Drug-resistant cytomegalovirus in transplant recipients: a French cohort study

Dynamics and Evolution of Donor-derived Cytomegalovirus Infection in 3 Solid Organ Transplant Recipients With the Same Multiorgan Donor

BACKGROUND

Cytomegalovirus (CMV) infection poses a significant risk to immunosuppressed transplant recipients, manifesting through primary infection, reinfection, or reactivation.

METHODS

We analyzed the emergence of drug resistance in CMV infection in 3 patients who were later found to have received an allograft from a shared, deceased donor. The seronegative transplant recipients developed symptomatic CMV infections after bowel/pancreas, kidney, or lung transplantation. Prospective Sanger sequencing was used to identify mutations in the viral DNA polymerase (DP) and protein kinase (PK). DP and PK variants were retrospectively quantified by targeted next-generation sequencing. The impact of the novel DP-A505G substitution on drug susceptibility was assessed using a recombinant virus. Whole-genome sequencing of clinical CMV samples was enabled through target DNA enrichment.

RESULTS

The DP-A505G substitution was found in all patient samples and could be associated with a natural polymorphism. A subsequent review of the patients' clinical histories revealed that they had all received organs from a single donor. The CMV infection exhibited divergent evolution among the patients: patient 1 developed resistance to ganciclovir and foscarnet because of 2 DP mutations (V715M and V781I), patient 2 showed no genotypic resistance, and patient 3 developed ganciclovir (PK-L595S) and maribavir resistance (PK-T409M). Interpatient variation across the entire CMV genome was minimal, with viral samples clustering in phylogenetic analysis.

CONCLUSIONS

All 3 transplant recipients were infected with the same donor-derived CMV strain and readily developed different drug susceptibility profiles. This underscores the importance of judicious antiviral drug use and surveillance in preventing antiviral resistance emergence.

Optimizing CMV therapy: Population pharmacokinetics and Monte Carlo simulations for letermovir and maribavir dosage

PURPOSE

This study seeks to reassess and enhance the dosing strategies of letermovir and maribavir for treating cytomegalovirus (CMV) infection, aiming to propose adjustments that could improve therapeutic effectiveness.

METHODS

Pre-existing population pharmacokinetic models were used alongside Monte Carlo simulations to evaluate the dosing strategies of letermovir and maribavir in CMV treatment. The simulations assessed the probability of target attainment for current and alternative dosing regimens, including scenarios with missed doses.

RESULTS

For letermovir, a loading dose on the first day of treatment initiation appeared more effective than the current strategy without a loading dose. Additionally, in cases of missed doses, doubling the dose upon resumption was more effective than returning to the normal dosage. For maribavir, the current 400mg BID regimen only covers the lower end of the inhibitory concentration 50 range, suggesting a potential benefit from increasing the doses. Simulations indicated that for missed doses, all tested regimens only covered the lower range of inhibitory concentrations, but the current strategy of resuming the normal dosage provided the lowest chances of target attainment.

CONCLUSION

Our findings suggest a strong rationale to reconsider and potentially modify the approved dosing guidelines for letermovir and maribavir in CMV treatment. Adjusting dosing regimens, including the use of loading doses and increased doses after missed doses, could enhance treatment outcomes by ensuring higher probabilities of achieving therapeutic targets and better managing missed doses.

Letermovir-inclusive combination therapy for a refractory and resistant infection by cytomegalovirus with UL54 mutation following a hematopoietic stem cell transplant for MHC class II deficiency

Cytomegalovirus (CMV) infection remains one of the most common and challenging post-transplant infections. Children with inborn errors of immunity (IEI) and T-cell dysfunction are at high risk for CMV infection, which can be complicated by refractory and/or resistant cases. This case describes a Nepalese girl with MHC class II deficiency, who presented at 3 months of age with CMV and Pneumocystis jirovecii pneumonia. Hematopoietic stem cell transplantation (HSCT) was planned as a curative treatment for IEI. Initial antiviral therapy with ganciclovir, followed by foscarnet, achieved undetectable CMV viral loads. However, the viral load rebounded during foscarnet therapy. HSCT was performed at 7 months of age using peripheral blood stem cells from her CMV-seropositive father, despite the recipient's high CMV viral load. Empiric combination therapy with cidofovir (an unapproved drug in Japan), foscarnet, leflunomide, and artesunate was initiated. CMV genetic testing revealed UL54 mutations conferring high-level resistance to foscarnet and moderate-level resistance to ganciclovir. The regimen was adjusted to letermovir, ganciclovir, leflunomide, and artesunate, which successfully suppressed the viral load following engraftment. At three months post-HSCT, combination therapy was discontinued after sustained undetectable CMV viral loads. Although CMV infection was controlled, the patient died from idiopathic pulmonary hemorrhage at five months post-HSCT. This case highlights the potential efficacy of a letermovir-inclusive therapy regimen in managing drug-resistant CMV with UL54 mutations in a pediatric HSCT recipient.

Dual Resistance to Maribavir and Ganciclovir in Transplant Recipients

BACKGROUND

Human cytomegalovirus (CMV) remains an important pathogen, especially for immunocompromised patients such as solid organ and hematopoietic stem cell recipients. Viral genomic mutations conferring drug resistance are an important impediment to effective CMV management and frequently lead to use of alternative antiviral drugs to treat CMV disease.

METHODS

Results from 1459 de-identified patient samples with both UL54 and UL97 sequencing results were analyzed for ganciclovir (GCV) and maribavir (MBV) resistance mutations. Genomic sequencing was performed by the Sanger method and resistance mutations were identified by comparison to CMV reference strain AD169.

RESULTS

Ganciclovir resistance was identified in 379 of 1459 (25.98%) of the samples tested, with most resistance-conferring mutations present in viral gene UL97. A total of 121 of 1459 (8.29%) samples had MBV resistance mutations, and 84 (69.42%) of the 121 samples with MBV resistance also had GCV resistance mutations. Of the 84 samples with resistance to both MBV and GCV, 35 (41.67%) had a single UL97 mutation conferring resistance to both drugs, either C480F or F342Y. The overall prevalence of C480F was increased relative to an earlier analysis of samples from this reference laboratory.

CONCLUSIONS

Although a high prevalence of CMV resistance mutations was identified, this must be taken in the context of healthcare providers submitting samples from patients with suspected CMV resistance. Most MBV-resistant samples were also resistant to GCV, suggesting that use of MBV as an alternative to GCV may benefit from genotypic resistance testing to achieve the effective control of CMV disease.

The emergence of letermovir and maribavir drug-resistant mutations: from clinical trials to real-world studies

PURPOSE OF REVIEW

Cytomegalovirus (CMV) infection is associated with severe clinical disease and high morbidity in immunocompromised hosts. Letermovir and maribavir, are two recently developed antiviral drugs used in the prevention and treatment of resistant and refractory CMV. Following the publication of landmark randomized trials and increased use, both clinical trial data and real-world experience has reported the development of antiviral drug resistance. The aim of this review was to comprehensively review the published literature on letermovir and maribavir drug resistance and to describe the clinical scenarios in which they may emerge.

RECENT FINDINGS

For letermovir, the most frequently detected resistance mutations occur in the UL56 gene (C325Y/W/F) and confer total resistance. Maribavir resistance mutations most often occur in the UL97 gene and resistance-associated variants (RAVs) T409M, H411Y, C480F have all been detected. The clinical context in which letermovir and maribavir resistance occurs include high viral loads at initiation, intensified immunosuppression, subtherapeutic drug exposure because of poor adherence, drug interactions, and inadequate central nervous system (CNS) penetration. Emergence of resistance mutations generally occurs within the first 3 months of initiation.

SUMMARY

The detection of letermovir and maribavir resistance mutations highlights an ongoing clinical challenge in the management of CMV.

Mutations in human cytymegalovirus (Orthoherpesviridae: Herpesvirales: Cytomegalovirus: Cytomegalovirus humanbeta 5) UL97 gene lead to increase in viremia duration and poor antiviral response in recipients of allogeneic hematopoietic stem cells

INTRODUCTION

Human cytomegalovirus (Orthoherpesviridae: Herpesvirales: Cytomegalovirus: Cytomegalovirus humanbeta 5) (HCMV) is one of the most commonly detected viruses in recipients of allogeneic hematopoietic stem cell (allo-HSCT) transplants. However, the emergence of resistance to antiviral drugs such as ganciclovir (GCV) poses a challenge in managing these patients. This study aims to investigate the prevalence and impact of mutations in the HCMV UL97 gene associated with resistance to GCV on the course of infection among allo-HSCT patients.

