, reversible alopecia, dermatitis, weight loss, and pancytopenia.
In conclusion, clinicians treating immunocompromised patients struggle with CMV infection. There are several antiviral medications, however extended drug use leads to drug-resistant virus. AIDS patients treated for CMV retinitis and bone marrow and solid organ transplant recipients are increasingly resistant to ganciclovir. Foscarnet and cidofovir have strong in vivo action against CMV but cause acute renal failure.
Thank you
Introduction
Mechanism of Action of Ganciclovir and Drug Resistance
Definition of resistance to ganciclovir
Prevalence and Risk Factors for Resistance
Treatment of Ganciclovir Resistant CMV Infection
—————————————————————————————————
Foscarnet
Combination therapy with dose reduced ganciclovir and foscarnet
Cidofovir
Leflunomide:
Reflection in practice:
We have used oral valganciclovir for routine CMV prophylaxis. We did not encounter any CMV disease or resistance to this agent.
Thank you.
Please summarise this article
Introduction:
In patients with AIDS and transplant recipients who are immunosuppressed, CMV infection poses a major risk for illness onset, disease progression, allograft failure, and mortality. Ganciclovir resistant CMV infections are rising.
Ganciclovir Mechanism of Action and Drug Resistance
Ganciclovir inhibits CMV DNA polymerase and resistance to Ganciclovir resulted from mutations in UL97 phosphotransferase and UL54, which can also confer cross-resistance to Foscarnet and Cidofovir. Prolonged exposure to Ganciclovir can give rise to these mutations simultaneously.
Definition
Ganciclovir resistance can be assayed either;
Phenotypically: (Gold Standard): plaque reduction or DNA hybridization IC50 of > 6µg/ml.
Genotypically: Analysis to assess for known mutations in the UL54 and UL97 genes.
Prevalence and Risk Factors for Resistance
Ganciclovir resistance is uncommon at baseline amongst untreated patients but arises rapidly after prolonged exposure to antiviral agents
The prevalence of CMV resistance ranges (from 0 -15%). The risk is varying according to the organ transplanted.
This is felt to reflect different degrees of immunosuppression and different protocols for the prophylaxis of CMV. Being the most among Lung transplant recipients 15.2% followed by heart transplant recipients at 5.3%.
Risk factors for the acquisition of ganciclovir resistance include:
· CMV seronegativity at transplant when receiving a seropositive organ,
· Degree of immunosuppression,
· Magnitude of CMV viremia,
· Prolonged exposure to the anti-CMV medication.
Prevention of Ganciclovir Resistant CMV Infection
Valganciclovir offered a potential means to decrease resistance while retaining the convenience and safety of an oral agent
Foscarnet
Foscarnet is the main substitute for ganciclovir in the management of CMV viremia and illness. Ganciclovir and foscarnet have comparable efficacy, although foscarnet is less well tolerated.
The major limitation to the greater use of foscarnet has been its adverse effect profile.
· Renal toxicity,
· Electrolyte abnormalities,
· Seizures.
Combination therapy with dose-reduced ganciclovir and foscarnet
Researchers reasoned that a synergistic interaction between the two drugs would allow for lower doses of each agent, so reducing their disparate toxicity profiles. AIDS trial data demonstrating that combination treatment outperforms monotherapy with the substitute drug alone,
Cidofovir
Another effective alternative. It must be taken intravenously, although just once or twice a week is necessary to be successful.
At first, cidofovir resistance is minor, but it increases when the drug is used frequently.
Notably, prolonged use of ganciclovir to treat CMV infection can also result in the emergence of cross-resistance to cidofovir.
The major toxicity
· Nephrotoxicity in as many as half of all patients.
· Bone marrow suppression
· Ocular disease including iritis, uveitis, and vitreous hypotonicity.
Leflunomide
Leflunomide is an immunomodulatory medication that was first created for the treatment of rheumatoid arthritis and was given FDA approval for its use in 1998. sparked a lot of interest because it has antiviral effects in addition to immunosuppressive ones.
The major toxicity of leflunomide is
· Transaminase elevation.
· Diarrhea
· Hypertension
· Reversible alopecia
· Rash
· Leflunomide is contraindicated in pregnancy due to reports of fetal death and teratogenesis in human subjects.
Conclusion
· The management of CMV infection is a challenge for clinicians caring for immunocompromised patients, as effective therapy requires prolonged drug use and is associated with the emergence of a drug-resistant virus.
· CMV resistance to ganciclovir is increasing in both AIDS patients and transplant recipients.
· Alternative therapies foscarnet and cidofovir have good in vivo activity against cytomegalovirus, but can cause acute renal failure.
· Reduced dose combination therapy may deliver potent antiviral therapy with less risk of nephrotoxicity, but further study is needed.
· Leflunomide is a novel immunomodulatory agent that both potentiate immunosuppression and suppresses CMV reproduction, but its long-term effectiveness, tolerability, and ideal settings remain to be determined.
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Please reflect on your practice
Generally, in our center, we see a good response to Ganciclovir provided that the patient has had a good preoperative risk assessment, proper prophylaxis & good compliance in a way that we didn’t have to resort to other agents in the treatment of CMV-infected patients.
Thank you.
CMV infection is a serious complication of immunosuppression in transplant recipients. Untreated infection carries the risk of allograft dysfunction, and death. First line treatment is ganciclovir, there is rising incidence of ganciclovir resistant.
Ganciclovir Mechanism of Action and Drug Resistance
Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase. It undergoes phosphorylation to a triphosphorylated form that acts as a competitive substrate for DNA polymerase and slows DNA replication. Phosphorylation occurs by phosphotransferase produced by UL97 gene. Mutations in UL97 phosphotransferase lead to resistance. Mutations in DNA polymerase gene UL54 also confer resistance. Different UL97 mutations causes different degrees of resistance. Most patients develop only UL97 mutations, prolonged ganciclovir exposure can lead to simultaneous UL54 and UL97 mutations which cause higher level resistance. UL54 mutations can confer cross resistance to foscarnet and cidofovir as they target CMV DNA polymerase. Ganciclovir resistance does not impair viral virulence.
Definition
Resistance can be assayed phenotypically or genotypically. The “gold standard” is the plaque reduction assay; fibroblasts are cultured with ganciclovir at various concentrations. CMV growth is quantified by viral plaque formation or DNA hybridization technique. Concentration required to inhibit 50% of growth is the IC50 value. Resistance is defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml. Analysis for mutations is less labour intensive, time consuming, and doesn’t need culture from patient. The correlation between genotype and phenotype is imperfect so genotype-based resistance needs to be interpreted cautiously.
Prevalence and Risk Factors for Resistance
Resistance arises rapidly after prolonged exposure to antivirals. In s study of AIDS patient with CMV retinitis, resistance has increased from 0.9% in blood and 2.7% in urine at baseline to 11.4% after 6 months of treatment and 27.5% at 9 months.
Resistance varies according to the organ transplanted, which reflect different degrees of immunosuppression and prophylaxis protocols.
Risk factors for resistance include CMV seronegativity receiving a seropositive organ, degree of immunosuppression, magnitude of CMV viremia, and prolonged exposure to anti-CMV medication. Seronegative recipients of seropositive organs are at risk of both infection and ganciclovir resistance. Patients with resistant disease has significant decreased survival compared to ganciclovir sensitive disease.
Prevention of Ganciclovir Resistant CMV Infection
The FDA approved valganciclovir in 2001 for prophylaxis and treatment, It is ten times more bioavailable than oral ganciclovir. As resistance is related to prolonged exposure to subtherapeutic doses, valganciclovir decrease resistance. It was equivalence to IV ganciclovir in risk of resistance in AIDS studies, while in transplant population, It was superior to oral ganciclovir for the prevention of resistant infection.
Foscarnet
Foscarnet was approved by the FDA in 1991. It is a direct competitive inhibitor of DNA polymerase, it does not need to be phosphorylated, so it retains activity against CMV with UL97 mutations. However, UL54 mutations, do confer foscarnet resistance which can be induced by prolonged ganciclovir therapy. The risk of resistance increases with duration of foscarnet therapy.
It was proven to be effective in ganciclovir resistant disease.
Studies showed that Foscarnet and ganciclovir have similar efficacy, Foscarnet is associated with renal toxicity, electrolyte abnormalities, and seizures but less neutropenia.
Combination therapy with dose reduced ganciclovir and foscarnet
Ganciclovir and foscarnet resistance are associated with different mutations, Trials showed that combination therapy is superior to monotherapy. Synergy between the two permit lower dosing and mitigation of toxicity.
In a study of six patient with infection refractory to IV ganciclovir. Patients were treated with half dose ganciclovir and foscarnet at two-thirds dose. Foscarnet was titrated to a therapeutic dose over a few days, patients also received CMV hyperimmunoglobulin. All patients had a clinical response in 72-96 hours and cleared their antigenemia in 4-8 weeks. No relapses seen after 12-36 months. All patients had significant hypomagnesemia requiring replacement.
In another trial, half-dose ganciclovir and half-dose foscarnet was associated with less negative PCR at 14 days compared to full dose ganciclovir which reflects the advantage of treating ganciclovir sensitive disease with full dose ganciclovir.
Cidofovir
Cidofovir was approved by FDA in 1996. It is a monophosphorylated cytosine analogue which is phosphorylated to a compound that impedes DNA polymerase. It is given intravenously once or twice per week. Resistance to cidofovir rises with exposure, prolonged treatment with ganciclovir lead to cross-resistance to cidofovir.
In series of 240 transplant recipients prophylaxed with oral ganciclovir, five had ganciclovir resistance. Four of them also had resistant to cidofovir. Likewise, treatment with cidofovir can confer resistance to ganciclovir.
In a cohort of AIDS patients with retinitis, 3 of 9 patients treated with cidofovir developed ganciclovir resistance.
Cidofovir can cause nephrotoxicity, this can be prevented by pre-hydration and probenecid, cidofovir can cause bone marrow suppression and ocular disease and proteinuria. Cidofovir at high dose significantly delayed progression of retinitis.
Leflunomide
Leflunomide was approved for rheumatoid arthritis in 1998. It is and immunosuppressant and antiviral. It a protein kinase competitive inhibitor of dihyrdoorotate dehydrogenase, an enzyme required for pyrimidine synthesis. It inhibits pyrimidine synthesis so inhibits activated lymphocyte.
It has a half-life of 15-18 days due to enterohepatic recirculation.
In a study transplant patients failing conventional immunosuppression, two thirds of patients treated with leflunomide were able to reduce cyclosporine and prednisone dose by a third.
Four out of five liver transplants who tolerated leflunomide were able to stop cyclosporine or FK-506 and the fifth reduced his dose by 65% with no cases of rejection.
In another study, leflunomide was substituted for antimetabolite in 22 kidney transplant failing conventional immunosuppression due to rejection, cyclosporine toxicity, or progressive dysfunction. Six months after conversion, creatinine declined by a mean of 5%, no episodes of rejection.
Leflunomide inhibits CMV by interfering with final virion assembly rather than with DNA synthesis. As such, its viral target is distinct from that targeted by ganciclovir, foscarnet, and cidofovir. So can inhibit a multidrug-resistant CMV.
The major toxicity is transaminitis. Hepatic necrosis and death from liver failure was reported but rare. It should be avoided in patient with pre-existing liver disease, heavy alcohol, or concurrent viral hepatitis. Other adverse effects include diarrhoea, hypertension, reversible alopecia and rash, weight loss and pancytopenia. It is is contraindicated in pregnancy due to reports of fetal death and teratogenesis.
In our centre we mainly use Foscarnet for Gaciclovir resistant disease.
Many thanks for sharing your own experience.
Summary:
Introduction:
Mechanism of action of Ganciclovir:
Resistant definition:
Prevalence & risk factors for Ganciclovir resistant:
Prevention of ganciclovir resistant CMV infection:
Foscarnet:
Cidofovir:
Leflunomide:
Reflection in our practice:
In our practice we use oral valganciclovir as prophylaxis in all the cases. We are not using Gancyclovir at all.
Many thanks for sharing your own experience.
Introduction
Ganciclovir is a guanosine analogue. It works by inhibiting CMV DNA polymerase. It is active in its triphosphorylated form which acts as a competitive substrate for DNA polymerase and slows down the replication of CMV DNA by DNA polymerase. Phosphorylation is achieved by phosphotransferase produced by the gene UL97. Mutations arising from UL97 phosphotransferase and from UL54 (DNA polymerase gene) lead to ganciclovir resistance. UL54 mutations can also lead to resistance in cidofovir and foscarnet and these agents also target CMV DNA polymerase. Ganciclovir resistance does not seem to impair the virulence of the virus.
Definition
There are 2 ways of assaying ganciclovir resistance:
The ‘gold standard’ test to assay ganciclovir resistance is the plaque reduction assay. Human fibroblasts are cultured with ganciclovir at various different concentrations. Counting the viral plaque formations or DNA hybridization can be used to quantify the CMV growth. This method involves detection of mutations in the UL54 and UL97 genes. However, the correlation between the genotype and phenotype is not well founded, hence the genotype-based resistance reports need to be interpreted with caution.
Prevalence & risk factors for resistance
Among solid organ transplant recipients, the prevalence of CMV resistance to ganciclovir ranges from 0-15%. The risk factors for acquiring resistance to ganciclovir include:
It was noted that patients with CMV that is resistant to ganciclovir had a significant reduction in survival compared to those with CMV that was sensitive to ganciclovir.
Patients who receive pancreas transplants receive more potent immune suppression. Investigators noted higher incidence rates of ganciclovir resistance among these patients.
Ganciclovir resistant to CMV disease has been diagnosed a median of 10 months after the transplant.
Treatment of Ganciclovir Resistant Infection
Valganciclovir
Valganciclovir is a valyl ester prodrug of ganciclovir, approved by the FDA in 2001. It is approximately 10 times more bioavailable than ganciclovir, hence it is a more potent option for CMV prophylaxis and maintenance therapy for CMV disease.
Foscarnet
Foscarnet is a direct competitive inhibitor of DNA polymerase, approved by the FDA in 1991. It does not need to be phosphorylated in order to inhibit DNA polymerase. It is the primary alternative to ganciclovir for the treatment of CMV infection. As it is not dependent on UL97 gene for activation, it can act despite those mutations. However, mutation of UL54 may still lead to foscarnet resistance. Similar to ganciclovir, the risk of foscarnet resistance increases with the duration of therapy. It has also been noted that patients treated with ganciclovir had an increased incidence of neutropenia, while patients treated with foscarnet had an increased incidence of electrolyte abnormalities and nephrotoxicity.
Overall, studies have shown that foscarnet has a similar efficacy to ganciclovir, but as foscarnet is less well tolerated it may be a useful alternative agent to use in CMV that is resistant to ganciclovir.
