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

Epidemiology, treatment patterns, and disease burden of cytomegalovirus in hematopoietic cell transplant recipients in selected countries outside of Europe and North America: A systematic review

BACKGROUND

Cytomegalovirus (CMV) disease impacts morbidity and mortality in hematopoietic cell transplant (HCT) recipients. This systematic review summarized data on the epidemiology, management, and burden of CMV post-HCT outside of Europe and North America.

METHODS

The MEDLINE, Embase, and Cochrane databases were searched for observational studies and treatment guidelines in HCT recipients across 15 selected countries from Asia-Pacific, Latin America, and Middle East (search period: 1 January 2011-17 September 2021). Outcomes included incidence of CMV infection/disease, recurrence, risk factors, CMV-related mortality, treatments, refractory, resistant CMV, and burden.

RESULTS

Of 2708 references identified, 68 were eligible (67 studies and one guideline; 45/67 studies specific to adult allogeneic HCT recipients). The rates of CMV infection and disease within 1 year of allogeneic HCT were 24.9%-61.2% (23 studies) and 2.9%-15.7% (10 studies), respectively. Recurrence occurred in 19.8%-37.9% of cases (11 studies). Up to 10% of HCT recipients died of CMV-related causes. In all countries, first-line treatment for CMV infection/disease involved intravenous ganciclovir or valganciclovir. Conventional treatments were associated with serious adverse events such as myelosuppression (10.0%) or neutropenia only (30.0%, 39.8%) and nephrotoxicity (11.0%) (three studies), frequently leading to treatment discontinuation (up to 13.6%). Refractory CMV was reported in 2.9%, 13.0%, and 28.9% of treated patients (three studies) with resistant CMV diagnosed in 0%-10% of recipients (five studies). Patient-reported outcomes and economic data were scarce.

CONCLUSION

The incidence of CMV infection and disease post-HCT is high outside of North America and Europe. CMV resistance and toxicity highlight a major unmet need with current conventional treatments.

Epidemiology, management, and burden of cytomegalovirus in solid organ transplant recipients in selected countries outside of Europe and North America: A systematic review

BACKGROUND

Cytomegalovirus (CMV) is a frequent infectious complication following solid organ transplantation (SOT). Considering significant differences in healthcare systems, a systematic review was conducted to describe the epidemiology, management, and burden of CMV post-SOT in selected countries outside of Europe and North America.

METHODS

MEDLINE, Embase, and Cochrane databases were searched for observational studies in SOT recipients across 15 countries in the regions of Asia, Pacific, and Latin America (search period: January 1, 2011 to September 17, 2021). Outcomes included incidence of CMV infection/disease, recurrence, risk factors, CMV-related mortality, treatment patterns and guidelines, refractory and/or resistant CMV, patient-reported outcomes, and economic burden.

RESULTS

Of 2708 studies identified, 49 were eligible (n = 43/49; 87.8% in adults; n = 34/49, 69.4% in kidney recipients). Across studies, selection of CMV preventive strategy was based on CMV serostatus. Overall, rates of CMV infection (within 1 year) and CMV disease post-SOT were respectively, 10.3%-63.2% (9 studies) and 0%-19.0% (17 studies). Recurrence occurred in 35.4%-41.0% cases (3 studies) and up to 5.3% recipients died of CMV-associated causes (11 studies). Conventional treatments for CMV infection/disease included ganciclovir (GCV) or valganciclovir. Up to 4.4% patients were resistant to treatment (3 studies); no studies reported on refractory CMV. Treatment-related adverse events with GCV included neutropenia (2%-29%), anemia (13%-48%), leukopenia (11%-37%), and thrombocytopenia (13%-24%). Data on economic burden were scarce.

CONCLUSION

Outside of North America and Europe, rates of CMV infection/disease post-SOT are highly variable and CMV recurrence is frequent. CMV resistance and treatment-associated adverse events, including myelosuppression, highlight unmet needs with conventional therapy.

Maribavir

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CMV hyperimmune globulin as salvage therapy for recurrent or refractory CMV infection in children undergoing hematopoietic stem cell transplantation

Cytomegalovirus (CMV) is a major cause of allogeneic hematopoietic stem cell transplant (HSCT)-related morbidity and mortality. Treatment failure continues to be a major issue in patients with CMV infection due to both drug resistance and intolerance. This single-center brief retrospective analysis of a case series aims to investigate the safety and efficacy of CMV-hyperimmune globulin as salvage therapy for CMV infection in children undergoing HSCT. Fifteen pediatric patients received human CMV-specific immunoglobulin (CMVIG) between July 2018 and December 2021 as a salvage therapy for refractory or recurrent CMV infection. At the time of CMVIG prescription, eight children presented with recurrent CMV infection and seven with refractory CMV infection. The overall response rate was 67% at 50 days from the CMVIG administration [95% confidence interval (CI): 44-88]. Overall survival (OS) from CMVIG administration at 100 days was 87% (95% CI: 56-96), and OS from HSCT at 1 year was 80% (95% CI: 50-93). Four patients died, three unrelated to CMV infection and one due to CMV pneumonia. CMVIG as salvage therapy was well tolerated, and no infusion-related adverse events were observed.

