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Raymund R Razonable1,2 1Division of Public Health, Infectious Diseases and Occupational Medicine, Mayo Clinic, Rochester, MN, USA; 2William J von Liebig Center for Transplantation and Clinical Regeneration, Mayo Clinic, Rochester, MN, USACorrespondence: Raymund R Razonable, Email razonable.raymund@mayo.eduAbstract: Cytomegalovirus (CMV) infection is arguably the most important infectious complication that negatively affects the outcome of solid organ transplantation. For decades, CMV management after transplantation has relied on antiviral drugs that inhibit viral DNA polymerase (ganciclovir, foscarnet, and cidofovir). However, their use has been complicated by myelosuppression, nephrotoxicity, and selection of drug-resistant viruses. During the past few years, the therapeutic armamentarium for the management of CMV in solid organ transplant recipients has expanded with the approval of letermovir for CMV prophylaxis in high-risk CMV D+/R- kidney recipients, and maribavir for the treatment of refractory and resistant CMV infection. Both drugs offer significant improvement when compared to standard anti-CMV therapies; letermovir was as efficacious for CMV prevention, whereas maribavir was more effective in treating refractory and resistant CMV infections. Both letermovir and maribavir have favorable safety profiles compared to CMV DNA polymerase inhibitors, without the risk of neutropenia and leukopenia associated with ganciclovir and renal toxicities associated with foscarnet and cidofovir. Moreover, letermovir and maribavir are orally bioavailable, which allows convenient outpatient treatment. However, letermovir and maribavir have a significant drug interaction potential in solid organ transplant recipients, resulting in higher levels of calcineurin inhibitors (cyclosporine and tacrolimus) and mTOR inhibitors (sirolimus and everolimus). Both letermovir and maribavir are CMV-specific and do not have clinical efficacy against other herpes viruses. Thus, there is a need for additional antiviral drugs to prevent herpes simplex and other herpes viruses when clinically indicated. This article provides a comprehensive review of the clinical data supporting the use of letermovir and maribavir in clinical practice. The author provides perspectives on the role of these newly approved drugs in the current management landscape of CMV infection in solid organ transplantation.Keywords: cytomegalovirus, maribavir, letermovir, ganciclovir, drug resistance, prophylaxis, treatment

We evaluated use of maribavir (MBV) for treatment of 15 episodes of refractory/resistant cytomegalovirus infection in 13 solid organ transplant recipients. Treatment failure due to treatment-emergent MBV resistance or early virological recurrence after MBV discontinuation occurred in 7 (47%) episodes. Sustained viral clearance was achieved in 6 (40%) episodes. [ABSTRACT FROM AUTHOR]

Despite the significant progress made, CMV infection is one of the most frequent infectious complications in transplant recipients. CMV infections that become refractory or resistant (R/R) to the available antiviral drugs constitute a clinical challenge and are associated with increased morbidity and mortality. Novel anti-CMV therapies have been recently developed and introduced in clinical practice, which may improve the treatment of these infections. In this review, we summarize the treatment options for R/R CMV infections in adult hematopoietic cell transplant and solid organ transplant recipients, with a special focus on newly available antiviral agents with anti-CMV activity, including maribavir and letermovir. [ABSTRACT FROM AUTHOR]

The effect of food composition, tablet crushing, and antacid coadministration on maribavir pharmacokinetics was assessed in 2 Phase 1 studies in healthy adults. In the first, a single maribavir 400‐mg dose was administered under fasting conditions, with a low‐fat/low‐calorie or a high‐fat/high‐calorie meal. In the second, a single maribavir 100‐mg dose was administered under fasting conditions, as a crushed tablet, or as a whole tablet alone or with an antacid. The 90% confidence intervals of the geometric mean ratios were within 80%‐125% for area under the concentration‐time curve (AUC), but not for maximum plasma concentration (Cmax) for low‐fat/low‐calorie and high‐fat/high‐calorie meals versus fasting or for whole tablet with antacid versus whole tablet alone. The 90% confidence intervals of the geometric mean ratios for AUC and Cmax were within 80%‐125% for crushed versus whole tablet. Maribavir median time to Cmax value in plasma under fed conditions was delayed versus fasting conditions, but there was no statistical difference for crushed versus whole tablet or with versus without antacid. As the antiviral efficacy of maribavir is driven by AUC but not Cmax, findings suggest that maribavir can be administered with food or antacids or as a crushed tablet. [ABSTRACT FROM AUTHOR]

Maribavir, an orally available antiviral agent, has been approved in multiple countries for the treatment of patients with refractory post‐transplant cytomegalovirus (CMV) infection and/or disease. Maribavir is primarily metabolized by CYP3A4; coadministration with CYP3A4 inducers and inhibitors may significantly alter maribavir exposure, thereby affecting its efficacy and safety. The effect of CYP3A4 inducers and inhibitors on maribavir exposure was evaluated based on a drug‐drug interaction (DDI) study and physiologically‐based pharmacokinetic (PBPK) modeling. The effect of rifampin (a strong inducer of CYP3A4 and moderate inducer of CYP1A2), administered at a 600 mg dose once daily, on maribavir pharmacokinetics was assessed in a clinical phase 1 DDI study in healthy participants. A full PBPK model for maribavir was developed and verified using in vitro and clinical pharmacokinetic data from phase 1 studies. The verified PBPK model was then used to simulate maribavir DDI interactions with various CYP3A4 inducers and inhibitors. The DDI study results showed that coadministration with rifampin decreased the maribavir maximum plasma concentration (Cmax), area under the plasma concentration‐time curve (AUC), and trough concentration (Ctrough) by 39%, 60%, and 82%, respectively. Based on the results from the clinical DDI study, the coadministration of maribavir with rifampin is not recommended. The PBPK model did not predict a clinically significant effect of CYP3A4 inhibitors on maribavir exposure; however, it predicted that strong or moderate CYP3A4 inducers, including carbamazepine, efavirenz, phenobarbital, and phenytoin, may reduce maribavir exposure to a clinically significant extent, and may prompt the consideration of a maribavir dosing increase, in accordance with local approved labels and/or regulations. [ABSTRACT FROM AUTHOR]

Human cytomegalovirus (CMV) infection is the most prevalent infection affecting organ transplant recipients, and it is a cause of morbidity and mortality in patients undergoing kidney transplantation. The introduction of ganciclovir (GCV) for both prophylaxis and treatment has vastly improved patient outcomes. GCV resistance can be caused by mutations in the UL97 phosphotransferase gene or the UL54 polymerase gene. It occurs in 1 to 2% of kidney transplant recipients with CMV infection or disease. Antiviral resistance should be considered when increased viral loads and disease progression are observed despite the administration of adequate antiviral therapy. The degree of resistance varies depending on the type of mutation present. We report a patient with resistance to GCV due to a UL97 del597-599 mutation who, despite typically requiring an 8-fold increase in GCV dose, showed a significant decrease in viral load with just a double dose increase. However, the patient’s overall clinical course remained complicated. Due to severe leukopenia, maribavir had to be started, with a good response. Nevertheless, he ultimately died due to indirect CMV-related complications. This case also highlights the complexity of transplant patients, who present multiple challenges ranging from infections to therapy management.