MATERIALS AND METHODS

The study examined the association between UL97 mutations and the clinical course of HCMV infection in allo-HSCT patients. Genetic sequencing was performed to identify mutations, and their impact on viral replication and resistance to GCV was assessed.

RESULTS AND DISCUSSION

Six mutations were identified (D490A, T502A, C592G, C592F, E596G, C603W). C592G, C592F, E596G, and C603W are associated with resistance to antiviral drugs, while D490A and T502A described for the first time. When comparing patients with wild-type and those carrying the mutant variant, several parameters of peripheral blood were significantly lower in the former group. The median time to peak viral load following allo-HSCT, duration of viremia, and rate of virological response to high-dose therapy also differed significantly between the two groups.

CONCLUSION

It was shown that approximately one third (4 out of 14) of allogeneic stem cell transplant recipients had mutations associated with resistance to GCV. Patients carrying the mutant variant of HCMV had longer viremia and took longer to achieve a negative virological test result after starting high-dose therapy. Performing genotyping may help make more evidence-based therapeutic decisions.

Efficacy and safety of adoptive T-cell therapy in treating cytomegalovirus infections post-haematopoietic stem cell transplantation: A systematic review and meta-analysis

Cytomegalovirus (CMV) infection poses significant risks in allogeneic haematopoietic stem cell transplant (allo-HSCT) recipients. Despite advances in antiviral therapies, issues such as drug resistance, side effects, and inadequate immune reconstitution remain. This systematic review and meta-analysis aim to evaluate the efficacy and safety of adoptive cell therapy (ATC) in managing CMV infections in allo-HSCT recipients. Adhering to preferred reporting items for systematic reviews and meta-analyses guidelines, we conducted a comprehensive database search through July 2023. A systematic review and meta-analysis were conducted on studies involving HSCT patients with CMV infections treated with ATC. The primary outcome was the response rate to ATC, and secondary outcomes included adverse events associated with ATC. The Freeman-Tukey transformation was applied for analysis. In the meta-analysis of 40 studies involving 953 participants, ATC achieved an overall integrated response rate of 90.16%, with a complete response of 82.59% and a partial response of 22.95%. ATC source, HLA matching, steroid intake, and age group markedly influenced response rates. Donor-derived T-cell treatments exhibited a higher response rate (93.66%) compared to third-party sources (88.94%). HLA-matched patients demonstrated a response rate of 92.90%, while mismatched patients had a lower rate. Children showed a response rate of 83.40%, while adults had a notably higher rate of 98.46%. Adverse events were minimal, with graft-versus-host disease occurring in 24.32% of patients. ATC shows promising response rates in treating CMV infections post-HSCT, with an acceptable safety profile. However, to establish its efficacy conclusively and compare it with other antiviral treatments, randomised controlled trials are essential. Further research should prioritise such trials over observational and one-arm studies to provide robust evidence for clinical decision-making.

Epidemiology and Management of Infections in Liver Transplant Recipients

Background: Improvements in liver transplant (LT) outcomes are attributed to advances in surgical techniques, use of potent immunosuppressants, and rigorous pre-LT testing. Despite these improvements, post-LT infections remain the most common complication in this population. Bacteria constitute the most common infectious agents, while fungal and viral infections are also frequently encountered. Multi-drug-resistant bacterial infections develop because of polymicrobial overuse and prolonged hospital stays. Immediate post-LT infections are commonly caused by viruses. Conclusions: Appropriate vaccination, screening of both donor and recipients before LT and antiviral prophylaxis in high-risk individuals are recommended. Antimicrobial drug resistance is common in high-risk LT and associated with poor outcomes; epidemiology and management of these cases is discussed. Additionally, we also discuss the effect of coronavirus disease 2019 (COVID-19) infection and monkeypox in the LT population.

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.

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.

Refractory human cytomegalovirus infection without evidence of genetic resistance in the UL-54 and UL-97 genes in a pediatric hematopoietic stem cell transplant recipient: a case report

Cytomegalovirus (CMV) infection is a common complication in patients undergoing hematopoietic stem cell transplantation (HSCT). Management of refractory CMV infections, especially in developing countries, can be challenging due to the limited availability of second and third-line antiviral drugs or alternative treatments. Here, we present a case of an 8 years-old patient diagnosed with acute myeloid leukemia. Eight months post-diagnosis, the patient underwent TCR-αβ+/CD19+-depleted haploidentical HSCT. Both the donor and recipient tested positive for anti-CMV IgG and negative for IgM antibodies. Before transplantation, the patient received CMV prophylaxis in the form of intravenous ganciclovir. Post-transplantation, the patient exhibited oscillating CMV viral loads and was diagnosed with a refractory infection. Treatment with ganciclovir, foscarnet, and cidofovir was unsuccessful. Sequencing of UL-54 and UL-97 genes was performed to rule out potential resistance to first-line treatment. Ten months after the HSCT, the child died from hypovolemic shock due to gastrointestinal bleeding. This is the first case reported in Peru and Latin America of a refractory CMV infection in a pediatric HSCT recipient without evidence of clinical symptoms and CMV genetic resistance. This case demonstrates the need for alternative treatments to manage refractory CMV infections, especially in haploidentical HSCT cases where drug resistance is frequent (~15%). Furthermore, this case highlights the importance of using highly sensitive genetic tools to detect mutations associated with virus resistance in a broader range of the viral genome.

Epidemiology of cytomegalovirus antiviral resistance testing for solid organ and bone marrow transplant patients from 2011 - 2019

BACKGROUND

CMV reactivation post-transplantation is common, with need for prompt identification of patients most at-risk for CMV antiviral drug resistance (AVDR).

OBJECTIVES

This study describes CMV AVDR frequencies, antiviral prescribing practices, and AVDR risk factors in patients from 2011 to 2019 in British Columbia, Canada.

STUDY DESIGN

Retrospective review of demographics, transplant type, viral loads, antiviral exposure duration, and 12-month mortality was conducted for all patients with samples submitted for CMV AVDR testing from 2011 to 2019. Genotyping of AVDR mutations occurred at the national reference laboratory. Mann-Whitney U, T-test or Fisher's exact tests examined differences between patients with and without AVDR.

RESULTS

Fifty-three plasma and three tissue/fluid specimens successfully underwent CMV AVDR testing; of these samples, 27/56 (48%) had AVDR mutations detected. The commonest AVDR mutations were at UL97 loci A594 (20%), H596 (12%) and L595 (12%). Mutations occurred more frequently in requests from solid organ than hematopoietic stem cell transplant patients (58% vs. 27%, p = 0.05). Previous resistance testing was a significant risk factor for AVDR (p < 0.001). Patients with AVDR had approximately 51 more days of antiviral therapy (p = 0.007) and took 9 days longer to clear viremia (p = 0.23). The median turnaround time from sample send-out to reporting was nine days. However, empiric use of second-line antivirals occurred in most cases (39/53, 74%) before results were available.

DISCUSSION

Laboratories should strive to provide timely CMV AVDR testing for transplant patients, to minimize unnecessary exposure to second-line antiviral agents. The findings of this study may help guide clinicians when selecting empiric antiviral therapy.

Cytomegalovirus Disease as a Risk Factor for Invasive Fungal Infections in Liver Transplant Recipients under Targeted Antiviral and Antimycotic Prophylaxis

Cytomegalovirus (CMV) infection is the most common opportunistic infection that occurs following orthotopic liver transplantation (OLT). In addition to the direct infection-related symptoms, it also triggers an immunological response that may contribute to adverse clinical outcomes. CMV disease has been described as a predictor of invasive fungal infections (IFIs) but its role under an antiviral prophylaxis regimen is unclear.

METHODS

We retrospectively analyzed the medical records of 214 adult liver transplant recipients (LTRs). Universal antiviral prophylaxis was utilized in recipients with CMV mismatch; intermediate- and low-risk patients received pre-emptive treatment.

