Maribavir for Refractory Cytomegalovirus Infections With or Without Resistance Post-Transplant: Results From a Phase 3 Randomized Clinical Trial

Management of cytomegalovirus infection after liver transplantation

Cytomegalovirus (CMV) infection is one of the primary causes of morbidity and mortality following liver transplantation (LT). Based on current worldwide guidelines, the most effective strategies for avoiding post-transplant CMV infection are antiviral prophylaxis and pre-emptive treatment. CMV- IgG serology is the established technique for pretransplant screening of both donors and recipients. The clinical presentation of CMV infection and disease exhibits variability, prompting clinicians to consistently consider this possibility, particularly within the first year post-transplantation or subsequent to heightened immunosuppression. At annual symposia to discuss CMV prevention and how treatment outcomes can be improved, evidence on the incorporation of immune functional tests into clinical practice is presented, and the results of studies with new antiviral treatments are evaluated. Although there are ongoing studies on the use of letermovir and maribavir in solid organ transplantation, a consensus reflected in the guidelines has not been formed. Determining the most appropriate strategy at the individual level appears to be the key to enhancing outcomes. Although prevention strategies reduce the risk of CMV disease, the disease can still occur in up to 50% of high-risk patients. A balance between the risk of infection and disease development and the use of immunosuppressants must be considered when talking about the proper management of CMV in solid organ transplant recipients. The objective of this study was to establish a comprehensive framework for the management of CMV in patients who have had LT.

Pathogen-specific cell-mediated immunity to guide the management of cytomegalovirus in solid organ transplantation: state of the art clinical review

INTRODUCTION

Cytomegalovirus (CMV) is a common opportunistic infection after solid organ transplantation, with significant impact on morbidity and long-term survival. Despite advances in diagnostics and therapeutics, the management of CMV remains very challenging.

AREAS COVERED

This article reviews emerging data on the clinical utility of laboratory assays that quantify cell-mediated immune responses to CMV. Observational studies have consistently demonstrated that a deficiency in pathogen-specific cell-mediated immunity is correlated with a heightened risk of primary, reactivation or recurrent CMV after transplantation. A limited number of interventional studies have recently investigated cell-mediated immune assays in guiding the prevention and treatment of CMV infection after solid organ transplantation.

EXPERT OPINION

The pathogenesis and outcome of CMV after solid organ transplantion reflect the interplay between viral replication and CMV-specific immune reconstitution. Research in CMV-specific cell-mediated immunity paved way for the development of several laboratory assays that may assist clinicians in predicting the risk of CMV after transplantation, individualize the approach to CMV disease prevention, guide the need and duration of treatment of CMV infection, and predict the risk of relapse after treatment. More interventional studies are needed to further solidify the role of cell-mediated immune assays in various clinical situations after transplantation.

Consensus Definitions of Cytomegalovirus (CMV) Infection and Disease in Transplant Patients Including Resistant and Refractory CMV for Use in Clinical Trials: 2024 Update From the Transplant Associated Virus Infections Forum

Cytomegalovirus (CMV) infection and disease are important causes of morbidity and mortality in transplant recipients. For the purpose of developing consistent reporting of CMV outcomes in clinical trials, definitions of CMV infection and disease were developed and most recently published in 2017. Since then, there have been major developments, including registration of new antiviral agents. Therefore, the Transplant Associated Virus Infections Forum, which consists of scientists, clinicians, regulators, and industry representatives, has produced an updated version of these definitions that incorporates recent knowledge with the aim of supporting clinical research and drug development. This also includes an update regarding the definition of resistant and refractory CMV infections previously published in 2019. As the field evolves, the need for updates of these definitions is clear, and collaborative efforts among clinicians, scientists, regulators, and industry representatives can provide a platform for this work.

[Management of Cytomegalovirus Infection in Allogeneic Hematopoietic Stem Cell Transplant Recipients]

Cytomegalovirus (CMV) is a type of double-stranded deoxyribonucleic acid virus belonging to the herpesviridae family. Following a primary infection, the virus becomes latent in various types of white blood cells. Cytomegalovirus infection can remain latent or become active, especially in immunocompromised individuals, such as those undergoing hematopoietic stem cell transplantation (HSCT), where CMV reactivation can occur. In this context, CMV infection is common and associated with high rates of morbidity and mortality. Pneumonia is one of the most serious complications, with mortality rates exceeding 50%. Additionally, even in the absence of organ-specific disease, CMV infection is related to increased mortality unrelated to hematologic neoplasm recurrence. Given the frequency and severity of this infection in HSCT patients, it is crucial to implement effective strategies for monitoring, prevention, and treatment. This guideline was developed to identify patient groups that benefit from a systematic approach to CMV infection and to define the most appropriate strategy for each group. Monitoring CMV viral load in peripheral blood is crucial, especially in patients at moderate to high risk of active infection. Primary prophylaxis with letermovir (an antiviral drug) is recommended to reduce the incidence of active infection, especially in high-risk patients. Secondary prophylaxis with valganciclovir (antiviral drug) is recommended after an episode of active infection, while preemptive and disease treatment is based on monitoring viral load and clinical response. The aim of this guideline is to improve the approach to CMV infection in HSCT patients, ensuring an effective and safe preventive and therapeutic approach.

Refractory/Resistant Cytomegalovirus Infection in Transplant Recipients: An Update

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.