Cytomegalovirus (CMV) remains a serious opportunistic infection in hematopoietic cell transplant (HCT) and solid-organ transplant (SOT) recipients. Traditional anti-CMV drugs are limited by toxicities and the development of resistance. Letermovir and maribavir are newly approved antivirals for the prevention and treatment of CMV. Prior reviews have discussed use of letermovir for prevention of CMV after HCT and maribavir for resistant or refractory (R/R) CMV post HCT or SOT. Subsequent data have expanded their use including letermovir for primary CMV prophylaxis in high-risk renal transplant recipients and new recommendations for extending prophylaxis through day + 200 in certain HCT patients. Data on the use of maribavir for first asymptomatic CMV infection post-HCT has also been published. This review compares the pharmacology of anti-CMV agents and discusses the updated literature of these new drugs in the prevention and treatment of CMV. Letermovir and maribavir are much needed tools that spare toxicities of ganciclovir, foscarnet, and cidofovir. High cost is a challenge preventing their integration into clinical practice in resource-limited countries. Transplant centers need to exercise restraint in overuse to avoid resistance, particularly in the setting of high viral loads. [ABSTRACT FROM AUTHOR]

Background: Cytomegalovirus (CMV) infections among hematopoietic stem cell transplant (HSCT) and solid organ transplant (SOT) recipients impose a significant health care resource utilization (HCRU)‐related economic burden. Maribavir (MBV), a novel anti‐viral therapy (AVT), approved by the United States Food and Drug Administration for post‐transplant CMV infections refractory (with/without resistance) to conventional AVTs has demonstrated lower hospital length of stay (LOS) versus investigator‐assigned therapy (IAT; valgancilovir, ganciclovir, foscarnet, or cidofovir) in a phase 3 trial (SOLSTICE). This study estimated the HCRU costs of MBV versus IAT. Methods: An economic model was developed to estimate HCRU costs for patients treated with MBV or IAT. Mean per‐patient‐per‐year (PPPY) HCRU costs were calculated using (i) annualized mean hospital LOS in SOLSTICE, and (ii) CMV‐related direct costs from published literature. Probabilistic sensitivity analysis with Monte‐Carlo simulations assessed model robustness. Results: Of 352 randomized patients receiving MBV (n = 235) or IAT (n = 117) for 8 weeks in SOLSTICE, 40% had HSCT and 60% had SOT. Mean overall PPPY HCRU costs of overall hospital‐LOS were $67,205 (95% confidence interval [CI]: $33,767, $231,275) versus $145,501 (95% CI: $62,064, $589,505) for MBV and IAT groups, respectively. Mean PPPY ICU and non‐ICU stay costs were: $32,231 (95% CI: $5,248, $184,524) versus $45,307 (95% CI: $3,957, $481,740) for MBV and IAT groups, and $82,237 (95% CI: $40,397, $156,945) MBV versus $228,329 (95% CI: $94,442, $517,476) for MBV and IAT groups, respectively. MBV demonstrated cost savings in over 99.99% of simulations. Conclusions: This analysis suggests that Mean PPPY HCRU costs were 29%–64% lower with MBV versus other‐AVTs. [ABSTRACT FROM AUTHOR]

This study evaluated the cost‐effectiveness of maribavir versus investigator‐assigned therapy (IAT; valganciclovir/ganciclovir, foscarnet, or cidofovir) for post‐transplant refractory cytomegalovirus (CMV) infection with or without resistance. A two‐stage Markov model was designed using data from the SOLSTICE trial (NCT02931539), real‐world multinational observational studies, and published literature. Stage 1 (0–78 weeks) comprised clinically significant CMV (csCMV), non‐clinically significant CMV (n‐csCMV), and dead states; stage 2 (78 weeks–lifetime) comprised alive and dead states. Total costs (2022 USD) and quality‐adjusted life years (QALYs) were estimated for the maribavir and IAT cohorts. An incremental cost‐effectiveness ratio was calculated to determine cost‐effectiveness against a willingness‐to‐pay threshold of $100 000/QALY. Compared with IAT, maribavir had lower costs ($139 751 vs $147 949) and greater QALYs (6.04 vs 5.83), making it cost‐saving and more cost‐effective. Maribavir had higher acquisition costs compared with IAT ($80 531 vs $65 285), but lower costs associated with administration/monitoring ($16 493 vs $27 563), adverse events (AEs) ($11 055 vs $16 114), hospitalization ($27 157 vs $33 905), and graft loss ($4516 vs $5081), thus making treatment with maribavir cost‐saving. Maribavir‐treated patients spent more time without CMV compared with IAT‐treated patients (0.85 years vs 0.68 years), leading to lower retreatment costs for maribavir (cost savings: −$42 970.80). Compared with IAT, maribavir was more cost‐effective for transplant recipients with refractory CMV, owing to better clinical efficacy and avoidance of high costs associated with administration, monitoring, AEs, and hospitalizations. These results can inform healthcare decision‐makers on the most effective use of their resources for post‐transplant refractory CMV treatment. [ABSTRACT FROM AUTHOR]

Background Neutropenia may limit the use of valganciclovir treatment for cytomegalovirus (CMV) infection following hematopoietic cell transplant (HCT). A phase 2 study indicated efficacy of maribavir with fewer treatment-limiting toxicities than valganciclovir. Methods In this multicenter, double-blind, phase 3 study, patients with first asymptomatic CMV infection post-HCT were stratified and randomized 1:1 to maribavir 400 mg twice daily or valganciclovir (dose-adjusted for renal clearance) for 8 weeks with 12 weeks of follow-up. The primary endpoint was confirmed CMV viremia clearance at week 8 (primary hypothesis of noninferiority margin of 7.0%). The key secondary endpoint was a composite of the primary endpoint with no findings of CMV tissue-invasive disease at week 8 through week 16. Treatment-emergent adverse events (TEAEs) were assessed. Results Among patients treated (273 maribavir; 274 valganciclovir), the primary endpoint of noninferiority of maribavir was not met (maribavir, 69.6%; valganciclovir, 77.4%; adjusted difference: −7.7%; 95% confidence interval [CI]: −14.98, −.36; lower limit of 95% CI of treatment difference exceeded −7.0%). At week 16, 52.7% and 48.5% of patients treated (maribavir and valganciclovir, respectively) maintained CMV viremia clearance without tissue-invasive disease (adjusted difference: 4.4%; 95% CI: −3.91, 12.76). With maribavir (vs valganciclovir), fewer patients experienced neutropenia (16.1% and 52.9%) or discontinued due to TEAEs (27.8% and 41.2%). Discontinuations were mostly due to neutropenia (maribavir, 4.0%; valganciclovir, 17.5%). Conclusions Although noninferiority of maribavir to valganciclovir for the primary endpoint was not achieved based on the prespecified noninferiority margin, maribavir demonstrated comparable CMV viremia clearance during post-treatment follow-up, with fewer discontinuations due to neutropenia. Clinical Trials Registration. NCT02927067 [AURORA]. [ABSTRACT FROM AUTHOR]