RESULTS

Six percent of patients developed CMV disease independent of their serostatus. The occurrence of CMV disease was associated with elevated virus load and increased incidence of leucopenia and IFIs. Furthermore, CMV disease was associated with higher one-year mortality and increased relapse rates within the first year of OLT.

CONCLUSIONS

CMV disease causes significant morbidity and mortality in LTRs, directly affecting transplant outcomes. Due to the increased risk of IFIs, antifungal prophylaxis for CMV disease may be appropriate. Postoperative CMV monitoring should be considered after massive transfusion, even in low-risk serostatus constellations. In case of biliary complications, biliary CMV monitoring may be appropriate in the case of CMV-DNA blood-negative patients.

Virus-Specific T-Cell Therapy for Viral Infections of the Central Nervous System: A Review

Opportunistic viral infections of the central nervous system represent a significant cause of morbidity and mortality among an increasing number of immunocompromised patients. Since antiviral treatments are usually poorly effective, the prognosis generally relies on the ability to achieve timely immune reconstitution. Hence, strategies aimed at reinvigorating antiviral immune activity have recently emerged. Among these, virus-specific T-cells are increasingly perceived as a principled and valuable tool to treat opportunistic viral infections. Here we briefly discuss how to develop and select virus-specific T-cells, then review their main indications in central nervous system infections, including progressive multifocal leukoencephalopathy, CMV infection, and adenovirus infection. We also discuss their potential interest in the treatment of progressive multiple sclerosis, or EBV-associated central nervous system inflammatory disease. We finish with the key future milestones of this promising treatment strategy.

Factors Associated With Genotypic Resistance and Outcome Among Solid Organ Transplant Recipients With Refractory Cytomegalovirus Infection

Genotypically resistant cytomegalovirus (CMV) infection is associated with increased morbi-mortality. We herein aimed at understanding the factors that predict CMV genotypic resistance in refractory infections and disease in the SOTR (Solid Organ Transplant Recipients) population, and the factors associated with outcomes. We included all SOTRs who were tested for CMV genotypic resistance for CMV refractory infection/disease over ten years in two centers. Eighty-one refractory patients were included, 26 with genotypically resistant infections (32%). Twenty-four of these genotypic profiles conferred resistance to ganciclovir (GCV) and 2 to GCV and cidofovir. Twenty-three patients presented a high level of GCV resistance. We found no resistance mutation to letermovir. Age (OR = 0.94 per year, IC95 [0.089-0.99]), a history of valganciclovir (VGCV) underdosing or of low plasma concentration (OR= 5.6, IC95 [1.69-20.7]), being on VGCV at infection onset (OR = 3.11, IC95 [1.18-5.32]) and the recipients' CMV negative serostatus (OR = 3.40, IC95 [0.97-12.8]) were independently associated with CMV genotypic resistance. One year mortality was higher in the resistant CMV group (19.2 % versus 3.6 %, p = 0.02). Antiviral drugs severe adverse effects were also independently associated with CMV genotypic resistance. CMV genotypic resistance to antivirals was independently associated with a younger age, exposure to low levels of GCV, the recipients' negative serostatus, and presenting the infection on VGCV prophylaxis. This data is of importance, given that we also found a poorer outcome in the patients of the resistant group.

Cytomegalovirus in children undergoing haematopoietic stem cell transplantation: a diagnostic and therapeutic approach to antiviral resistance

Cytomegalovirus (CMV) is a ubiquitous virus which causes a mild illness in healthy individuals. In immunocompromised individuals, such as children receiving haematopoietic stem cell transplantation, CMV can reactivate, causing serious disease and increasing the risk of death. CMV can be effectively treated with antiviral drugs, but antiviral resistance is an increasingly common complication. Available therapies are associated with adverse effects such as bone marrow suppression and renal impairment, making the choice of appropriate treatment challenging. New agents are emerging and require evaluation in children to establish their role. This review will discuss established and emerging diagnostic tools and treatment options for CMV, including antiviral resistant CMV, in children undergoing haematopoietic stem cell transplant.

Genetic Variants Associated with Drug Resistance of Cytomegalovirus in Hematopoietic Cell Transplantation Recipients

Cytomegalovirus (CMV) infection is a serious complication in hematopoietic cell transplantation (HCT) recipients. Drug-resistant strains make it more challenging to treat CMV infection. This study aimed to identify variants associated with CMV drug resistance in HCT recipients and assess their clinical significance. A total of 123 patients with refractory CMV DNAemia out of 2271 HCT patients at the Catholic Hematology Hospital between April 2016 and November 2021 were analyzed, which accounted for 8.6% of the 1428 patients who received pre-emptive therapy. Real-time PCR was used to monitor CMV infection. Direct sequencing was performed to identify drug-resistant variants in UL97 and UL54. Resistance variants were found in 10 (8.1%) patients, and variants of uncertain significance (VUS) were found in 48 (39.0%) patients. Patients with resistance variants had a significantly higher peak CMV viral load than those without (p = 0.015). Patients with any variants had a higher risk of severe graft-versus-host disease and lower one-year survival rates than those without (p = 0.003 and p = 0.044, respectively). Interestingly, the presence of variants reduced the rate of CMV clearance, particularly in patients who did not modify their initial antiviral regimen. However, it had no apparent impact on individuals whose antiviral regimens were changed due to refractoriness. This study highlights the importance of identifying genetic variants associated with CMV drug resistance in HCT recipients for providing appropriate antiviral treatment and predicting patient outcomes.

Prevalence of cytomegalovirus antiviral drug resistance in transplant recipients

Cytomegalovirus (CMV) is a significant human pathogen, especially for immunocompromised patients, often treated with one or more antiviral drugs. Although the prevalence of resistance is low, the impact of drug resistant CMV infections on patient outcomes is high and genotypic testing is recommended when resistance is suspected. To assess the prevalence of CMV drug resistance mutations among samples submitted for genotypic testing, 2750 patient sample results were analyzed. Testing was performed by sequencing for ganciclovir (GCV), cidofovir (CDV), foscarnet (FOS), maribavir (MBV) and/or letermovir (LMV) resistance conferring mutations. Of the 2750 patient samples, 826 (30.04%) had resistance to one or more anti-CMV drug. Resistance mutations were most common in UL97, with 27.64% and 9.96% of samples having GCV and MBV mutations, respectively. Resistance mutations in UL54 were less common, with 6.11%, 5.98% and 1.76% of samples having GCV, CDV and FOS mutations, respectively. For LMV, resistance mutations in UL56 were present in 7.17% of samples, with mutations at codon 325 representing 80.95% of the observed LMV resistance mutations. Resistance to two drugs was identified in 215 samples and to 3 or more drugs in 35 samples. While a high prevalence of CMV resistance mutations was identified, this must be taken in the context of healthcare providers submitting samples from patients with suspected resistant CMV strains. For these patients, rapid monitoring for resistance allows treatment modifications based on objective results rather than empiric drug selection, which is particularly relevant given the presence of mutations conferring resistance to more than one drug.

Myocarditis: causes, mechanisms, and evolving therapies

INTRODUCTION

Myocarditis is a severe lymphocyte-mediated inflammatory disorder of the heart, mostly caused by viruses and immune checkpoint inhibitors (ICIs). Recently, myocarditis as a rare adverse event of mRNA vaccines for SARS-CoV-2 has caused global attention. The clinical consequences of myocarditis can be very severe, but specific treatment options are lacking or not yet clinically proven.

AREAS COVERED

This paper offers a brief overview of the biology of viruses that frequently cause myocarditis, focusing on mechanisms important for viral entry and replication following host infection. Current and new potential therapeutic targets/strategies especially for viral myocarditis are reviewed systematically. In particular, the immune system in myocarditis is dissected with respect to infective viral and non-infective, ICI-induced myocarditis.

EXPERT OPINION

Vaccination is an excellent emerging preventative strategy for viral myocarditis, but most vaccines still require further development. Anti-viral treatments that inhibit viral replication need to be considered following viral infection in host myocardium, as lower viral load reduces inflammation severity. Understanding how the immune system continues to damage the heart even after viral clearance will define novel therapeutic targets/strategies. We propose that viral myocarditis can be best treated using a combination of antiviral agents and immunotherapies that control cytotoxic T cell activity.

New Insights on CMV Management in Solid Organ Transplant Patients: Prevention, Treatment, and Management of Resistant/Refractory Disease

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.