Current Perspectives on the Management of Herpesvirus Infections in Solid Organ Transplant Recipients

Solid organ transplant recipients (SOTRs) are at high risk of human herpesvirus (HHV)-related morbidity and mortality due to the use of immunosuppressive therapy. We aim to increase awareness and understanding of HHV disease burden in SOTRs by providing an overview of current prevention and management strategies as described in the literature and guidelines. We discuss challenges in both prevention and treatment as well as future perspectives.

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.

An Update on Current Antiviral Strategies to Combat Human Cytomegalovirus Infection

Human cytomegalovirus (HCMV) remains an essential global concern due to its distinct life cycle, mutations and latency. As HCMV is a herpesvirus, it establishes a lifelong persistence in the host through a chronic state of infection. Immunocompromised individuals are at risk of significant morbidity and mortality from the virus. Until now, no effective vaccine has been developed to combat HCMV infection. Only a few antivirals targeting the different stages of the virus lifecycle and viral enzymes are licensed to manage the infection. Therefore, there is an urgent need to find alternate strategies to combat the infection and manage drug resistance. This review will provide an insight into the clinical and preclinical antiviral approaches, including HCMV antiviral drugs and nucleic acid-based therapeutics.

Another tool against cytomegalovirus after allogeneic hematopoietic cell transplantation

Cytomegalovirus (CMV) viremia from reactivation of latent infection is a common complication after allogeneic hematopoietic cell transplantation (HCT). Untreated, CMV viremia can progress to affect other organs, resulting in organ dysfunction with high morbidity and mortality. In this issue of the JCI, Prockop and authors demonstrate that third-party donor T cells sensitized ex vivo to CMV pp65-derived overlapping pentadecapeptides are safe and effective for the treatment of CMV reactivation or CMV disease refractory to first-line pharmacotherapies occurring after HCT. They also provide insight into the biological differences between responders and nonresponders. This work confirms the utility of third-party CMV pp65 VSTs and suggests strategies for further improving the efficacy of this cell-therapy approach.

How I prevent viral reactivation in high-risk patients

Preventing viral infections at an early stage is a key strategy for successfully improving transplant outcomes. Preemptive therapy and prophylaxis with antiviral agents have been successfully used to prevent clinically significant viral infections in hematopoietic cell transplant recipients. Major progress has been made over the past decades in preventing viral infections through a better understanding of the biology and risk factors, as well as the introduction of novel antiviral agents and advances in immunotherapy. High-quality evidence exists for the effective prevention of herpes simplex virus, varicella-zoster virus, and cytomegalovirus infection and disease. Few data are available on the effective prevention of human herpesvirus 6, Epstein-Barr virus, adenovirus, and BK virus infections. To highlight the spectrum of clinical practice, here we review high-risk situations that we handle with a high degree of uniformity and cases that feature differences in approaches, reflecting distinct hematopoietic cell transplant practices, such as ex vivo T-cell depletion.

Assessment of Covalently Binding Warhead Compounds in the Validation of the Cytomegalovirus Nuclear Egress Complex as an Antiviral Target