Purpose: To determine whether maribavir is effective at treating ganciclovir-resistant cytomegalovirus retinitis. Methods: Retrospective case report of a lung-transplant patient with bilateral cytomegalovirus retinitis documented with serum and aqueous humor studies and color fundus photographs. Results: A 72-year-old lung-transplant patient with active ganciclovir-resistant cytomegalovirus was treated with intravitreal foscarnet therapy in one eye. Retinitis developed in the contralateral eye and was managed with systemic maribavir alone. Active retinitis regressed in both the eye treated with intravitreal foscarnet and the uninjected eye. Conclusion: This patient's results suggest that systemic maribavir is an effective treatment for treatment-resistant cytomegalovirus retinitis. [ABSTRACT FROM AUTHOR]

Background This drug resistance analysis of a randomized trial includes 234 patients receiving maribavir and 116 receiving investigator-assigned standard therapy (IAT), where 56% and 24%, respectively, cleared cytomegalovirus DNA at week 8 (treatment responders). Methods Baseline and posttreatment plasma samples were tested for mutations conferring drug resistance in viral genes UL97 , UL54, and UL27. Results At baseline, genotypic testing revealed resistance to ganciclovir, foscarnet, or cidofovir in 56% of patients receiving maribavir and 68% receiving IAT, including 9 newly phenotyped mutations. Among them, 63% (maribavir) and 21% (IAT) were treatment responders. Detected baseline maribavir resistance mutations were UL27 L193F (n = 1) and UL97 F342Y (n = 3). Posttreatment, emergent maribavir resistance mutations were detected in 60 (26%) of those randomized to maribavir, including 49 (48%) of 103 nonresponders and 25 (86%) of the 29 nonresponders where viral DNA initially cleared then rebounded while on maribavir. The most common maribavir resistance mutations were UL97 T409M (n = 34), H411Y (n = 26), and C480F (n = 21), first detected 26 to 130 (median 56) days after starting maribavir. Conclusions Baseline maribavir resistance was rare. Drug resistance to standard cytomegalovirus antivirals did not preclude treatment response to maribavir. Rebound in plasma cytomegalovirus DNA while on maribavir strongly suggests emerging drug resistance. Clinical Trials Registration NCT02931539. [ABSTRACT FROM AUTHOR]

Cytomegalovirus (CMV) infections may increase morbidity and mortality in immunocompromised patients. Until recently, standard antiviral drugs against CMV were limited to viral DNA polymerase inhibitors (val)ganciclovir, foscarnet and cidofovir with a risk for cross-resistance. These drugs may also cause serious side effects. This narrative review provides an update on new antiviral agents that were approved for the prevention and treatment of CMV infections in transplant recipients. Letermovir was approved in 2017 for CMV prophylaxis in CMV-seropositive adults who received an allogeneic hematopoietic stem cell transplant. Maribavir followed four years later, with an indication in the treatment of adult and pediatric transplant patients with refractory/resistant CMV disease. The target of letermovir is the CMV terminase complex (constituted of pUL56, pUL89 and pUL51 subunits). Letermovir prevents the cleavage of viral DNA and its packaging into capsids. Maribavir is a pUL97 kinase inhibitor, which interferes with the assembly of capsids and the egress of virions from the nucleus. Both drugs have activity against most CMV strains resistant to standard drugs and exhibit favorable safety profiles. However, high-level resistance mutations may arise more rapidly in the UL56 gene under letermovir than low-grade resistance mutations. Some mutations emerging in the UL97 gene under maribavir can be cross-resistant with ganciclovir. Thus, letermovir and maribavir now extend the drug arsenal available for the management of CMV infections and their respective niches are currently defined. [ABSTRACT FROM AUTHOR]

Despite current prophylaxis regimens, cytomegalovirus (CMV) is common in hematopoietic cell transplantation (HCT) and solid organ transplantation (SOT) and remains a significant cause of morbidity and mortality. Newer antiviral medications are reshaping the landscape for prevention and treatment of CMV DNAemia, infection, and disease. Letermovir is approved for CMV prevention in adult HCT patients and is attractive due to the absence of marrow suppression seen with ganciclovir/valganciclovir. Letermovir should not be routinely used for CMV treatment due to its low threshold for resistance. Maribavir is approved for the treatment of refractory or resistant CMV disease in HCT and SOT recipients ≥12 years of age, though it has no current role in CMV prevention. More research is needed to fully elucidate the roles, efficacy, and safety of these newer agents in prevention and treatment of CMV in pediatric transplant recipients. [ABSTRACT FROM AUTHOR]

The instructional case is a pediatric haploidentical TCRαβ+/CD19+ depleted allogeneic hematopoietic cell transplantation recipient who developed early onset CMV infection, which was complicated by resistant CMV (both UL97 and UL54) and successfully managed with maribavir and haploidentical CMV-specific T lymphocytes. Novel approaches to resistant CMV infection are reviewed and effective utilization of recent advances in diagnosis and management of resistant CMV in pediatric HCT are highlighted.

Cytomegalovirus (CMV) infections may increase morbidity and mortality in immunocompromised patients. Until recently, standard antiviral drugs against CMV were limited to viral DNA polymerase inhibitors (val)ganciclovir, foscarnet and cidofovir with a risk for cross-resistance. These drugs may also cause serious side effects. This narrative review provides an update on new antiviral agents that were approved for the prevention and treatment of CMV infections in transplant recipients. Letermovir was approved in 2017 for CMV prophylaxis in CMV-seropositive adults who received an allogeneic hematopoietic stem cell transplant. Maribavir followed four years later, with an indication in the treatment of adult and pediatric transplant patients with refractory/resistant CMV disease. The target of letermovir is the CMV terminase complex (constituted of pUL56, pUL89 and pUL51 subunits). Letermovir prevents the cleavage of viral DNA and its packaging into capsids. Maribavir is a pUL97 kinase inhibitor, which interferes with the assembly of capsids and the egress of virions from the nucleus. Both drugs have activity against most CMV strains resistant to standard drugs and exhibit favorable safety profiles. However, high-level resistance mutations may arise more rapidly in the UL56 gene under letermovir than low-grade resistance mutations. Some mutations emerging in the UL97 gene under maribavir can be cross-resistant with ganciclovir. Thus, letermovir and maribavir now extend the drug arsenal available for the management of CMV infections and their respective niches are currently defined.