Combination therapy with dose reduced ganciclovir and foscarnet
The rationale behind this approach is based on the fact that their resistance stems from different mutations, reducing their dosage may consequently mitigate their different toxicity profiles, and hence the medications may be better tolerated. One study demonstrated that combination therapy used for patients not responding to ganciclovir cleared the viremia and no relapses were seen. However, the incidence of nephrotoxicity was still increased despite the reduced dose of foscarnet.
Cidofovir
Cidofovir is a monophosphorylated cytosine analogue, which requires further phosphorylation intracellularly to form a compound that acts against DNA polymerase. It was approved by the FDA in 1996 for the treatment of CMV infection. It only requires to be administered once or twice a week. Sustained drug pressure increases the resistance to cidofovir. It has also been noted that prolonged treatment of CMV infection with ganciclovir can lead to the development of cross-resistance to cidofovir and likewise, treatment with cidofovir alone can lead to the resistance to ganciclovir. Cidofovir can lead to nephrotoxicity in as many as half of its patients. This adverse effect can be reduced by prehydration and probenecid, but these methods may also reduce its tolerance. Other adverse effects include bone marrow suppression and ocular disease.
Leflunomide
Leflunomide was approved by the FDA in 1998 to be used for the treatment rheumatic arthritis. Leflunomide acts as a protein kinase inhibitor and as a competitive inhibitor of dihyrdoorotate dehydrogenase, the intracellular enzyme required for pyrimidine synthesis. It is a prodrug that requires to be metabolized into an active form. It requires a loading dose as it has a long half life. It has limited renal excretion. It has been studies that leflunomide has the potential to inhibit multi-drug resistant CMV disease. Its major adverse effect is the elevation of transaminase. There have been cases reported of hepatic necrosis and liver failure due to leflunamide, but it is noted to be rare. Other adverse effects include diarrhea, hypertension, reversible alopecia and skin rashes. Further studies are required to ascertain the level of liver toxicity and its benefits in the use for multi drug resistant CMV infection.
Conclusion
Treatment of CMV disease is especially challenging in transplant recipients. There are a few drug options. Ganciclovir resistance is reportedly increasing, and the use of foscarnet and cidofovir is limited due to their nephrotoxic properties. Leflunomide appears to be promising, but it requires further studies and careful monitoring due to its potential to cause liver toxicity.
Local Practice:
In Kenya, we use IV ganciclovir for treating CMV disease for 5 – 7 days and then convert to valgancicovir once the patient is stable. We have not had a reported case of ganciclovir resistance. We also don’t routinely use valganciclovir for prophylaxis unless if we have used ATG. We monitor patients for CMV immediately post-transplant and then treat if we detect CMV disease
Thank you.
1. Please summarise this article
Treatment of Ganciclovir Resistant Cytomegalovirus Infection
Treatment strategies:
1. Ganciclovir
Mechanism of Action & Resistance
It is a guanosine analogue that inhibits CMV DNA polymerase. It must be phosphorylated (3 phases) before it may become active.
The phosphotransferase produced by the UL97 gene is responsible for phosphorylation.
Ganciclovir resistance results from UL97 phosphotransferase mutations. Changes in the DNA polymerase gene UL54 also result in ganciclovir resistance.
Resistance assays:
The plaque reduction assay:
Is the “gold standard” test
Human fibroblasts are grown with ganciclovir at different specified doses, CMV growth can be measured using a DNA hybridization method or by counting the number of viral plaques that develop.
Genotyping analysis
Mutations in the UL54 & UL97 genes indicate resistance.
It takes less time and effort compared culture CMV method.
Be aware of imperfection in the link between genotype and phenotype.
Prevalence
It is uncommon at first, but it quickly develops following prolonged antiviral exposure.
The prevalence of CMV resistance in SOTs ranges from 0% to 15%.
The risk of developing ganciclovir resistance is highest among lung TXs and is least among liver TXs; this may reflect the degree of IS & protocols used for CMV prophylaxis.
Risk Factors for Resistance
CMV seronegativity at TX when receiving a seropositive organ
Degree of IS
Magnitude of CMV viremia
Number of CMV episodes in the past
Prolonged exposure to anti-CMV medication
Prior exposure to IV ganciclovir
D+/R- organs are at particular risk of both CMV infection & ganciclovir resistance
Pancreas recipients
Prevention of Ganciclovir Resistant CMV Infection
No published RCTs.
No clearly efficacious 2ndline therapy.
FDA approved valganciclovir (a prodrug of ganciclovir) in 2001 as a more potent option for CMV prophylaxis & maintenance therapy of disease.
Through the use of valganciclovir, it may be possible to reduce resistance while maintaining the benefits and security of an oral medication.
Foscarnet
A DNA polymerase that is direct competitive inhibitor.
The main substitute for ganciclovir in the management of CMV viremia & illness.
FDA approval in 1991.
It does not require phosphorylation, unlike ganciclovir, in order to prevent CMV DNA polymerase from working.
It retains effectiveness against CMV isolates that have UL97 mutations and are resistant to ganciclovir because it is not reliant on the CMV phosphotransferase UL97.
However, mutations in the DNA polymerase gene UL54 can sometimes give foscarnet resistance.
Adverse effect profile has been the main barrier to wider adoption of Foscarnet; it is linked to electrolyte imbalances, convulsions, and kidney damage.
Foscarnet & ganciclovir are of similar efficacy but foscarnet is less well tolerated.
Combination therapy with dose reduced ganciclovir & foscarnet
Rationale:
Resistance to ganciclovir & foscarnet is linked to different gene alterations.
Synergy between the two agents even against ganciclovir resistant isolates (in vitro).
Combination is superior to monotherapy with the alternative agent alone.
Synergy between the two agents would permit lower dosing of each agent & lower toxicity profiles.
Cidofovir
FDA approved in 1996 for the treatment of CMV infection. It is a monophosphorylated cytosine analogue that, similar to ganciclovir, further phosphorylation to be able to inhibits DNA polymerase activity.
It is given IV once or twice/week.
Similar to ganciclovir & foscarnet, cidofovir has modest baseline resistance that increases in response to persistent drug pressure.
The toxicity profile of cidofovir restrict its appeal; nephrotoxicity in 50%. This can be mitigated by pre-hydrating & using probenecid.
Other S/Es: iritis, uveitis, vitreous hypotonicity, & bone marrow suppression.
Leflunomide
Leflunomide is an immunomodulatory drug.
It is active against viruses.
It selectively inhibits activated lymphocytes.
It is a prodrug that is rapidly metabolized to the active metabolite, A77 1726.
Has a long-half life (15-18 days).
Leflunomide has potential as a treatment for CMV since it potentiates immunosuppression & inhibits CMV reproduction.
It is not nephrotoxic, in contrast to foscarnet and cidofovir, but it can raise transaminases.
Leflunomide’s long-term efficacy, tolerability, & appropriateness are still being determined by research.
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2. Please reflect on your practice
We have never encountered a true, or confirmed, ganciclovir resistant CMV infection in our transplant center. However, this does not necessarily reflect the real situation; it rather indicates under estimation of the problem. Due to financial issues, many of the logistics for confirming resistant case are lacking.
Thank you. Agree regarding ganciclovir resistance. I have not seen it either.
Summary
Introduction.
Ganciclovir is a guanosine analogue that inhibits DNA polymerase. It is activated by phosphorylation to its triphosphorylated form.
Phosphorylation is accomplished by phosphotransferase produced by gene UL97.
Mutations in UL97 leads to ganciclovir resistance.
Other mutations that confer ganciclovir resistance is UL54 which also causes resistance to cidofovir and forscanet that also inhibit DNA polymerase.
Risk factors
1.Prolonged antiviral exposure.
Initially patients develop UL97 mutations but prolonged exposure to ganciclovir will lead to simultaneous UL54 and UL 97 mutations.
Similarly studies have shown patients with CMV disease not exposed to antivirals have low prevalence of mutations, but with prolonged exposure the prevalence increases.
2.Type of organ transplanted
The risk of resistance seem to be high in heart and lung transplants in comparison to kidney transplants.
This could be associated with the high degree of immunosuppression.
3.Donor and recipients CMV serostatus.
D+/R- have a high risk of CMV infection and resistance.
This could be due to repeated CMV episodes, high exposure of ganciclovir and higher degree of immunosuppression.
Prevention
1.Use of valganciclovir
Valganciclovir is 10 times more bioavailable than oral ganciclovir.
Resistance is thought to occur due to exposure of subtherapeutic plasma concentrations of ganciclovir.
Studies comparing IV ganciclovir and PO valganciclovir, have shown patients treated with IV ganciclovir have higher rate of resistance.
2.Forscanent
Direct inhibitor of DNA polymerase that doesn’t need phosphorylation hence retains activity against UL97 mutated CMV.
However it under goes UL54 mutation resistance which increases with increased exposure.
Forscanet is of similar efficacy as ganciclovir however it is less tolerated due to its side effects profile, thus reserved for ganciclovir resistant CMV.
3.Combination of ganciclovir and forscanet
One study compared the efficacy of combined ganciclovir and forscanet in reduced doses. The rationale behind this is, their activity is synergistic and they undergo different mutations thus can have activity against resistant strains.This study all patients cleared their antigenimia with no recurrence after. The only adverse effect was hypomagnesemia with no other adverse effects.
However a UK study that compared full dose ganciclovir compared with combined reduced forscanet and ganciclovir, had different results. Patients in the combined arm were less likely to have a negative CMV PCR at two weeks and were more likely to have nephrotoxicity and electrolyte imbalance.
4.Cidofovir
It is a monophosphorylated cytosine analogue that required phosphorylation to inhibit DNA polymerase.
Thus there is cross resistance between cidofovir and ganciclovir.
Its use is also limited by its side effect profile that include nephrotoxicity, bone marrow suppression and ocular disease.
Limited data on its use for ganciclovir resistant CMV.
5.Leflunomide
It’s an immunomodulatory drug with activity against viruses.
Its viral target is different from that of ganciclovir, cidofovir and forscanet hence permitting its use in ganciclovir resistant CMV.
Conclusion
Treatment of CMV in the immunocompromised patient is a challenge.
Effective therapy requires prolonged exposure which leads to resistance.
Cidofovir and forscanet have good activity against CMV but limited by their side effect profiles.
Use of combined reduced antivirals may deliver potent therapy with reduced nephrotoxicity though requires further research.
Leflonomide hold promise for the future further studies are thus required.
My practise
I have not come across any ganciclovir resistance could be due to the fact that we mainly use valganciclovir or we don’t routinely look for it.
Thank you.
Introduction.
CMV infection is usually treated with ganciclovir, treatment resistance have been reported. Different treatment strategies available to treat ganciclovir-resistant CMV infection.
Ganciclovir Mechanism of Action
GCV; guanosine analogue that competitively inhibits CMV DNA polymerase, to become active it first undergoes phosphorylation is accomplished by the phosphotransferase produced by the gene UL97.
Drug Resistance
Resulted from mutations in UL97 phosphotransferase or UL54, simultaneous UL54 and UL97 mutations resulted in higher level resistance.
Definition
Ganciclovir resistance can be assayed either :
– Phenotypically; plaque reduction or DNA hybridization IC50 of > 6μg/ml ( IC50 is the concentration value required to inhibit 50% of CMV growth )
-or Genotypically; analysis to assess for known mutations in the UL54 and UL97 genes.
Prevalence;
The prevalence in SOT ranges between 0 and 15%, it vary according to the organ transplanted likely reflect different degrees of immunosuppression.
Risk Factors;
CMV R-/ D+ ; risk of both CMV infection and ganciclovir resistance.
Degree of IS.
Magnitude of CMV viremia.
Prolonged exposure to anti-CMV medication.
Prevention of Ganciclovir Resistant CMV Infection.
– Studies showed the resistance decrease with use of vGCV.
– Valganciclovir vGCV ; a more potent option for CMV prophylaxis and maintenance therapy, 10 times more bioavailable than oral ganciclovir , had similar safety profile except for higher incidence of neutropenia.
Foscarnet
-The primary alternative to ganciclovir, is a direct competitive inhibitor of DNA polymerase and does not need phosphorylation.
-Retains activity against CMV isolates with UL97 mutations, but not UL54
-Risk of resistance increases with the duration of foscarnet therapy.
– Adverse effect profile; renal toxicity, electrolyte abnormalities, and seizures.
-All toxic reactions resolved after discontinuing foscarnet.
Combination therapy with dose reduced ganciclovir and foscarnet
-The rationale; ganciclovir and foscarnet resistance are usually associated with different gene mutations, in vitro demonstration of synergy between the two agents even against ganciclovir resistant isolates.
-Trial showed that combination therapy is superior to monotherapy with the alternative agent alone.
-Permit lower dosing of each agent and consequent mitigation of their different toxicity profiles.
Cidofovir
-It is a monophosphorylated cytosine analogue, require phosphorylation to impedes DNA polymerase activity.
– Given IV once or twice per week.
-Prolonged treatment with ganciclovir can also lead to cross-resistance to cidofovir. Likewise, treatment with cidofovir alone can confer resistance to ganciclovir
-Adverse effect profile; nephrotoxicity reduced by (pre-hydration and the use of probenecid), bone marrow suppression and ocular disease.
Leflunomide
– It is a protein kinase inhibitor and as a competitive inhibitor of dihyrdoorotate dehydrogenase, the intracellular enzyme required for pyrimidine synthesis hence selectively inhibits activated lymphocytes
-It is an immunomodulatory and additional activity against viruses, simultaneous immunosuppressive and anti-infective properties.
– Inhibits CMV by interfering with final virion assembly rather than with DNA synthesis
– It has a long-half life on the order of 15-18 days.
– Potential to inhibit a multidrug-resistant CMV
-The major toxicity; transaminase elevation. Others include; diarrhea, hypertension, reversible alopecia, and rash, weight loss and pancytopenia.
– It is contraindicated in pregnancy
Conclusion
-The management remains a challenge, effective therapy requires prolonged drug use which in turn is associated with emergence of drug resistant virus.
-The alternative therapies foscarnet and cidofovir both appear to have good in vivo activity against CMV, the adverse side effect limits their attractiveness as anti-CMV agents.
-The use of reduced dose combination therapy appears requires further study.
-The of leflunomide holds promise as a future agent for the management of CMV since it both potentiates immunosuppression and suppresses CMV reproduction.
Level of evidence: Level 5 narrative review.
Please reflect on your practice
I have not came across CMV resistance cases. Leflunomide therapy looks promising and has attractive properties .
Thank you. I may disagree with you regarding leflunomide. I do not think it is an effective treatment.