Benzimidazole-based structure optimization to discover novel anti-gastric cancer agents targeting ROS/MAPK pathway

Given the malignancy of gastric cancer, developing highly effective and low-toxic targeted drugs is essential to prolong patient survival and improve patient outcomes. In this study, we conducted structural optimizations based on the benzimidazole scaffold. Notably, compound 8 f presented the most potent antiproliferative activity in MGC803 cells and induced cell cycle arrest at the G0/G1 phase. Further mechanistic studies demonstrated that compound 8 f caused the apoptosis of MGC803 cells by elevating intracellular reactive oxygen species (ROS) levels and activating the mitogen-activated protein kinase (MAPK) signaling pathway, accompanied by corresponding markers change. In vivo investigations additionally validated the inhibitory effect of compound 8 f on tumor growth in xenograft models bearing MGC803 cells without obvious toxicity. Our studies suggest that compound 8 f holds promise as a potential and safe lead compound for developing anti-gastric cancer agents.

The changing landscape of infections in the lung transplant recipient

PURPOSE OF REVIEW

Infections in lung transplant recipients remain a major challenge and can affect lung allograft function and cause significant morbidity and mortality. New strategies for the prevention and treatment of infection in lung transplantation have emerged and are reviewed.

RECENT FINDINGS

For important vaccine preventable infections (VPIs), guidance has been updated for at risk solid organ transplant (SOT) recipients. However, data on the efficacy of newer vaccines in lung transplant, including the respiratory syncytial virus (RSV) vaccine, are limited. Studies demonstrate improved vaccination rate with Infectious Diseases consultation during pretransplant evaluation. Two new antiviral agents for the treatment and prevention of cytomegalovirus (CMV) in SOT, letermovir and maribavir, are being incorporated into clinical care. CMV-specific cell-mediated immune function assays are more widely available. Antibiotics for the management of multidrug resistant pathogens and Burkholderia cepacia complex have been described in case series and case reports in lung transplant.

SUMMARY

Although new vaccines and novel therapies for preventing and treating infections are available, larger studies evaluating efficacy in lung transplant recipients are needed.

Real-World Experience With Maribavir for Treatment of Cytomegalovirus Infection in High-Risk Solid Organ Transplant Recipients

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.

Advances and prospect in herpesviruses infections after haematopoietic cell transplantation: closer to the finish line?

BACKGROUND

Herpesviruses represent common and significant infectious complications after allogeneic haematopoietic cell transplantation (HCT). In the last decade, major advances in the prevention and treatment of these infections were accomplished.

OBJECTIVES

The aim of this paper is to review the recent advances in the prophylaxis and treatment of herpesvirus infections after allogeneic HCT, to assess the persisting challenges, and to offer future directions for the prevention and management of these infections.

SOURCES

We searched PubMed for relevant literature regarding specific herpesviruses complicating allogeneic HCT through March 2024.

CONTENT

The largest advances in this past decade were witnessed for cytomegalovirus (CMV) with the advent of letermovir for primary prophylaxis and the development of maribavir as an option for refractory and/or resistant CMV infections in transplant recipients. For varicella zoster virus, prevention of reactivation with the recombinant zoster vaccine offers an additional prophylactic intervention. Pritelivir is being explored for the treatment of drug-resistant or refractory Herpes simplex virus infections. Although rituximab is now an established option for preemptive therapy for Epstein-Barr virus, Human Herpesvirus-6 remains the most elusive virus of the herpesvirus family, with a lack of evidence supporting the benefit of any agent for prophylaxis or for optimal preemptive therapy.

IMPLICATIONS

Although considerable advances have been achieved for the treatment and prevention of herpes virus infections, most notably with CMV, the coming years should hold additional opportunities to tame the beast in these herpesviruses postallogeneic HCT, with the advent of new antivirals, cell-mediated immunity testing, and cytotoxic T lymphocytes infusions.

Virus-specific T cell therapy to treat refractory viral infections in solid organ transplant recipients

Solid organ transplant recipients require ongoing immunosuppression to prevent acute rejection, which puts them at risk of opportunistic infections. Viral infections are particularly challenging to prevent and treat as many establish latency and thus cannot be eliminated, whereas targets for small molecule antiviral medications are limited. Resistance to antivirals and unacceptable toxicity also complicate treatment. Virus-specific T cell therapies aim to restore host-specific immunity to opportunistic viruses that is lacking due to ongoing immunosuppressive therapy. This minireview will provide a state-of-the-art update of the current virus-specific T cell pipeline and translational research that is likely to lead to further treatment options for viral infections in solid organ transplant recipients.

Adenovirus- and cytomegalovirus-specific adoptive T-cell therapy in the context of hematologic cell transplan or HIV infection - A single-center experience

BACKGROUND

Reactivation of viral infections, in particular cytomegalovirus (CMV) and adenovirus (ADV), cause morbidity and non-relapse-mortality in states of immune deficiency, especially after allogeneic hematopoietic cell transplantation (allo-HCT). Against the background of few available pharmacologic antiviral agents, limited by toxicities and resistance, adoptive transfer of virus-specific T-cells (VST) is a promising therapeutic approach.

METHODS

We conducted a single-center retrospective analysis of adult patients treated with ADV- or CMV-specific T-cells in 2012-2022. Information was retrieved by review of electronic health records. Primary outcome was a response to VST by decreasing viral load or clinical improvement. Secondary outcomes included overall survival and safety of VST infusion, in particular association with graft-versus-host disease (GVHD).

RESULTS

Ten patients were included, of whom four were treated for ADV, five for CMV, and one for ADV-CMV-coinfection. Cells were derived from stem cell donors (6/10) or third-party donors (4/10). Response criteria were met by six of 10 patients (4/4 ADV, 2/5 CMV, and 0/1 ADV-CMV). Overall survival was 40%. No infusion related adverse events were documented. Aggravation of GVHD after adoptive immunotherapy was observed in two cases, however in temporal association with a conventional donor lymphocyte infusion and a stem cell boost, respectively.