Human cytomegalovirus (HCMV) is one of the main causes of serious complications in immunocompromised patients and after congenital infection. There are currently drugs available to treat HCMV infection, targeting viral polymerase, whose use is complicated by toxicity and the emergence of resistance. Maribavir and letermovir are the latest antivirals to have been developed with other targets. The approval of letermovir represents an important innovation for CMV prevention in hematopoietic stem cell transplant recipients, whereas maribavir allowed improving the management of refractory or resistant infections in transplant recipients. However, in case of multidrug resistance or for the prevention and treatment of congenital CMV infection, finding new antivirals or molecules able to inhibit CMV replication with the lowest toxicity remains a critical need. This review presents a range of molecules known to be effective against HCMV. Molecules with a direct action against HCMV include brincidofovir, cyclopropavir and anti-terminase benzimidazole analogs. Artemisinin derivatives, quercetin and baicalein, and anti-cyclooxygenase-2 are derived from natural molecules and are generally used for different indications. Although they have demonstrated indirect anti-CMV activity, few clinical studies were performed with these compounds. Immunomodulating molecules such as leflunomide and everolimus have also demonstrated indirect antiviral activity against HCMV and could be an interesting complement to antiviral therapy. The efficacy of anti-CMV immunoglobulins are discussed in CMV congenital infection and in association with direct antiviral therapy in heart transplanted patients. All molecules are described, with their mode of action against HCMV, preclinical tests, clinical studies and possible resistance. All these molecules have shown anti-HCMV potential as monotherapy or in combination with others. These new approaches could be interesting to validate in clinical trials. [ABSTRACT FROM AUTHOR]

Despite the significant progress made, CMV infection is one of the most frequent infectious complications in transplant recipients. CMV infections that become refractory or resistant (R/R) to the available antiviral drugs constitute a clinical challenge and are associated with increased morbidity and mortality. Novel anti-CMV therapies have been recently developed and introduced in clinical practice, which may improve the treatment of these infections. In this review, we summarize the treatment options for R/R CMV infections in adult hematopoietic cell transplant and solid organ transplant recipients, with a special focus on newly available antiviral agents with anti-CMV activity, including maribavir and letermovir.

OBJECTIVES: Cytomegalovirus (CMV) infection represents a serious post-transplantation complication, particularly among transplant recipients with resistant or refractory (R/R) infection. Despite the improvement made in CMV prevention and treatment, remains a need for new therapies that are better tolerated and safer for patients, especially for refractory or resistant (R/R) infections. This analysis investigates the cost-effectiveness of maribavir versus investigator-assigned therapy (IAT) for treatment of post-transplant R/R CMV in the Italian context. METHODS: The analysis was conducted from the National Health Service (NHS) perspective using a Markov model previously developed in Excel® to evaluate the cost-effectiveness of maribavir versus IAT for the treatment of post-transplant R/R CMV. Health event rates and transition probabilities were informed by data from observational studies and from SOLSTICE clinical trial, which compared maribavir to conventional antiviral treatments for transplant patients with R/R CMV infections. Utilities were from SOLSTICE and a utility vignette study. Costs inputs were derived from published literature and Italian national tariffs for outpatient and hospital services. Costs and outcomes were discounted by 3%. RESULTS: Maribavir compared to the IAT used for the treatment of post-transplant R/R CMV achieved an incremental cost of € 11,455 for an incremental quality adjusted life year (QALY) gain of 0.313. This resulted in an incremental cost-effectiveness ratio of € 36,626/QALY, for maribavir compared to IAT, which is below the generally accepted, national willingness-to-pay threshold for orphan drugs (€ 37,000/QALY). CONCLUSIONS: This analysis showed that maribavir, an orphan drug treatment, is cost-effective compared to the current antiviral treatments used for treatment of post-transplant R/R CMV.

Human cytomegalovirus (HCMV) is one of the main causes of serious complications in immunocompromised patients and after congenital infection. There are currently drugs available to treat HCMV infection, targeting viral polymerase, whose use is complicated by toxicity and the emergence of resistance. Maribavir and letermovir are the latest antivirals to have been developed with other targets. The approval of letermovir represents an important innovation for CMV prevention in hematopoietic stem cell transplant recipients, whereas maribavir allowed improving the management of refractory or resistant infections in transplant recipients. However, in case of multidrug resistance or for the prevention and treatment of congenital CMV infection, finding new antivirals or molecules able to inhibit CMV replication with the lowest toxicity remains a critical need. This review presents a range of molecules known to be effective against HCMV. Molecules with a direct action against HCMV include brincidofovir, cyclopropavir and anti-terminase benzimidazole analogs. Artemisinin derivatives, quercetin and baicalein, and anti-cyclooxygenase-2 are derived from natural molecules and are generally used for different indications. Although they have demonstrated indirect anti-CMV activity, few clinical studies were performed with these compounds. Immunomodulating molecules such as leflunomide and everolimus have also demonstrated indirect antiviral activity against HCMV and could be an interesting complement to antiviral therapy. The efficacy of anti-CMV immunoglobulins are discussed in CMV congenital infection and in association with direct antiviral therapy in heart transplanted patients. All molecules are described, with their mode of action against HCMV, preclinical tests, clinical studies and possible resistance. All these molecules have shown anti-HCMV potential as monotherapy or in combination with others. These new approaches could be interesting to validate in clinical trials.

Despite advances in monitoring and treatment, cytomegalovirus (CMV) infections remain one of the most common complications after solid organ transplantation (SOT). CMV infection may fail to respond to standard first- and second-line antiviral therapies with or without the presence of antiviral resistance to these therapies. This failure to respond after 14 days of appropriate treatment is referred to as "resistant/refractory CMV." Limited data on refractory CMV without antiviral resistance are available. Reported rates of resistant CMV are up to 18% in SOT recipients treated for CMV. Therapeutic options for treating these infections are limited due to the toxicity of the agent used or transplant-related complications. This is often the challenge with conventional agents such as ganciclovir, foscarnet and cidofovir. Recent introduction of new CMV agents including maribavir and letermovir as well as the use of adoptive T cell therapy may improve the outcome of these difficult-to-treat infections in SOT recipients. In this expert review, we focus on new treatment options for resistant/refractory CMV infection and disease in SOT recipients, with an emphasis on maribavir, letermovir, and adoptive T cell therapy. [ABSTRACT FROM AUTHOR]

Despite advances in monitoring and treatment, cytomegalovirus (CMV) infections remain one of the most common complications after solid organ transplantation (SOT). CMV infection may fail to respond to standard first- and second-line antiviral therapies with or without the presence of antiviral resistance to these therapies. This failure to respond after 14 days of appropriate treatment is referred to as "resistant/refractory CMV." Limited data on refractory CMV without antiviral resistance are available. Reported rates of resistant CMV are up to 18% in SOT recipients treated for CMV. Therapeutic options for treating these infections are limited due to the toxicity of the agent used or transplant-related complications. This is often the challenge with conventional agents such as ganciclovir, foscarnet and cidofovir. Recent introduction of new CMV agents including maribavir and letermovir as well as the use of adoptive T cell therapy may improve the outcome of these difficult-to-treat infections in SOT recipients. In this expert review, we focus on new treatment options for resistant/refractory CMV infection and disease in SOT recipients, with an emphasis on maribavir, letermovir, and adoptive T cell therapy. [ABSTRACT FROM AUTHOR]