● Management of CMV infection remains a substantial challenge for clinicians caring for immunocompromised patients
● Effective therapy requires prolonged drug use which associated with emergence of drug resistant virus
● Ganciclovir resistance can be assayed either phenotypically or genotypically.
● The “gold standard” test is the plaque reduction assay in which human fibroblasts are cultured with ganciclovir at various defined concentrations.
● IC50 is The concentration of ganciclovir required to inhibit 50% of CMV growth
● Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml.
● Ganciclovir resistance genotypically by detected mutations in UL54 , UL97 genes.
● Detection of resistance via gene mutations is :
• less labour intensive
• less time consuming
• is not limited by the need to culture CMV from patient specimens.
● Risk Factors for Resistance
☆ CMV seronegativity at transplant when receiving a seropositive organ
☆ Degree of immunosuppression
☆ Magnitude of CMV viremia
☆ prolonged exposure to anti-CMV medication.
● Seronegative recipients of seropositive organs appear to be at particular risk of both CMV infection and ganciclovir resistance.
● Patients with ganciclovir resistant suffered a significant decrease in survival ● valganciclovir offered a potential means to decrease resistance than gancyclovir in SOT transplants but more neutropenia
● Foscarnet is the primary alternative to ganciclovir for the treatment of CMV viremia and disease
● Foscarnet is a direct competitive inhibitor of DNA polymerase it does not need to be phosphorylated in order to inhibit CMV DNA polymerase.
● The risk of resistance increases with the duration of foscarnet therapy.
● Foscarnet is associated with renal toxicity, electrolyte abnormalities, and seizures.
● Foscarnet and ganciclovir are of similar efficacy but foscarnet is less well tolerated so treatment will be limited in some patients .
● Combination therapy of ganciclovir and foscarnet at reduced doses is A promising step for ganciclovir resistant CMV infection
● Cidofovir is further phosphorylated
intracellularly to form a compound that impedes DNA polymerase activity.
● cidofovir resistance was low but increases when :
Prolong treatment with cidofovir or ganciclovir ( cross-resistance )
● Cidofovir has nephrotoxicity “proteinuria”
, bone marrow suppression and ocular disease
● The risk of renal failure with foscarnet and cidofovir limits their attractiveness as anti-CMV agents
● Leflunomide is an immunomodulatory drug, in addition to immunosuppressive
properties it is active against viruses.
● Leflunomide has a long-half life “15-18” days it takes two months to achieve steady-state plasma concentrations and it can take two years to clear the drug.
● leflunomide inhibits CMV by interfering with final virion assembly rather than with DNA synthesis.
● The major toxicity of leflunomide is transaminase elevation
● Contraindications for leflunomide :
☆ Patients with pre-existing liver disease
☆ Heavy alcohol intake
☆ Concurrent viral hepatitis
☆ pregnancy
● In our centre we have CMV infection and CMV disease all of them were responsed to treatment with IV gancyclovir and oral valgancyclovir
We haven’t resistant cases
Other drugs aren’t avaliable
Thank you.
Please summarise this article
Introduction:
Cytomegalovirus (CMV) infection is common in immunocompromised patients with serious complications, graft loss and death.
The drug of choice of CMV infection is ganciclovir, that has reported drug resistance, mandating foundation of new drugs for prevention and treatment of it.
Ganciclovir Mechanism of Action and Drug Resistance
Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase.
Mutations arising in UL97 phosphotransferase lead to ganciclovir resistance.
Simultaneous UL54 and UL97 mutations. This is associated with higher level resistance to ganciclovir. UL54 mutations can confer cross-resistance to foscarnet and cidofovir since these agents also target CMV DNA polymerase.
Definition
Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml, or via genotype analysis to assess for known mutations in the UL54 and UL97 genes.( less labour intensive, less time consuming, and is not limited by the need to culture).
The “gold standard” test is the plaque reduction assay in which human fibroblasts are cultured with ganciclovir at various defined concentrations.
The concentration of ganciclovir required to inhibit 50% of CMV growth is the IC50 value.
Prevalence and Risk Factors for Resistance
– Prolonged exposure to antiviral agents.
– The baseline prevalence of ganciclovir resistance was 0.9% in blood specimens and 2.7% in urine specimens.
– After six months of treatment prevalence of 11.4%, increased to almost third for those treated for 9 months.
– The type of organ transplanted lung>heart>liver> kidney.
– CMV –ve R /+ve D.
– Potent immunosuppressive drugs.
– Severity of viremia.
– Almost 60% of patients treated for resistant CMV, suffered allograft loss, foscarnet nephrotoxicity, or rejection.
Prevention of Ganciclovir Resistant CMV Infection
Valyl ester prodrug of ganciclovir= valganciclovir.
CMV viremia was less frequent during the prophylactic period (2.9% versus 10.4%; P=.001), a mechanistically fitting observation for the observed difference in subsequent rates of resistance.
Treatment of Ganciclovir Resistant CMV
Foscarnet
– A direct competitive inhibitor of DNA polymerase.
– It retains activity against CMV isolates with UL97 mutations that are resistant to ganciclovir.
– Mutations in the DNA polymerase gene UL54, however, do confer foscarnet resistance.
– The risk of resistance increases with the duration of foscarnet therapy.
– Foscarnet is associated with renal toxicity, electrolyte abnormalities, and seizures.
– Excess mortality in the ganciclovir group was unclear when compared to Foscrnet group in a trial treating AIDS associated retinitis, however the mortality difference might be explained by the fact that patients in the ganciclovir arm were significantly less likely to be receiving concurrent antiretroviral therapy.
– In other study; Neutropenia significantly more in the ganciclovir group, genital ulcers, nephrotoxicity, electrolyte imbalance, and infusion related symptoms were more in foscarnet group and more patients were shifted to other treatment option.
Combination therapy with dose reduced ganciclovir and foscarnet
– The rationale for this strategy stems from the recognition that ganciclovir and foscarnet resistance are usually associated with different gene mutations, in vitro demonstration of synergy between the two agents even against ganciclovir resistant isolates.
– All patients also received CMV hyperimmunoglobulin. All patients had a clinical response within 72-96 hours and completely cleared their antigenemia within 4-8 weeks. No relapses were seen after 12-36 months of follow-up. But experienced significant hypomagnesemia requiring treatment.
Cidofovir
– A monophosphorylated cytosine analogue which, like ganciclovir, is further phosphorylated intracellularly to form a compound that impedes DNA polymerase activity, administered IV once or twice a week.
– Resistance increased by treatment time, even prolonged treatment of CMV infection with ganciclovir can also lead to the development of cross-resistance to cidofovir.
– Nephrotoxicity occurs in 50% of cases that may halted by hydration and use of probenecid, bone marrow suppression and ocular disease including iritis, uveitis, and vitreous hypotonicity.
Leflunomide
– An immunomodulatory drug, a protein kinase inhibitor and as a competitive inhibitor of dihyrdoorotate dehydrogenase, the intracellular enzyme required for pyrimidine synthesis, originally developed for the treatment of rheumatoid arthritis, e in addition to immunosuppressive properties it is active against viruses, so can reduce the risk of rejection and treating the virus.
– It would take nearly two months to achieve steady-state plasma concentrations, and takes almost two years to clear the drug- not excreted by kidneys.
– It inhibits CMV by interfering with final virion assembly rather than with DNA synthesis.
– Side effects includes anemia, one case of liver enzyme elevation, drug drug interaction requiring CNI dose reduction by 70%, diarrhea, hypertension, reversible alopecia, and rash, hepatic necrosis and death(rare).
– A 4 renal transplant patients from India with symptomatic gastrointestinal CMV disease who were treated with leflunomide because they could not afford intravenous ganciclovir. All four patients had detectable CMV viremia via quantitative PCR. The patients were treated with a 100mg oral loading dose once daily for three days followed by 20mg/day for three months. All experienced clinical and endoscopic resolution of their disease as well as clearance of serum viremia. No significant adverse effects were reported.
– The data are limited with few case series, in BMT, lung transplant…etc.
Conclusion:
The management of CMV infection is challenging, requiring prolonged treatment course, increasing the risk of drug resistance.
Foscarnet and cidofovir have ag good in vivo activity againt the virus but both can cause acute kidney injury.
The use of reduced dose combination therapy appears to deliver potent antiviral therapy with less risk of nephrotoxicity but this approach requires further study.
The longterm effectiveness, tolerability, and ideal settings for the use of leflunomide remain to be defined by ongoing and future studies.
Please reflect on your practice
In our center we did not face any CMV resistant strains, this could be due to the use of Valgancyclovir. However, this review article makes us understand how to deal with such cases in the future.
Thank you.
CMV infection is a common complication of immune suppression.
The first line treatment is ganciclovir. There is rising trend of drug resistance. This review explains the treatment strategies available to treat ganciclovir-resistant CMV infection. This also includes approved alternative agents foscarnet and cidofovir, the use of combination ganciclovir and foscarnet at reduced doses, and leflunomide.
Ganciclovir Mechanism of Action and Drug Resistance
Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase. It acts as a competitive substrate for DNA polymerase and slows the replication of CMV DNA by DNA polymerase. Phosphorylation is accomplished by the phosphotransferase produced by the gene UL97.
Mutations arising in UL97 phosphotransferase lead to ganciclovir resistance.
Different UL97 mutations are associated with different degrees of ganciclovir resistance.
Definition of resistane
The best test is the plaque reduction assay in which human fibroblasts are cultured with ganciclovir at various defined concentrations.
The concentration of ganciclovir required to inhibit 50% of CMV growth is the IC50 value.
Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml.
Prevalence and Risk Factors for Resistance
Among solid organ transplant recipients, the prevalence of CMV resistance ranges between 0 and 15%. The risk of developing ganciclovir resistance does seem to vary according to the organ transplanted.
Risk factors for the acquisition of ganciclovir resistance include –
CMV seronegativity at transplant when receiving a seropositive organ
Degree of immunosuppression, magnitude of CMV viremia
Prolonged exposure to anti-CMV medication
Treatment
Foscarnet
Foscarnet is a direct competitive inhibitor of DNA polymerase.
The risk of resistance increases with the duration of foscarnet therapy
Foscarnet is associated with renal toxicity, electrolyte abnormalities, and seizures
Foscarnet and ganciclovir are of similar efficacy but that foscarnet is less well tolerated
Combination therapy with dose reduced ganciclovir and foscarnet
The rationale for this strategy stems from the recognition that ganciclovir and foscarnet resistance are usually associated with different gene mutations
combination therapy has been shown to be effective in pre-emptive therapy of CMV antigenemia in nonganciclovir resistant bone marrow transplant patients
Cidofovir
It is a monophosphorylated cytosine analogue which is further phosphorylated intracellularly to form a compound that impedes DNA polymerase activity
Prolonged treatment of CMV infection with ganciclovir can also lead to the development of cross-resistance to cidofovir
Cidofovir can cause nephrotoxicity, bone marrow suppression and ocular disease including iritis, uveitis, and vitreous hypotonicity.
Leflunomide
Leflunomide is an immunomodulatory drug originally developed for the treatment of rheumatoid arthritis and approved for that indication by the FDA in 1998.
It is protein kinase inhibitor and as a competitive inhibitor of dihyrdoorotate dehydrogenase, the intracellular enzyme required for pyrimidine synthesis.
The half life on the order of 15-18 days
The major toxicity of leflunomide is transaminase elevation
Other side effects includes, diarrhoea, rash , hypertension and Pancytopenia.
Conclusions
The management of CMV infection remains a substantial challenge for clinicians
Effective therapy requires prolonged drug use which in turn is associated with emergence of drug resistant virus
CMV resistance to ganciclovir has been reported with increasing frequency
Foscarnet and cidofovir both appear to have good in vivo activity against cytomegalovirus but both are limited by their propensity to cause acute renal failure
The novel immunomodulatory agent leflunomide holds promise as a future agent for the management of CMV since it both potentiates immunosuppression and suppresses CMV reproduction.
Reflection on Practice
I have not seen a case of CMV resistance and have experience with its pharmacotherapy.
Thank you.
I also never came across gancyclovir resistance.
Treatment of Ganciclovir Resistant Cytomegalovirus Infection
– Ganciclovir is a guanosine analogue when phosphorylated it competitively inhibits
CMV DNA polymerase and decrease CMV replications.
– Phosphorylation is accomplished by the phosphotransferase produced by the
gene UL97 and UL54. So mutations cause ganciclovir resistance.
– UL54 mutations can confer cross-resistance to foscarnet and cidofovir.
Definition:
– Phenotypically: ganciclovir resistance has been defined as a plaque reduction
or DNA hybridization IC50 (The concentration of ganciclovir required to inhibit
50% of CMV growth) of > 6μg/ml.
– Genetically: mutations in genes UL97 and UL54.
Prevalence:
– Ganciclovir resistance is uncommon at baseline amongst untreated patients but
arises rapidly after prolonged exposure to antiviral agents.
– In solid organ transplant, the prevalence of CMV resistance ranges between 0 and
15% and does not vary according to the organ transplanted.
Risk factors:
– CMV seronegativity at transplant when receiving a seropositive organ
– Degree of immunosuppression (with more potent IS ).
– Magnitude of CMV viremia
– Prolonged exposure to anti-CMV medication.
Prevention of Ganciclovir Resistant CMV Infection:
1- Valganciclovir (10 time more bioavailable, FDA approved in 2001) offered a
potential means to decrease resistance while retaining the convenience and safety
of an oral agent.
2- Foscarnet:
– It is an alternative to ganciclovir for the treatment of CMV viremia and disease.
– Direct competitive inhibitor of DNA polymerase without need for phosphorylation.
– So, it retains activity against CMV isolates with UL97 mutations that are resistant
to ganciclovir.
– However, UL54 mutation does confer foscarnet resistance.
– The risk of resistance increases with the duration of foscarnet therapy.
– Foscarnet is associated with renal toxicity, electrolyte abnormalities
(hypocalcaemia, hypomagnesemia, hypokalemia and hypophosphatemia), genital
ulcers and seizures.
– Foscarnet is useful agent to use against ganciclovir resistant CMV but
treatment will be limited by the increased side effects.
3- Combination therapy with dose reduced ganciclovir and foscarnet:
– The rationale for this strategy stems from the recognition that ganciclovir and
foscarnet resistance are usually associated with different gene mutations.
– Data on those with ganciclovir resistant CMV is limited to a retrospective study
included six SOT patients with good response.
4- Cidofovir:
– It is a monophosphorylated cytosine analogue which, like ganciclovir, is further
phosphorylated intracellularly to form a compound that impedes DNA polymerase
activity.
– It has to be given intravenously but need only be administered once or twice per
week
– Resistance to cidofovir is low at baseline but rises.
– Prolonged treatment of CMV infection with ganciclovir can also lead to the
development of cross-resistance to cidofovir.