Herpesviral nuclear egress is a regulated process of viral capsid nucleocytoplasmic release. Due to the large capsid size, a regular transport via the nuclear pores is unfeasible, so that a multistage-regulated export pathway through the nuclear lamina and both leaflets of the nuclear membrane has evolved. This process involves regulatory proteins, which support the local distortion of the nuclear envelope. For human cytomegalovirus (HCMV), the nuclear egress complex (NEC) is determined by the pUL50-pUL53 core that initiates multicomponent assembly with NEC-associated proteins and capsids. The transmembrane NEC protein pUL50 serves as a multi-interacting determinant that recruits regulatory proteins by direct and indirect contacts. The nucleoplasmic core NEC component pUL53 is strictly associated with pUL50 in a structurally defined hook-into-groove complex and is considered as the potential capsid-binding factor. Recently, we validated the concept of blocking the pUL50-pUL53 interaction by small molecules as well as cell-penetrating peptides or an overexpression of hook-like constructs, which can lead to a pronounced degree of antiviral activity. In this study, we extended this strategy by utilizing covalently binding warhead compounds, originally designed as binders of distinct cysteine residues in target proteins, such as regulatory kinases. Here, we addressed the possibility that warheads may likewise target viral NEC proteins, building on our previous crystallization-based structural analyses that revealed distinct cysteine residues in positions exposed from the hook-into-groove binding surface. To this end, the antiviral and NEC-binding properties of a selection of 21 warhead compounds were investigated. The combined findings are as follows: (i) warhead compounds exhibited a pronounced anti-HCMV potential in cell-culture-based infection models; (ii) computational analysis of NEC primary sequences and 3D structures revealed cysteine residues exposed to the hook-into-groove interaction surface; (iii) several of the active hit compounds exhibited NEC-blocking activity, as shown at the single-cell level by confocal imaging; (iv) the clinically approved warhead drug ibrutinib exerted a strong inhibitory impact on the pUL50-pUL53 core NEC interaction, as demonstrated by the NanoBiT assay system; and (v) the generation of recombinant HCMV ∆UL50-ΣUL53, allowing the assessment of viral replication under conditional expression of the viral core NEC proteins, was used for characterizing viral replication and a mechanistic evaluation of ibrutinib antiviral efficacy. Combined, the results point to a rate-limiting importance of the HCMV core NEC for viral replication and to the option of exploiting this determinant by the targeting of covalently NEC-binding warhead compounds.

The Ten Most Common Questions on Cytomegalovirus Infection in Hematopoietic Stem Cell Transplant Patients

With the rising number of patients undergoing hematopoietic stem cell transplantation (HSCT), clinicians are more likely to encounter infectious complications in immunocompromised hosts, particularly cytomegalovirus (CMV) infection. Besides the high mortality of CMV end-organ disease, patients with detectable CMV viremia may have worse outcomes and decreased survival even in the absence of end-organ disease. In view of the implications on morbidity and mortality, clinicians should maintain a high index of suspicion and initiate antiviral drugs promptly when CMV infection is confirmed. High-risk patients should be identified in order to provide optimal management. Additionally, novel antiviral agents with a good safety profile and minor adverse events are now available for prophylaxis in high-risk patients and for treatment of resistant or refractory CMV infection. The following review provides concise, yet comprehensive, guidance on the burden and risk factors of CMV in this population, as well as an update on the latest evidence for the management of CMV infection.

Advances of Artificial Intelligence in Anti-Cancer Drug Design: A Review of the Past Decade

Anti-cancer drug design has been acknowledged as a complicated, expensive, time-consuming, and challenging task. How to reduce the research costs and speed up the development process of anti-cancer drug designs has become a challenging and urgent question for the pharmaceutical industry. Computer-aided drug design methods have played a major role in the development of cancer treatments for over three decades. Recently, artificial intelligence has emerged as a powerful and promising technology for faster, cheaper, and more effective anti-cancer drug designs. This study is a narrative review that reviews a wide range of applications of artificial intelligence-based methods in anti-cancer drug design. We further clarify the fundamental principles of these methods, along with their advantages and disadvantages. Furthermore, we collate a large number of databases, including the omics database, the epigenomics database, the chemical compound database, and drug databases. Other researchers can consider them and adapt them to their own requirements.

Optimizing the treatment of cytomegalovirus infection in allo-HSCT recipients

INTRODUCTION

Cytomegalovirus (CMV) infection continues to negatively impact the prognosis after allogeneic hematopoietic stem cell transplantation (allo-HSCT), even with active monitoring and preemptive strategies. Recent progress in pharmacology, immunotherapy, and vaccines has improved the strategy of CMV management.

AREAS COVERED

We summarized recent advances in managing CMV infection post allo-HSCT, including diagnosis, prophylaxis, and treatment. In this review, we mainly focused on approaches that have optimized or might optimize the management of CMV infection after allo-HSCT.

EXPERT OPINION

In our opinion, optimized management covers aspects including the serial monitoring of CMV-DNA and CMI, an accurate diagnosis, effective prophylaxis, and a rational preemptive therapy integrating antiviral drugs and cell therapies. Strategies based on the understanding of CMV pathogenesis and CMV-related immune reconstitution after allo-HSCT will be a direction in future studies.

CMV antiviral stewardship: navigating obstacles to facilitate target attainment

PURPOSE OF REVIEW

Despite the availability of potent antivirals, consensus guidelines and decades of research, cytomegalovirus (CMV) continues to be associated with negative outcomes after solid organ transplant. This has been attributed to postprophylaxis CMV infection and a lack of development of CMV-specific cell mediated immunity (CMI). A shift from a focus on antiviral prevention to a focus on CMI target attainment is needed to improve CMV outcomes after transplantation.