Cytomegalovirus (CMV) is an opportunistic pathogen responsible for substantial morbidity after solid organ transplantation and haematopoietic stem cell transplantation. Treatment of CMV disease involves a two-pronged approach with antiviral drug treatment coupled with strategies to minimize the intensity of immune suppression. This narrative review examines the evidence for the current treatment of CMV disease in transplant recipients, including the use of oral antiviral drugs. Literature search was performed on PubMed with keywords cytomegalovirus, transplantation, ganciclovir, valganciclovir, maribavir, letermovir, cidofovir, and foscarnet. Intravenous and oral valganciclovir are the standard first-line treatment of cytomegalovirus disease after transplantation. Oral maribavir has demonstrated superior efficacy and safety over CMV DNA polymerase inhibitors for the treatment of refractory or resistant CMV infection. Transplant patients with severe and life-threatening CMV disease, those with very high viral load, and patients with impaired gastrointestinal absorption should still be treated initially with intravenous antiviral drugs, including ganciclovir and foscarnet. Criteria for the safe transition from intravenous therapies to oral antiviral drugs include achieving clinical improvement and satisfactory decline in viral load. Recurrence of CMV viremia and disease is common, particularly among transplant patients who are lymphopenic and have impaired CMV-specific immunity. Oral antiviral drugs for the treatment of CMV infection and disease in transplant recipients have improved the CMV landscape, because they reduce the cost and mitigate the inconvenience and risks related to prolonged hospitalization and the need for long-term intravascular access. However, their antiviral efficacy should be complemented by an intentional strategy of reducing the degree of immune suppression to allow for immunologic recovery that ensures durable control of CMV infection. [ABSTRACT FROM AUTHOR]

This article discusses a case of cytomegalovirus (CMV) resistance to both valganciclovir and maribavir in a renal transplant patient. CMV is a common virus that can cause complications after kidney transplantation. Maribavir is a new oral drug that is effective against CMV strains resistant to traditional antiviral drugs. However, in this case, the patient developed resistance to both valganciclovir and maribavir. The article emphasizes the need for clinicians to be vigilant when initiating treatment with maribavir and suggests that foscarnet may be a preferred option for treating refractory CMV infections. [Extracted from the article]

Despite advances in monitoring and treatment, cytomegalovirus (CMV) infections remain one of the most common complications after solid organ transplantation (SOT). CMV infection may fail to respond to standard first- and second-line antiviral therapies with or without the presence of antiviral resistance to these therapies. This failure to respond after 14 days of appropriate treatment is referred to as “resistant/refractory CMV.” Limited data on refractory CMV without antiviral resistance are available. Reported rates of resistant CMV are up to 18% in SOT recipients treated for CMV. Therapeutic options for treating these infections are limited due to the toxicity of the agent used or transplant-related complications. This is often the challenge with conventional agents such as ganciclovir, foscarnet and cidofovir. Recent introduction of new CMV agents including maribavir and letermovir as well as the use of adoptive T cell therapy may improve the outcome of these difficult-to-treat infections in SOT recipients. In this expert review, we focus on new treatment options for resistant/refractory CMV infection and disease in SOT recipients, with an emphasis on maribavir, letermovir, and adoptive T cell therapy.

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This phase I study compared pharmacokinetics and safety of maribavir in Japanese and White participants, and evaluated dose proportionality in Japanese participants. Under fasting conditions, 12 healthy adult participants of Japanese descent and 12 matched White participants received a single 400‐mg dose of maribavir. Japanese participants received 2 further doses of maribavir: 200 mg and 800 mg, or 800 mg and 200 mg, separated by a ≥72‐hour washout period. Serial blood samples were collected up to 24 hours after dosing for pharmacokinetic assessments. Following the 400‐mg dose, the geometric mean ratios (90% confidence interval) of Japanese versus White participants were 110% (91.7%–133%) for maximum plasma concentration, 122% (96.8%–155%) for area under the plasma concentration–time curve (AUC) from time of dosing to the last measurable concentration, and 125% (98.0%–160%) for AUC extrapolated to infinity. In Japanese participants, maribavir AUC extrapolated to infinity and AUC from time of dosing to the last measurable concentration increased in a dose‐proportional fashion over 200–800 mg; maximum plasma concentration increased less than dose proportionally. Seven participants reported treatment‐emergent adverse events (TEAEs; Japanese participants, 400 mg: 2 [16.7%], 200 mg: 1 [8.3%]; White participants, 400 mg: 4 [33.3%]), all mild and most commonly dysgeusia. No serious TEAEs or TEAEs leading to discontinuation were reported. This study demonstrated higher maribavir systemic exposure in Japanese than White participants and similar safety outcomes. This difference in exposure is not considered clinically important and its significance remains to be determined. [ABSTRACT FROM AUTHOR]

Objective: To review the efficacy and safety of maribavir for management of cytomegalovirus (CMV) in solid organ transplant recipients. Data Sources: A literature search of PubMed and the Cochrane Controlled Trials Register (1960 to early July 2022) was performed using the following search terms: maribavir, 1263W94, and cytomegalovirus. Study Selection and Data Extraction: All relevant English-language studies were reviewed and considered, with a focus on phase 3 trials. Data Synthesis: Maribavir, an orally available benzimidazole riboside with minimal adverse effects, was originally studied for universal prophylaxis in phase 3 trials but failed to demonstrate noninferiority over placebo and oral ganciclovir. It was effective for preemptive treatment in a dose-finding Phase 2 study. Maribavir is FDA approved for treatment of refractory/resistant CMV infection based on improved response rate at 8 weeks compared with investigator-assigned therapy (IAT) when initiated at median viral loads less than approximately 10 000 IU/mL (55.7% vs 23.9%, P < 0.001). Recurrence after 8-week treatment for refractory/resistant CMV was high (maribavir 50% vs IAT 39%). Significant drug interactions exist and must be managed by a pharmacotherapy expert to prevent harm. Relevance to Patient Care and Clinical Practice: The addition of maribavir to the antiviral armamentarium should improve the management of refractory/resistant CMV, allowing early transition from toxic, high-cost, intravenous agents such as foscarnet and outpatient management. Optimal timing of initiation, duration, and potential alternative uses are unclear. Conclusion: Future studies are needed to fully elucidate the role of maribavir in the management of CMV after transplant. [ABSTRACT FROM AUTHOR]

Abstract Cytomegalovirus (CMV) infection can have both direct and indirect effects after solid-organ transplantation, with a significant impact on transplant outcomes. Prevention strategies decrease the risk of CMV disease, although CMV still occurs in up to 50% of high-risk patients. Ganciclovir (GCV) and valganciclovir (VGCV) are the main drugs currently used for preventing and treating CMV. Emerging data suggest that letermovir is as effective as VGCV with fewer hematological side effects. Refractory and resistant CMV also still occur in solid-organ-transplant patients. Maribavir has been shown to be effective and have less toxicity in the treatment of refractory and resistant CMV. In this review paper, we discuss prevention strategies, refractory and resistant CMV, and drug-related side effects and their impact, as well as optimal use of novel anti-CMV therapies.