– Its use is limited by its adverse effect profile. Cidofovir can cause nephrotoxicity in
as many as half of all patients, bone marrow suppression and ocular disease
including iritis, uveitis, and vitreous hypotonicity.
5- Leflunomide:
– An immunomodulatory drug with anti-viral activity.
– Leflunomide acts as a protein kinase inhibitor and as a competitive inhibitor of
dihyrdoorotate dehydrogenase required for pyrimidine synthesis. Thus inhibit
activated lymphocytes.
– It is rapidly metabolized to the active metabolite and has a long half-life (15-18
days)
– It is used for treatment of rheumatoid arthritis and can be used as IS for patients
with poor response to conventional IS in SOT.
– Reported complications includes: elevated liver enzymes, diarrhea, hypertension,
reversible alopecia, weight loss, pancytopenia and rash.
– It is contraindicated in patients with liver disease, viral hepatitis, alcoholic and in
pregnancy.
Conclusion:
both AIDS patients treated for CMV retinitis and in recipients of both bone marrow
and SOT.
II- In the last 2 years, was diagnosed few cases with CMV and they responded well with slandered treatment.
Thank you for your excellent reply.
Summary
CMV infection is prevelant in solid organ transplantation( SOT ) patient and if not apprioratlytreated it will lead to graft failure and increased mortality gancyclover has been recommended as the 1st line of treatment and prophylaxis but a rising incidence of drug resistance incidence has been reported
Mechanism of action
Gancyclover is a competitive inhibitor of DNA polymerase that is responsible for replication of CMV DNA
The medication become active through 3 steps enzymatic phosphorylation , mutation( UL 97) in such enzyme will affect active drug generation andhence resistance develop . Another well known mutation which is UL 54 which make DNA polymerase resistant to the effect of the active phosphorylated gancyclover metabolite , making drug resistance is possible . both mutation can present at same time
Prevelance and risk factors
Prevelance of Resistance in SOT is ranging from 0- 15%
risk factors are
· CMV seronegativity at transplant when receiving a seropositive organ,
· degree of immunosuppression,
· magnitude of CMV viremia, and
· prolonged exposure to anti-CMV medication
Prevention of Ganciclovir Resistant CMV Infection
· Use of Valganciclover which is FDA approved in 2001 and it is 10 times more potent than ganciclover so it will shorten the treatment course and reduce resistance . but on cohort studies which has small number of patients it showed no difference in incidence of resistance in some and others showed high resistance incidence with gancyclover
· Use of Foscarnet : it has a direct competitive inhibitor of DNA without the need for phosphorylation and hence is not affected by mutation in UL97 gen but mutation affecting DNA polymerase can create Foscarnet drug resistance .Foscarnet is associated with renal toxicity, electrolyte abnormalities, and seizures.Accordingly , Foscarnet is agood alternative for treatment of incase of Ganciclover resistance but the risk of nephrotoxicity limit its use
· Combination therapy with dose reduced ganciclovir and foscarnet: both medication has synrgitic effect and reduction of dose will reduce SideEffects the evidence to support this hypothesis is still low
· Cidofovir : approved for CMV treatment by FDA in 1994 and acting in away similar to Gancyclover but taken IV in twicewekly dose but again resistance incidence is rising . Notably, prolonged treatment of CMV infection with ganciclovir can also lead to the development of cross-resistance to cidofovir.
· Leflunomide: acts as a protein kinase inhibitor and as a competitive inhibitor of dihyrdoorotate dehydrogenase, the intracellular enzyme required for pyrimidine synthesis. It specifically inhibits denovo pyrimidine synthesis. It is immunomodulator and has antiviral activity and basically used ibn rheumatoid arthritis treatment but found to be helpful to reduce or completely stop immunsupression while using leflunoamide without incidence of acute rejection . it has long half-life and its side effected noted from clinical studies are anamia and elevation of liver function test in addition to minor incidence of diarrhea, hypertension, reversible alopecia , and rash .
Conclusion
1. CMV resistance to ganciclovir has been reported with increasing frequency in recipients of both bone marrow and solid organ transplants.
2. The alternative therapies foscarnet and cidofovir both appear to have good in vivo activity against cytomegalovirus but both are limited by their propensity to cause acute renal failure.
3. The use of reduced dose combination therapy appears to deliver potent antiviral therapy with less risk of nephrotoxicity but this approach requires further study
4. leflunomide holds promise as a future agent for the management of CMV since it both potentiates immunosuppression and suppresses CMV reproduction
reflection on practice
balancing approach with use of antiviral reduction of IS with close monitoring shorten course of antiviral to reduce resistance keeping patient oriented by the risk andbenefit of each sttigy accordingly
Thank you.
CMV infection carries a high risk for the development and progression of CMV disease, allograft dysfunction, and death. Usually we start treatment for CMV infections and disease with ganciclovir, however, many centres have reported a small but rising incidence of ganciclovir resistant CMV infections.
Mechanism of action of ganciclovir:
Ganciclovir is targeting CMV DNA as a competitive inhibitor to CMV DNA polymerase via phosphorylation which is done by the phosphotransferase produced by the gene UL97
Mutations arising in UL97 phosphotransferase lead to ganciclovir resistance. mutations arising in the DNA polymerase gene UL54 also carries resistance to ganciclovir. Different UL97 mutations are associated with different degrees of ganciclovir resistance. Also resistance is increasing with prolonged exposure to ganciclovir
Of Note: Foscarnet has cross resistance with ganciclovir as it is also targeting CMV DNA also
Diagnosis of ganciclovir resistance:
– Phenotypically : The gold standard plaque reduction assay in which human fibroblasts are cultured with ganciclovir at various defined concentrations. CMV growth can be quantified by counting viral plaque formation or by a DNA hybridization technique. The concentration of ganciclovir required to inhibit 50% of CMV growth is the IC50 value. Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml.5
– Genotypically: genotype analysis to assess for known mutations in the UL54 and UL97 genes
Prevalence of ganciclovir resistance in CMV:
# The risk of developing ganciclovir resistance varies according to the organ transplanted ,being around 45% in kidney transplant and highest in lung transplant 99%.data from 2 chicago transplant centers in 1994-2001.
# Risk factors for ganciclovir resistance :
1. CMV seronegativity at transplant when receiving a seropositive organ: Seronegative recipients of seropositive organs appear to be at particular risk of both CMV infection and ganciclovir resistance, also decreased survival.
2. Degree of immunosuppression
3. Magnitude of CMV viremia
4. Prolonged exposure to anti-CMV medication.
The FDA approval of the valyl ester prodrug of ganciclovir valganciclovir in 2001, introduced a more potent option for CMV prophylaxis and maintenance therapy of disease in both transplant recipients and AIDS patients. Valganciclovir is approximately ten times more bioavailable than oral ganciclovir. Since ganciclovir resistance is thought to be related to prolonged exposure to subtherapeutic plasma concentrations of ganciclovir.
2 important studies in using valgancyclovir vs ganciclovir regarding resistance:
1-: AIDS patients with CMV retinitis demonstrated equivalence to intravenous ganciclovir in the risk of emergence of ganciclovir resistance, while in the solid organ transplant population, valganciclovir was shown to be superior to oral ganciclovir for the prevention of resistant CMV infection,after 6 months from follow up: ganciclovir resistance mutations in UL97 were found in 9.5% of patients, divided equally between the group induced with valganciclovir and the group induced with intravenous ganciclovir.
2- 301 D+/R– solid organ transplant patients prophylaxed with either valganciclovir 900mg PO qd or ganciclovir 1000mg PO tid for 100 days post-transplant. At the end of 100 days, none of the valganciclovir treated patients had become infected with resistant virus versus 2% of patients in the ganciclovir group. After one year post-transplant, the rate of CMV disease associated with ganciclovir resistant virus remained at zero for the valganciclovir group but had risen to 6% in the ganciclovir group.also there was neutropenia more evident of valgancyclovir group.
Foscarnet:
The primary alternative to ganciclovir for the treatment of CMV viremia and disease .
Mech of action:it is a direct competitive inhibitor of DNA polymerase. Unlike ganciclovir, it does not need to be phosphorylated in order to inhibit CMV DNA polymerase. Since it is not dependent on the CMV phosphotransferase UL97 it retains activity against CMV isolates with UL97 mutations that are resistant to ganciclovir.
Mutations in the DNA polymerase gene UL54, however, do confer foscarnet resistance and can sometimes be selected for by prolonged ganciclovir therapy. Like ganciclovir, the risk of resistance increases with the duration of foscarnet therapy.
Limitation of use: renal toxicity, electrolyte abnormalities, and seizures
Combination therapy with dose reduced ganciclovir and foscarnet:
Data from the AIDS literature showing that combination therapy is superior to monotherapy with the alternative agent alone,27 and that combination therapy has been shown to be effective in pre-emptive therapy of CMV antigenemia in non ganciclovir resistant bone marrow transplant patient ,also it will lead to decreasing the doses of both drugs ,therefore decreasing their toxicity profile.
Cidofovir :
Mech of action:
It is a monophosphorylated cytosine analogue which, like ganciclovir, is further phosphorylated intracellularly to form a compound that impedes DNA polymerase activity.
Administration: it has to be given intravenously but need only be administered once or twice per week.
Like ganciclovir and foscarnet, resistance to cidofovir is low at baseline but rises
Limitation of use:
Nephrotoxicity (in some studies it it was irreversible):could be decreased by good hydration and probenecid but this also can decrease tolerability.
bone marrow suppression
Ocular disease including iritis, uveitis, and vitreous hypotonicity
Leflunomide:
Leflunomide is an immunomodulatory drug originally developed for the treatment of rheumatoid arthritis and approved for that indication by the FDA in 1998.
Leflunomide has attracted particular interest from the transplant community because it has immunosuppressive actions as it acts on pyrimidine synthesis and in some kidney transplant cases replaced azathioprinr ,MMF and cNI .
Mech of action: acts as a protein kinase inhibitor and as a competitive inhibitor of dihyrdoorotate dehydrogenase, the intracellular enzyme required for pyrimidine synthesis. It specifically inhibits denovo pyrimidine synthesis and hence selectively inhibits activated lymphocytes since resting lymphocytes are able to synthesize pyrimidines via a salvage pathway.
Pharmacology: is a prodrug that is rapidly metabolized to the active metabolite, A77 1726. The drug has a long-half life on the order of 15-18 days potentiated by substantial enterohepatic recirculation. Without a loading dose it is estimated that it would take nearly two months to achieve steady-state plasma concentrations. Likewise, after discontinuation of the medication it can take as long as two years for the body to entirely clear the drug.
Mech of action in CMV infection: leflunomide inhibits CMV by interfering with final virion assembly rather than with DNA synthesis. As such, the viral target for leflunomide is distinct from that targeted by ganciclovir, foscarnet, and cidofovir.
Side effects:increased transaminases,0.02%-0.04% liver necrosis and LCF, diarrhea (17-33%), hypertension (6-12%), reversible alopecia (8-11%), and rash (10-14%)
Literature: four renal transplant patients from India with symptomatic gastrointestinal CMV disease who were treated with leflunomide because they could not afford intravenous ganciclovir. All four patients had detectable CMV viremia via quantitative PCR. The patients were treated with a 100mg oral loading dose once daily for three days followed by 20mg/day for three months. All experienced clinical and endoscopic resolution of their disease as well as clearance of serum viremia. No significant adverse effects were reported
Another case of use of leflunomide in an allogeneic bone marrow transplant recipient who developed CMV infection refractory to sequential therapy with ganciclovir, foscarnet, and cidofovir. The patient had multiple comorbidities including severe pre-existing graft-versus-host disease. After starting a combination of leflunomide and foscarnet, the patient’s CMV viral load decreased from 226,000 copies per ml to an undetectable level over the course of six weeks. Leflunomide was stopped after three weeks of therapy due to hyperbilirubinemia. Four weeks after stopping therapy, the patient’s CMV viremia recurred. She expired soon thereafter from bacterial sepsis. So there is both the potential and some of the dilemmas in the use of leflunomide for resistant CMV disease. While the agent was clearly effective in clearing the patient’s CMV viremia, it is possible that it contributed to her death from progressive liver failure.
Regarding our practice , I will write in another box
Thank you Dr Rehab for your excellent answer.
Cytomegalovirus (CMV) infection is a common and serious complication of immunosuppression in solid organ and bone marrow transplant recipients, and in patients with AIDS.
CMV infection is associated with a high risk for the development and progression of CMV disease,allograft dysfunction, and death.
First line treatment for CMV infections and disease is ganciclovir, many centres have reported a small but rising incidence of ganciclovir resistant CMV infections.
I shall emphasise treatment strategies available to treat ganciclovir-resistant CMV infection including the currently approved alternative agents foscarnet and cidofovir , the use of combination ganciclovir and foscarnet at reduced doses, and the novel immunomodulatory agent, leflunomide.
Ganciclovir mechanism of action and drug resistance
Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase.
Mutations arising in the DNA polymerase gene UL54 confer resistance to ganciclovir..
Most patients develop only UL97 mutations, prolonged exposure to ganciclovir can give rise to simultaneous UL54 and UL97 mutations.
The “gold standard” test is the plaque reduction assay in which human fibroblasts are cultured with ganciclovir at various defined concentrations.
The concentration of ganciclovir required to inhibit 50% of CMV growth is the IC50 value.
Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6μg/ml..
Ganciclovir resistance can be detected via genotype analysis to assess for known mutations in the UL54 and UL97 genes.
Detection of resistance via gene mutations is attractive since it is less labour intensive, less time consuming, and is not limited by the need to culture CMV from patient specimens.
The correlation between genotype and phenotype, is imperfect so genotype-based resistance reports need to be interpreted with caution.
Gancicilvir resistentce is uncommon at baseline amongst untreated patients but arises rapidly after prlonged exposure to antiviral agents
In one cohort of AIDS patients newly diagnosed with CMV retinitis, samples of vitreous were assayed for baseline gene mutations associated with ganciclovir resistance.
Blood and urine cultures from 108 AIDS patients newly diagnosed with CMV retinitis were prospectively tested for ganciclovir resistance.
The baseline prevalence of ganciclovir resistance was 0.9% in blood specimens and 2.7% in urine specimens.
After six months of treatment predominantly with intravenous ganciclovir, the prevalence of patients with resistant blood or urine isolates rose to 11.4%.
Identification of a ganciclovir resistant isolate was correlated with the development of CMV retinitis in the contralateral eye..
The risk of developing ganciclovir resistance does seem to vary according to the organ transplanted.
This is felt to reflect different degrees of immunosuppression and different protocols for the prophylaxis of CMV.
Organ total number of patients with CMV infection
Risk factors for the acquisition of ganciclovir resistance include CMV seronegativity at transplant when receiving a seropositive organ, degree of immunosuppression, magnitude of CMV viremia, and prolonged exposure to anti-CMV medication.
