Extended-duration letermovir prophylaxis for cytomegalovirus infection after cord blood transplantation in adults

Nipping cytomegalovirus in the bud for umbilical cord blood transplantation

Real data confirm an excellent toxicity profile and effectiveness of letermovir prophylaxis with decreased cytomegalovirus reactivation and resistance in umbilical cord blood transplantation for both paediatric and adult patients. Commentary on: Yan et al. Letermovir prophylaxis reduced cytomegalovirus reactivation and resistance post umbilical cord blood transplantation. Br J Haematol 2024;204:2378-2389.

Letermovir for cytomegalovirus infection in allogeneic hematopoietic stem-cell transplantation: tips and notes for effective use in clinical practice

INTRODUCTION

Cytomegalovirus (CMV) infection remains a major complication after allogeneic hematopoietic stem cell transplantation (allo-HSCT). While conventional antiviral agents such as ganciclovir can be used for CMV prophylaxis, toxicities such as myelosuppression are a major concern.

AREA COVERED

This work aimed to summarize the latest information and practical issues regarding a new anti-CMV agent, letermovir (LET).

EXPERT OPINION

LET inhibits CMV replication by binding to components of the DNA terminase complex. A phase 3 trial in allo-HSCT recipients showed a reduced incidence of clinically significant CMV infection in the LET group. In 2017, this agent was first approved for CMV prophylaxis in adult CMV-seropositive allo-HSCT recipients in the United States, and is now used worldwide. While LET has an excellent toxicity profile, there are issues to be aware of, such as interactions with other drug classes (e.g. immunosuppressants and antifungals) and reactivation of CMV infection following LET cessation. While LET is the current standard of care for CMV prophylaxis, there are no established protocols for preemptive treatment of asymptomatic CMV viremia or for treatment of developed CMV disease. Further research is needed to maximize the benefits of LET, including the discovery of biomarkers.

Differential clinical impact of letermovir prophylaxis according to graft sources: a KSGCT multicenter retrospective analysis

ABSTRACT

Clinically significant cytomegalovirus infection (csCMVi) is frequently observed after allogeneic hematopoietic stem cell transplantation (HSCT) and prophylaxis with letermovir is commonly adopted. However, the clinical benefit of letermovir prophylaxis according to graft sources has not been sufficiently elucidated. We retrospectively analyzed 2194 recipients of HSCT who were CMV-seropositive (236 with letermovir prophylaxis and 1958 without prophylaxis against CMV). csCMVi was significantly less frequent in patients with letermovir prophylaxis than in those without (23.7% vs 58.7% at 100 days after HSCT, P < .001) and the same trend was seen when recipients of bone marrow (BM), peripheral blood stem cell (PBSC), or cord blood (CB) transplantation were separately analyzed. In recipients of BM, nonrelapse mortality (NRM) was significantly lower in the letermovir group at 6 months after HSCT (5.0% vs 14.9%, P = .018), and the same trend was observed in recipients of PBSCs (14.7% vs 24.8%, P = .062); however, there was no statistical significance at 1 year (BM, 21.1% vs 30.4%, P = .67; PBSCs, 21.2% vs 30.4%, P = .096). In contrast, NRM was comparable between recipients of CB with and without letermovir prophylaxis throughout the clinical course (6 months, 23.6% vs 24.3%, P =.92; 1 year, 29.3% vs 31.0%, P = .77), which was confirmed by multivariate analyses. In conclusion, the impact of letermovir prophylaxis on NRM and csCMVi should be separately considered according to graft sources.

Efficacy and safety of extended duration letermovir prophylaxis in recipients of haematopoietic stem-cell transplantation at risk of cytomegalovirus infection: a multicentre, randomised, double-blind, placebo-controlled, phase 3 trial

BACKGROUND

In a pivotal phase 3 trial of cytomegalovirus prophylaxis with letermovir for up to 100 days after allogeneic haematopoietic stem-cell transplantation (HSCT), 12% of participants developed clinically significant cytomegalovirus infection after letermovir was discontinued. We aimed to evaluate the efficacy and safety of extending the duration of letermovir prophylaxis for clinically significant cytomegalovirus infection from 100 days to 200 days following HSCT.