Maribavir, an orally bioavailable antiviral, has shown superior activity against posttransplant cytomegalovirus infection compared with conventional antivirals. It is primarily metabolized in the liver. This open-label, single-center study evaluated the effect of hepatic impairment on the pharmacokinetics of maribavir in nontransplant participants. A single 200-mg dose of maribavir was administered orally under fasting conditions to participants with moderate hepatic impairment (Child-Pugh class B) (n = 10) and healthy controls (n = 10) matched for age, weight, sex, and smoking status. Compared with participants with normal hepatic function, maximum plasma concentration (Cmax) and area under the plasma concentration-time curve (AUC) from time 0 to infinity values for maribavir in participants with moderate hepatic impairment were 1.346-fold (90%CI of geometric mean ratio, 1.091-1.660) and 1.261-fold (0.889-1.787) higher, respectively. However, Cmax and AUC values for unbound maribavir were comparable. For VP 44469, the main metabolite of maribavir, the Cmax and AUC from time 0 to infinity values were 1.190-fold (0.836-1.693) and 1.309-fold (1.007-1.702) higher, respectively, in participants with moderate hepatic impairment. In total, 7 mild treatment-emergent adverse events were reported, all in the moderate hepatic impairment group. Dysgeusia was the most frequently reported treatment-emergent adverse event, at a frequency of 50%. These results indicated that total maribavir concentrations were mildly increased in participants with moderate hepatic impairment, while unbound concentrations were unaffected. Similar maribavir pharmacokinetics in participants with moderate hepatic impairment and normal hepatic function suggest that dose adjustment may not be required for patients with moderate hepatic impairment. [ABSTRACT FROM AUTHOR]

Cytomegalovirus (CMV) infection can have both direct and indirect effects after solid-organ transplantation, with a significant impact on transplant outcomes. Prevention strategies decrease the risk of CMV disease, although CMV still occurs in up to 50% of high-risk patients. Ganciclovir (GCV) and valganciclovir (VGCV) are the main drugs currently used for preventing and treating CMV. Emerging data suggest that letermovir is as effective as VGCV with fewer hematological side effects. Refractory and resistant CMV also still occur in solid-organ-transplant patients. Maribavir has been shown to be effective and have less toxicity in the treatment of refractory and resistant CMV. In this review paper, we discuss prevention strategies, refractory and resistant CMV, and drug-related side effects and their impact, as well as optimal use of novel anti-CMV therapies. [ABSTRACT FROM AUTHOR]

This article discusses the limited penetration of the antiviral drug maribavir into the central nervous system (CNS) based on a case study of a solid organ transplant recipient with drug-resistant cytomegalovirus (CMV) infection. The patient was treated with foscarnet and maribavir, but maribavir concentrations in the cerebrospinal fluid (CSF) remained below the lower limit of quantification. Despite meningeal inflammation, which typically increases the permeability of anti-infective therapies in the CSF, maribavir failed to treat and prevent the development of CMV disseminated disease. The study suggests that maribavir should not be used for the treatment of CMV meningitis and/or encephalitis, and more data are needed to confirm its poor diffusion into the CNS. [Extracted from the article]

The burden that cytomegalovirus (CMV) portends for haematopoietic and solid-organ transplant recipients cannot be understated. Valganciclovir and ganciclovir have successfully been used for prevention and treatment of CMV infections, although with serious side effects such as leucopenia and some development of resistance. Until recently, available therapies for ganciclovir-resistant CMV have significant toxicities. Although advances have been made in the field, the unmet medical needs for effective and well-tolerated therapies are significant. This review aims to summarise the current and emerging CMV antiviral drugs and discusses future perspectives in the field. Sources: We searched for relevant articles with pertinent keywords: "Cytomegalovirus OR CMV", "Transplant" and "Antiviral". Articles published after 2019 were given preference. Articles were reviewed by the authors for relevance and impact to the subject of interest. We outline in this review current advances in prophylaxis of CMV infection with letermovir, breakthrough CMV infections while on or after prophylaxis, the development of resistant and refractory CMV infections, and the newly approved anti-CMV agent, maribavir, in haematopoietic and solid-organ transplant recipients. Prevention of CMV infections after transplant has improved greatly over the past few years. Despite major advancements, breakthrough CMV infections and development of refractory and resistant CMV infections remain major complications post transplantation. We highlight emerging therapeutics that tolerably and effectively prevent and treat CMV infections, especially refractory and resistant cases. [ABSTRACT FROM AUTHOR]

Ronak G Gandhi,1 Camille N Kotton2 1Department of Pharmacy, Massachusetts General Hospital, Boston, MA, USA; 2Infectious Diseases Division, Massachusetts General Hospital, Boston, MA, USACorrespondence: Ronak G Gandhi, Senior Attending Pharmacist – Infectious Diseases, Department of Pharmacy, Massachusetts General Hospital, 55 Fruit Street, GRB 005, Boston, MA 02114, USA, Tel +1 617-643-6570, Fax +1 617-726-9232, Email rggandhi@partners.orgPurpose of Review: Cytomegalovirus (CMV) infections are a common complication in solid organ (SOT) and hematopoietic stem cell transplant (HSCT) recipients, leading to increased morbidity and mortality. Currently available treatment options have reduced the burden of infection, but utilization of these agents can be limited by toxicities such as nephrotoxicity and/or myelosuppression as well as emergence of resistance. The expansion of our current armamentarium towards CMV infection is crucial. Here, we review an emerging therapy, maribavir, and the safety and efficacy of this potential new agent for the prophylaxis and treatment of CMV infections including resistant/refractory disease.Recent Findings: Maribavir is a novel agent with CMV activity approved by Federal Food and Drug Administration (FDA) in December 2021 for resistant/refractory disease. Compared to currently available treatment for CMV infection, maribavir has a unique mechanism of action, retains activity against most (val)ganciclovir resistant strains, provides a more predictable pharmacokinetic profile, and fewer severe toxicities. Maribavir has been studied in phase 2 and 3 studies with ongoing phase 3 studies. While maribavir failed to meet the primary endpoints in the initial phase 3 study for prophylaxis therapy in allogeneic-HSCT and liver transplant recipients, results from the phase 2 study when used for pre-emptive therapy after HSCT show similar efficacy to valganciclovir, and results from the phase 3 study examining resistant/refractory disease demonstrate superiority to investigator-initiated therapy of (val)ganciclovir, foscarnet, or cidofovir.Summary: Maribavir provides a new agent for the management of resistant/refractory CMV infection. Results of the recently published phase 3 study provide further insight into the role of this novel therapy.Keywords: cytomegalovirus, maribavir, safety, efficacy

Keywords: Cytomegalovirus; Maribavir; Renal Impairment; Kidney Impairment EN Cytomegalovirus Maribavir Renal Impairment Kidney Impairment 1 3 3 06/19/23 20230601 NES 230601 Dear Editors, Cytomegalovirus (CMV) infection remains an important problem for solid organ transplant recipients and has been associated with significant morbidity and mortality.[1] Therapeutic options to treat CMV are limited by cytopenias, nephrotoxicity, and resistance. In patients with mild renal impairment, there were fewer emergent kidney-related adverse events observed with MBV (7%, I n i = 5) than IAT (21%, I n i = 9).[9] However, in patients with moderate-to-severe renal impairment, emergent kidney-related adverse events were noted in 32% ( I n i = 22) of patients on MBV and 24% ( I n i = 6) of patients on IAT. The inactive MBV metabolite VP 44469 demonstrated a higher plasma area under the curve (AUC) in those with renal impairment, though the clinical significance of this is not known.[[5]] In a phase II MBV dose-finding study, renal impairment was noted in 8% ( I n i = 3) of patients on MBV 400 mg twice daily, 18% ( I n i = 7) of patients on MBV 800 mg twice daily, and 23% ( I n i = 9) of patients on MBV 1200 mg twice daily, with all but one of these patients having a prior history of renal impairment.[7] Though a numeric association between MBV dose and renal impairment is noted, these adverse events were deemed by investigators to be related to MBV in 3 only patients. [Extracted from the article]