Seronegative recipients of seropositive organs appear to be at particular risk of both CMV infection and ganciclovir resistance.
In a cohort of 240 liver, kidney, and pancreas recipients who took oral ganciclovir prophylaxis for three months after transplantation, 25 developed invasive CMV disease over the course of one year ofollow-up.
Five of these patients (20%) had isolates with ganciclovir resistance.
All five patients with ganciclovir resistant CMV disease were CMV seronegative recipients of organs from seropositive donors.
The risk of developing ganciclovir resistant CMV among D+/R– patients did not differ if patients were treated for CMV with a prophylactic or preemptive strategy.
Prevention of ganciclovir resistant CMV infection
The treatment of ganciclovir resistant CMV infections has not been comprehensively studied.
The FDA approval of the valyl ester prodrug of ganciclovir valganciclovir in 2001, introduced a more potent option for CMV prophylaxis and maintenance therapy of disease in both transplant recipients and AIDS patients.
A study conducted in AIDS patients with CMV retinitis demonstrated equivalence to intravenous ganciclovir in the risk of emergence of ganciclovir resistance, while in the solid organ transplant population, valganciclovir was shown to be superior to oral ganciclovir for the prevention of resistant CMV infection.
In the former study, valganciclovir was compared to intravenous ganciclovir in an open label trial of 148 AIDS patients with CMV retinitis.
Trials comparing ganciclovir and foscarnet in unselected patients give a sense of the relative effectiveness and frequency of adverse effects of these two agents
This information needs to be interpreted with caution as the data were derived from patients with wild type CMV infection rather than ganciclovir resistant isolates.
In the inpatient setting where both these variables can be closely monitored and often pre-empted foscarnet seems to be a reasonable choice but a more challenging option in the management of outpatients.
Combination therapy with dose reduction of ganciclovir and foscarnet
A promising avenue for the future treatment of ganciclovir resistant CMV infection has been the use of combination ganciclovir and foscarnet at reduced doses
The rationale for this strategy stems from the recognition that ganciclovir and foscarnet resistance are usually associated with different gene mutations, in vitro demonstration of synergy between the two agents even against ganciclovir resistant isolates, trial data from the AIDS literature showing that combination therapy is superior to monotherapy with the alternative agent alone, and that combination therapy has been shown to be effective in pre-emptive therapy of CMV antigenemia in nonganciclovir resistant bone marrow transplant patients..
The incidence of nephrotoxicity seen with reduced dose foscarnet combination therapy is disappointing relative to the success of the strategy in the ganciclovir resistant CMV trial above
It is probably a more accurate reflection of the adverse effect profile of foscarnet, given the greater number of patients treated in this trial and the well described association of foscarnet with renal dysfunction.
Findings
After six months of treatment predominantly with intravenous ganciclovir, the prevalence of patients with resistant blood or urine isolates rose to 11.4%.
When patients were re-evaluated one year post-transplant, the rate of CMV disease associated with ganciclovir resistant virus remained at zero for the valganciclovir group but had risen to 6% in the ganciclovir group..
In AIDS patients with CMV retinitis, for example, the incidence of resistance at 6, 9, and 12 months of therapy rose from 13% to 24% to.
Patients treated with combination therapy were less likely to have PCR negative blood at 14 days.
Among 39 renal transplant patients treated with high-dose leflunomide as an immunosuppressant, the mean hematocrit dropped by an average of 15%.
Conclusion
The management of CMV infection remains a substantial challenge for clinicians caring for immunocompromised patients.
While there are a number of agents active against the virus, effective therapy requires prolonged drug use which in turn is associated with emergence of drug resistant virus.
CMV resistance to ganciclovir has been reported with increasing frequency in both AIDS patients treated for CMV retinitis and in recipients of both bone marrow and solid organ transplants.
The alternative therapies foscarnet and cidofovir both appear to have good in vivo activity against CMV but both are limited by their propensity to cause acute renal failure.
Given the often tenuous medical status of immuncompromised patients and the frequent need to simultaneously administer nephrotoxic agents, the risk of renal failure with foscarnet and cidofovir limits their attractiveness as anti-CMV agents.
In our center very few cases was diagnosed with CMV and they responded well with slandered treatment.
Thank you.
Introduction:
Cytomegalovirus (CMV) infection is serious condition in immune compromised patients especially solid organ transplant on immunosuppressive therapy.
Main treatment of CMV is ganciclovir but nowaday some centers shows increase incidence of drug resistance. This review study evidence of foscarnet and cidofovir, or novel immunomodulatory agent, leflunomide in ganciclovir resistance cases.
Mechanism of action of ganciclovir:
It’s inhibit CMV DNA https://s.w.org/images/core/emoji/14.0.0/svg/1f9ec.svg polymerase and ganciclovir resistance arise from defect in Phosphorylation because mutations of UL97 phosphotransferase.
Side effects of ganciclovir is neutropenia.
Prevalence and Risk Factors for Resistance:
Prolong exposure to ganciclovir
CMV seronegativity at transplant when receiving a seropositive organ.
Degree of immunosuppression
Magnitude of CMV viremia.
Prevention of ganciclovir resistance:
valganciclovir is a prodrug of ganciclovir and more potent than ganciclovir and ten times more bioavailability in comparison to ganciclovir.
Foscarnet:
It’s used as alternative to ganciclovir in case of resistance of ganciclovir to treat CMV infection.
It’s competitive inhibitors to CMV DNA polymerase.
Foscarnet resistance occur due to prolonged exposure. Drug resistance was associated with an increased risk of retinitis progression.
Side effects of foscarnet is nephrotoxicity, electrolyte abnormalities, and seizures.
Withdrawal of foscarnet are high because of its toxicity.
Cidofovir:
It’s a monophosphorylated cytosine analogue similar to ganciclovir.
It’s given twice per week and resistance to cidofovir is low.
It’s used to treat CMV retinitis.
Also prolonged treatment of CMV infection with ganciclovir may lead to the development of cross-resistance to cidofovir.
Side effects of cidofovir is nephrotoxic and ocular toxicity.
Leflunomide:
It’s immunomodulatory drug used for treatment of rheumatoid arthritis.
Leflunomide is a prodrug acts as a protein kinase inhibitor and as a competitive inhibitor of dihyrdoorotate dehydrogenase, the intracellular enzyme required for pyrimidine synthesis.
Side effects of Leflunomide is anemia and raised liver enzymes.
Other side effects are alopacia and skin rach , hypertension and pancytopenia.
Thank you.
Please reflect on your practice.
Treatment of Ganciclovir Resistant CMV infection:
Ganciclovir Mechanism of Action and Drug Resistance:
Risk factors for resistance:
Resistance isolates per type of organ transplant in 2 Chicago transplant centers, 1994-2001:
Prevention of Ganciclovir-resistant CMV infection:
Foscarnet:
Combined therapy:
Combined Ganciclovir and Foscarnet offer more promising treatment with less dose and side effects.
Other observations show less target treatment response and more side effects as electrolyte abnormality.
Cidofovir:
Leflunomide:
Conclusion:
In local practice:
Adjusted doses of antiviral with balanced reduced doses of IS, with timing of treatment and follow up of kidney function
Thank you.
Please summarise this article
Ganciclovir Mechanism of Action and Drug Resistance
-Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase. In order to become active it must first be phosphorylated in three steps to a triphosphorylated form. Once phosphorylated, it acts as a competitive substrate for DNA polymerase and slows the replication of CMV DNA by DNA polymerase.
-Phosphorylation is accomplished by the phosphotransferase produced by the gene UL97. Mutations arising in UL97 phosphotransferase lead to ganciclovir resistance and mutations arising in the DNA polymerase gene UL54 also confer resistance to ganciclovir.
– Prolonged exposure to ganciclovir can give rise to simultaneous UL54 and UL97 mutations. This is associated with higher level resistance to ganciclovir. UL54 mutations can confer cross-resistance to foscarnet and cidofovir .
Definition
-Ganciclovir resistance can be assayed either phenotypically or genotypically. The “gold standard” test is the plaque reduction assay.
– Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6μg/ml.5
-Ganciclovir resistance can also be detected via genotype analysis to assess for known mutations in the UL54 and UL97 genes.
Prevalence and Risk Factors for Resistance
-Ganciclovir resistance is uncommon at baseline amongst untreated patients but arises rapidly after prolonged exposure to antiviral agents.
-Among solid organ transplant recipients, the prevalence of CMV resistance ranges between 0 and 15%.
-The risk of developing ganciclovir resistance does seem to vary according to the organ transplanted . This is felt to reflect different degrees of immunosuppression and different protocols for the prophylaxis of CMV.
Risk factors for the acquisition of ganciclovir resistance:
– include CMV seronegativity at transplant when receiving a seropositive organ, degree of immunosuppression, magnitude of CMV viremia, and prolonged exposure to anti-CMV medication.
– Patients with ganciclovir resistant disease suffered a statistically significant decrease in survival compared to those with ganciclovir sensitive disease.
-Ganciclovir resistance was common amongst pancreas recipients who receive more potent immunosuppression than other solid organ recipients.
-The risk of developing ganciclovir resistant CMV among D+/R– patients did not differ if patients were treated for CMV with a prophylactic or preemptive strategy.
Prevention of Ganciclovir Resistant CMV Infection
-The FDA approval of the valyl ester prodrug of ganciclovir valganciclovir in 2001, introduced a more potent option for CMV prophylaxis and maintenance therapy of disease in both transplant recipients and AIDS patients.
-Valganciclovir is approximately ten times more bioavailable than oral ganciclovir.
-Valganciclovir’s ability to temper ganciclovir resistance has been demonstrated in comparative studies.
-In the solid organ transplant population, valganciclovir was shown to be superior to oral ganciclovir for the prevention of resistant CMV infection.
-The safety profile was generally similar between ganciclovir and valganciclovir except that patients treated with valganciclovir had a higher incidence of neutropenia .
Foscarnet
-The primary alternative to ganciclovir for the treatment of CMV viremia and disease is foscarnet.
-It is a direct competitive inhibitor of DNA polymerase.
-The risk of resistance increases with the duration of foscarnet therapy. -Drug resistance was associated with an increased risk of retinitis progression.
– Foscarnet is associated with renal toxicity, electrolyte abnormalities, and seizures.
Combination therapy with dose reduced ganciclovir and foscarnet
-The rationale for this strategy stems from the recognition that ganciclovir and foscarnet resistance are usually associated with different gene mutations, in vitro demonstration of synergy between the two agents even against ganciclovir resistant isolates.
Cidofovir
-It is a monophosphorylated cytosine analogue which, like ganciclovir, is further phosphorylated intracellularly to form a compound that impedes DNA polymerase activity.
-Prolonged treatment of CMV infection with ganciclovir can lead to the development of cross-resistance to cidofovir.
-Cidofovir can cause nephrotoxicity in as many as half of all patients ,marrow suppression and ocular disease including iritis, uveitis, and vitreous hypotonicity.
Leflunomide
-Leflunomide is an immunomodulatory drug originally developed for the treatment of rheumatoid arthritis .
-Leflunomide has immunosuppressive properties and active against viruses.
– Leflunomide is a prodrug that is rapidly metabolized to the active metabolite.
-It suggested that leflunomide inhibits CMV by interfering with final virion assembly rather than with DNA synthesis. As such, the viral target for leflunomide is distinct from that targeted by ganciclovir, foscarnet, and cidofovir.
-The major toxicity of leflunomide is transaminase elevation.
– Patients with pre-existing liver disease, heavy alcohol intake, or concurrent viral hepatitis should not be given leflunomide.
-Leflunomide is contraindicated in pregnancy due to reports of fetal death and teratogenesis in human subjects.
-2.Please reflect on your practice
-We had a few cases of CMV disease and they had a good response to treatment (no CMV resistant case)
Thank you.
Introduction:
Ganciclovir mechanism of action:
Resistant definition:
Prevalence & risk factors for Ganciclovir resistant:
Prevention of ganciclovir resistant CMV infection:
Foscarnet:
Cidofovir:
Leflunomide:
In my practice we use oral valganciclovir as prophylaxis (D+/R- for 3-6 months) & treatment of CMV infection.