RECENT FINDINGS

There are many obstacles to CMI target attainment. Antiviral stewardship programs (AVS) have been employed to improve patient outcomes through appropriate antiviral use, reduction of unnecessary exposure and resistance mitigation. By focusing on the patient's unique substrate of conglomerate risk factors and addressing these factors specifically with evidenced based methodology, the AVS can address these obstacles, increasing rates of CMI and subsequently reducing risk of future CMV infection and negative outcomes.

SUMMARY

With its multidisciplinary composition utilizing decades of experience from antimicrobial stewardship principles and practices, the AVS is uniquely poised to facilitate the shift from a focus on prevention to CMI target attainment and be the supporting pillar for the frontline transplant clinician caring for transplant patients with CMV.

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.

Cytomegalovirus DNAemia Requiring (Val)Ganciclovir Treatment for More Than 8 Weeks Is a Key Factor in the Development of Antiviral Drug Resistance

Background

Prolonged (val)ganciclovir [(V)GCV] exposure for ≥6 weeks is a known predisposing factor for cytomegalovirus (CMV) drug resistance. However, the selection of this threshold was based on limited data. In this study, we sought to reappraise the risk factors for the development of (V)GCV resistance through a specific focus on kidney transplant recipients (KTRs).

Methods

This single-center retrospective study included 313 consecutive KTRs treated for a first CMV episode. Adjusted Cox multivariate regression analysis was used for identifying independent risk factors.

Results

Antiviral drug resistance was identified in 20 (6%) KTRs. A cumulative (V)GCV exposure for more than 6 weeks (regardless of the viral load) was not associated with antiviral drug resistance (hazard ratio [HR] = 2.45, 95% confidence interval [CI] = 0.33-18.30, P = .38). In contrast, persistent CMV DNAemia requiring (V)GCV treatment for more than 8 weeks was the main independent risk factor for antiviral drug resistance (HR = 11.68, 95% CI = 2.62-52.01, P = .001). The (V)GCV treatment for more than 8 weeks was given to 9% and 18% of patients who had persistent or recurrent CMV DNAemia, respectively. These scenarios were associated with the occurrence of drug resistance in 39% and 12% of cases, respectively.

Conclusions

Cumulative (V)GCV exposure ≥6 weeks regardless of the viral load is not associated with antiviral drug resistance. In contrast, prolonged exposure to (V)GCV during CMV replication (with a cutoff ³8 weeks) seems to be a key factor.

Maribavir Pharmacokinetics and Safety in Participants With Moderate Hepatic Impairment: A Phase 1, Open-Label, Single-Dose, Parallel Group Study

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

Cytomegalovirus Therapy: Role of Letermovir in Prophylaxis and Treatment in Transplant Recipients

Cytomegalovirus (CMV) is a common viral pathogen in the transplant population and is associated with significant morbidity and mortality. CMV prevention is paramount; however, selecting the best preventive strategy depends on many factors including donor-recipient CMV serostatus, transplant-specific risks, antiviral toxicities and cost. Novel CMV therapeutics such as letermovir (LTV) are desperately needed to optimize CMV management. Uniquely among CMV antiviral therapies, LTV inhibits the viral terminase complex in the CMV DNA synthesis pathway and disrupts viral genome packaging. Further, it lacks side effects frequently associated with other CMV antiviral therapies and evades common mechanisms of resistance. LTV is approved by the US Food and Drug Administration for CMV prevention in adult CMV-seropositive hematopoietic cell transplant recipients but is increasingly applied off-label for prophylaxis and treatment. This review summarizes important concepts of CMV management in transplantation, with a specific focus on LTV pharmacology and clinical experience to date alongside future prospects for its application.

New trends in the management of cytomegalovirus infection after allogeneic hematopoietic cell transplantation: a survey of the Infectious Diseases Working Pary of EBMT

The management of cytomegalovirus (CMV) infection was assessed with a survey performed in 2020 by the Infectious Diseases Working Party of European Society for Blood and Marrow Transplantation (EBMT). One-hundred-eighty of the 579 EBMT centres (31%) responded. CMV monitoring with quantitative PCR for CMV-DNAemia was used by 97% of centres while the duration of monitoring was variable according to the patient immune recovery and the ongoing immunosuppressive therapy. CMV prophylaxis for high-risk patients was used in 101 (56%) of centres: letermovir in 62 centres (61%), aciclovir/valaciclovir in 19 centres (19%), ganciclovir/valganciclovir in 17 centres (17%), foscarnet in 3 (3%). The most used trigger for pre-emptive therapy was a threshold of >10³ copies/ml or >10³ IU/ml. Ganciclovir/valganciclovir confirmed the preferred first line treatment both for pre-emptive and CMV disease therapy. CMV-cytotoxic T-cells were used mainly in the setting of relapsing/refractory CMV disease. Forty-eight centres reported CMV refractory/resistant infection due to mutated CMV strain.This survey showed that letermovir prophylaxis is adopted by more than half of centres using a prophylaxis approach for CMV infection. How letermovir prophylaxis will modify other important pillars of daily CMV management, such as frequency of CMV-DNAemia monitoring and preemptive therapy, remain a matter of investigation.