Background Therapies for refractory cytomegalovirus infections (with or without resistance [R/R]) in transplant recipients are limited by toxicities. Maribavir has multimodal anti-cytomegalovirus activity through the inhibition of UL97 protein kinase. Methods In this phase 3, open-label study, hematopoietic-cell and solid-organ transplant recipients with R/R cytomegalovirus were randomized 2:1 to maribavir 400 mg twice daily or investigator-assigned therapy (IAT; valganciclovir/ganciclovir, foscarnet, or cidofovir) for 8 weeks, with 12 weeks of follow-up. The primary endpoint was confirmed cytomegalovirus clearance at end of week 8. The key secondary endpoint was achievement of cytomegalovirus clearance and symptom control at end of week 8, maintained through week 16. Results 352 patients were randomized (235 maribavir; 117 IAT). Significantly more patients in the maribavir versus IAT group achieved the primary endpoint (55.7% vs 23.9%; adjusted difference [95% confidence interval (CI)]: 32.8% [22.80–42.74]; P  < .001) and key secondary endpoint (18.7% vs 10.3%; adjusted difference [95% CI]: 9.5% [2.02–16.88]; P  = .01). Rates of treatment-emergent adverse events (TEAEs) were similar between groups (maribavir, 97.4%; IAT, 91.4%). Maribavir was associated with less acute kidney injury versus foscarnet (8.5% vs 21.3%) and neutropenia versus valganciclovir/ganciclovir (9.4% vs 33.9%). Fewer patients discontinued treatment due to TEAEs with maribavir (13.2%) than IAT (31.9%). One patient per group had fatal treatment-related TEAEs. Conclusions Maribavir was superior to IAT for cytomegalovirus viremia clearance and viremia clearance plus symptom control maintained post-therapy in transplant recipients with R/R cytomegalovirus. Maribavir had fewer treatment discontinuations due to TEAEs than IAT. Clinical Trials Registration. NCT02931539 (SOLSTICE). [ABSTRACT FROM AUTHOR]

Background: In separate phase 2 trials, 120 patients received maribavir for cytomegalovirus (CMV) infection failing conventional therapy (trial 202) and 119 received maribavir for asymptomatic infection (trial 203). Overall, 172 cleared their CMV infection (CMV DNA <200 copies/mL) within 6 weeks.Methods: Baseline and posttreatment plasma samples were tested for mutations in viral genes UL97, UL54, and/or UL27. Selected viral mutants were phenotyped for drug susceptibility.Results: Baseline samples revealed UL54 mutations newly phenotyped as conferring resistance to standard DNA polymerase inhibitor(s), including K493N, P497S, K513T, L565V, V823A, A987V, and E989D. Of 29 patients (including 25 from trial 202) who cleared but later experienced recurrent CMV infection while on maribavir, 23 had available UL97 genotyping data; 17 had known resistance mutations (T409M or H411Y) and 5 additional had UL97 C480F alone. The newly phenotyped mutation C480F conferred high-grade maribavir resistance and low-grade ganciclovir resistance. Among 25 who did not respond to >14 days of therapy, 9 showed T409M or H411Y and 4 others showed C480F alone.Conclusions: After maribavir therapy (400-1200 mg twice daily), UL97 mutations T409M, H411Y, or C480F emerge to confer maribavir resistance in patients with recurrent CMV infection while on therapy or no response to therapy.Clinical Trials Registration: NCT01611974 and EudraCT 2010-024247-32. [ABSTRACT FROM AUTHOR]

What is known and objective: Management of pan‐resistant cytomegalovirus infection (CMVi) requires a multifaceted approach, including host defence optimization by reducing immunosuppression, and standard or experimental antiviral therapy. Case description: A 36‐year‐old man with anaplastic lymphoma kinase (ALK)‐negative anaplastic large cell lymphoma, who underwent allogeneic haematopoietic stem cell transplant (alloHCT) with resultant graft‐versus‐host disease treated with immunosuppressive therapy, developed pan‐resistant CMVi. He was successfully treated with combination therapy of maribavir and letermovir. What is new and conclusion: Combination therapy, used for other infections to prevent cross‐resistant, may apply for CMVi. [ABSTRACT FROM AUTHOR]

Two transplant recipients (1 kidney and 1 hematopoietic stem cell) received maribavir (MBV) after cytomegalovirus (CMV) infection clinically resistant to standard therapy. Both patients achieved CMV DNA clearance within 30 and 18 days; however, the UL97 C480F variant emerged, causing recurrent CMV infection after a cumulative 2 months of MBV and 15 or 4 weeks of ganciclovir treatment, respectively. C480F was not detected under ganciclovir before MBV treatment. Recombinant phenotyping showed that C480F conferred the highest level of MBV resistance and ganciclovir cross-resistance, with impaired viral growth. Clinical follow-up and genotypic and phenotypic studies are essential for the assessment and optimization of patients with suspected MBV resistance. [ABSTRACT FROM AUTHOR]

As some of those who were lucky enough to have been mentored by Dr Francisco Marty in transplant infectious diseases, we stand with the larger medical community in mourning his untimely death and in commemorating him as a uniquely exceptional and talented physician, investigator, teacher, mentor, friend, artist, and human being. [ABSTRACT FROM AUTHOR]

Therapeutic use of maribavir for human cytomegalovirus infection has renewed attention to the extent of cross-resistance with ganciclovir as the existing standard therapy. Each drug selects in vivo for a characteristic set of resistance mutations in the viral UL97 kinase gene. To improve the calibration of relative susceptibilities to each drug, genetic variants at relevant UL97 codons were extensively phenotyped using the same baseline viral clone, cell culture conditions and growth readout. Ganciclovir-selected mutations at codons 460, 520, 592, 594, 595 and 603 conferred 2.8-fold (C603Y) to 12-fold (M460I) increases in ganciclovir 50% inhibitory concentrations (EC50) over wild type baseline, while conferring maribavir EC50 fold changes ranging from 0.21-fold (M460I) to 1.9-fold (A594V). Maribavir-selected mutations at codons 409, 411 and 480 conferred maribavir EC50 fold changes ranging from 17 (H411Y) to 210 (C480F), while conferring ganciclovir EC50 fold changes ranging from 0.7 (H411Y) to 2.3 (C480F). The P-loop substitution F342Y, selected by either drug, is confirmed to confer 4.7-fold and 6-fold increases in maribavir and ganciclovir EC50s respectively, and suggests this part of the ATP-binding domain of UL97 to be involved in moderate resistance to both drugs. The maribavir hypersensitivity of M460I and M460V may be advantageous. • Cytomegalovirus UL97 mutations selected after ganciclovir or maribavir exposure were phenotyped to assess cross-resistance. • Mutations preferentially selected by either drug seldom confer resistance to the other. • The P-loop substitution F342Y confers clinically significant ganciclovir and maribavir cross resistance. • Ganciclovir-selected substitutions M460I and M460V confer maribavir hypersensitivity. • The low-grade ganciclovir cross resistance of C480F may not prevent its use as alternative therapy. [ABSTRACT FROM AUTHOR]