I like your summary of these guidelines. I like your reflection of current practice in your hospital in relation to these (similar) guidelines
Please summarise this article
Introduction
First line treatment for CMV infections and disease is ganciclovir, but there is a small risk ganciclovir resistant CMV infection
Aim of the study: treatment of ganciclovir resistance (foscarnet and cidofovir, combination ganciclovir and foscarnet, and immunomodulatory agent, leflunomide)
Ganciclovir Resistance
Definition
Can be assayed either phenotypically or genotypically
*A plaque reduction or DNA hybridization IC50 of > 6µg/ml (IC50 value is the concentration of ganciclovir required to inhibit 50% of CMV growth)
*Detection via genotype analysis to assess for UL54 and UL97 genes
Mechanism of Action
*Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase
*First phosphorylated to a triphosphorylated form (this acts as a competitive substrate for DNA polymerase and slows the replication of CMV DNA by DNA polymerase)
*Phosphorylation is accomplished by the phosphotransferase produced by the gene UL97
*Mutations in UL97 phosphotransferase lead to ganciclovir resistance (also mutation in UL54)
*UL54 mutations can cause resistance to foscarnet and cidofovir
Prevalence and Risk Factors
Incidence is 0-15% in SOT. Vary according to the organ transplanted (different degrees of immunosuppression and different protocols for the prophylaxis)
Risk factors include:
1. R-/D+
2. Degree of immunosuppression
3. Magnitude of CMV viremia
4. Prolonged exposure to anti-CMV medication
Prevention
*Valganciclovir is approximately ten times more bioavailable than oral ganciclovir
*Ganciclovir resistance maybe related to prolonged exposure to subtherapeutic plasma concentrations of ganciclovir
*Valganciclovir offered a decrease resistance according to many studies
Foscarnet
*Approved by the FDA in 1991
*Direct competitive inhibitor of DNA polymerase (no need for phosphorylation)
*Active against CMV isolates with UL97
*The risk of resistance increases with the duration of foscarnet therapy
The major limitation of foscarnet use is its adverse effect:
1. Renal toxicity
2. Electrolyte abnormalities
3. Seizures
*Less well tolerated for pre-emptive management of CMV viremia (can be used in selected inpatient cases)
*Useful for ganciclovir resistant CMV but treatment will be limited in some patients by nephrotoxicity and/or electrolyte abnormalities
Combination of low dose ganciclovir and foscarnet
*The rationale is that ganciclovir and foscarnet resistance are usually associated with different gene mutations
*Combination would permit lower dosing of each agent and consequent toxicity
show a promising results
Cidofovir
*Approved by the FDA in 1996 for the treatment CMV infection
*A monophosphorylated cytosine analogue (phosphorylated and then impedes DNA polymerase activity)
*Given intravenously (once or twice per week)
*Resistance is low at baseline but rises (Like ganciclovir and foscarnet)
*Prolonged treatment with ganciclovir can also lead to the development of cross-resistance to cidofovir
Its use limited by its adverse effect profile:
1. Nephrotoxicity (half of patients). Rehydration and and use of probenecid can reduce toxicity
2. Bone marrow suppression
3. Ocular disease (iritis, uveitis, and vitreous hypotonicity)
*In the AIDS population using cidofovir to treat CMV retinitis that had recurred or was progressive despite therapy with ganciclovir, foscarnet or both, it delayed progression of retinitis (high nephrotoxicity)
Immunomodulatory therapy (leflunomide)
*Approved for by the FDA in 1998 RA)
*Immunosuppressive and ant-viral
*A protein kinase inhibitor and as a competitive inhibitor of dihyrdoorotate dehydrogenase, the intracellular enzyme required for pyrimidine synthesis
*Specifically inhibits denovo pyrimidine synthesis and hence selectively inhibits activated lymphocytes since resting lymphocytes are able to synthesize pyrimidines via a salvage pathway
*Is a prodrug that is rapidly metabolized to the active metabolite
*Has a long-half life (15-18 days)
*Renal excretion is limited
*Inhibits CMV by interfering with final virion assembly rather than with DNA synthesis (viral target is distinct from that targeted by ganciclovir, foscarnet, and cidofovir)
Adverse effects include:
1. Transaminase elevation (major toxicity)
2. Diarrhea (17-33%)
3. Hypertension (6-12%)
4. Reversible alopecia (8-11%)
5. Rash (10-14%)
6. Weight loss
*Contraindicated in pregnancy (fetal death and teratogenicity)
*Limited use in renal transplant patients and allogeneic bone marrow transplant with sustained reduction or clearance of viremia
Conclusion
*Prolonged drug use is associated with drug resistant virus
*The alternative therapies for ganciclovir resistance are foscarnet and cidofovir both appear to have good in vivo activity against CMV but both are limited by nephrotoxicity
*Risk of renal failure with foscarnet and cidofovir limits use
*The use of reduced dose combination therapy appears to be with less risk of nephrotoxicity (requires further study)
*The immunomodulatory agent leflunomide holds promise for the management of CMV since it both potentiates immunosuppression and suppresses CMV reproduction (not nephrotoxic but can cause transaminase elevation)
Please reflect on your practice
I did not see any case of CMV resistance before. I have no experience with the above medications.
This is anarrative study (level v)
i like your analysis regarding the level of evidence of this study
CMV infection is common infection and complications can happen in immunocompromised patients and post solid organ transplant SOT, can be extended to be CMV syndrome include the presence of clinical manifestations with leucopenia or thrombocytopenia with detection of CMV DNA in the blood , and can be extended to be tissue invasive disease which may be life threatening condition, also CMV infection itself is a risk factor for ACR or even humoral rejection, so early detection and treatment by ganciclovir is a crucial step.
Ganciclovir is guanosine analogue that inhibits DNA polymerase of CMV DNA , but to be activated, should be phosphorylated, then will act as a competitive inhibitor to DNA polymerase.
This phosphorylation process is mediated by phosphotransferase enzyme, which is produced by UL97 gene, so any mutation in this gene leads to inactive ganciclovir and resistance to it. In addition, mutation in DNA polymerase gene UL54 will results in the resistance, and prolonged intake of iv ganciclovir will induce mutations of both genes.
Definition of ganciclovir resistance :
Ganciclovir resistance can be assayed either phenotypically or genotypically. The “gold standard” test is the plaque reduction assay in which human fibroblasts are cultured with ganciclovir at various defined concentrations. CMV growth can be quantified by counting viral plaque formation or by a DNA hybridization technique. The concentration of ganciclovir required to inhibit 50% of CMV growth is the IC50 value. Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml.
Ganciclovir resistance can also be detected via genotype analysis to assess for known mutations in the UL54 and UL97 genes. Detection of resistance via gene mutations is attractive since it is less labour intensive, less time consuming, and is not limited by the need to culture CMV from patient specimens. The correlation between genotype and phenotype, however, is imperfect so genotype-based resistance reports need to be interpreted with caution.
Risk factors:
Prevelance of ganciclovir resistance in SOT 0-15%
1- Prolonged exposure to antiviral agents
2- CMV seronegativity at transplant when receiving a seropositive organ
3- degree of immunosuppression
4- magnitude of CMV viremia
Prevention of Ganciclovir Resistant CMV Infection:
No well established protocol yet.
1- valganciclovir is ten times more bioavailable than oral ganciclovir, it decreases resistance while retaining the convenience and safety of an oral agent. It is superior to oral ganciclovir for the prevention of resistant CMV infection.
2- Foscarnet it is direct competitive inhibitor of DNA polymerase, it does not depent on phosphotransferase enzyme as no need for phosphorylation, so it is not affected by mutations in UL97 gene, but can be affected by mutation in UL54 gene, so prolonged exposure to Foscarnet can leads to resistance from that point. This medication has renal toxicity, electrolyte abnormalities, and seizures as adverse effects, these limits its use.
3- foscarnet and ganciclovir are of similar efficacy but that foscarnet is less well tolerated. As such, foscarnet is useful agent to use against ganciclovir resistant CMV but treatment will be limited in some patients by nephrotoxicity and/or electrolyte abnormalities.
4- Combination therapy with dose reduced ganciclovir and foscarnet is superior to monotherapy with the alternative agent alone.
5- Cidofovir it is monophosphorylated cytosine analogue, prolonged treatment of CMV infection with ganciclovir can also lead to the development of cross-resistance to cidofovir, its use is limited because of its adverse effects like nephrotoxicity, ocular diseases and BM suppression.
6- Leflunomide it is immunomodulatory drug used in the treatment of rheumatoid arthritis, it is immunosuppressive medication with anti-infective properties against viruses. major toxicity is transaminase elevation, can be used in multi-drug CMV resistant cases.
in my practice we used valganciclovir (valcyte) in prophylaxis in high risk patient D+/R- or D+/R+ or when using ATG as induction or in the treatment of ACR for 3-6 months.
and we used iv ganciclovir in treating suspected tissue invasive CMV disease
of course renal dose adjustment is needed and requested
I suggest that you use bold or underline for heading or sub-headings that make it easier to read.
I like your summary of these guidelines.
I like your reflection of current practice in your hospital in relation to these (similar) guidelines
noted Prof.
Drugs for treatment of CMV
1. Ganciclovir: is a guanosine analogue that inhibits CMV DNA polymerase. In order to become
active it must first be phosphorylated in three steps to a triphosphorylated form. Once
phosphorylated, it acts as a competitive substrate for DNA polymerase and slows the replication
of CMV DNA by DNA polymerase. Phosphorylation is accomplished by the phosphotransferase
produced by the gene UL97. Mutations arising in UL97 phosphotransferase leads to ganciclovir
resistance. Also, mutations arising in the DNA polymerase gene UL54 leads to resistance to ganciclovir.
2. Valganciclovir: is valyl ester prodrug of ganciclovir and approximately ten times more bioavailable than oral ganciclovir
3. Foscarnet: Foscarnet is a direct competitive inhibitor of DNA polymerase. Unlike ganciclovir, it does not need to be phosphorylated in order to inhibit CMV DNA polymerase. Since it is not dependent on the CMV phosphotransferase foscarnet is effective in UL97 mutations that are resistant to ganciclovir but mutations in the DNA polymerase gene UL54 leads to foscarnet resistance.
4. Cidofovir: It is a monophosphorylated cytosine analogue which, like ganciclovir, is further phosphorylated intracellularly to form a compound that impedes DNA polymerase activity. Its given intravenously once or twice per week.
5. Leflunomide: is immunomodulator and its activity against cytomegalovirus is achieved by inhibition of construction of virions which is dependent upon protein kinase rather than with DNA synthesis. Its protein kinase inhibitor and as a competitive inhibitor of dihydroorotate dehydrogenase, the intracellular enzyme required for pyrimidine synthesis. It specifically inhibits denovo pyrimidine synthesis and hence selectively inhibits activated lymphocytes since resting lymphocytes are able to synthesize pyrimidines via a salvage pathway. Leflunomide is a prodrug that is rapidly metabolized to the active metabolite, A77 1726. The drug has a long-half life on the order of 15-18 days potentiated by substantial enterohepatic recirculation. Without a loading dose it is estimated that it would take nearly two months to achieve steady-state plasma concentrations. Likewise, after discontinuation of the medication it can take as long as two years. for the body to entirely clear the drug. Renal excretion is limited.
Some definitions
· IC50 value is the inhibitory concentration needed by the drug to cause 50% of its therapeutic effect which in ganciclovir equal 6μg/ml.
· Ganciclovir CMV resistance definition either phenotypically or genotypically.
1. Phenotypically means although target level of ganciclovir achieved (IC50 of > 6μg/ml) and no CMV reduction by counting plaque formation or by PCR.
2. Genotype analysis to assess for known mutations in the UL54 and UL97 genes.
3. The “gold standard” test still is viral culture with ganciclovir at various defined concentrations.
Risk factors
1. CMV seronegative at transplant when receiving a seropositive organ.
2. degree of immunosuppression.
3. magnitude of CMV viremia.
4. prolonged exposure to anti-CMV medication especially to subtherapeutic plasma concentrations of ganciclovir.
Prevention and treatment of Ganciclovir Resistant CMV Infection:
Usage of valganciclovir: valganciclovir afford more stable therapeutic level in long term use and prevent resistance.
Foscarnet use: still its use limited for CMV resistant cases either as monotherapy of as combination with ganciclovir with reduced dose (half-dose ganciclovir (5mg/kg IV q24h) and half-dose foscarnet (90mg/kg
IV q24h) because of its side effects and availability.
It’s usually cause nephrotoxicity and electrolytes disturbance in the form of sever hypomagnesaemia, hypocalcemia, hypokalemia. Studies evaluated foscarnet for newly diagnosed CMV cases as monotherapy of as combination with ganciclovir with reduced dose showed inferiority in comparison to ganciclovir monotherapy and more side effects.
Cidofovir: its use still limited to limited cases because of adverse effect in the form of nephrotoxicity This can be attenuated by pre-hydration and the use of probenecid but these two interventions can also limit tolerance. In addition, cidofovir has been noted in case reports to cause bone marrow suppression and ocular disease including iritis, uveitis, and vitreous hypotonicity.
Leflunomide: still also limited to ganciclovir resistant cases and the major toxicity of leflunomide is transaminase elevation, hepatic necrosis and death from liver failure have been reported but are rare, diarrhea , hypertension , reversible alopecia, and rash.
In my transplant center we used to divide cases into
1. High risk patients (D+ to R-): for such patients we used to give ganciclovir therapeutic dose for 5-7 days post-transplant then switch to valganciclovir therapeutic for 3weaks then prophylactic for 3-6m.
2. Medium risk patient (D+ to R+) who received depleting induction or desensitization we used to give them valganciclovir prophylactic dose for 3-6m post-transplant
3. Low risk patients (D+ to R+) with low immunological risk who didn’t receive depleting induction we follow frequent monitoring of CMV PCR and preemptive treatment.
CMV infection used to treat with ganciclovir in severe cases and valganciclovir in mild cases.
Therapeutic dose continued for at least 2 PCR -ve then switch to prophylactic dose beside decrease immunosuppression to accepted levels according to duration of transplant and severity of infection then switched to prophylactic dose for 6-9m by valganciclovir.
CMV resistance diagnosed by PCR quantitive titer which not responding or increasing although therapeutic optimum ganciclovir dose obtained according to eGFR for such cases we used to give CMV specific IVIG with stop MMF and CNI on the lower level.
We have no experience in use of cidofovir for CMV and we used only leflunomide for BK nephropathy.
I like your summary of these guidelines.
I like your reflection of current practice in your hospital in relation to these (similar) guidelines. I note your mention about challenges of resistance.
Thanks Professor Ajay
-Summary
Ganciclovir Mechanism of Action and it’s Resistance
Ganciclovir active forum is triphosphorylated forum done by the phosphotransferase
produced by the gene UL97,it acts by inhibiting CMV DNA polymerase decreasing CMV replication.
Mutations in UL97 phosphotransferase and DNA polymerase gene UL54can cause the resistance, the mutations can occur separately or simultaneously.
UL54 mutations can lead to cross resistance to foscarnet and cidofovir .
Definition
Ganciclovir resistance phenotypic assay which is the gold standard test is the reduction assay of the plaques where human fibroblasts are cultured with ganciclovir .
Ganciclovir resistance represents plaque reduction or DNA hybridization IC50 of > 6µg/ml.
Ganciclovir resistance genotypic assay includes detection of the gene mutation
Correlation between both assays is not well established
Prevalence and resistance risk factors
It is uncommon for untreated cases but develops rapidly after extended courses of antiviral medications.
CMV resistance ranges from 0-15% in SOT cases varies according to immunosuppression and organ transplanted with highest prevalence in lung transplants and the least is the kidney transplants
Ganciclovir resistance risk factors are CMV D+/R-, immunosuppression regimen and doses, CMV viral load and prolonged exposure to anti-CMV medication.
Ganciclovir Resistant CMV Infection prevention
Valganciclovir was introduced in 2001, it is nearly 10 times more bioavailable than oral ganciclovir. Valganciclovir can decrease ganciclovir resistance caused by prolonged subtherapeutic doses of ganciclovir while keeping the advantages of an oral agent.
Valganciclovir is better than oral ganciclovir for the prevention of resistant CMV infection in SOT but it can increase neutropenia risk.
Foscarnet
It is a direct inhibitor of DNA polymerase without needing to be phosphorylated therefore it can maintain it’s effect against CMV isolates with UL97 mutations resistant to ganciclovir.
Meanwhile DNA polymerase gene UL54 mutations and prolonged foscarnet treatment can lead to foscarnet resistance.
Foscarnet side effects that limited it’s use are renal toxicity, electrolyte abnormalities, and seizures.
A study concluded that both ganciclovir and foscarnet have the same efficacy.
Combination therapy of ganciclovir and foscarnet with dose reduction
This was an acceptable protocol of ganciclovir resistant CMV infection treatment as ganciclovir and foscarnet resistance can occur with different gene mutations.
Data suggested that combination therapy can be efficient in pre-emptive therapy of CMV antigenemia in non ganciclovir resistant bone marrow transplant patients as well as dose reduction can decrease toxic side effects .
