Positive HCMV DNAemia in stem cell recipients undergoing letermovir prophylaxis is expression of abortive infection

Evaluating the efficacy and safety of letermovir compared to valganciclovir for the prevention of human cytomegalovirus disease in adult lung transplant recipients

BACKGROUND

Lung transplant recipients are at high risk for severe cytomegalovirus (CMV) disease. Off-label use of letermovir (LET) may avert myelotoxicity associated with valganciclovir (VGCV), but data in lung transplantation are limited. This study aims to evaluate the outcomes of LET prophylaxis among lung transplant recipients.

METHODS

This retrospective, matched cohort study included lung transplant recipients who received LET for primary CMV prophylaxis following VGCV intolerance. Patients were matched 1:1 to historical VGCV controls based on age, serostatus group, and time from transplant. The primary outcome was CMV breakthrough within 1 year post-LET initiation; secondary outcomes included hematologic changes.

RESULTS

A total of 124 lung transplant recipients were included per group (32% CMV mismatch, D+R-), with LET initiated a median of 9.6 months post-transplantation. One CMV breakthrough event (0.8%) was observed in the LET group versus four (3.2%) in the VGCV group (p = .370). The median (interquartile range) white blood cell (WBC) count was 3.1 (2.1-5.6) at LET initiation which increased to 5.1 (3.9-7.2) at the end of follow-up (p <.001). For VGCV controls, WBC was 4.8 (3.4-7.2) at baseline and 5.4 (3.6-7.2) at the end of follow-up; this difference was not statistically significant (p = .395). Additionally, 98.4% of LET patients experienced ≥1 leukopenia episode in the year prior to LET compared to 71.8% the year after initiation (p <.001). Similar results were observed for neutropenia (48.4% and 17.7%, p <.001).

CONCLUSION

LET prophylaxis was associated with a low rate of CMV reactivation and leukopenia recovery. LET may represent a reasonable prophylaxis option for lung transplant recipients unable to tolerate VGCV.

Real-life use of letermovir prophylaxis for cytomegalovirus in heart transplant recipients

INTRODUCTION

Cytomegalovirus (CMV) remains the predominant opportunistic infection following solid organ transplantation (SOT). While valganciclovir is the drug of choice for CMV prophylaxis, its utility can be compromised due to the risk of cytopenia. Letermovir, a novel agent approved for CMV prophylaxis in allogeneic hematopoietic stem cell transplant recipients and high-risk kidney transplant recipients, exhibits reduced toxicity. This study aims to present the practical application of letermovir as both primary and secondary prophylaxis against CMV in heart transplant recipients (HTR).

METHODS

In this observational, retrospective, single-center study, we included all consecutive adult HTRs from June 2020 to January 2022 who were administered letermovir for CMV prophylaxis. We documented instances of CMV breakthrough infections, side effects related to letermovir, changes in neutropenia following the switch from valganciclovir to letermovir, and any drug interactions with the immunosuppressive regimen.

RESULTS

The study comprised 10 patients: two received primary prophylaxis with letermovir due to a high risk of CMV infection (donor-positive, recipient-negative serostatus), and eight received it as secondary prophylaxis following a CMV infection. The median duration of letermovir administration was 8 months (range 3-12 months). No CMV breakthrough infections were reported while on prophylaxis. However, three patients experienced CMV breakthrough infections after discontinuing letermovir prophylaxis (30%). No significant side effects were observed, although one patient reported digestive intolerance. Among the nine patients on tacrolimus, six needed reduced doses after switching to letermovir.

CONCLUSION

This real-life study appears to support the effectiveness of letermovir prophylaxis in HTR. Nonetheless, the risk of CMV infection post-treatment cessation is notable. Further drug monitoring and research on the efficacy of letermovir for CMV prophylaxis in SOT patients is warranted.

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.

Letermovir for Cytomegalovirus infection in pediatric patients undergoing allogenic hematopoietic stem cell transplantation: a real-life study by the Infectious Diseases Working Group of Italian Association of Pediatric Hematology-Oncology (AIEOP)

Letermovir prophylaxis revolutionized the approach to Cytomegalovirus infection in adult hematopoietic stem cell transplant (HCT), while data in pediatric setting are still lacking. We retrospectively analyzed 87 HCT children transplanted in 11 AIEOP centers receiving letermovir as off-label indication between January 2020 and November 2022. Letermovir was used as primary, secondary prophylaxis or CMV treatment in 39, 26 and 22 cases, respectively; no discontinuation due to toxicity was reported. Median duration was 100 days (14-256) for primary and 96 days (8-271) for secondary prophylaxis, respectively. None of the patients experienced CMV-clinically significant reactivation during Letermovir primary prophylaxis; one patient developed breakthrough infection during secondary prophylaxis, and 10 and 1 patient experienced asymptomatic CMV-reactivation and CMV-primary infection after drug discontinuation, respectively. Median duration of letermovir in CMV treatment was 40 days (7-134), with 4/22 patients suffering CMV-pneumonia, with an overall response rate of 86.4%. With a median follow-up of 10.7 months (8.2-11.8), estimated 1-year overall survival was 86%; no CMV-related deaths were reported in prophylaxis groups. This is the largest report on Letermovir use in pediatric HCT; real-life data confirm an excellent toxicity profile, with high efficacy as CMV prophylaxis; results in CMV-infection treatment should be investigated in larger, prospective trials.