Cytomegalovirus infection in transplant recipients: newly approved additions to our armamentarium

BACKGROUND

The burden that cytomegalovirus (CMV) portends for haematopoietic and solid-organ transplant recipients cannot be understated. Valganciclovir and ganciclovir have successfully been used for prevention and treatment of CMV infections, although with serious side effects such as leucopenia and some development of resistance. Until recently, available therapies for ganciclovir-resistant CMV have significant toxicities. Although advances have been made in the field, the unmet medical needs for effective and well-tolerated therapies are significant.

OBJECTIVES

This review aims to summarise the current and emerging CMV antiviral drugs and discusses future perspectives in the field.

SOURCES

We searched for relevant articles with pertinent keywords: "Cytomegalovirus OR CMV", "Transplant" and "Antiviral". Articles published after 2019 were given preference. Articles were reviewed by the authors for relevance and impact to the subject of interest.

CONTENT

We outline in this review current advances in prophylaxis of CMV infection with letermovir, breakthrough CMV infections while on or after prophylaxis, the development of resistant and refractory CMV infections, and the newly approved anti-CMV agent, maribavir, in haematopoietic and solid-organ transplant recipients.

IMPLICATIONS

Prevention of CMV infections after transplant has improved greatly over the past few years. Despite major advancements, breakthrough CMV infections and development of refractory and resistant CMV infections remain major complications post transplantation. We highlight emerging therapeutics that tolerably and effectively prevent and treat CMV infections, especially refractory and resistant cases.

Prevention and management of CMV infection in pediatric solid organ transplant recipients

Human cytomegalovirus (CMV) remains one of the most common opportunistic infections following solid organ transplantation in children. CMV causes morbidity and mortality through direct tissue-invasive disease and indirect immunomodulatory effects. In recent years, several new agents have emerged for the prevention and treatment of CMV disease in solid organ transplant recipients. However, pediatric data remain scarce, and many of the treatments are extrapolated from the adult literature. Controversies exist about the type and duration of prophylactic therapies and the optimal dosing of antiviral agents. This review provides an up-to-date overview of treatment modalities used to prevent and treat CMV disease in solid organ transplant (SOT) recipients.

Evaluation of Two Different CMV-Immunoglobulin Regimens for Combined CMV Prophylaxis in High-Risk Patients following Lung Transplant

BACKGROUND

The clinical benefits of the common off-label use of cytomegalovirus (CMV)-specific immunoglobulin (CMV-Ig) combined with antivirals in organ transplantation have not been previously assessed. The objective was to compare the risk of CMV infection and other post-transplantation outcomes between two CMV-Ig prophylaxis regimens in lung transplant recipients; Methods: Retrospective study of 124 donor CMV positive/recipient negative (D+/R-) patients receiving preventive ganciclovir/valganciclovir for 12 months, of whom 62 received adjunctive CMV-Ig as per label indication (short regimen [SR-Ig]; i.e., 7 doses over 2.5 months) and were compared to 62 who received an extended off-label regimen (ER-Ig) consisting of 17 doses over one year after transplantation.

RESULTS

The incidence of CMV infection or disease, acute rejection, chronic lung allograft dysfunction, and survival did not differ between the two CMV-Ig schedules. Although the time to the first CMV infection after transplantation was shorter in the ER-Ig than in the SR-Ig adjunctive group (log-rank: p = 0.002), the risk was independently predicted by antiviral cessation (odds ratio = 3.74; 95% confidence interval = 1.04-13.51; p = 0.030), whereas the CMV-Ig schedule had no effect.

CONCLUSIONS

Extending the adjunctive CMV-Ig prophylaxis beyond the manufacturer's recommendations up to one year does not confer additional clinical benefits regarding lung post-transplantation outcomes.