CONCLUSION

In this cohort, CMV- and ADV-specific T-cell therapy appear to be safe and effective. We describe the first reported case of virus-specific T-cell therapy for CMV reactivation not associated with transplantation but with advanced HIV infection. This encourages further evaluation of adoptive immunotherapy beyond the context of allo-HCT.

Engineered HCMV-infected APCs enable the identification of new immunodominant HLA-restricted epitopes of anti-HCMV T-cell immunity

Complications due to HCMV infection or reactivation remain a challenging clinical problem in immunocompromised patients, mainly due to insufficient or absent T-cell functionality. Knowledge of viral targets is crucial to improve monitoring of high-risk patients and optimise antiviral T-cell therapy. To expand the epitope spectrum, genetically-engineered dendritic cells (DCs) and fibroblasts were designed to secrete soluble (s)HLA-A*11:01 and infected with an HCMV mutant lacking immune evasion molecules (US2-6 + 11). More than 700 HLA-A*11:01-restricted epitopes, including more than 50 epitopes derived from a broad range of HCMV open-reading-frames (ORFs) were identified by mass spectrometry and screened for HLA-A*11:01-binding using established prediction tools. The immunogenicity of the 24 highest scoring new candidates was evaluated in vitro in healthy HLA-A*11:01+/HCMV+ donors. Thus, four subdominant epitopes and one immunodominant epitope, derived from the anti-apoptotic protein UL36 and ORFL101C (A11SAL), were identified. Their HLA-A*11:01 complex stability was verified in vitro. In depth analyses revealed highly proliferative and cytotoxic memory T-cell responses against A11SAL, with T-cell responses comparable to the immunodominant HLA-A*02:01-restricted HCMVpp65NLV epitope. A11SAL-specific T cells were also detectable in vivo in immunosuppressed transplant patients and shown to be effective in an in vitro HCMV-infection model, suggesting their crucial role in inhibiting viral replication and improvement of patient's outcome. The developed in vitro pipeline is the first to utilise genetically-engineered DCs to identify naturally presented immunodominant HCMV-derived epitopes. It therefore offers advantages over in silico predictions, is transferable to other HLA alleles, and will significantly expand the repertoire of viral targets to improve therapeutic options.

Effect of Food, Crushing of Tablets, and Antacid Coadministration on Maribavir Pharmacokinetics in Healthy Adult Participants: Results From 2 Phase 1, Open-Label, Randomized, Crossover Studies

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.

Case Report: Approaches for managing resistant cytomegalovirus in pediatric allogeneic hematopoietic cell transplantation recipients

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.

Prevention and management of cytomegalovirus infection and disease in kidney transplant: A consensus statement of the Transplantation Society of Taiwan

Kidney transplant recipients have an increased risk of cytomegalovirus (CMV) infection and disease. A strategy for mitigating the risk of CMV infection in kidney transplant recipients has not yet been established in Taiwan. The Transplantation Society of Taiwan aimed to develop a consensus by expert opinion on the prevention and management of CMV infection. Based on the results of Consensus Conference, we suggested low-dose valganciclovir prophylaxis (450 mg once daily) for kidney transplant recipients. The prophylaxis duration was ≥6 months for high-risk (D+/R-) patients and 3 months for moderate-risk (R+) patients. Even for low-risk (D-/R-) patients, prophylaxis for at least 3 months is recommended because of the high seroprevalence of CMV in Taiwan. CMV prophylaxis was suggested after anti-thymocyte globulin treatment but not after methylprednisolone pulse therapy. Routine surveillance after prophylaxis, secondary prophylaxis after CMV disease treatment, and mTOR inhibitors for primary CMV prophylaxis were not recommended. Letermovir and marabavir are emerging CMV agents used for prophylaxis and refractory CMV disease. CMV immunoglobulins have been used to treat refractory CMV disease in Taiwan. We hope this consensus will help professionals manage patients with CMV in Taiwan to improve the quality of care.

Approaches and Challenges in the Current Management of Cytomegalovirus in Transplant Recipients: Highlighting the Role of Advanced Practice Providers (Nurse Practitioners and Physician Assistants)

Cytomegalovirus (CMV) infection is associated with increased morbidity and mortality in hematopoietic cell transplant (HCT) and solid organ transplant (SOT) recipients, with traditional anti-CMV therapies limited by their associated toxicities and the development of resistance. Clinical providers are often faced with challenging and complicated CMV infections that require multiple courses of antiviral therapies. Increasingly, advanced practice providers (APPs) are playing an important role in the day-to-day management of transplant recipients with CMV infection, including resistant/refractory CMV and other complex CMV syndromes. Here, we provide an overview of current preventative and treatment strategies for CMV infection in HCT and SOT recipients, highlighting the challenging aspects of current management and the potential utility of newer antiviral agents. This article also focuses on how a multidisciplinary team, orchestrated by APPs, can improve CMV-associated patient outcomes. Protocols using antiviral agents for the prevention or treatment of CMV infections require carefully designed and meticulously implemented strategies to ensure the best clinical outcomes for patients. APPs, who have increasingly become the frontline providers of outpatient care for transplant recipients, are ideally positioned to design and carry out these protocols.