Purpose of Review: CMV DNA polymerase inhibitors such as ganciclovir and foscarnet have dramatically reduced the burden of CMV infection in the HCT recipient. However, their use is often limited by toxicities and resistance. Agents with novel mechanisms and favorable toxicity profiles are critically needed. We review recent developments in CMV antivirals and immune-based approaches to mitigating CMV infection. Recent Findings: Letermovir, an inhibitor of the CMV terminase complex, was approved in 2017 for primary CMV prophylaxis in adult seropositive allogeneic HCT recipients. Maribavir, an inhibitor of the CMV UL97 kinase, is currently in two phase 3 treatment studies. Adoptive immunotherapy using third-party T cells has proven safe and effective in preliminary studies. Vaccine development continues, with several promising candidates currently under study. Summary: No longer limited to DNA polymerase inhibitors, the prevention and treatment of CMV infections in the HCT recipient is a rapidly evolving field which should translate into improvements in CMV-related outcomes. [ABSTRACT FROM AUTHOR]

The development of therapeutics for cytomegalovirus (CMV) infections, while progressing, has not matched the pace of new treatments of human immunodeficiency virus (HIV) infections; nevertheless, recent developments in the treatment of CMV infections have resulted in improved human health and perhaps will encourage the development of new therapeutic approaches. First, the deployment of ganciclovir and valganciclovir for both the prevention and treatment of CMV infections and disease in transplant recipients has been further improved with the licensure of the efficacious and less toxic letermovir. Regardless, late-onset CMV disease, specifically pneumonia, remains problematic. Second, the treatment of congenital CMV infections with valganciclovir has beneficially improved both hearing and neurologic outcomes, both fundamental advances for these children. In these pediatric studies, viral load was decreased but not eliminated. Thus, an important lesson learned from studies in both populations is the need for new antiviral agents and the necessity for combination therapies as has been shown to be beneficial in the treatment of HIV infections, among others. The development of monoclonal antibodies, sirtuins, and cyclopropovir may provide new treatment options. [ABSTRACT FROM AUTHOR]

Cytomegalovirus (CMV) viraemia continues to be a frequent complication in the post‐haemopoietic stem cell transplantation period despite a low incidence of CMV end‐organ disease. Several significant advances in the understanding and management of CMV infection have occurred in the last few years including improved diagnostics, monitoring of CMV immunity, availability of novel anti‐CMV drugs, and emerging use of immunotherapies including CMV‐specific T‐cell infusions. In addition to reviewing these advances we also explore some of the more practical prescribing issues of the older and newer CMV drugs including cost, toxicity and drug interactions to help clinicians navigate this new era of CMV management. [ABSTRACT FROM AUTHOR]

Maribavir is an investigational drug being evaluated in transplant recipients with cytomegalovirus infection. To understand potential drug‐drug interactions, we examined the effects of multiple doses of maribavir on cytochrome P450 (CYP) 2D6 and P‐glycoprotein (P‐gp) activity using probe substrates in healthy volunteers. During this phase 1 open‐label study (NCT02775240), participants received the probe substrates digoxin (0.5 mg) and dextromethorphan (30 mg) before and after maribavir (400 mg twice daily for 8 days). Serial plasma samples were analyzed for digoxin, dextromethorpha, dextrorphan, and maribavir concentrations. Pharmacokinetic parameters were calculated (noncompartmental analysis) and analyzed with a linear mixed‐effects model for treatment comparison to estimate geometric mean ratios (GMRs) and 90% confidence intervals (CIs). CYP2D6 polymorphisms were genotyped using polymerase chain reaction. Overall, 17 of 18 participants (94.4%) completed the study. All participants were genotyped as CYP2D6 intermediate/extensive metabolizers. GMR (90%CI) of digoxin Cmax, AUClast, and AUC0‐∞ with and without maribavir was 1.257 (1.139‐1.387), 1.187 (1.088‐1.296), and 1.217 (1.110‐1.335), respectively, outside the "no‐effect" window (0.8‐1.25). GMR (90%CI) of dextromethorphan AUClast and AUClast ratio of dextromethorphan/dextrorphan were 0.877 (0.692‐1.112) and 0.901 (0.717‐1.133), respectively, marginally outside the no‐effect window, although large variability was observed in these pharmacokinetic parameters. Pharmacokinetic parameters of dextrorphan were unaffected. Maribavir inhibited P‐gp activity but did not affect CYP2D6 activity. Maribavir's effect on the pharmacokinetics of P‐gp substrates should be evaluated individually, and caution should be exercised with P‐gp substrates with narrow therapeutic windows. [ABSTRACT FROM AUTHOR]

2022; 75 (4): 690 - 701. https://doi.org/10.1093/cid/ciab988 2 Hirji I, Cocks K, Moreno-Koehler A, Sundberg A. Healthcare resource utilization of maribavir versus investigator-assigned therapy in transplant recipients with cytomegalovirus infection refractory (with or without genotypic resistance) to prior treatment: exploratory analysis of the Phase 3 SOLSTICE trial. Because maribavir treatment extended further into the 8 week treatment phase compared to IAT, the average risk of hospitalization on maribavir treatment days was likely lower than on IAT treatment days. Keywords: cytomegalovirus; maribavir; healthcare resource utilization EN cytomegalovirus maribavir healthcare resource utilization 1 2 2 06/19/23 20230601 NES 230601 Abbreviations CMV cytomegalovirus IAT investigator assigned therapy LOS length of stay R/R refractory/resistant TMP-SMX trimethoprim-sulfamethoxazole Treatment of refractory cytomegalovirus (CMV) infections, with or without resistance (R/R), has historically been limited by adverse effects of antiviral therapies and logistical difficulties of their intravenous administration. [Extracted from the article]

Unfortunately, the patient's CMV VL increased to 259,000 IU/ml on day 57 of maribavir and a CMV resistance assay demonstrated a new UL97 mutation (T409M), indicating maribavir resistance, though the prior UL97 mutation was no longer present indicating a mixed CMV population. On day 72 of maribavir treatment, CMV DNAemia was again detectable with a viral load of 2100 IU/ml and a resistance assay demonstrated a UL97 mutation (C480F) conferring resistance to ganciclovir and maribavir. At the time of maribavir initiation, the CMV viral load (VL) was 2900 IU/ml and the most recent CMV genotype was negative for any mutations. [Extracted from the article]