METHODS

We conducted a multicentre, randomised, double-blind, placebo-controlled, phase 3 trial at 32 sites in six countries (France, Germany, Italy, Japan, the UK, and the USA). Cytomegalovirus‑seropositive HSCT recipients (aged ≥18 years) who had received letermovir prophylaxis for up to 100 days following HSCT and who remained at high risk of late clinically significant cytomegalovirus infection (with no previous history of clinically significant cytomegalovirus infection, defined as initiation of pre-emptive therapy for documented cytomegalovirus viraemia, onset of cytomegalovirus end-organ disease, or both) were eligible. Participants were randomly assigned (2:1) to receive either an additional 100 days (ie, a total of 200 days; letermovir group) of oral or intravenous letermovir 480 mg once daily, adjusted to 240 mg once daily for participants on cyclosporin A, or 100 days of a placebo comparator for letermovir (ie, a total of 100 days of letermovir; placebo group), following HSCT. Randomisation was done using a central interactive response technology system, stratified by study centre and haploidentical donor (yes or no). Participants, investigators, and sponsor personnel were masked to the treatment allocation. The primary efficacy endpoint was the proportion of participants from randomisation to week 28 (200 days after HSCT) with clinically significant cytomegalovirus infection, analysed using the full analysis set population (ie, those who received at least one dose of study intervention). Safety was analysed in all participants as treated (ie, those who received at least one dose according to the study intervention they were assigned to). This study is registered with ClinicalTrials.gov, NCT03930615, and is complete.

FINDINGS

Between June 21, 2019, and March 16, 2022, 255 patients were screened for eligibility and 220 (86%) were randomly assigned (145 [66%] in the letermovir group and 75 [34%] in the placebo group). Between randomisation and week 28, four (3%) of 144 participants in the letermovir group and 14 (19%) of 74 in the placebo group developed clinically significant cytomegalovirus infection (treatment difference -16·1% [95% CI -25·8 to -6·5]; p=0·0005). The most common adverse events among participants in the letermovir group versus the placebo group were graft-versus-host disease (43 [30%] vs 23 [31%]), diarrhoea (17 [12%] vs nine [12%]), nausea (16 [11%] vs 13 [18%]), pyrexia (13 [9%] vs nine [12%]), and decreased appetite (six [4%] vs nine [12%]). The most frequently reported serious adverse events were recurrent acute myeloid leukaemia (six [4%] vs none) and pneumonia (three [2%] vs two [3%]). No deaths were considered to be drug-related by the investigator.

INTERPRETATION

Extending the duration of letermovir prophylaxis to 200 days following HSCT is efficacious and safe in reducing the incidence of late clinically significant cytomegalovirus infection in patients at risk.

FUNDING

Merck Sharp & Dohme LLC.

Efficacy and safety of letermovir prophylaxis for cytomegalovirus infection after hematopoietic stem cell transplantation

Letermovir is a specific inhibitor of cytomegalovirus (CMV) terminase complex. Several studies have reported that letermovir can effectively prevent CMV activation after allogeneic hematopoietic stem cell transplantation (allo-HSCT). We aimed to identify the efficacy and safety of letermovir prophylaxis for CMV infection after allo-HSCT with a systemic review and meta-analysis. A literature search was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-analyses statement. PubMed and Embase databases were searched. A total of 28 studies were included. The incidence of CMV activation at 14 weeks after HSCT was 0.10 (95% confidence interval [CI], 0.06-0.18), which was 0.10 (95% CI, 0.04-0.21) and 0% in adult and children (2 studies were included and both of them were 0%). In addition, the incidence of CMV activation at 14 weeks after allo-HSCT was 0.11 (95% CI, 0.06-0.21) and 0.07 (only 1 study included), respectively, in retrospective and prospective studies. The incidence of CMV activation at 100 and 200 days after HSCT was 0.23 (95% CI, 0.16-0.33) and 0.49 (95% CI, 0.32-0.67), respectively. The incidence of CMV disease at 14 weeks and at 6 months after HSCT was 0.01 (95% CI, 0.01-0.02) and 0.03 (95% CI, 0.01-0.09), respectively. Thus, our systemic review and meta-analysis suggested that letermovir prophylaxis was safe and effective for CMV activation after allo-HSCT.