Challenges, Recent Advances and Perspectives in the Treatment of Human Cytomegalovirus Infections

Human cytomegalovirus (HCMV) is ubiquitous worldwide and elicits global health problems. The diseases associated with HCMV are a serious threat to humans, especially for the sick, infant, elderly and immunocompromised/immunodeficient individuals. Although traditional antiviral drugs (e.g., ganciclovir, valganciclovir, cidofovir, foscarnet) can be used to treat or prevent acute HCMV infections, their efficacy is limited because of toxicity, resistance issues, side effects and other problems. Fortunately, novel drugs (e.g., letermovir and maribavir) with less toxicity and drug/cross-resistance have been approved and put on the market in recent years. The nucleic acid-based gene-targeting approaches including the external guide sequences (EGSs)-RNase, the clustered regularly interspaced short palindromic repeats (CRISPRs)/CRISPRs-associated protein 9 (Cas9) system and transcription activator-like effector nucleases (TALENs) have been investigated to remove both lytic and latent CMV in vitro and/or in vivo. Cell therapy including the adoptive T cell therapy (ACT) and immunotherapy have been tried against drug-resistant and recurrent HCMV in patients receiving hematopoietic stem cell transplantation (HSCT) or solid organ transplant (SOT), and they have also been used to treat glioblastoma (GBM) associated with HCMV infections. These newly developed antiviral strategies are expected to yield fruitful results and make a significant contribution to the treatment of HCMV infections. Despite this progress, the nucleic acid-based gene-targeting approaches are still under study for basic research, and cell therapy is adopted in a small study population size or only successful in case reports. Additionally, no current drugs have been approved to be indicated for latent infections. Therefore, the next strategy is to develop antiviral strategies to elevate efficacy against acute and/or latent infections and overcome challenges such as toxicity, resistance issues, and side effects. In this review, we would explore the challenges, recent advances and perspectives in the treatment of HCMV infections. Furthermore, the suitable therapeutic strategies as well as the possibility for compassionate use would be evaluated.

Cytomegalovirus in the transplant setting: Where are we now and what happens next? A report from the International CMV Symposium 2021

The CMV Symposium in September 2021 was an international conference dedicated to cytomegalovirus (CMV) infection after solid organ or hematopoietic stem cell transplantation. This review provides an overview of the presentations given by the expert faculty, supplemented with educational clinical cases. Topics discussed include CMV epidemiology and diagnosis, the burden of CMV infection and disease, CMV-specific immunity and management of CMV in transplant settings. Major advances in the prevention and treatment of CMV in the past decade and increased understanding of CMV immunity have led to improved patient outcomes. In the future, management algorithms may be individualized based on the transplant recipient's immune profile, which will mark the start of a new era for patients with CMV.

The human cytomegalovirus decathlon: Ten critical replication events provide opportunities for restriction

Human cytomegalovirus (HCMV) is a ubiquitous human pathogen that can cause severe disease in immunocompromised individuals, transplant recipients, and to the developing foetus during pregnancy. There is no protective vaccine currently available, and with only a limited number of antiviral drug options, resistant strains are constantly emerging. Successful completion of HCMV replication is an elegant feat from a molecular perspective, with both host and viral processes required at various stages. Remarkably, HCMV and other herpesviruses have protracted replication cycles, large genomes, complex virion structure and complicated nuclear and cytoplasmic replication events. In this review, we outline the 10 essential stages the virus must navigate to successfully complete replication. As each individual event along the replication continuum poses as a potential barrier for restriction, these essential checkpoints represent potential targets for antiviral development.

[Resistance to antiviral drugs in human viruses from the subfamily Betaherpesvirinae]

The review provides information on the mechanisms of the emergence of resistance to antiviral drugs in human viruses from the subfamily Betaherpesvirinae. Data on the principles of action of antiviral drugs and their characteristics are given. The occurrence rates of viral resistance in various groups of patients is described and information about the possible consequences of the emergence of resistance to antiviral drugs is given. Information is provided regarding the virus genes in which mutations occur that lead to viral resistance, and a list of such mutations that have described so far is given. The significance of the study of mutations leading to the resistance of the virus to antiviral drugs for medical practice is discussed.

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.

Maribavir for the Management of Cytomegalovirus in Adult Transplant Recipients: A Review of the Literature and Practical Considerations

OBJECTIVE

To review the efficacy and safety of maribavir for management of cytomegalovirus (CMV) in solid organ transplant recipients.

DATA SOURCES

A literature search of PubMed and the Cochrane Controlled Trials Register (1960 to early July 2022) was performed using the following search terms: maribavir, 1263W94, and cytomegalovirus.

STUDY SELECTION AND DATA EXTRACTION

All relevant English-language studies were reviewed and considered, with a focus on phase 3 trials.

