Outcomes of allogeneic hematopoietic cell transplantation under letermovir prophylaxis for cytomegalovirus infection

Heterogeneity of Survival Benefit Conferred by Letermovir

BACKGROUND

Variation in treatment effects based on individual patient characteristics-known as treatment effect heterogeneity or effect modification-has recently gained significant attention. A previous clinical trial and its post hoc analysis suggested that letermovir (LTV) may reduce mortality more in some patients than in others. We hypothesized that the survival benefit of LTV differs according to each patient's specific characteristics.

PURPOSE

This study aimed to identify patient characteristics that are associated with significant survival benefits from LTV.

STUDY DESIGN

Patients who underwent transplantation between 2018 and 2022 were randomly divided into training (n=5779) and validation groups (n=2865). We developed two models: one using a proportional hazards model with interaction terms (PI), and another using a modern machine learning (ML) approach to detect heterogeneity in the survival benefit-specifically, to identify patient characteristics associated with greater benefit from LTV.

RESULTS

In our cohort, 60% of patients received LTV as prophylaxis. In the training cohort, the final PI model, using additive interactions, identified advanced age (≥60), high comorbidities (HCT-CI ≥3), umbilical cord blood (UCB), and haploidentical HCT with post cyclophosphamide as highly beneficial factors. Meanwhile, the ML model, using a causal forest algorithm, classified the top 60% of patients based on the estimated individual treatment effect as the high benefit group. In the validation group, 67.1% and 59.9% of patients were considered to be high benefit by the PI and ML models, respectively. The absolute difference in 6-month NRM (LTV vs. no LTV) in the high benefit group (PI model: 9.8% vs. 16.3%; ML model: 11.3% vs. 16.3%) was greater than that in the low benefit group (PI model: 4.3% vs. 6.9%; ML model: 4.1% vs. 6.2%). Most patients (>80%) with advanced age, high comorbidities, or UCB were classified as high benefit by the ML model, supporting the robustness of the PI model.

CONCLUSION

Our models successfully identified patients who could be expected to experience lower NRM with LTV prophylaxis, underscoring the importance of personalized medicine.

Clinical burden of late-onset, clinically significant CMV infection beyond 100 days in allo-HSCT patients after letermovir prophylaxis

OBJECTIVE

Letermovir (LET) is effective for preventing cytomegalovirus infection (CMVi) and CMV disease in patients after allogeneic hematopoietic stem cell transplantation (allo-HSCT). However, clinically significant (cs)-CMVi can occur after LET cessation. We retrospectively evaluated the clinical burden of late-onset cs-CMVi in patients who had received LET following allo-HSCT in Japan.

METHODS

The Japan Medical Data Center health insurance claims database was interrogated for adult patients who had received LET ≤100 days after allo-HSCT (May 28, 2018, to December 31, 2022). Cohorts 1 and 2 (primary analyses) comprised cs-CMVi-positive and -negative patients, respectively, followed for ≥180 days after the first cs-CMVi-related claim; Cohorts 3 and 4 (exploratory analysis) included patients meeting Cohort 1 or 2 criteria, respectively, but without follow-up duration limitation.

RESULTS

Data for 155 patients (Cohort 1, n = 47; Cohort 2, n = 108) were analyzed. cs-CMVi rates were higher in patients at high (n = 72) versus low risk (n = 83) of CMVi (43.4% vs 15.3%; p = 0.0003), with no difference in frequency of CMV disease. In Cohort 1, median time from 100 days post-transplantation to first cs-CMVi was 35.0 days. Rates of hospital admissions were higher in Cohort 1 versus Cohort 2 (p = 0.0061), and mean duration of anti-CMV drug prescription was longer in high- versus low-risk patients (p = 0.0024). New-onset graft-versus-host disease occurred ≥101 days post-transplantation in three patients (all Cohort 1).

CONCLUSION

This study demonstrates the great burden of late-onset cs-CMVi in patients after allo-HSCT. Extended LET prophylaxis beyond 100 days post-transplant may benefit especially those at high risk of cs-CMVi.

Risk-Adapted Letermovir Prophylaxis Based on a Scoring System Predicting a Higher Burden of Cytomegalovirus Exposure After Allogeneic Hematopoietic Cell Transplantation