High burden of CMV infections after simultaneous pancreas-kidney transplantation-a nationwide cohort study

Cytomegalovirus (CMV) infections remain a common problem after solid-organ transplantation. We characterized the burden of CMV infections, and adverse events of CMV prophylaxis after simultaneous pancreas-kidney transplantation (SPK). We included all SPK patients (n = 236) since 2010 in our country. Immunosuppression was ATG, tacrolimus, mycophenolate, and steroids. Valganciclovir prophylaxis was given to all CMV D+/R- patients for six months, and to seropositive SPK patients for three months since February 2019. CMV DNAemia was monitored with quantitative PCR from plasma. Among D+/R- SPK recipients, post prophylaxis CMV infection was detected in 41/60 (68%) during follow-up. In seropositive SPK recipients with no prophylaxis, CMV infection was detected in 53/95 (56%), vs. 28/78 (36%) in those who received 3 months of prophylaxis (P = 0.01). CMV was symptomatic in 35 (15%) patients, of which 10 required hospitalization. Mean duration of viremia was 28 days (IQR 21-41). Leukopenia was detected in 63 (46%) of the 138 patients with valganciclovir prophylaxis. 7/122 (6%) of the CMV infections detected were defined as refractory to treatment, and three patients had confirmed ganciclovir resistance. SPK recipients experience a high burden of CMV infections despite CMV prophylaxis. Leukopenia is common during valganciclovir prophylaxis.

Recent advances in cytomegalovirus infection management in solid organ transplant recipients

PURPOSE OF REVIEW

Human cytomegalovirus (CMV) continues to be the most important infectious complication following solid organ transplantation (SOT).

RECENT FINDINGS

Universal prophylaxis and preemptive therapy are the most adopted strategies for prevention of CMV disease globally. Prophylaxis with valganciclovir is the most widely used approach to CMV prevention, however leukopenia and late onset CMV disease after discontinuation of prophylaxis requires new strategies to prevent this complication. The use of assays detecting CMV-specific T cell-mediated immunity may individualize the duration of antiviral prophylaxis after transplantation. Letermovir has been recently approved for prophylaxis in kidney transplant recipients. CMV-RNAemia used together with CMV-DNAemia in the viral surveillance of CMV infection provides accurate information on viral load kinetics, mostly in patients receiving letermovir prophylaxis/therapy. The development of refractory and resistant CMV infection remains a major challenge and a new treatment with maribavir is currently available. In the present paper we will review the most recent advances in prevention and treatment of CMV diseases in SOT recipients.

SUMMARY

Recent findings, summarized in the present paper, may be useful to optimize prevention and treatment of CMV infection in SOT.

Cost-effectiveness of maribavir versus conventional antiviral therapies for post-transplant refractory cytomegalovirus infection with or without genotypic resistance: A US perspective

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.

What's New: Updates on Cytomegalovirus in Solid Organ Transplantation

Cytomegalovirus (CMV) is one of the most common infections occurring after solid organ transplantation. This high burden of disease, which incurs sizeable morbidity, may be worsening with the proportion of high-risk D+/R- solid organ transplantation recipients increasing in some regions globally. Cohort studies continue to support either universal prophylaxis or preemptive therapy as effective prevention strategies. Letermovir prophylaxis was noninferior to valganciclovir in adult high-risk D+/R- kidney transplant recipients with fewer drug-related adverse events in a recent clinical trial and has now been approved for such use in some regions. Maribavir preemptive therapy failed to demonstrate noninferiority when compared with valganciclovir in hematopoietic stem cell transplant recipients but looked promising for safety. Donor matching could be useful in prevention CMV disease with a survival advantage demonstrated in seronegative recipients waiting up to 30 mo for a seronegative kidney. Immune-guided prophylaxis resulted in fewer CMV infection episodes in lung transplant recipients when compared with fixed-duration prophylaxis in a recent clinical trial. For treatment of refractory or resistant CMV infection, maribavir was more efficacious and better tolerated when compared with investigator-initiated therapy in its registration trial for this condition. Further research regarding best treatment and prophylaxis of resistant or refractory CMV infection is needed to reflect best clinical practice choices. Optimal use of immune globulin or CMV-specific T cells for prevention or treatment of CMV disease remains undefined. Standardized definitions for the design of CMV clinical trials have been developed. In this review, we highlight recent updates in the field from data published since 2018.

Use of Maribavir for Multidrug Resistant Cytomegaloviremia in a Pediatric Oncology Patient

Resistant and refractory cytomegalovirus (CMV) viremia can limit the provision of chemotherapy due to myelosuppression and end-organ dysfunction. Few therapies are available for children with clinically significant CMV viremia. We successfully used maribavir for a 4-year-old patient with lymphoma to complete his chemotherapy course. Resistance to maribavir did result after many months of therapy.

Adoptive therapy with cytomegalovirus-specific cytotoxic T lymphocytes for refractory cytomegalovirus DNAemia and disease after allogeneic haematopoietic stem cell transplantation

Cytomegalovirus (CMV) DNAemia and disease are common complications in patients undergoing allogeneic haematopoietic stem cell transplantation (allo-HSCT). Few studies have compared the efficacy and safety of the HSCT donor and third-party CMV-specific cytotoxic T lymphocytes (CMV-CTLs) in the treatment of CMV DNAemia and disease. In this study, we retrospectively compared the efficacy and safety of HSCT donor and third-party CMV-CTLs in patients with refractory CMV DNAemia or disease after allo-HSCT at our centre from January 2017 to September 2021. Fifty-three patients who received CMV-CTL therapy were enrolled, including 40 in the donor group and 13 in the third-party group, and they were adults aged 18 years or older. Within 6 weeks of treatment, 26 (65.0%) and 9 (69.2%) patients achieved complete response in the donor and third-party groups (p = 1.000). The 2-year overall survival was 59.6% (95% CI 46.1%-77.1%) and 53.8% (32.6%-89.1%) in the donor and third-party groups (p = 0.860). Four (10.0%) patients in the donor group and two (15.4%) patients in the third-party group developed acute graft-versus-host disease within 3 months after CMV-CTL infusions. In conclusion, our data suggest that donor and third-party CMV-CTLs have comparable efficacy and safety for refractory CMV DNAemia and disease.