A study tested the combination therapy with acceptable results apart from hypomagnesemia that was treated
A study evaluated combination therapy and isolated ganciclovir in preemptive therapy for recipients with CMV viremia revealing that cases receiving isolated ganciclovir were more likely to have negative PCR after 14 days and less adverse events compared to combination therapy.
Cidofovir
It has to be phosphorylated as ganciclovir to inhibit DNA polymerase.
It has low resistance risk at baseline but can increase with prolonged usage also it has cross resistance with ganciclovir.
Cidofovir use is limited due to it’s toxicity in the forum of nephrotoxicity and bone marrow suppression and ocular diseases.
Leflunomide
It is an immunomodulatory drug with immunosuppressive anti -infective properties,it has a long half life due to enterohepatic circulation ,with limited renal excretion ,it can be totally cleared from the body after years .
It can inhibit multidrug-resistant CMV isolate as confirmed by plaque reduction assays , it acts through interfering with final virion assembly.
It’s side effect include elevated liver enzymes that resolve after stopping the drug as well as diarrhea ,hypertension and rashes.
Conclusion
CMV infection therapy is challenging in immunocompromised cases ,as Ganciclovir resistance is detected in SOT recipients treated with prolonged courses , Foscarnet and Cidofovir are alternativies but carry high risk of nephrotoxicity thereby limiting their use.
Combination therapy with reduced doses to lesson side effects needs further evaluation
Leflunomide as an immunomodulator with antiviral effect is under further studies ,it causes elevation of liver enzymes.
-My practice
Ganciclovir resistance is challenging so it can be treated with Foscarnet but with caution due to it’s nephrotoxicity
I like your summary of these guidelines.
I like your reflection of current practice in your hospital in relation to these (similar) guidelines. I like your summary of these guidelines.
I note your mention about challenges of ganciclovir resistance.
Drug Resistance to Ganciclovir
Guanosine analog ganciclovir inhibits CMV DNA polymerase. It must be phosphorylated three times to become active. Phosphorylated, it competes with DNA polymerase and reduces CMV DNA replication. UL97 phosphotransferase phosphorylates. UL97 phosphotransferase mutations cause ganciclovir resistance. UL54 DNA polymerase gene mutations also provide ganciclovir resistance.
Definition
Ganciclovir resistance may be tested phenotypically or genotypically. Ganciclovir-cultured human fibroblasts are the “gold standard” test. Viral plaque development or DNA hybridization may measure CMV growth. Ganciclovir’s IC50 inhibits 50% of CMV growth. Plaque reduction or DNA hybridization IC50 > 6 g/mL indicates ganciclovir resistance.
Risk factors for drug resistance:
Ganciclovir resistance is associated with CMV seronegativity upon transplant when receiving a seropositive organ, immunosuppression, CMV viremia, and chronic anti-CMV drug use. Seronegative recipients of seropositive organs are at risk of CMV infection and ganciclovir resistance.
Preventing Ganciclovir-Resistant CMV
Ganciclovir-resistant CMV infections are unstudied.
Only case reports and case series on resistant infection treatment results exist. Controlled trials evaluating alternate techniques have not been reported. Preventing ganciclovir resistance is important because it can cause a lot of illnesses, and there isn’t a good second-line treatment for it.
Foscarnet
Foscarnet is the most important medication that may be used instead of ganciclovir for the treatment of CMV viremia and illness.
Dose-reduced ganciclovir with foscarnet treatment
A combination of ganciclovir and foscarnet at decreased dosages may treat CMV infections resistant to ganciclovir. Ganciclovir and foscarnet resistance are frequently caused by separate gene mutations, which justifies this technique.
Cidofovir
Cytomegalovirus therapy with cidofovir was FDA-approved in 1996. Like ganciclovir, it is an analog of monophosphorylated cytosine that is phosphorylated inside cells to make a DNA polymerase inhibitor. Cidofovir must be taken intravenously, but only once or twice a week. Like ganciclovir and foscarnet, cidofovir resistance starts low but builds.
Leflunomide
The FDA authorized leflunomide in 1998 to treat rheumatoid arthritis. Leflunomide’s antiviral qualities make it appealing to transplant patients. Researchers found that leflunomide was effective against cytomegalovirus when they thought that the high number of phosphoproteins in CMV would show that intracellular virions depend on protein kinase.
I did not face any cases of CMV resistant to gancyclovir. I did not use Foscarnet or Cidofovir.
I used leflunomide for BK nephropathy.
I like your summary of these guidelines.
I like that your reflection of current practice in your hospital in relation to these (similar) guidelines. I note your mention about your experience in using leflunomide for BKV.
Yes, we are using leflunomide off-label with weak evidence in BK nephropathy and as a substitute for the antiproliferative medication (MMF).
Mechanism of action and resistance of gancyclovir
Diagnosis of gancyclovir resistance
Risk factors for gancyclovir resistance
Treatment of Ganciclovir Resistant CMV Infection
1- Foscarent
·
2- Combination therapy with reduced doses of ganciclovir and foscarnet
3- Cidofovir
4- Leflunamide
In my practice
I like your summary of these guidelines.
I like your reflection of current practice in your hospital in relation to these (similar) guidelines. I note your mention about challenges of ganciclovir resistance.
Treatment of Ganciclovir Resistant Cytomegalovirus Infection
1-Please summarise this article;
Ganciclovir;
Mechanism of Action and Drug Resistance;
-Ganciclovir was approved by the FDA in 1989.
-Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase. In order to become active it must first be phosphorylated in three steps to a triphosphorylated form.
-Mutations arising in UL97 phosphotransferase lead to ganciclovir resistance. Similarly, mutations arising in the DNA polymerase gene UL54 also confer resistance to ganciclovir.
-The “gold standard” test is the plaque reduction assay in which human fibroblasts are cultured with ganciclovir at various defined concentrations. CMV growth can be quantified by counting viral plaque formation or by a DNA hybridization technique.
-Ganciclovir resistance is uncommon at baseline amongst untreated patients but arises rapidly after prolonged exposure to antiviral agents.
-Among solid organ transplant recipients, the prevalence of CMV resistance ranges
between 0 and 15%.
Risk factors;
-Seronegative recipients of seropositive organs appear to be at particular risk of both CMV infection and ganciclovir resistance.
-Degree of immunosuppression,
-Magnitude of CMV viremia,
-Prolonged exposure to anti-CMV medication,
Prevention of Ganciclovir Resistant CMV Infection;
-The treatment of ganciclovir resistant CMV infections has not been comprehensively studied.
-The FDA approval of the valyl ester prodrug of ganciclovir valganciclovir in 2001, introduced a more potent option for CMV prophylaxis and maintenance therapy of disease in both transplant recipients and AIDS patients.
-Valganciclovir is approximately ten times more bioavailable than oral ganciclovir.
-In some studies valganciclovir was shown to be superior to oral ganciclovir for the prevention of resistant CMV infection.
-The safety profile was generally similar between the two groups except that patients treated with valganciclovir had a higher incidence of neutropenia (8.2%, vs 3.2%).
Foscarnet;
-The primary alternative to ganciclovir for the treatment of CMV viremia and disease is foscarnet.
-Foscarnet was approved by the FDA in 1991. Foscarnet is a direct competitive inhibitor of DNA polymerase.Unlike ganciclovir, it does not need to be phosphorylated in order to inhibit CMV DNA polymerase.
-Since it is not dependent on the CMV phosphotransferase UL97 it retains activity against CMV isolates with UL97 mutations that are resistant to ganciclovir.
-Mutations in the DNA polymerase gene UL54.
-The risk of resistance increases with the duration of foscarnet therapy.
-The major limitation to greater use of foscarnet has been its adverse effect profile;
Nephrotoxicity,
Electrolytes Disturbances (Hypocalcemia , Hypomagnesemia , Hypokalemia, Hypophosphatemia),
Seizures,
Genital ulcers,
Infusion-related symptoms (fatigue, anxiety, nausea, numbness/tingling).
Combination therapy with dose reduced ganciclovir and foscarnet;
-Combination therapy has been shown to be effective in pre-emptive therapy of CMV antigenemia in non-ganciclovir resistant bone marrow transplant patients.
-Moreover, investigators reasoned that synergy between the two agents would permit lower dosing of each agent and consequent mitigation of their different toxicity profiles.
-Combination therapy was also more likely to cause renal dysfunction and electrolyte
abnormalities (seen in 25% of combination patients versus 0% of monotherapy patients,
-The relative inferiority of reduced dose combination therapy in this trial perhaps reflects the obvious advantage in treating ganciclovir sensitive isolates with full dose ganciclovir.
Cidofovir;
-Cidofovir was approved by the FDA in 1996 for the treatment of cytomegalovirus infection.
-It is a monophosphorylated cytosine analogue which, like ganciclovir, is further phosphorylated intracellularly to form a compound that impedes DNA polymerase activity.
-The pharmacology of cidofovir is such that it has to be given intravenously but need only be administered once or twice per week.
-Like ganciclovir and foscarnet, resistance to cidofovir is low at baseline but rises.
-Notably, prolonged treatment of CMV infection with ganciclovir can also lead to the
development of cross-resistance to cidofovir.
-The popularity of cidofovir therapy has been limited by its adverse effect profile.
-Cidofovir can cause nephrotoxicity in as many as half of all patients.This can be attenuated by pre-hydration and the use of probenecid but these two interventions can also limit tolerance.
-In addition, cidofovir has been noted in case reports to cause bone marrow suppression and ocular disease including iritis, uveitis, and vitreous hypotonicity.
Leflunomide;
-Leflunomide is an immunomodulatory drug originally developed for the treatment of rheumatoid arthritis and approved for that indication by the FDA in 1998.
-Leflunomide has attracted particular interest from the transplant community because in addition to immunosuppressive properties it is active against viruses.
-It specifically inhibits denovo pyrimidine synthesis and hence selectively inhibits activated lymphocytes since resting lymphocytes are able to synthesize pyrimidines via a salvage pathway.
-The drug has a long-half life on the order of 15-18 days potentiated by substantial enterohepatic recirculation.
-Without a loading dose it is estimated that it would take nearly two months to achieve steady-state plasma concentrations.
-The major toxicity of leflunomide is transaminase elevation. Cases of hepatic necrosis and death from liver failure have been reported but are rare.
-The FDA has estimated the incidence of hepatic necrosis to be 0.02 to 0.04%.
-Patients with pre-existing liver disease, heavy alcohol intake, or concurrent viral hepatitis should not be given leflunomide.
-Leflunomide is contraindicated in pregnancy due to reports of fetal death and teratogenesis in human subjects.
-Other averse effects; diarrhea (17-33%), hypertension (6-12%), reversible alopecia (8-11%), and rash (10-14%).
-In addition, there have been case reports of weight loss and pancytopenia.
–This article considered a narrative review; (level V)
2-Please reflect on your practice;
-In our practice; we have oral valganciclovir for treatment of CMV and for Prophylaxis protocol.
-We have experience with the use iv ganciclovir in treatment (tissue invasive CMV).
-We use (foscarnet) in case (post kidney transplant with CMV colitis) with ganciclovir resistence,but unfortunately developed deterioration of graft function and lost graft and starting haemodialysis.
-We have no experience in our service with the use of Leflunomide.
–The novel immunomodulatory agent leflunomide holds promise as a future agent for the management of CMV since it both potentiates immunosuppression and suppresses CMV reproduction.
-Management of CMV resistance is challenging due to difficulty of getting the viral genotype testing and availability of the second line therapy.
I like your summary of these guidelines.
I like your reflection of current practice in your hospital in relation to these (similar) guidelines. I note your mention about challenges of genotyping.
Ganciclovir Mechanism of Action and Drug Resistance;
——————————————————————————————–
Ganciclovir is a guanosine analogue that inhibits CMV DNA polymerase. The active triphosphorylated form acts as a competitive substrate for DNA polymerase and slows the replication of CMV DNA by DNA polymerase. Phosphorylation is accomplished by the phosphotransferase produced by the gene UL97. Mutations arising in UL97 phosphotransferase lead to ganciclovir resistance. Similarly, mutations arising in the DNA polymerase gene UL54 also confer resistance to ganciclovir.
Definition ;
————————————————
Ganciclovir resistance can be assayed either;
1-Phenotypically ;
The “gold standard” test is the plaque reduction assay in which human fibroblasts are cultured with ganciclovir at various defined concentrations. CMV growth can be quantified by counting viral plaque formation or by a DNA hybridization technique.
Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6μg/ml.
2-Genotypically.
Ganciclovir resistance can also be detected via genotype analysis to assess for known mutations in the UL54 and UL97 genes. Detection of resistance via gene mutations is attractive since it is less labour intensive, less time consuming, and is not limited by the need to culture CMV from patient specimens. The correlation between genotype and phenotype, however, is imperfect so genotype-based resistance reports need to be interpreted with caution.
Prevalence and Risk Factors for Resistance;
—————————————————————————
Among solid organ transplant recipients, the prevalence of CMV resistance ranges between 0 and 15%.
Risk factors for the acquisition of ganciclovir resistance include;
1- CMV seronegativity at transplant when receiving a seropositive organ
2- degree of immunosuppression
3- magnitude of CMV viremia
4- prolonged exposure to anti-CMV medication.
Patients with ganciclovir resistant disease suffered a statistically significant decrease in survival compared to those with ganciclovir sensitive disease.
Prevention of Ganciclovir Resistant CMV Infection;
————————————————————————-
1-introduction of more potent option for CMV prophylaxis and maintenance therapy of disease in both transplant recipients and AIDS patients .
a-Valganciclovir;
is approximately ten times more bioavailable than oral ganciclovir. Since ganciclovir resistance is thought to be related to prolonged exposure to subtherapeutic plasma concentrations of ganciclovir, valganciclovir offered a potential means to decrease resistance while retaining the convenience and safety of an oral agent.
b- Foscarnet;
Unlike ganciclovir, it does not need to be phosphorylated in order to inhibit CMV DNA polymerase.
Since it is not dependent on the CMV phosphotransferase UL97 it retains activity against CMV isolates with UL97 mutations that are resistant to ganciclovir. Mutations in the DNA polymerase gene UL54, however, do confer foscarnet resistance and can sometimes be selected for by prolonged ganciclovir therapy.
Like ganciclovir, the risk of resistance increases with the duration of foscarnet therapy. Drug resistance was associated with an increased risk of retinitis progression.
Foscarnet is associated with renal toxicity, electrolyte abnormalities, and seizures .
c- Combination therapy with dose reduced ganciclovir and foscarnet;
1-The rationale for this strategy stems from the recognition that ganciclovir and foscarnet resistance are usually associated with different gene mutations .
2-In vitro demonstration of synergy between the two agents even against ganciclovir resistant isolates.
3-Trial data from the AIDS literature showing that combination therapy is superior to monotherapy with the alternative agent alone.