We previously reported that the area under the curve of log-transformed cytomegalovirus antigenemia (CMV-AUC) until 100 days after allogeneic hematopoietic cell transplantation (allo-HCT) was associated with an increased risk of non-relapse mortality. We applied a risk-adapted letermovir (LTV) prophylaxis strategy guided by a risk score that predicts a higher CMV-AUC. First, we retrospectively analyzed 278 allo-HCT recipients between 2007 and 2017 (Period 1). We scored risk factors for higher CMV-AUC by odds ratios: malignant lymphoma including adult T cell leukemia/lymphoma (1 point), an unrelated or haploidentical donor (1 point), and recipient/donor CMV serostatus (+/+; 2 points, +/-; 3 points). We have administered LTV to patients with a total score of ≥ 4 points. We then focused on 143 patients who underwent allo-HCT when we applied this strategy (Period 2). Forty patients (28%) in Period 2 received LTV prophylaxis. Two patients (5.4%) exhibited higher CMV-AUC among 37 patients in the higher-risk group (≥ 4 points). However, as many as 33% of the patients with 3 points in Period 2 experienced higher CMV-AUC. Notably, in the lower-risk patients of Period 2, 68% of patients who received systemic steroids for acute graft-versus-host-disease (GVHD) developed higher CMV-AUC. Our risk-adapted LTV prophylaxis strategy effectively prevented higher CMV-AUC in the higher-risk group and reduced the use of LTV. Additionally, including the use of systemic steroids for acute GVHD in this risk-adapted approach is preferable.

Reduction in Length of Hospital Stays for Allogeneic Hematopoietic Stem-Cell Transplantation in the Letermovir Era

BACKGROUND

In recent years, letermovir has been routinely used for cytomegalovirus (CMV) infection prophylaxis in patients receiving allogeneic hematopoietic stem-cell transplantation (HSCT). The reduction effect of letermovir on CMV infection rates and the impact on survival have been studied, but other potential benefits of letermovir remain underexplored.

METHODS

This retrospective study included patients who underwent first-time allogeneic HSCT between October 2013 and August 2023. We compared the length of hospital stay between eras before and after the introduction of letermovir ("nonletermovir group" and "letermovir group," respectively). Secondary outcomes included clinically significant CMV infection rates and hospitalization costs.

RESULTS

A total of 59 patients were analyzed in the nonletermovir group and 65 patients in the letermovir group. The median length of hospital stay was 51 days in the nonletermovir group and 42 days in the letermovir group (p < 0.001). Among standard-risk disease patients, the letermovir group also had significantly shorter hospital stays (p = 0.0048). Additionally, the cumulative incidence of clinically significant CMV infection and grade II-IV acute graft-versus-host disease were both lower in the letermovir group. Hospitalization costs were not significantly different between the two groups.

CONCLUSION

The length of hospital stays after HSCT was observed to be shorter following the introduction of letermovir in this study. This reduction in hospital stays did not decrease hospitalization costs in relation to allogeneic HSCT, but it may alleviate the burden on both patients and healthcare providers.

Cytomegalovirus in haematopoietic cell transplantation - The troll is still there

Patients undergoing allogeneic haematopoietic cell transplantation are prone to complications caused by viral infections. Cytomegalovirus (CMV) considerably impacts transplantation as it frequently requires antiviral intervention that evokes substantial side effects depending on the antiviral drug. Intermittent antiviral treatment may become necessary if CMV DNAemia cannot be permanently suppressed, and drug resistance may emerge that hampers and prolongs treatment. Despite sedulous endeavours, vaccination against CMV is not yet available. This review concisely summarises current approaches in managing CMV infection comprising risk factors, diagnostics including indications for resistance testing, and therapeutic options from antiviral drugs to virus-specific T cells.

Real-world experience with letermovir for cytomegalovirus-prophylaxis after allogeneic hematopoietic cell transplantation: A multi-centre observational study

OBJECTIVES

Efficacy and safety of letermovir as prophylaxis for clinically significant cytomegalovirus infections (csCVMi) was evaluated in randomised controlled trials while most of the real-world studies are single-centre experiences.

METHODS

We performed a retrospective, multi-centre case-control study at six German university hospitals to evaluate clinical experiences in patients receiving CMV prophylaxis with letermovir (n = 200) compared to controls without CMV prophylaxis (n = 200) during a 48-week follow-up period after allogeneic hematopoietic cell transplantation (aHCT).

RESULTS

The incidence of csCMVi after aHCT was significantly reduced in the letermovir (34%, n = 68) compared to the control group (56%, n = 112; p < 0.001). Letermovir as CMV prophylaxis (OR 0.362) was found to be the only independent variable associated with the prevention of csCMVi. Patients receiving letermovir showed significantly better survival compared to the control group (HR = 1.735, 95% CI: 1.111-2.712; p = 0.014). Of all csCMVi, 46% (n = 31) occurred after discontinuation of letermovir prophylaxis. Severe neutropenia (<500 neutrophils/µL) on the day of the stem cell infusion was the only independent variable for an increased risk of csCMVi after the end of letermovir prophylaxis.

CONCLUSIONS

Our study highlights the preventive effects of letermovir on csCMVi after aHCT. A substantial proportion of patients developed a csCMVi after discontinuation of letermovir. In particular, patients with severe neutropenia require specific attention after drug discontinuation.

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.