DATA SYNTHESIS

Maribavir, an orally available benzimidazole riboside with minimal adverse effects, was originally studied for universal prophylaxis in phase 3 trials but failed to demonstrate noninferiority over placebo and oral ganciclovir. It was effective for preemptive treatment in a dose-finding Phase 2 study. Maribavir is FDA approved for treatment of refractory/resistant CMV infection based on improved response rate at 8 weeks compared with investigator-assigned therapy (IAT) when initiated at median viral loads less than approximately 10 000 IU/mL (55.7% vs 23.9%, P < 0.001). Recurrence after 8-week treatment for refractory/resistant CMV was high (maribavir 50% vs IAT 39%). Significant drug interactions exist and must be managed by a pharmacotherapy expert to prevent harm.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

The addition of maribavir to the antiviral armamentarium should improve the management of refractory/resistant CMV, allowing early transition from toxic, high-cost, intravenous agents such as foscarnet and outpatient management. Optimal timing of initiation, duration, and potential alternative uses are unclear.

CONCLUSION

Future studies are needed to fully elucidate the role of maribavir in the management of CMV after transplant.

A year in pharmacology: new drugs approved by the US Food and Drug Administration in 2021

The second year of the COVID-19 pandemic had no adverse effect on the number of new drug approvals by the US Food and Drug Administration (FDA). Quite the contrary, with a total of 50 new drugs, 2021 belongs to the most successful FDA years. We assign these new drugs to one of three levels of innovation: (1) first drug against a condition ("first-in-indication"), (2) first drug using a novel molecular mechanism ("first-in-class"), and (3) "next-in-class", i.e., a drug using an already exploited molecular mechanism. We identify 21 first-in-class, 28 next-in-class, and only one first-in-indication drugs. By treatment area, the largest group is once again cancer drugs, many of which target specific genetic alterations. Every second drug approved in 2021 targets an orphan disease, half of them being cancers. Small molecules continue to dominate new drug approvals, followed by antibodies and non-antibody biopharmaceuticals. In 2021, the FDA continued to approve drugs without strong evidence of clinical effects, best exemplified by the aducanumab controversy.

Immunocompromised host section: Adoptive T-cell therapy for dsDNA viruses in allogeneic hematopoietic cell transplant recipients

PURPOSE OF REVIEW

Double-stranded DNA (dsDNA) viruses remain important causes of morbidity and mortality after allogeneic hematopoietic cell transplantation (HCT). As treatment options are limited, adoptive therapy with virus-specific T cells (VST) is promising in restoring immunity and thereby preventing and treating virus infections. Here we review current evidence and recent advances in the field of VST for dsDNA viruses in allogeneic HCT recipients.

RECENT FINDINGS

Four different protocols for VST generation are currently used in clinical trials, and various products including multivirus-specific and off-the-shelf products are under investigation for prophylaxis, preemptive therapy or treatment. Data from nearly 1400 dsDNA-VST applications in allogeneic HCT patients have been published and demonstrated its safety. Although Epstein-Barr virus, cytomegalovirus, and adenovirus-specific T-cell therapy studies have predominated over the past 25 years, additional human herpes viruses were added to multivirus-specific T cells over the last decade and clinical evidence for polyomavirus-specific VST has just recently emerged. Response rates of around 70-80% have been reported, but cautious interpretation is warranted as data are predominantly from phase 1/2 studies and clinical efficacy needs to be confirmed in phase 3 studies.

SUMMARY

Investigation on the 'ideal' composition of VST is ongoing. Several products recently entered phase 3 trials and may allow widespread clinical use in the near future.

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.

Cytomegalovirus Management in Solid Organ Transplant Recipients: A Pre-COVID-19 Survey From the Working Group of the European Society for Organ Transplantation

Infections are leading causes of morbidity/mortality following solid organ transplantation (SOT) and cytomegalovirus (CMV) is among the most frequent pathogens, causing a considerable threat to SOT recipients. A survey was conducted 19 July–31 October 2019 to capture clinical practices about CMV in SOT recipients (e.g., how practices aligned with guidelines, how adequately treatments met patients’ needs, and respondents’ expectations for future developments). Transplant professionals completed a ∼30-minute online questionnaire: 224 responses were included, representing 160 hospitals and 197 SOT programs (41 countries; 167[83%] European programs). Findings revealed a heterogenous approach to CMV diagnosis and management and, sometimes, significant divergence from international guidelines. Valganciclovir prophylaxis (of variable duration) was administered by 201/224 (90%) respondents in D+/R− SOT and by 40% in R+ cases, with pre-emptive strategies generally reserved for R+ cases: DNA thresholds to initiate treatment ranged across 10–10,000 copies/ml. Ganciclovir-resistant CMV strains were still perceived as major challenges, and tailored treatment was one of the most important unmet needs for CMV management. These findings may help to design studies to evaluate safety and efficacy of new strategies to prevent CMV disease in SOT recipients, and target specific educational activities to harmonize CMV management in this challenging population.