Adoptive Immunotherapy for Prophylaxis and Treatment of Cytomegalovirus Infection

Cytomegalovirus (CMV), a member of the Herpesviridae family, is frequent among hematopoietic cell transplant (HCT) and solid organ transplant (SOT) recipients in absence of antiviral prophylaxis, and is a major cause of morbidity and mortality in these vulnerable populations. Antivirals such ganciclovir, valganciclovir, and foscarnet are the backbone therapies, however drug toxicity and antiviral resistance may render these agents suboptimal in treatment. Newer therapies such as letermovir and maribavir have offered additional approaches for antiviral prophylaxis as well as treatment of drug resistant CMV infection, though may be limited by cost, drug intolerance, or toxicity. Adoptive immunotherapy, the transfer of viral specific T-cells (VSTs), offers a new approach in treatment of drug-resistant or refractory viral infections, with early clinical trials showing promise with respect to efficacy and safety. In this review, we will discuss some of the encouraging results and challenges of widespread adoption of VSTs in care of immunocompromised patients, with an emphasis on the clinical outcomes for treatment and prophylaxis of CMV infection among high-risk patient populations.

New Perspectives on Antimicrobial Agents: Maribavir

Maribavir was approved by the U.S. Food and Drug Administration in November 2021 for the treatment of adult and pediatric patients with post-transplant cytomegalovirus (CMV) infection/disease that is refractory to treatment (with or without genotypic resistance) with ganciclovir, valganciclovir, cidofovir, or foscarnet. Maribavir is an oral benzimidazole riboside with potent and selective multimodal anti-CMV activity. It utilizes a novel mechanism of action which confers activity against CMV strains that are resistant to traditional anti-CMV agents, and also offers a more favorable safety profile relative to the dose-limiting side effects of previously available therapies. Maribavir was initially studied as an agent for CMV prophylaxis in solid organ and hematopoietic stem cell recipients, but initial phase III trials failed to meet clinical efficacy endpoints. It has been more recently studied as a therapeutic agent at higher doses for refractory-resistant (R-R) CMV infections with favorable outcomes. After an overview of maribavir's chemistry and clinical pharmacology, this review will summarize clinical efficacy, safety, tolerability, and resistance data associated with maribavir therapy.

Intra-host diversity of drug-resistant cytomegalovirus: A case report of cytomegalovirus infection after allogeneic hematopoietic cell transplantation

Cytomegalovirus (CMV) is a major infectious agent causing severe complications in allogeneic hematopoietic cell transplantation (HCT) recipients, thereby warranting the need for aggressive preemptive or targeted antiviral therapy. However, prolonged or repeated use of antiviral agents, such as ganciclovir (GCV), foscarnet (FOS), and cidofovir (CDV), can result in drug-resistant CMV infection, posing challenges to successful outcomes. Here, we report a case of a patient with acute myeloid leukemia and drug-resistant CMV infection who presented with persistent CMV DNAemia, colitis, pneumonia, and encephalitis. An intra-host diversity of UL97 and UL54 mutations were detected through the genotypic resistance testing conducted on two blood samples (D+199 and D+224) and a cerebrospinal fluid (CSF) specimen (D+260) collected from the patient. UL97 L595W/L595F and L595W mutations were detected in the blood and CSF samples, respectively, that conferred GCV resistance. UL54 F412L mutation detected in all three samples conferred GCV/CDV resistance. However, the V787L mutation of UL54, conferring GCV/FOS resistance, was observed only in the D+224 blood sample. Despite combination therapy with FOS and high dose GCV and adjunctive therapy with leflunomide, the patient died from CMV infection and multiple organ failure on D+279. Further data on resistant mutations and intra-host diversity of CMV should be accumulated to elucidate the antiviral resistance and related outcomes.

Detection of Ganciclovir-Resistant Cytomegalovirus in a Prospective Cohort of Kidney Transplant Recipients Receiving Subtherapeutic Valganciclovir Prophylaxis

Cytomegalovirus infection during antiviral prophylaxis occurs in transplant recipients despite individualized regimens based on renal function. Fifty kidney transplant recipients were assessed between 2016 and 2019 for valganciclovir dosing, ganciclovir exposure, cytomegalovirus infection, and genotypic resistance markers during the first year posttransplant. Ganciclovir plasma concentrations were measured using mass spectrometry. Population pharmacokinetics was used to determine individual ganciclovir exposure and to evaluate the ability of manufacturer dosing guidelines to meet therapeutic target daily area under the curve (AUC24) of 40 to 50 μg·h/mL. Full-length UL54 and UL97 were assessed using high-throughput sequencing in cytomegalovirus DNA-positive patient specimens. Valganciclovir doses administered to recipients with creatinine clearance of <40 mL/min were higher than specified by guidelines, and they were lower for recipients with creatinine clearance of ≥40 mL/min. The mean ganciclovir AUC24 was 33 ± 13 μg·h/mL, and 82% of subjects did not attain the therapeutic target. Pharmacokinetic simulations showed that the guidelines similarly could not attain the therapeutic target in 79% of individuals. Cytomegalovirus breakthrough occurred in 6% (3/50) of recipients, while 12% (6/50) developed late-onset infection. The mean AUC24s of recipients with (n = 3) and without (n = 47) infection were not significantly different (P = 0.528). However, one recipient with an AUC24 of 20 μg·h/mL acquired two UL97 ganciclovir resistance mutations. Current prophylaxis guidelines resulted in subtherapeutic ganciclovir exposure in several study recipients, including the emergence of resistance genotypes. IMPORTANCE This study examined the pharmacokinetics and viral genomic data from a prospective cohort of kidney transplant recipients undergoing valganciclovir prophylaxis for cytomegalovirus (CMV) prevention. We showed for the first time using high-throughput sequencing the detection of ganciclovir resistance mutations in breakthrough CMV infection during subtherapeutic plasma ganciclovir as indicated by the pharmacokinetic parameter daily area under the curve (AUC24). In addition, we found that current valganciclovir dosing guidelines for CMV prophylaxis are predicted to attain therapeutic targets in only 21% of recipients, which is consistent with previous pharmacokinetic studies. The novel findings of resistance mutations during subtherapeutic ganciclovir exposure presented here can inform future studies investigating the dynamics of drug selection pressure and the emergence of resistance mutations in vivo.

Cytomegalovirus and other herpesviruses after hematopoietic cell and solid organ transplantation: From antiviral drugs to virus-specific T cells

Herpesviruses can either cause primary infection or may get reactivated after both hematopoietic cell and solid organ transplantations. In general, viral infections increase post-transplant morbidity and mortality. Prophylactic, preemptive, or therapeutically administered antiviral drugs may be associated with serious side effects and may induce viral resistance. Virus-specific T cells represent a valuable addition to antiviral treatment, with high rates of response and minimal side effects. Even low numbers of virus-specific T cells manufactured by direct selection methods can reconstitute virus-specific immunity after transplantation and control viral replication. Virus-specific T cells belong to the advanced therapy medicinal products, and their production is regulated by appropriate legislation; also, strict safety regulations are required to minimize their side effects.

Evaluation of treatment patterns, healthcare resource utilization, and costs among patients receiving treatment for cytomegalovirus following allogeneic hematopoietic cell or solid organ transplantation

AIM

Management of cytomegalovirus (CMV) infection/disease in transplant recipients may be complicated by toxicities and resistance to conventional antivirals, adding to the overall healthcare burden. We characterized treatment patterns, healthcare resource utilization (HCRU), and costs to elucidate the healthcare burden associated with CMV therapies post-transplant.

MATERIALS AND METHODS

A retrospective, longitudinal cohort study of transplant recipients using data from a US commercial insurance claims database (2013-2017) was conducted. Patients with a claim for post-transplant CMV diagnosis and anti-CMV treatment (ganciclovir, valganciclovir, foscarnet, or cidofovir) were identified (Treated CMV cohort) and compared with patients with neither a claim for CMV diagnosis nor anti-CMV treatment (No CMV cohort) for outcomes including HCRU and associated costs. Allogeneic hematopoietic cell transplantation (HCT) or solid organ transplantation (SOT) recipients were analyzed separately. Anti-CMV treatment patterns were assessed in the Treated CMV cohort. Costs were evaluated among subgroups with myelosuppression or nephrotoxicity.