Advances in pharmacotherapies for cytomegalovirus infection: what is the current state of play?

INTRODUCTION

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.

AREAS COVERED

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.

EXPERT OPINION

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.

Cytomegalovirus related hospitalization costs among hematopoietic stem cell and solid organ transplant recipients treated with maribavir versus investigator-assigned therapy: A US-based study

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.

Treatment for First Cytomegalovirus Infection Post-Hematopoietic Cell Transplant in the AURORA Trial: A Multicenter, Double-Blind, Randomized, Phase 3 Trial Comparing Maribavir With Valganciclovir

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].

Cytomegalovirus Treatment in Solid Organ Transplantation: An Update on Current Approaches

OBJECTIVE

The article reviews the safety and efficacy of treatments for cytomegalovirus (CMV) in solid organ transplantation.

DATA SOURCES

A literature review was conducted in PubMed, MEDLINE, and Clinicaltrials.gov from database inception through January 2024, using terms CMV, therapy, and solid organ transplantation.

STUDY SELECTION AND DATA EXTRACTION

Clinical trials, meta-analyses, cohort studies, case reports, and guidelines were included. Letters to the editor, reviews, and commentaries were excluded.

DATA SYNTHESIS

After abstract screening and full-text review of 728 citations for eligibility, 53 were included. Valganciclovir and intravenous ganciclovir are drugs of choice for CMV management and, until recently, the availability of alternative options has been restricted due to toxicity. For instance, foscarnet and cidofovir serve as second-line agents due to potential bone marrow and renal toxicity. In patients with refractory or resistant CMV, maribavir, a novel oral agent, has proven efficacy and a lower adverse effect profile. However, in refractory or resistant CMV, foscarnet and cidofovir are preferred in invasive disease (CMV gastritis, CMV retinitis, and CMV encephalitis), high viral loads, and inability to tolerate oral preparations.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

Consensus guidelines have not been revised since approval of novel antivirals in solid organ transplantation. Valganciclovir and ganciclovir remain drugs of choice for initial CMV therapy. Foscarnet, cidofovir, and maribavir are treatments for refractory or resistant-CMV.

CONCLUSIONS

Selection of CMV antiviral treatment should be determined by patient-specific factors, including severity of illness, resistant or refractory disease, dose-limiting adverse effects, and the preferred route of administration.

A time trade-off study to determine health-state utilities of transplant recipients with refractory cytomegalovirus infection with or without resistance

BACKGROUND

Health-state utility values (HSUVs) for post-transplant refractory cytomegalovirus (CMV) infection (with or without resistance [R/R]) were determined using a time trade-off (TTO) survey completed by 1,020 members of the UK general public.

METHODS

Existing literature and qualitative interviews with clinicians experienced in treating R/R CMV were used to develop initial draft vignettes of health states. The vignettes were refined to describe three clinical states of R/R CMV: clinically significant and symptomatic (CS-symptomatic CMV); clinically significant and asymptomatic (CS-asymptomatic CMV); and non-clinically significant (non-CS CMV). Each clinical state was valued independently and combined with three events of interest: graft-versus-host disease; kidney graft loss; and lung graft loss to generate twelve vignettes. The final vignettes were evaluated by a sample of the UK general public using an online TTO survey. Exclusion criteria were applied to the final data to ensure that responses included in the analysis met pre-defined quality control criteria.

RESULTS

Overall, 738 participants met the inclusion criteria and were included in the analysis. The sample was representative of the UK general population in terms of age and sex. Non-CS CMV had the highest mean HSUV (95% confidence interval) (0.815 [0.791, 0.839]), followed by CS-asymptomatic CMV (0.635 [0.602, 0.669]), and CS-symptomatic CMV (0.443 [0.404, 0.482]). CS-symptomatic CMV with lung graft loss had the lowest mean HSUV (0.289), with none of the health states considered on average worse than dead.

CONCLUSIONS

Post transplant R/R CMV has substantial impact on the health-related quality of life of patients. The utility values obtained in this study may be used to support economic evaluations of therapies for R/R CMV infection.

Resource Use and Financial Impact of Oral Step-Down Therapy for Resistant Cytomegalovirus in Solid Organ Transplant Recipients

BACKGROUND

Cytomegalovirus (CMV) infections are common opportunistic infections in solid organ transplants (SOT) with increased health care resource USE and costs. Costs are further increased with ganciclovir-resistance (GR). This study aimed to evaluate the real-world impact of conversion to oral step-down therapy on duration of foscarnet and hospital length of stay (LOS) for treatment of GR-CMV infections in SOT.

METHODS

This study included adult recipients of kidney or lung transplants who received foscarnet for genotypically documented GR-CMV while admitted at the University of Wisconsin Hospital from October 1, 2015, to January 31, 2022. Patients in the oral step-down group were converted from standard of care (SOC; foscarnet) to maribavir or letermovir; patients in the historical control group were treated with SOC.