4-The combination therapy has been shown to be effective in pre-emptive therapy of CMV antigenemia in non- ganciclovir resistant bone marrow transplant patients.
5-Investigators reasoned that synergy between the two agents would permit lower dosing of each agent and consequent mitigation of their different toxicity profiles.
d -Cidofovir;
It is a monophosphorylated cytosine analogue which, like ganciclovir, is further phosphorylated intracellularly to form a compound that impedes DNA polymerase activity.
The pharmacology of cidofovir is such that it has to be given intravenously but need only be administered once or twice per week. Like ganciclovir and foscarnet, resistance to cidofovir is low at baseline but rises under sustained drug pressure.
Prolonged treatment of CMV infection with ganciclovir can also lead to the development of cross-resistance to cidofovir. Treatment with cidofovir alone can confer resistance to ganciclovir .
Cidofovir can cause nephrotoxicity in as many as half of all patients. In addition, cidofovir has been noted in case reports to cause bone marrow suppression and ocular disease including iritis, uveitis, and vitreous hypotonicity.
Clinical reports of the use of cidofovir in ganciclovir-resistant infection are scarce.
Leflunomide ;
Leflunomide is an immunomodulatory drug . Leflunomide acts as a protein kinase inhibitor and as a competitive inhibitor of dihyrdoorotate dehydrogenase, the intracellular enzyme required for pyrimidine synthesis.
Leflunomide’s activity against cytomegalovirus was discovered when investigators hypothesized that the predominance of phosphoproteins within CMV might imply that intracellular construction of virions is dependent upon protein kinase.
The major toxicity of leflunomide is transaminase elevation. Patients with pre-existing liver disease, heavy alcohol intake, or concurrent viral hepatitis should not be given leflunomide.
Other adverse effects reported in the major trials of leflunomide for the treatment of rheumatoid arthritis include diarrhea , hypertension , reversible alopecia , and rash .In addition, there have been case reports of weight loss and pancytopenia.
Conclusion;
——————————————
The management of CMV infection remains a substantial challenge for clinicians caring for immunocompromised patients. While there are a number of agents active against the virus, effective therapy requires prolonged drug use which in turn is associated with emergence of drug resistant virus.
CMV resistance to ganciclovir has been reported with increasing frequency in both AIDS patients treated for CMV retinitis and in recipients of both bone marrow and solid organ transplants.
The alternative therapies foscarnet and cidofovir both appear to have good in vivo activity against cytomegalovirus but both are limited by their propensity to cause acute renal failure.
The use of reduced dose combination therapy appears to deliver potent antiviral therapy with less risk of nephrotoxicity but this approach requires further study.
The novel immunomodulatory agent leflunomide holds promise as a future agent for the management of CMV since it both potentiates immunosuppression and suppresses CMV reproduction..
Please reflect on your practice;
———————————————————-
I have no previous experience in treating Ganciclovir resistant CMV infection . No other available options of therapy rather than valganciclovir and Ganciclovir .We depend upon the clinical index of suspicion in the diagnosis of Ganciclovir resistant .
What is your analysis regarding the level of evidence, limitations and strengths of this publication? I like your reflection of your own practice mentioning challenges of genotyping.
Typing the whole sentence in bold or capitals amounts to ‘shouting’.
Thanks professor
Level V
limitation ;
———————-
1-almost of trials are small in sample size.
2- Experimental data on the use of leflunomide in human beings is extremely limited and remains on the case report level.
I like your summary of these guidelines. Typing the whole sentences as the past paragraph amounts to shouting.
I like your reflection of current practice in your hospital in relation to these (similar) guidelines. I note your mention about challenges of genotyping.
Ganciclovir resistance:
CMV infection is commonly encountered in the context of transplantation. It might lead to progressive disease with excessive morbidity and mortality.
Ganciclovir is first line therapy for CMV infection. However, it was increasingly noticed that Ganciclovir resistance is increasing among transplant patients .
Mechanism of Ganciclovir resistance :
Ganciclovir is guanosine analogue that impair proliferation of CMV virus resultant in remission of CMV disease.
its usually activated by triple phosphorylation mediated by phosphotransferase enzyme.
Phosphotransferase enzyme is encoded by UL97 gene, therefore any mutation in that gene would result in Ganciclovir resistant.
after phosphorylation , ganciclovir utilized as a substrate for DNA polymerase enzyme competing with CMV DNA , resultant in inhibition of CMV proliferation.
DNA polymerase enzyme: is encoded by UL54 gene, therefore any mutation in that gene lead to abnormal enzyme DNA polymerase with resistance to Ganciclovir therapy.
UL54 mutation might result in resistance to foscarnet and cidofovir medicines as both of them are utilizing same enzyme DNA polymerase .
Risk factors for CMV resistance:
1] Primary ganciclovir resistance is uncommon, however, after extended administration of the medicine , an increased prevalence is observed , mediated via mutation of UL97 gene and UL54 gene.
2] Its higher with lung transplant reaching to 15%.
3] Seronegative recipient of a seronegative donor.
4] Intensity of immune suppression, with lymphocye depleting agent at induction time.
5] volume of CMV virus.
Reducing incidence of ganciclovir resistance:
prescribing valganciclovir is associated with less incidence of resistance in comparison to ganciclovir. Alternatively, using foscarnet was linked to less risk of resistance. Its side effects limit its use , which include renal toxicity, seizure and electrolytes disturbance.
Combined Ganciclovir and foscarnet protocol:
Owing to different enzymes mutation reported with each of ganciclovir and Foscarnet , a combination protocol was advocated to overcome the resistance risk related to each one.
Cidofovir :
Similar to other medication, resistance to Cidofovir might emerge from cross-resistance to Foscarnet and Ganciclovir, in particular , after prolonged courses of the latter.
Leflunomide:
is a promising immunomodulating therapy less reported to be associated with resistance.
I like your summary. I wish you could write your reflection of your own practice.
I like your summary of these guidelines.
What is your reflection of current practice in your hospital in relation to these (similar) guidelines?
SUMMARY.
Introduction.
IntroductionCMV infection and disease is very common among the solid organ transplantation patient due to partly the effect of the immunosuppressive state and the CMV status either the donors or the recipients. Moreso, some degree of resistance have been noticed among patient that received ganciclovir for treatmentof the CMV disease.
Ganciclovir mechanism of action and drug resistance.
Ganciclovir resistance can be efined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml. Tis could be asseyed phenotypically or genetically
Prevalence and risk factors for resistance
-CMV D+/R-
-degree of immunosuppression
-magnitude of CMV viraemia
-prolong exposure to anti-CMV medication
Prevention of Ganciclovir Resistant CMV Infection
-Valganciclovir, Foscarnate, Cidofovir, and Leflunomide
Conclusion
One of the fall outs of solid organ transplantation is the occurrence of CMV infection or disease which can cause graft failure if not detected early. Also the prolong use of antiviral agent like ganciclovir has resulted in resistance and paving way for others like valganciclovir, foscarnate, cidofovir, and leflunomide.
Reflect on your practice
In my country of practice then, the available drugs are ganciclovir and Valganciclovir. Unfortunately, for most patients that might have developed resistance are likely to lose their kidney allograft as the facility to even test the CMV genotype variant is scarce and out of the reach of the majority to pay for such an investigation
What is your analysis regarding the level of evidence, limitations and strengths of this publication? I like your reflection of your own practice mentioning challenges of genotyping.
I like your summary of these guidelines.
I like your reflection of current practice in your hospital in relation to these (similar) guidelines. I note your mention about challenges of genotyping.
This study is a narrative review evaluating alternatives for Cytomegalovirus treatment for immunosuppressed patients (either by AIDS, solid organ transplantation, or bone marrow transplantation) who develop resistance to standard Ganciclovir treatment.
Resistance
CMV infection can lead to graft loss and death if not properly treated. Ganciclovir works on two key genes, UL97 and UL54, decreasing the ability of the virus to multiply. Mutation at these loci leads to drug resistance. Mutations in UL54 can cause cross-resistance to cidofovir and Foscarnet.
Two tests can be used. Detection of UL97 and UL54 mutations (genotypically) or increase in a minimum inhibitory concentration greater than 6microgamma/mL (phenotypically).
Risk factors for resistance
– Prolonged use of antivirals
– Degree of immunosuppression
– Magnitude of viral load
– Giver+/Recipient-
Valganciclovir was released as therapy and prophylaxis. After six months of use, an increase in resistance was found, but smaller when compared to the group that used ganciclovir.
foscarnet
It does not use the UL97 gene, but it can interfere with resistance with the UL54 gene. Associated with nephrotoxicity, electrolyte disturbances, and convulsions. It can be used in combination with Ganciclovir in an attempt to reduce the dose of both and, consequently, their toxicity.
Cidofovir
It can also be mutated by UL54. It presents greater resistance throughout its duration when compared to the previous drugs. Significant nephrotoxicity, which is why its use is sometimes added with dilution and probenecid.
Leflunomide
It is an immunomodulator that has an indirect action on CMV, impacting at the same time as an immunosuppressant and antiviral. Its side effects include the elevation of liver transaminases.
Conclusion
In Brazil, we do not have Cidofovir. We had no experience in our service with the use of Leflunomide. Due to the difficulty in importing Foscarnet, there is a tendency to raise the dose of Ganciclovir to 15mg/kg/day and titrate it depending on the side effects of the drug.
We do not have Valganciclovir, which also limits the therapy.
Recently, Letermovir was approved for the prophylaxis of Bone Marrow Transplantation and the use of Maribavir and Enriched Immunoglobulin for CMV is currently in the process of being validated.
What is your analysis regarding the level of evidence, limitations and strengths of this publication? Please type headings and subheadings in bold or underline to make it easy to read.
I like your reflection of your own practice.
I suggest that you use bold or underline for heading or sub-headings that make it easier to read.
I like your summary of these guidelines.
I like your reflection of current practice in your hospital in relation to these (similar) guidelines
I will improve next time
Thank you, Professor
A-Summary
Gancyclovir mechanism of action & drug resistance:
Definition:
Prevalence and risk factors for resistance:
Prevalence: between 0 to 15% according to the type organ transplanted (highest in lung transplantation)
Risk factors: D+/ R- status, amount of immune-suppression, degree of CMV viremia, prolonged anti-viral therapy
Prevention of Ganciclovir Resistance CMV infection:
-Oral valganciclovir (higher bioavailability):
-Foscarnt:
-Combination therapy with dose reduced ganciclovir and foscarnet:
-Cidofovir:
-Leflunomide:
Conclusion;
B.My practice:
C. This was a narrative review, level 5
I like your analysis regarding the level of evidence. You need not to type the whole sentence in bold or capitals. That amounts to ‘shouting.’
I like your reflection of your own practice.
Thanks prof, well noted
Ganciclovir Drug Resistance
Mutations can occur as followings:
· Arising in UL97 phosphotransferase. Different UL97 mutations are associated with different degrees of ganciclovir resistance. Most patients develop only UL97 mutations.
· Arising in the DNA polymerase gene UL54 also confer resistance to ganciclovir.
· Prolonged exposure to ganciclovir can give rise to simultaneous UL54 and UL97 mutations. This is associated with higher level resistance to ganciclovir.
Definition of Ganciclovir resistance:
Can be assayed either phenotypically or genotypically. The “gold standard” test is the plaque reduction assay in which human fibroblasts are cultured with ganciclovir at various defined concentrations. CMV growth can be quantified by counting viral plaque formation or by a DNA hybridization technique. The concentration of ganciclovir required to inhibit 50% of CMV growth is the IC50 value.
Ganciclovir resistance has been defined as a plaque reduction or DNA hybridization IC50 of > 6µg/ml.
Risk factors for the acquisition of ganciclovir resistance include:
· CMV seronegativity at transplant when receiving a seropositive organ,
· Degree of immunosuppression,
· Magnitude of CMV viremia, and
· Prolonged exposure to anti-CMV medication.
The primary alternative to ganciclovir for the treatment of CMV viremia and disease:
1. Foscarnet. Like ganciclovir, the risk of resistance increases with the duration of foscarnet therapy. Foscarnet and ganciclovir are of similar efficacy but that foscarnet is less well tolerated. The major limitation to greater use of foscarnet has been its adverse effect profile. Foscarnet is associated with renal toxicity, electrolyte abnormalities, and seizures.
2. Combination therapy with dose-reduced ganciclovir and foscarnet.
3. Cidofovir. The popularity of cidofovir therapy has been limited by its adverse effect profile. Cidofovir can cause nephrotoxicity in as many as half of all patients.
4. Leflunomide. Electron micrographic evaluation suggested that leflunomide inhibits CMV by interfering with final virion assembly rather than with DNA synthesis. The major toxicity of leflunomide is transaminase elevation. Other adverse effects reported include diarrhea (17-33%), hypertension (6-12%), reversible alopecia (8-11%), rash (10-14%), and pancytopenia. In an experience from India, 4 patients were treated with a 100mg oral loading dose once daily for three days followed by 20mg/day for three months. All experienced clinical and endoscopic resolution of their disease as well as clearance of serum viremia. No significant adverse effects were reported.
Reflection on our practice: till date, we never came across cases resistant to ganciclovir therapy, however, if it happened probably we can try Leflunomide and observe its effects, it’s less toxic compared to another Rx.
What is your analysis regarding the level of evidence, limitations and strengths of this publication?
I like your attempt at reflection of your own practice.
it’s a review analysis, level evidence 5
II. Treatment of Ganciclovir Resistant Cytomegalovirus Infection
Please summarise this article
===========================================================
Ganciclovir Mechanism of Action and Drug Resistance
================================================================
Definition
==================================================================
Prevalence and Risk Factors for Resistance
==================================================================
Prevention of Ganciclovir Resistant CMV Infection
===================================================================
Foscarnet
====================================================================
Combination therapy with dose reduced ganciclovir and foscarnet
====================================================================
Cidofovir
===================================================================
Leflunomide
====================================================================
Conclusion
===================================================================
Please reflect on your practice
Yes of course
I’m going to learn more about the treatment plan and examine the perceived advantages of the therapy. I’ll also learn more about how frequently hospitals provide clinical trials that patients can take advantage of.
I like that you use bold for heading or sub-headings that make it easier to read.
I like your summary of this article. What is the level of evidence that this publication provides?
Thanks alot for you Prof.Sharma.. noted
What is the level of evidence that this publication provides?
The level evidence is V
What is your analysis regarding the level of evidence, limitations and strengths of this publication?
I like your attempt at reflection of your own practice, but it is very fuzzy. I am not sure what your current practice is
Thanks verey much Prof.Shama .noted
What is your analysis regarding the level of evidence, limitations and strengths of this publication?
Evidence from a number of descriptive or qualitative studies’ meta-syntheses
Yes, level 5.
Many thanks Prof.Sharma