RESULTS

Overall, 412 allogeneic HCT and 899 SOT patients were included in the Treated CMV cohorts, of which 41.7% and 52.5%, respectively, received multiple antiviral courses. Treated CMV cohorts compared with No CMV cohorts had higher mean monthly healthcare visits per patient (allogeneic HCT: 8.83 vs 6.61, SOT: 5.61 vs 4.45) and had an incremental adjusted mean monthly cost per patient differences of $8,157 (allogeneic HCT, p < .004) and $2,182 (SOT, p < .004). Among Treated CMV cohorts, HCRU and costs increased with additional CMV antiviral treatment courses. Mean monthly costs were higher for patients with than without myelosuppression or nephrotoxicity.

LIMITATIONS

Results may not be generalizable to patients covered by government insurance or outside the USA.

CONCLUSIONS

CMV post-transplant managed with conventional treatment is associated with substantial HCRU and costs. The burden remains particularly high for patients requiring multiple treatment courses for post-transplant CMV or for transplant recipients who develop myelosuppression or nephrotoxicity.

A rapid evidence assessment exploring whether antimicrobial resistance complicates non-infectious health conditions and healthcare services, 2010-20

Antimicrobial resistance (AMR) is one of the greatest public health threats at this time. While there is a good understanding of the impacts of AMR on infectious diseases, an area of less focus is the effects AMR may be having on non-communicable health conditions (such as cancer) and healthcare services (such as surgery). Therefore, this study aimed to explore what impact AMR is currently having on non-communicable health conditions, or areas of health services, where AMR could be a complicating factor impacting on the ability to treat the condition and/or health outcomes. To do this, a rapid evidence assessment of the literature was conducted, involving a systematic approach to searching and reviewing the evidence. In total, 101 studies were reviewed covering surgery, organ transplants, cancer, ICUs, diabetes, paediatric patients, immunodeficiency conditions, liver and kidney disease, and physical trauma. The results showed limited research in this area and studies often use a selective population, making the results difficult to generalize. However, the evidence showed that for all health conditions and healthcare service areas reviewed, at least one study demonstrated a higher risk of death for patients with resistant infections, compared with no or drug-susceptible infections. Poor health outcomes were also associated with resistant infections in some instances, such as severe sepsis and failure of treatments, as well as a greater need for invasive medical support. While there are gaps in the evidence base requiring further research, efforts are also needed within policy and practice to better understand and overcome these challenges.

Incidence of refractory cytomegalovirus infection after allogeneic hematopoietic stem cell transplantation

Post-transplant cytomegalovirus (CMV) disease can be almost completely avoided by current infection control procedures. However, CMV reactivation occurs in more than half of patients, and some patients can develop clinically resistant CMV infections. Whether resistance is due to the host's immune status or a viral resistance mutation is challenging to confirm. Therefore, a prospective observational analysis of refractory CMV infection was conducted in 199 consecutive patients who received allogeneic hematopoietic stem cell transplantation at a single institution. Among them, 143 (72%) patients received anti-CMV drugs due to CMV reactivation, and only 17 (8.5%) exhibited refractory CMV infection. These patients had clinically refractory infection. However, viral genome analysis revealed that only one patient exhibited a mutation associated with the anti-CMV drug resistance. Clinical resistance was mainly correlated with host immune factors, and the incidence of resistance caused by gene mutations was low at the early stage after a transplantation.

Letermovir treatment of cytomegalovirus infection or disease in solid organ and hematopoietic cell transplant recipients

BACKGROUND

Few options are available for cytomegalovirus (CMV) treatment in transplant recipients resistant, refractory, or intolerant to approved agents. Letermovir (LET) is approved for prophylaxis in hematopoietic cell transplant (HCT) recipients, but little is known about efficacy in CMV infection. We conducted an observational study to determine the patterns of use and outcome of LET treatment of CMV infection in transplant recipients.

METHODS

Patients who received LET for treatment of CMV infection were identified at 13 transplant centers. Demographic and outcome data were collected.

RESULTS

Twenty-seven solid organ and 21 HCT recipients (one dual) from 13 medical centers were included. Forty-five of 47 (94%) were treated with other agents prior to LET, and 57% had a history of prior CMV disease. Seventy-seven percent were intolerant to other antivirals; 32% were started on LET because of resistance concerns. Among 37 patients with viral load < 1000 international units (IU)/ml at LET initiation, two experienced >1 log rise in viral load by week 12, and no deaths were attributed to CMV. Ten patients had viral load > 1000 IU/ml at LET initiation, and six of 10 (60%) had a CMV viral load < 1000 IU/ml at completion of therapy or last known value. LET was discontinued in two patients for an adverse event.

CONCLUSIONS

Patients treated with LET with viral load < 1000 IU/ml had good virologic outcomes. Outcomes were mixed when LET was initiated at higher viral loads. Further studies on combination therapy or alternative LET dosing are needed.

Prevalence of UL97 gene mutations and polymorphisms in cytomegalovirus infection in the colon associated with or without ulcerative colitis

Cytomegalovirus (CMV) reactivation in the colon is common in patients with severe ulcerative colitis (UC). Ganciclovir (GCV) resistance conferring CMV UL97 gene mutations have been reported in recent years. However, the prevalence of UL97 gene mutations in GCV-naive CMV infection in the colon remains unknown. We investigated the prevalence of CMV UL97 gene mutations in patients with colonic CMV infection associated with or without UC. Twenty-two GCV-naive patients with colonic CMV infection, 15 with UC and 7 with other diseases, were enrolled. Frozen biopsy samples or formalin-fixed paraffin-embedded samples were used for nested polymerase chain reaction (PCR) amplification of the UL97 gene. Sanger DNA sequencing was performed. In comparison with AD169 reference strain, natural polymorphisms were frequently detected in codons N68D (100%), I244V (100%), and D605E (86.4%). Seven polymorphisms were detected infrequently (< 10%) outside the kinase domain. However, no known GCV resistance mutations were found. There seemed to be no difference between the ratio of polymorphisms in patients with and without UC. In conclusions, we did not detect UL97 gene mutations associated with GCV resistance in GCV-naive patients with or without UC. Consistent with previous reports, D605E polymorphism may be used as a genetic marker for CMV in East Asian countries.

Use of Letermovir-Valganciclovir combination as a step-down treatment after Foscarnet for Ganciclovir-resistant CMV infection in kidney transplant recipients

Background

Letermovir (LTV) might be an alternative treatment to nephrotoxic foscarnet (FOS) in Ganciclovir (GCV) resistant cytomegalovirus (CMV) infection. However, its efficacy in controlling active CMV viremia is unclear, as it is only approved for CMV prophylaxis in hematopoietic stem‐cell transplantation.

Methods

This case series describes 14 kidney transplant recipients (KTR) with moderate‐level GCV resistant CMV infection, treated by different step‐down strategies after initial FOS therapy: (1) Observation without antiviral follow‐up or switch to valganciclovir (VGCV) (pre‐LTV era), and (2) Switch to LTV±VGCV (LTV era).

Results

One patient died under FOS. Thirteen patients were followed under step‐down regimens. All but two patients had ongoing CMV viremia when stopping FOS. In pre‐LTV era, 5/9 (56%) experienced a CMV breakthrough > 10 000 IU/ml calling for another course of FOS, as compared to 1/4 (25%) in the LTV era. Addition of VGCV to LTV at low‐level viral breakthrough, addressing a possible developing resistance against LTV, prevented viral surge in two patients. In the pre‐LTV era, CMV‐related death or graft loss occurred in three of nine (33%), compared to no death or graft loss in the LTV era.

Conclusion

A step‐down strategy combining LTV+VGCV, might allow to safely stop FOS at ongoing low‐level viremia.

Cytomegalovirus Infection and the Implications of Drug-Resistant Mutations in Pediatric Allogeneic Hematopoietic Stem Cell Transplant Recipients: A Retrospective Study from a Tertiary Hospital in China

INTRODUCTION

Drug-resistant cytomegalovirus (CMV) infection remains a challenge in the management of pediatric recipients of hematopoietic stem cell transplantation (HSCT). In this study, we retrospectively reviewed the clinical data on pediatric recipients of HSCT and identified known and unknown drug-resistant CMV variants.