RESULTS

Twenty-six patients met the inclusion criteria: 5 in the intervention group and 21 in the SOC group. The median viral load at foscarnet initiation was 11,435 IU/mL. Patients who received oral step-down conversion had shorter mean foscarnet duration than those who received SOC (7 ± 4 vs 37 ± 25 days, P = .017). Mean hospital LOS in the oral step-down group (16 ± 3 days) was shorter than the SOC group (33 ± 21 days; P < .001). In the SOC group, 9 patients lost their graft, and 9 patients died; 2 deaths were attributed to CMV. There were 2 deaths in the oral step-down group, neither of which was attributed to CMV.

CONCLUSION AND RELEVANCE

In this real-world case series of patients receiving treatment for GR-CMV infection, oral step-down conversion decreased foscarnet therapy duration and hospital LOS. Future studies are needed to evaluate better the effect of oral step-down in treating GR-CMV infection on treatment duration and cost-savings.

Cytomegalovirus infection is associated with impaired myocardial flow reserve after heart transplantation

BACKGROUND

Cardiac allograft vasculopathy (CAV) limits long-term survival after heart transplantation (HT). This study evaluates the relationship between clinically significant cytomegalovirus infection (CS-CMVi) and CAV using cardiac positron emission tomography (PET).

METHODS

We retrospectively evaluated HT patients from 2005 to 2019 who underwent cardiac PET for CAV evaluation. Multivariable linear and logistic regression models were used to evaluate the association between CS-CMVi and myocardial flow reserve (MFR). Kaplan-Meier and Cox regression analyses were used to assess the relationship between CS-CMV, MFR, and clinical outcomes.

RESULTS

Thirty-two (31.1%) of 103 HT patients developed CS-CMVi at a median 9 months after HT. Patients with CS-CMVi had a significantly lower MFR at year 1 and 3, driven by reduction in stress myocardial blood flow. Patients with CS-CMVi had a faster rate of decline in MFR compared to those without infection (-0.10 vs -0.06 per year, p < 0.001). CS-CMVi was an independent predictor of abnormal MFR (<2.0) (odds ratio: 3.8, 95% confidence intervals (CI): 1.4-10.7, p = 0.001) and a lower MFR (β = -0.39, 95% CI: -0.63 to -0.16, p = 0.001) at year 3. In adjusted survival analyses, both abnormal MFR (log-rank p < 0.001; hazard ratio [HR]: 5.7, 95% CI: 4.2-7.2) and CS-CMVi (log-rank p = 0.028; HR: 3.3, 95% CI: 1.8-4.8) were significant predictors of the primary outcome of all-cause mortality, retransplantation, heart failure hospitalization, and acute coronary syndrome.

CONCLUSIONS

CS-CMVi is an independent predictor of reduced MFR following HT. These findings suggest that CMV infection is an important risk factor in the development and progression of CAV.

EFFICACY OF MARIBAVIR IN VALGANCICLOVIR-RESISTANT CYTOMEGALOVIRUS RETINITIS

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.

'Getting Better'-Is It a Feasible Strategy of Broad Pan-Antiherpesviral Drug Targeting by Using the Nuclear Egress-Directed Mechanism?

The herpesviral nuclear egress represents an essential step of viral replication efficiency in host cells, as it defines the nucleocytoplasmic release of viral capsids. Due to the size limitation of the nuclear pores, viral nuclear capsids are unable to traverse the nuclear envelope without a destabilization of this natural host-specific barrier. To this end, herpesviruses evolved the regulatory nuclear egress complex (NEC), composed of a heterodimer unit of two conserved viral NEC proteins (core NEC) and a large-size extension of this complex including various viral and cellular NEC-associated proteins (multicomponent NEC). Notably, the NEC harbors the pronounced ability to oligomerize (core NEC hexamers and lattices), to multimerize into higher-order complexes, and, ultimately, to closely interact with the migrating nuclear capsids. Moreover, most, if not all, of these NEC proteins comprise regulatory modifications by phosphorylation, so that the responsible kinases, and additional enzymatic activities, are part of the multicomponent NEC. This sophisticated basis of NEC-specific structural and functional interactions offers a variety of different modes of antiviral interference by pharmacological or nonconventional inhibitors. Since the multifaceted combination of NEC activities represents a highly conserved key regulatory stage of herpesviral replication, it may provide a unique opportunity towards a broad, pan-antiherpesviral mechanism of drug targeting. This review presents an update on chances, challenges, and current achievements in the development of NEC-directed antiherpesviral strategies.

Current and Emerging Antiviral Agents in the Prevention and Treatment of Cytomegalovirus in Pediatric Transplant Recipients

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.

Human Cytomegalovirus (HCMV) Genetic Diversity, Drug Resistance Testing and Prevalence of the Resistance Mutations: A Literature Review

Human cytomegalovirus (HCMV) is a pathogen with high prevalence in the general population that is responsible for high morbidity and mortality in immunocompromised individuals and newborns, while remaining mainly asymptomatic in healthy individuals. The HCMV genome is 236,000 nucleotides long and encodes approximately 200 genes in more than 170 open reading frames, with the highest rate of genetic polymorphisms occurring in the envelope glycoproteins. HCMV infection is treated with antiviral drugs such as ganciclovir, valganciclovir, cidofovir, foscarnet, letermovir and maribavir targeting viral enzymes, DNA polymerase, kinase and the terminase complex. One of the obstacles to successful therapy is the emergence of drug resistance, which can be tested phenotypically or by genotyping using Sanger sequencing, which is a widely available but less sensitive method, or next-generation sequencing performed in samples with a lower viral load to detect minority variants, those representing approximately 1% of the population. The prevalence of drug resistance depends on the population tested, as well as the drug, and ranges from no mutations detected to up to almost 50%. A high prevalence of resistance emphasizes the importance of testing the patient whenever resistance is suspected, which requires the development of more sensitive and rapid tests while also highlighting the need for alternative therapeutic targets, strategies and the development of an effective vaccine.