Cytomegalovirus infection and rehospitalization rates after allogeneic hematopoietic stem cell and solid organ transplantation: a retrospective cohort study using German claims data

PURPOSE

This study aimed to describe the cytomegalovirus (CMV) infection rate, rehospitalizations, and comorbidities following allogeneic hematopoietic stem cell transplantation (allo-HSCT) and solid organ transplantation (SOT).

METHODS

Patients who received allo-HSCT or SOT in 01/07/2015-30/06/2018 were identified using anonymized German claims data. The transplantation-related hospital admission date was defined as the index date, and patients were followed for up to 12 months (or death, first event relevant). The frequency of CMV infections (confirmed outpatient/inpatient diagnoses, ICD-10-GM codes: B25.-/B27.1) and the rate, number, and duration of all-cause rehospitalizations in the follow-up period were evaluated.

RESULTS

A total of 226 allo-HSCT and 250 SOT patients were identified (mean age 52.8 years, 38.9% female). During the 12 months after transplantation, 29.2% of allo-HSCT patients and 16.8% of SOT patients received a CMV diagnosis. The majority of these diagnoses were given during the initial hospitalization or within the following 3 months. Across transplantation types, CMV patients had more hospital readmission days per patient-year (allo-HSCT 93.3 vs. 49.4, p = 0.001; SOT 42.0 vs. 20.7, p = 0.005), with a longer mean duration of readmissions (allo-HSCT 22.4 vs. 15.4 days, p < 0.001; SOT 11.6 vs. 7.5 days, p = 0.003). Comorbidity burden in transplantation patients was substantial, with several diagnoses being significantly more common among patients with CMV vs. non-CMV. One-year mortality did not differ significantly between patients with/without CMV.

CONCLUSION

Burden of transplant recipients with CMV in terms of rehospitalizations and comorbidities is substantial, highlighting the need for improved CMV prevention and treatment.

Evaluating the Safety of Maribavir for the Treatment of Cytomegalovirus

Purpose of Review

Cytomegalovirus (CMV) infections are a common complication in solid organ (SOT) and hematopoietic stem cell transplant (HSCT) recipients, leading to increased morbidity and mortality. Currently available treatment options have reduced the burden of infection, but utilization of these agents can be limited by toxicities such as nephrotoxicity and/or myelosuppression as well as emergence of resistance. The expansion of our current armamentarium towards CMV infection is crucial. Here, we review an emerging therapy, maribavir, and the safety and efficacy of this potential new agent for the prophylaxis and treatment of CMV infections including resistant/refractory disease.

Recent Findings

Maribavir is a novel agent with CMV activity approved by Federal Food and Drug Administration (FDA) in December 2021 for resistant/refractory disease. Compared to currently available treatment for CMV infection, maribavir has a unique mechanism of action, retains activity against most (val)ganciclovir resistant strains, provides a more predictable pharmacokinetic profile, and fewer severe toxicities. Maribavir has been studied in phase 2 and 3 studies with ongoing phase 3 studies. While maribavir failed to meet the primary endpoints in the initial phase 3 study for prophylaxis therapy in allogeneic-HSCT and liver transplant recipients, results from the phase 2 study when used for pre-emptive therapy after HSCT show similar efficacy to valganciclovir, and results from the phase 3 study examining resistant/refractory disease demonstrate superiority to investigator-initiated therapy of (val)ganciclovir, foscarnet, or cidofovir.

Summary

Maribavir provides a new agent for the management of resistant/refractory CMV infection. Results of the recently published phase 3 study provide further insight into the role of this novel therapy.

Antiviral Therapeutics in Pediatric Transplant Recipients

Recipients of solid organ and hematopoietic stem cell transplantation undergo substantial immune suppression, placing them at risk for opportunistic viral infection. Few randomized controlled trials have been dedicated to the treatment of viral infections in children, and current practices are extrapolated from data generated from adult patients. Here we discuss the prevention and treatment of viral infections using available antiviral drugs, as well as novel agents that may provide benefit to pediatric patients in the future.

Maribavir: First Approval

Maribavir (LIVTENCITY^TM), a cytomegalovirus (CMV) enzyme pUL97 kinase inhibitor, is being developed by Takeda Pharmaceuticals for the treatment of CMV infections. Maribavir was recently approved in the USA for the treatment of post-transplant CMV infection/disease that is refractory to treatment (with or without genotypic resistance) with ganciclovir, valganciclovir, cidofovir or foscarnet in adults and paediatric (≥ 12 years of age and weighing ≥ 35 kg) patients. This article summarizes the milestones in the development of maribavir leading to this first approval for CMV infections.