METHODS

A total of 221 children underwent allogeneic HSCT between October 2017 and November 2019 at Shenzhen Children's Hospital; of these, 35 patients were suspected of having drug-resistant CMV infections and were tested for drug-resistant mutations in the UL97 and UL54 genes by Sanger sequencing.

RESULTS

Mutations in UL97 or UL54, or in both, were detected in 11 patients. Most of these mutations have not been previously reported. The UL97 mutation (A582V) was detected in only one patient who also harbored two UL54 mutations (T760X and R876W). One patient with both the G604S and T691A mutations in the UL54 gene died of CMV pneumonia. We investigated the risk factors associated with the development of drug-resistant CMV infection. Patients in whom both the donor and recipient had positive CMV serostatuses were less likely to have drug-resistant mutations (Fisher's exact test, p < 0.05).

CONCLUSION

Newly and previously detected CMV mutations in UL97 and UL54 may be associated with the development of drug-resistant CMV infection. The detection of these mutations may provide guidance for the management of post-transplant CMV infections.

Refractory and Resistant Cytomegalovirus after Hematopoietic Cell Transplant in the Letermovir Primary Prophylaxis Era

BACKGROUND

Cytomegalovirus (CMV) reactivation is one of the most common infectious complications after allogeneic hematopoietic cell transplant (HCT) and may result in significant morbidity and mortality. Primary prophylaxis with letermovir demonstrated a reduction in clinically significant CMV infections (CS-CMVi) in clinical trials of CMV-seropositive HCT recipients. This study aims at exploring the effect of primary letermovir prophylaxis in this population on the incidence and outcomes of refractory or resistant CMV infections.

METHODS

This is a single-center, retrospective cohort study of 537 consecutive CMV-seropositive allogeneic HCT recipients cared for during March 2016 to October 2018. Baseline demographics, HCT characteristics, CMV infections, treatment and mortality data were collected from the electronic medical record. CMV outcomes were defined according to the recently standardized definitions for clinical trials. Characteristics and outcomes were assessed according to receipt of primary letermovir prophylaxis.

RESULTS

Of 537 patients identified, 123 received letermovir for primary prophylaxis during the first 100 days after HCT, and 414 did not. In a multivariate analysis, primary prophylaxis with letermovir was associated with reductions in CS-CMVi (hazard ratio [HR] 0.26, 95% CI 0.16-0.41), CMV end-organ disease (HR 0.23, 95% CI 0.10-0.52), refractory or resistant CMV infection (HR 0.15, 95% CI 0.04-0.52), and non-relapse mortality at week 48 (HR 0.55, 95% CI 0.32-0.93). There was neither resistant CMV nor CMV-related mortality in the primary letermovir prophylaxis group.

CONCLUSIONS

Primary letermovir prophylaxis effectively prevents refractory or resistant CMV infections and decreases non-relapse mortality at week 48, as well as CS-CMVi and CMV disease after allogeneic HCT.

Molecular Epidemiology of Cytomegalovirus UL97 and UL54 variants in Taiwan

BACKGROUND

The antiviral resistance of cytomegalovirus (CMV) infections is associated with mutations in the CMV UL54 and UL97 gene regions and is a serious problem in immunocompromised patients. However, the molecular epidemiology of UL54 and UL97 in Taiwan is unclear.

METHODS

We conducted a retrospective study of patients with CMV infections between January and December 2016 in two tertiary hospitals, one regional hospital in Taiwan. CMV DNAemia was confirmed by elevated CMV DNA titers. Then the regions of the UL54 and UL97 mutations were amplified by PCR and sequenced.

RESULTS

Of 729 patients with CMV syndrome, 112 CMV DNAemia patients were enrolled. Twelve novel variants in UL54 (P342S, S384F, K434R, S673F, T754M, R778H, C814S, M827I, G878E, S880L, E888K, and S976N) and one novel variant in UL97 (M615T) were discovered. UL97 antiviral resistance mutations (L595S, M460I, and M460V) were found in four patients (3.6%). In the drug resistance strains, the mutation events occurred after 83-150 days of therapy, and drug resistance was also observed in these patients. The following high frequency variants were observed: D605E in UL97 and A885T, N898D, V355A, N685S, and A688V in UL54.

CONCLUSION

The results demonstrate that the positive rate of CMV DNAemia was 15.3% (112/729) among the patients with clinical CMV infection symptoms. The proportion of antiviral resistance CMV strains within CMV DNAemia patients was 3.6%. With the information of polymorphism incidence in the UL54 and UL97 patients from our study, determination of the genetic profile of UL54 and UL97 among immunocompromised populations with refractory CMV infection is recommended.

How I treat CMV reactivation after allogeneic hematopoietic stem cell transplantation

Cytomegalovirus (CMV) reactivation remains one of the most common and life-threatening infectious complications following allogeneic hematopoietic stem cell transplantation, despite novel diagnostic technologies, several novel prophylactic agents, and further improvements in preemptive therapy and treatment of established CMV disease. Treatment decisions for CMV reactivation are becoming increasingly difficult and must take into account whether the patient has received antiviral prophylaxis, the patient's individual risk profile for CMV disease, CMV-specific T-cell reconstitution, CMV viral load, and the potential drug resistance detected at the time of initiation of antiviral therapy. Thus, we increasingly use personalized treatment strategies for the recipient of an allograft with CMV reactivation based on prior use of anti-CMV prophylaxis, viral load, the assessment of CMV-specific T-cell immunity, and the molecular assessment of resistance to antiviral drugs.

Emergence of letermovir resistance in solid organ transplant recipients with ganciclovir resistant cytomegalovirus infection: A case series and review of the literature

Ganciclovir (GCV)-resistant cytomegalovirus (CMV) infection is a common problem among solid organ transplant (SOT) recipients without prior CMV immunity (CMV D+/R-). GCV-resistant CMV represents a particular challenge for CMV management. Letermovir is a recently licensed antiviral agent for primary CMV prophylaxis in allogenic hematopoietic stem cell transplant (HSCT) recipients. Given the favorable safety profile and its oral bioavailability letermovir may be considered a valuable off-label option for secondary prophylaxis of GCV-resistant CMV in SOT recipients. Here, we describe our experience with letermovir as secondary prophylaxis for GCV-resistant CMV in two renal transplant recipients and review the literature in regard of previously published cases. Letermovir resistance emerged after a few months of secondary prophylaxis in the two renal transplant recipients. In both cases, the previously described UL56 C325Y letermovir resistance mutation was detected. In vitro studies of letermovir suggest a relatively low genetic barrier to resistance. Therefore, caution is warranted when using letermovir as secondary prophylaxis for GCV-resistant CMV infection.

Resistant or refractory cytomegalovirus infections after hematopoietic cell transplantation: diagnosis and management

PURPOSE OF REVIEW

Refractory or resistant cytomegalovirus (CMV) infections are challenging complications after hematopoietic cell transplantation (HCT). Most refractory or resistant CMV infections are associated with poor outcomes and increased mortality. Prompt recognition of resistant or refractory CMV infections, understanding the resistance pathways, and the treatment options in HCT recipients are imperative.

RECENT FINDINGS

New definitions for refractory and resistant CMV infections in HCT recipients have been introduced for future clinical trials. Interestingly, refractory CMV infections are more commonly encountered in HCT recipients when compared with resistant CMV infections. CMV terminase complex mutations in UL56, UL89, and UL51 could be associated with letermovir resistance; specific mutations in UL56 are the most commonly encountered in clinical practice. Finally, brincidofovir, maribavir, letermovir, and CMV-specific cytotoxic T-cell therapy expanded our treatment options for refractory or resistant CMV infections.

SUMMARY

Many advances have been made to optimize future clinical trials for management of refractory or resistant CMV infections, and to better understand new resistance mechanisms to novel drugs. New drugs or strategies with limited toxicities are needed to improve outcomes of difficult to treat CMV infections in HCT recipients.