Drug Resistance Assessed in a Phase 3 Clinical Trial of Maribavir Therapy for Refractory or Resistant Cytomegalovirus Infection in Transplant Recipients

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.

Five-year single-center analysis of cytomegalovirus viremia in kidney transplant recipients and possible implication for novel prophylactic therapy approaches

BACKGROUND

Cytomegalovirus (CMV) infections are a common complication after kidney transplantation (KTx) and negatively affecting patient outcome. Valganciclovir (VGC) prophylaxis is often limited by drug-induced side effects and dose reduction due to decline in kidney function.

METHOD

In the present study, episodes of CMV viremia in the first year after KTx in a cohort of 316 recipients were analyzed retrospectively to identify risk factors linked to persistent infections.

RESULTS

In the studied cohort, 18.7% of patients showed a high-risk (HR) constellation (D+/R-) for CMV infections. CMV viremia affected 22% of our cohort, with HR patients being the most affected cohort (44.1%). Within this group, most viremic events (65.3%) occurred while patients were still on prophylactic therapy, showing significantly higher viral loads and a longer duration compared to seropositive recipients.

CONCLUSION

The analysis at hand revealed that detection of viremia under ongoing antiviral prophylaxis bears an increased risk for sustained viral replication and antiviral drug resistance in HR patients. We identified low estimated glomerular filtration rate (eGFR) and lower dose VGC prophylaxis post-KTx as a risk factor for breakthrough infections in HR patients in our single center cohort. These patients might benefit from a closer CMV monitoring or novel prophylactic agents as letermovir.

Ganciclovir and maribavir cross-resistance revisited: Relative drug susceptibilities of canonical cytomegalovirus mutants

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.

Slaying the "Troll of Transplantation"-new frontiers in cytomegalovirus management: A report from the CMV International Symposium 2023

The 2023 International CMV Symposium took place in Barcelona in May 2023. During the 2-day meeting, delegates and faculty discussed the ongoing challenge of managing the risk of cytomegalovirus infection (the Troll of Transplantation) after solid organ or hematopoietic cell transplantation. Opportunities to improve outcomes of transplant recipients by applying advances in antiviral prophylaxis or pre-emptive therapy, immunotherapy, and monitoring of cell-mediated immunity to routine clinical practice were debated and relevant educational clinical cases presented. This review summarizes the presentations, cases, and discussions from the meeting and describes how further advances are needed before the Troll of Transplantation is slain.

Management of Cytomegalovirus Infections in the Era of the Novel Antiviral Players, Letermovir and Maribavir

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.

Bring it on again: antimicrobial stewardship in transplant infectious diseases: updates and new challenges

Advancement in solid organ transplantation and hematopoietic stem cell transplant continues to improve the health outcomes of patients and widens the number of eligible patients who can benefit from the medical progress. Preserving the effectiveness of antimicrobials remains crucial, as otherwise transplant surgeries would be unsafe due to surgical site infections, and the risk of sepsis with neutropenia would preclude stem cell transplant. In this review, we provide updates on three previously discussed stewardship challenges: febrile neutropenia, Clostridioides difficile infection, and asymptomatic bacteriuria. We also offer insight into four new stewardship challenges: the applicability of the "shorter is better" paradigm shift to antimicrobial duration; antibiotic allergy delabeling and desensitization; colonization with multidrug-resistant gram-negative organisms; and management of cytomegalovirus infections. Specifically, data are accumulating for "shorter is better" and antibiotic allergy delabeling in transplant patients, following successes in the general population. Unique to transplant patients are the impact of multidrug-resistant organism colonization on clinical decision-making of antibiotic prophylaxis in transplant procedure and the need for antiviral stewardship in cytomegalovirus. We highlighted the expansion of antimicrobial stewardship interventions as potential solutions for these challenges, as well as gaps in knowledge and opportunities for further research.

Risk Factors Associated with Survival Following Ganciclovir Prophylaxis through Day +100 in Cytomegalovirus At-Risk Pediatric Allogeneic Stem Cell Transplantation Recipients: Development of Cytomegalovirus Viremia Associated with Significantly Decreased 1-Year Survival