Extended duration letermovir in allogeneic hematopoietic stem cell transplant

OBJECTIVES

Despite the use of antiviral prophylaxis in recipients of allogeneic hematopoietic cell transplants (HCT), cytomegalovirus (CMV) is a common clinically significant infection and is associated with significant morbidity and mortality in this patient population. Based on current approval, letermovir is initiated within 28 days following allogeneic HCT for CMV seropositive recipients and continued through 100 days post-transplant. However, it is unknown whether patients who receive extended duration CMV prophylaxis with letermovir would result in less CMV reactivation and reactivation compared to those who do not. This study aimed to evaluate the efficacy of letermovir prophylaxis in CMV seropositive patients when continued for greater than 100 days post-allogeneic stem cell transplant.

METHODS

A single-center retrospective chart review was conducted on recipients of allogeneic HCT from November 2017 to July 2021. Patients were eligible for inclusion if they were at least 18 years of age, received an allogeneic HCT, CMV seropositive, and initiated letermovir between days 0-28 post-transplant. The primary endpoint of this study is to compare rates of CMV reactivation in patients who stopped letermovir prophylaxis at 100 days post-transplant (standard duration group) versus those who continued letermovir prophylaxis past day 100 (extended duration group).

RESULTS

A total of 87 patients met the eligibility criteria for inclusion. The median duration of letermovir prophylaxis was 78 days in the standard duration group versus and 132 days in the extended duration group. There were more CMV reactivations in the standard duration group versus the extended duration group, 28% versus 19% respectively. CMV pneumonitis was observed in one of the patients in the standard duration group. All-cause mortality at day 200 post-transplant was similar between the two groups.

CONCLUSION

The results of this study suggest that extended duration letermovir prophylaxis may be associated with less CMV reactivation compared to the standard duration of prophylaxis.

CMV prevention strategies in allogeneic hematopoietic cell transplantation; the role of prophylaxis and pre-emptive monitoring in the era of letermovir

The preferred strategy for preventing CMV in at-risk populations in alloHCT has undergone a significant practice shift in recent years where the pendulum has swung from a pre-emptive approach to now offering letermovir prophylaxis to all CMV seropositive recipients. Letermovir prophylaxis has resulted in significant reductions in post-transplant clinically significant CMV infection (csCMVi) as well as other important outcomes such as CMV disease, resistant, and refractory CMV infections and nonrelapse mortality. However, prophylactic strategies are not without some limitations, namely delayed onset CMV infections, delayed CMV-specific T cell immune reconstitution, increased drug costs and limited data within pediatric populations. Thus, this review aims to provide an overview of prophylaxis and pre-emptive CMV preventative strategies, and how they are applicable in the current era of letermovir prophylaxis.

Human Cytomegalovirus (HCMV) - specific T-cell response after letermovir prophylaxis is predictive for subsequent HCMV reactivation in haematopoietic stem cell transplant recipients

BACKGROUND

Human Cytomegalovirus (HCMV) is still one of the major concerning infection in hematopoietic stem cell transplant (HSCT) recipients. Letermovir (LTV) has been recently introduced for HCMV prophylaxis in adult patients who received allogeneic HSCT. However, many aspects related to immune reconstitution need to be further explored. The aim of this study was to define the prognostic role of HCMV-specific T-cell frequency measured at the end of LTV prophylaxis in predicting the risk for clinically significant HCMV infection (i.e. infection requiring antiviral treatment) after the stop of the prophylaxis.

METHODS

Sixty-six adult patients who underwent allogeneic HSCT were enrolled and HCMV DNAemia was prospectively monitored. Additionally, HCMV-specific T-cell response was evaluated using ELISpot assay against two different antigens (HCMV infected cell lysate and pp65 peptide pool).

RESULTS

Ten patients (15.2%) developed at least one positive HCMV DNAemia episode during LTV prophylaxis, whereas 50/66 (75.8%) patients developed at least one positive HCMV DNA event after LTV prophylaxis. Of note, 25 of them (50%) experienced a clinically significant HCMV infection. The median HCMV-specific T-cell response measured against HCMV lysate but not against pp65 peptide pool was lower in patients who developed HCMV clinically significant infection after prophylaxis. A ROC analysis revealed that the level of 0.04 HCMV-specific T cells/µl should be used as cut-off for development of clinically significant HCMV reactivation after prophylaxis.

CONCLUSION

Assessment of HCMV-specific immunity upon discontinuation of universal prophylaxis with LTV should be considered as a method for identification of patients at risk for clinically significant HCMV infection.

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.