Comparison of different cytomegalovirus diseases following haploidentical hematopoietic stem cell transplantation

Cytomegalovirus (CMV) can cause end-organ diseases including pneumonia, gastroenteritis, retinitis, and encephalitis in hematopoietic stem cell transplantation recipients. Potential differences among different CMV diseases remain uncertain. This study aimed to compare the clinical characteristics, risk factors, and mortality among different CMV diseases. A retrospective nested case-control study was performed based on a cohort of 3862 patients who underwent haploidentical hematopoietic stem cell transplantation at a single-center. CMV diseases occurred in 113 (2.92%) of 3862 haplo-HSCT recipients, including probable CMV pneumonia (CMVP, n = 34), proven CMV gastroenteritis (CMVG, n = 34), CMV retinitis (CMVR, n = 31), probable CMV encephalitis (CMVE, n = 7), and disseminated CMV disease (Di-CMVD, n = 7). Most (91.2%) cases of CMVG developed within 100 days, while most (90.3%) cases of CMVR were late onset. Refractory CMV infection and CMV viral load at different levels were associated with an increased risk of CMVP, CMVG, and CMVR. Compared with patients without CMV diseases, significantly higher non-relapse mortality at 1 year after transplantation was observed in patients with CMVP and CMVR, rather than CMVG. Patients with CMVP, Di-CMVD, and CMVE had higher overall mortality after diagnosis than that of patients with CMVG and CMVR (61.7%, 57.1%, 40.0% vs 27.7%, 18.6%, P = 0.001). In conclusion, the onset time, viral dynamics, and mortality differ among different CMV diseases. The mortality of CMV diseases remains high, especially for CMVP, Di-CMVD, and CMVE.

Maribavir for Refractory or Resistant Cytomegalovirus Infections in Hematopoietic-cell or Solid-organ Transplant Recipients: A Randomized, Dose-ranging, Double-blind, Phase 2 Study

Background

Cytomegalovirus (CMV) infections that are refractory or resistant (RR) to available antivirals ([val]ganciclovir, foscarnet, cidofovir) are associated with higher mortality in transplant patients. Maribavir is active against RR CMV strains.

Methods

Hematopoietic-cell or solid-organ transplant recipients ≥12 years old with RR CMV infections and plasma CMV deoxyribonucleic acid (DNA) ≥1000 copies/mL were randomized (1:1:1) to twice-daily dose-blinded maribavir 400, 800, or 1200 mg for up to 24 weeks. The primary efficacy endpoint was the proportion of patients with confirmed undetectable plasma CMV DNA within 6 weeks of treatment. Safety analyses included the frequency and severity of treatment-emergent adverse events (TEAEs).

Results

From July 2012 to December 2014, 120 patients were randomized and treated (40 per dose group): 80/120 (67%) patients achieved undetectable CMV DNA within 6 weeks of treatment (95% confidence interval, 57–75%), with rates of 70%, 63%, and 68%, respectively, for maribavir 400, 800, and 1200 mg twice daily. Recurrent on-treatment CMV infections occurred in 25 patients; 13 developed mutations conferring maribavir resistance. Maribavir was discontinued due to adverse events in 41/120 (34%) patients, and 17/41 discontinued due to CMV infections. During the study, 32 (27%) patients died, 4 due to CMV disease. Dysgeusia was the most common TEAE (78/120; 65%) and led to maribavir discontinuation in 1 patient. Absolute neutrophil counts <1000/µL were noted in 12/106 (11%) evaluable patients, with rates similar across doses.

Conclusions

Maribavir ≥400 mg twice daily was active against RR CMV infections in transplant recipients; no new safety signals were identified.

Clinical Trials Registration

NCT01611974.

Study of cytomegalovirus resistance in allogeneic hematopoietic cell transplant recipients

INTRODUCTION

Cytomegalovirus (CMV) is the most important opportunistic pathogen associated with transplant. The objective of this study was the characterization of CMV resistance mutations in allogeneic haematopoietic cell transplant recipients (allo-TPH) and the study of associated factors.

METHODS

A retrospective study of a cohort of allo-TPH recipients with post-transplant CMV reactivations with stable or increasing viral loads (CV), despite adequate antiviral treatment for at least 2weeks. The study of resistance mutations of the UL97 and UL54 genes was carried out by Sanger sequencing.

RESULTS

Refractory CMV infection in our group of allo-TPH patients corresponded with a 21.43% rate of resistant virus infection (3 of 14 patients). All patients with resistance mutations had multiple reactivation episodes (P-value .01). The mutations found were A594V and H520Q in the UL97 gene that confers high-grade resistance to ganciclovir (GCV). One of the 3 cases with antiviral resistance was documented with a low VL (< 1000 copies/ml) and short accumulated GCV treatment (41 days).

CONCLUSION

Most of the failures in the treatment of CMV were possibly due to clinical resistance; the lack of satisfactory response to antiviral treatment is not always accompanied by virological resistance. However, the appearance of resistances can occur early after the start of the treatment and with VL below 1000 copies / ml. The number of episodes of reactivation was higher among patients with virological resistance than those who did not.

Evaluation of the Effect of Maribavir on Cardiac Repolarization in Healthy Participants: Thorough QT/QTc Study

Maribavir is an orally bioavailable benzimidazole riboside in clinical development for treatment of cytomegalovirus infection in patients who undergo transplantation. Maribavir was evaluated in a thorough QT (TQT) study to determine any effects on cardiac repolarization. The effect of maribavir 100 and 1,200 mg oral doses on the baseline-adjusted and placebo-adjusted corrected QT (QTc) interval (delta delta QTc (ddQTc)) and other electrocardiogram (ECG) parameters was assessed in a randomized, phase I, placebo-controlled, four-period crossover study in healthy participants (men and women ages 18-50 years). Additionally, maribavir pharmacokinetics, safety, and tolerability were investigated. Moxifloxacin (400 mg) was used as a positive control to demonstrate the study's ability to detect QT prolongation. Digital 12-lead Holter ECG monitoring was performed over 22 hours following study drug administration. Individual, Fridericia's, and Bazett's QTc intervals were calculated. Of 52 randomized participants (29 ± 8.1 years old; 31 men (60%)), 50 (96%) completed the study. For both 100-mg and 1200-mg doses of maribavir, analysis of ddQTc demonstrated that the upper bound of the two-sided 90% confidence interval was below the 10-ms threshold at all time points. The concentration-effect analysis demonstrated no relationship between ddQTc and plasma concentrations of maribavir (and its metabolite). There were no clinically meaningful changes in heart rate and systolic blood pressure. The most common adverse event was dysgeusia; no serious adverse events were reported. This TQT study demonstrated that maribavir did not have impact on cardiac repolarization.

The trimeric artesunate derivative TF27 exerts strong anti-cytomegaloviral efficacy: Focus on prophylactic efficacy and oral treatment of immunocompetent mice

Human cytomegalovirus (HCMV) causes serious and even life-threatening diseases, particularly upon congenital or post-transplant infection. Treatment of HCMV infections with currently available drugs targeting viral enzymes is often limited by severe side effects and the emergence of drug-resistant viruses. To avoid this problem, novel therapeutic options directed to host proteins involved in virus replication are being investigated. Recently, we described the pronounced antiherpesviral activity of the trimeric artesunate derivative TF27 at low nanomolar concentrations in vitro and in vivo. In the present study, we report first data on the prophylactic efficacy of TF27 against human and murine CMV and the oncogenic avian alphaherpesvirus Marek's disease virus (MDV). The main findings of this study are (i) a pronounced activity of the experimental drug TF27 against alpha- and betaherpesviruses in vitro upon prophylactic treatment and (ii) a therapeutic and prophylactic efficacy upon oral treatment in an immunocompetent mouse model. Moreover, our data highlight (iii) the tolerability of orally administered TF27 free of compound-associated adverse events and further confirm (iv) the suitability of cellular factors as primary antiviral targets. Thus, we provide evidence for therapeutic and prophylactic antiherpesviral efficacy of TF27 upon oral treatment in immunocompetent hosts and thereby underline its potential for future antiviral drug development.

Global estimate of phenotypic and genotypic ganciclovir resistance in cytomegalovirus infections among HIV and organ transplant patients; A systematic review and meta-analysis

Human cytomegalovirus (CMV), an opportunistic pathogen belonging to Herpesviridae family, is considered as one of the major causes of morbidity and mortality among wide variety of patients, particularly in transplant recipients and HIV positive patients. As this virus can be resistant to treatment, frequency of CMV in patients who receive organ transplantation and people suffering from AIDS was studied between 1980 and 2019. Medline (via PubMed), Embase, Web of Science, and the Iranian Database were reviewed, and Comprehensive Meta-Analysis (V2.0, Biostat) software analyzed all data. Finally, we used Cochran's Q-statistic to encounter heterogeneity between different studies. Meta-analyses indicated, GCV resistance was 14.1% (95% CI 11.2-17.7); however, in patients suffering from AIDS and organ transplantation were 19.5% (95% CI 14.7-25.4) and 11.4% (95% CI 8.1-15.8), respectively. There were increasing rates in the prevalence of GCV resistance in CMV among transplant recipients, and HIV positive patients. Therefore, evaluation of these refractory infections is beneficial.