Cytomegalovirus (CMV) reactivation is a major cause of morbidity and nonrelapse mortality (NRM) in pediatric allogeneic stem cell transplantation (alloSCT) recipients. Approximately 80% of CMV seropositive alloHCT recipients will experience CMV reactivation without prophylaxis. The impacts of ganciclovir prophylaxis and subsequent CMV viremia on 1-year survival and 1-year NRM are unknown. The primary objective of this study was to determine the effect of CMV viremia on the probability of 1-year survival and 1-year NRM in pediatric alloSCT recipients receiving 100 days of ganciclovir prophylaxis. The secondary objective was to determine the effect of other risk factors on 1-year survival and 1-year NRM. All patients age 0 to 26 years who underwent alloSCT between June 2011 and May 2020 and received ganciclovir prophylaxis for 100 days at Westchester Medical Center, an academic medical center, were analyzed. Ganciclovir was administered to at-risk alloSCT recipients (donor and or recipient CMV+ serostatus) as 5 mg/kg every 12 hours from the first day of conditioning through day -1 (recipient CMV+ only) followed by 6 mg/kg every 24 hours on Monday through Friday beginning on the day of an absolute neutrophil count >750/mm3 and continuing through day +100. National Cancer Institute Common Terminology Criteria for Adverse Events 5.0 criteria were used to grade toxicity. NRM was analyzed using competing survival analysis with relapse death as a competing event. The log-rank and Gray tests were performed to compare the 1-year survival probabilities and NRM cumulative incidence between patients who experienced CMV viremia post-alloSCT and those who did not. Univariate Cox regression analysis was performed for the following risk factors: CMV viremia, donor source, sex, malignant disease, disease risk index, conditioning intensity, receipt of rabbit antithymocyte globulin (rATG)/alemtuzumab, graft-versus-host disease (GVHD) prophylaxis, CMV donor/recipient serostatus, grade II-IV acute GVHD, and grade 3/4 neutropenia necessitating discontinuation of ganciclovir, treating the last 3 factors as time-dependent covariates. Those with P values < .2 were included in the multivariate Cox regression analysis. Eighty-four alloSCT recipients (41 males, 43 females; median age, 10.8 years [range, .4 to 24.4 years]) were analyzed. Multivariate analysis showed significantly lower 1-year survival and significantly higher 1-year NRM in patients who developed CMV viremia compared to those who did not (P = .0036). No other risk factors were significantly associated with 1-year survival or 1-year NRM. One-year survival was significantly decreased and 1-year NRM was significantly increased in pediatric alloSCT recipients who developed CMV viremia following ganciclovir prophylaxis. No other risk factors were found to be associated with 1-year survival or 1-year NRM. Alternative CMV prophylaxis regimens that reduce CMV viremia should be investigated in pediatric alloSCT recipients at risk for CMV infection.

Maribavir: Mechanism of action, clinical, and translational science

Maribavir is an oral benzimidazole riboside for treatment of post-transplant cytomegalovirus (CMV) infection/disease that is refractory to prior antiviral treatment (with or without resistance). Through competitive inhibition of adenosine triphosphate, maribavir prevents the phosphorylation actions of UL97 to inhibit CMV DNA replication, encapsidation, and nuclear egress. Maribavir is active against CMV strains with viral DNA polymerase mutations that confer resistance to other CMV antivirals. After oral administration, maribavir is rapidly and highly absorbed (fraction absorbed >90%). The approved dose of 400 mg twice daily (b.i.d.) achieves a steady-state area under the curve per dosing interval of 128 h*μg/mL and trough concentration of 4.90 μg/mL (13.0 μM). Maribavir is highly bound to human plasma proteins (98%) with a small apparent volume of distribution of 27.3 L. Maribavir is primarily cleared by hepatic CYP3A4 metabolism; its major metabolite, VP44669 (pharmacologically inactive), is excreted in the urine and feces. There is no clinically relevant impact on maribavir pharmacokinetics by age, sex, race/ethnicity, body weight, transplant type, or hepatic/renal impairment status. In phase II dose-ranging studies, maribavir showed similar rates of CMV viral clearance across 400, 800, or 1200 mg b.i.d. groups, ranging from 62.5-70% in study 202 (NCT01611974) and 74-83% in study 203 (EudraCT 2010-024247-32). In the phase III SOLSTICE trial (NCT02931539), maribavir 400 mg b.i.d. demonstrated superior CMV viremia clearance at week 8 versus investigator-assigned treatments, with lower treatment discontinuation rates. Dysgeusia, nausea, vomiting, and diarrhea were commonly experienced adverse events among patients treated with maribavir in clinical trials.

Letermovir Rescue Therapy in Kidney Transplant Recipients with Refractory/Resistant CMV Disease

(1) Background: CMV infections remain a problem after kidney transplantation, particularly if patients are refractory or resistant (r/r) to treatment with valganciclovir (VGCV) or ganciclovir (GCV). (2) Methods: In a single-center retrospective study, kidney transplant recipients (KTR) receiving letermovir (LTV) as rescue therapy for VGCV-/GCV-r/r CMV disease were analyzed regarding CMV history, immunosuppression, and outcomes. (3) Results: Of 201 KTR treated for CMV between 2017 and 2022, 8 patients received LTV following treatment failure with VGCV/GCV. All patients received CMV prophylaxis with VGCV according to the center's protocol, and 7/8 patients had a high-risk (D+/R-) CMV constellation. In seven of eight cases, rising CMV levels occurred during prophylaxis. In seven of eight patients, a mutation in UL97 associated with a decreased response to VGCV/GCV was detected. In four of eight patients, LTV resulted in CMV clearance after 24 ± 10 weeks (16-39 weeks), two of eight patients stabilized at viral loads <2000 cop/mL (6-20 weeks), and two of eight patients developed LTV resistance (range 8-10 weeks). (4) Conclusion: LTV, which is currently evaluated for CMV prophylaxis in kidney transplantation, also shows promising results for the treatment of patients with VGCV/GCV resistance despite the risk of developing LTV resistance. Additional studies are needed to further define its role in the treatment of patients with CMV resistance.

Refractory cytomegalovirus infections in Chinese patients receiving allogeneic hematopoietic cell transplantation: a review of the literature

In the absence of prophylactic therapy, cytomegalovirus (CMV) viremia is a common complication following allogeneic hematopoietic cell transplantation (allo-HCT) and represents a significant cause of morbidity and mortality. Approximately 25% of allo-HCT happen in China, where the development and refinement of the 'Beijing protocol' has enabled frequent and increasing use of haploidentical donors. However, refractory CMV infection (an increase by >1 log10 in blood or serum CMV DNA levels after at least 2 weeks of an appropriately dosed anti-CMV medication) is more common among patients with haploidentical donors than with other donor types and has no established standard of care. Here, we review the literature regarding refractory CMV infection following allo-HCT in China.