Highlighting of a LAGLIDADG and a Zing Finger Motifs Located in the pUL56 Sequence Crucial for HCMV Replication

The human cytomegalovirus (HCMV) terminase complex is part of DNA-packaging machinery that delivers a unit-length genome into a procapsid. Sequence comparison of herpesvirus homologs allowed us to identify a potential LATLNDIERFL and zinc finger pattern in N-terminal part of pUL56. Recombinant viruses were generated with specific serine or alanine substitutions in these putative patterns. We identified a LATLNDIERFL pattern characteristic of LAGLIDADG homing endonucleases and a metal-binding pattern involving the cysteine and histidine residues C₁₉₁-X2-C₁₉₄-X22-C₂₁₇-X-H₂₁₉ (CCCH) close to the region conferring letermovir resistance. These patterns are crucial for viral replication, suggesting that they are essential for pUL56 structure and function. Thus, these patterns represent potential targets for the development of new antivirals such as small molecules or peptides and may allow to better understand the letermovir mechanism of action.

CMV infection management in transplant patients in Italy

Transplant represents an effective strategy in the management of chronic organ dysfunction. Nonetheless, life threatening risks remain, especially in the post-transplant; among them, human cytomegalovirus (CMV) is a major concern, currently causing active infections in at least one-third of transplant recipients. Microbiologist and transplant scientific societies redefined guidance on CMV disease prevention and the best use for universal prophylaxis and pre-emptive virological monitoring. Developments in molecular diagnostic supported the spread of the pre-emptive strategy, and quantitative Real Time-PCR assays has unravelled the potential of viral load measurement as a predictor of the infection development in CMV post-transplant management. However, despite the WHO 1st CMV International Standard, the standardization of diagnostic and clinical practice has been limited by the absence of algorithms for calculating conversion factor to International Units and the lack of shared monitoring procedure, both at national and international level. At a regional level, the Italian scientific societies, AMCLI (Italian Clinical Microbiologist Association), SITO (Organ Transplant Italian Society), GITMO (Italian Group for Bone Marrow Transplant), recently tried to define a consensus for post-transplant monitoring. The concerted practice encompasses molecular quantitative PCR assays technical aspects and endorses the relevance of immunologic monitoring for improvement in patient risk stratification and prognosis. Here, we provide an overview of the state of the art of CMV management strategies, with a specific focus on the clinical practices and on the scientific societies' initiatives that aim to implement international standardization guidelines at a national level.

Analysis of Ganciclovir-Resistant Cytomegalovirus Infection Caused by the UL97 Gene Mutation in Codons 460 and 520 in Pediatric Patients: A Case Series

Background

Drug-resistant cytomegalovirus (CMV) infection has been increasingly recognized. However, there are limited data in pediatric patients. In this study, the prevalence and factors associated with CMV infection with UL97 mutations in pediatric patients treated with ganciclovir but not responding to treatment were evaluated.

Methods

This retrospective study was conducted from January 2013 to December 2017. All patients who were suspected of having ganciclovir-resistant CMV infection and had never had ganciclovir prophylaxis were included. Genotypic assay for UL97 mutations in codons 460 and 520 conferring ganciclovir resistance was performed. Factors associated with the presence of UL97 mutations were analyzed.

Results

Of 34 patients included, 10 patients (29.4%) had a genotypically confirmed UL97 mutation. The median age (interquartile range [IQR]) was 3 (0.85–8.68) years. Ganciclovir resistance was tested at a median time (IQR) of 22.5 (14.3–31) days after initiation of ganciclovir. All resistant isolates harbored a UL97 mutation in codon 460. Compared with patients infected with CMV without UL97 mutation, those infected with UL97 mutation strains were younger (median age [IQR], 3.02 [0.85–8.68] vs 10.45 [2.7–16.4] years) and had a higher maximum viral load (median [IQR], 5.06 [4.74–6.05] vs 4.42 [4.03–4.87] copies/mL). Six of 10 (60%) patients were successfully treated with high-dose ganciclovir (7.5 mg/kg twice daily).

Conclusions

UL97 mutation ganciclovir-resistant CMV infection was not uncommon in the pediatric population. Screening for this mutation should be considered in patients experiencing virological worsening while ganciclovir is given, even if patients have not previously received ganciclovir prophylaxis.

Maribavir for Preemptive Treatment of Cytomegalovirus Reactivation

BACKGROUND

Maribavir is a benzimidazole riboside with activity against cytomegalovirus (CMV). The safety and efficacy of maribavir for preemptive treatment of CMV infection in transplant recipients is not known.

METHODS

In a phase 2, open-label, maribavir dose-blinded trial, recipients of hematopoietic-cell or solid-organ transplants (≥18 years of age, with CMV reactivation [1000 to 100,000 DNA copies per milliliter]) were randomly assigned to receive maribavir at a dose of 400, 800, or 1200 mg twice daily or the standard dose of valganciclovir for no more than 12 weeks. The primary efficacy end point was the percentage of patients with a response to treatment, defined as confirmed undetectable CMV DNA in plasma, within 3 weeks and 6 weeks after the start of treatment. The primary safety end point was the incidence of adverse events that occurred or worsened during treatment.

RESULTS

Of the 161 patients who underwent randomization, 159 received treatment, and 156 had postbaseline data available - 117 in the maribavir group and 39 in the valganciclovir group. The percentage of patients with postbaseline data available who had a response to treatment within 3 weeks was 62% among those who received maribavir and 56% among those who received valganciclovir. Within 6 weeks, 79% and 67% of patients, respectively, had a response (risk ratio, 1.20; 95% confidence interval, 0.95 to 1.51). The percentages of patients with a response to treatment were similar among the maribavir dose groups. Two patients who had a response to treatment had a recurrence of CMV infection within 6 weeks after starting maribavir at a dose of 800 mg twice daily; T409M resistance mutations in CMV UL97 protein kinase developed in both patients. The incidence of serious adverse events that occurred or worsened during treatment was higher in the maribavir group than in the valganciclovir group (52 of 119 patients [44%] vs. 13 of 40 [32%]). A greater percentage of patients in the maribavir group discontinued the trial medication because of an adverse event (27 of 119 [23%] vs. 5 of 40 [12%]). A higher incidence of gastrointestinal adverse events was reported with maribavir, and a higher incidence of neutropenia was reported with valganciclovir.

CONCLUSIONS

Maribavir at a dose of at least 400 mg twice daily had efficacy similar to that of valganciclovir for clearing CMV viremia among recipients of hematopoietic-cell or solid-organ transplants. A higher incidence of gastrointestinal adverse events - notably dysgeusia - and a lower incidence of neutropenia were found in the maribavir group. (Funded by ViroPharma/Shire Development; EudraCT number, 2010-024247-32.).

Cytomegalovirus Infections after Hematopoietic Stem Cell Transplantation: Current Status and Future Immunotherapy

Cytomegalovirus (CMV) infection after hematopoietic stem cell transplantation (HSCT) is one of the critical infectious complications related to host immune recovery. The spectrum of CMV infection is quite extensive, from asymptomatic CMV reactivation presenting mainly as CMV DNAemia to fatal CMV diseases involving gut, liver, lungs, or brain. In addition to organ involvement, CMV reactivation can exert indirect effects such as immunosuppression or graft failure that may result in the development of concurrent infectious complications. Currently, preemptive therapy, which is based on PCR-based monitoring of CMV from blood, is a mainstay enabling improvement in CMV-related outcomes. During the past decades, new antiviral drugs, clinical trials for prophylaxis in high-risk groups, and vaccines for preventing CMV infection have been introduced. In addition, data for immunologic monitoring and adoptive immunotherapy have also been accumulated. Here, we review the current status and recent updates in this field, with future perspectives including immunotherapy in HSCT recipients.