Letermovir use may impact on the Cytomegalovirus DNA fragmentation profile in plasma from allogeneic hematopoietic stem cell transplant recipients

Cytomegalovirus (CMV) DNA in plasma is mainly unprotected and highly fragmented. The size of the amplicon largely explains the variation in CMV DNA loads quantified across PCR platforms. In this proof-of-concept study, we assessed whether the CMV DNA fragmentation profile may vary across allogeneic hematopoietic stem cell transplant recipients (allo-SCT), within the same patient over time, or is affected by letermovir (LMV) use. A total of 52 plasma specimens from 14 nonconsecutive allo-SCT recipients were included. The RealTime CMV PCR (Abbott Molecular), was used to monitor CMV DNA load in plasma, and fragmentation was assessed with a laboratory-designed PCR generating overlapping amplicons (around 90-110 bp) within the CMV UL34, UL80.5, and UL54 genes. Intrapatient, inter-patient, and LMV-associated qualitative and quantitative variations in seven amplicons were observed. These variations were seemingly unrelated to the CMV DNA loads measured by the Abbott PCR assay. CMV DNA loads quantified by UL34_4, UL54.5, and UL80.5_1 PCR assays discriminate between LMV and non-LMV patients. Our observations may have relevant implications in the management of active CMV infection in allo-SCT recipients, either treated or not with LMV, although the data need further validation.

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

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

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.

A new direction for cytomegalovirus prophylaxis among transplant recipients: Benefits and nonviral outcomes of letermovir use as primary CMV prophylaxis

PURPOSE OF REVIEW

Letermovir has changed the game of primary prophylaxis against cytomegalovirus (CMV) for hematopoietic stem cell transplant (HSCT) and more recently, solid organ transplant recipients. This is largely due to letermovir's similar efficacy in protecting against CMV reactivation and disease, along with its superior safety profile, notably reduced myelotoxicity, and lack of renal dose adjustment compared to standard agents like valganciclovir. This review will describe the potential benefits and clinical considerations of letermovir as prophylaxis among transplant recipients, with a focus on recent evidence describing nonviral outcomes of CMV.

RECENT FINDINGS

Recent evidence has demonstrated improved safety (e.g., less myelosuppression) and tolerability with no difference in rates of CMV infection or disease in kidney transplant recipients given letermovir compared to valganciclovir. Real-world studies and meta-analyses in HSCT populations have explored various nonviral outcomes with letermovir use. Letermovir prophylaxis was associated with reduced mortality, lower rates of graft versus host disease, delayed CMV immune reconstitution, improved tolerability with extended durations, and decreased healthcare utilization.

SUMMARY

Letermovir is an effective antiviral agent for CMV prevention and has demonstrated enhanced safety, which may allow for extended durations of primary prophylaxis among transplant recipients along with other improved clinical outcomes by mitigating the indirect effects of CMV.

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.

Dynamics of polyclonal immuno-reconstitution after allogeneic transplant with post-transplant cyclophosphamide and letermovir

Cytomegalovirus (CMV) reactivations are strong stimulators of immune-reconstitution (IR) in hematopoietic stem cell transplantation (HSCT) recipients. Herein, we analyzed 317 CMV-seropositive consecutive patients (n = 109 letermovir, LTV; n = 208 no-LTV), undergoing HSCT with post-transplant cyclophosphamide (PTCy) and calcineurin inhibitor- (CNI) free graft-versus-host-disease (GvHD) prophylaxis. At day+90, median CD19+/mm3 was higher in LTV-cohort: 5.5 [0;439] versus 2 [0;294], p = 0.008; median CD3+/mm3 counts were lower in LTV-cohort, with no differences in CD4+, CD8+ and NK-cells. At day+180 median CD3+, CD4+ and CD8+/mm3 values were comparable between groups. Higher CD19+/mm3 counts were observed in LTV-cohort: 62 [0; 2983] versus 42 [0; 863]. Significantly higher median NK/mm3 values were seen in LTV-cohort: 225.5 [0;763] versus 163.5 [0;1181], p = 0.0003. The impact of LTV on B-cell IR at 3 months and NK-cell levels at 6 months was retained in multivariate analysis (p < 0.01), whereas the effect on T-cells was not confirmed. Moreover, we confirmed a significant reduction of clinically-relevant CMV, and moderate-to- severe chronic GvHD in LTV-cohort. Overall, in our study the use of LTV was associated with a slight improvement of B-cell and NK-cells reconstitution, with only minor impact on T-cell subsets, giving new insights on polyclonal IR for HSCT recipients in the LTV era.

Cytomegalovirus Infection after Allogeneic Hematopoietic Cell Transplantation under 100-Day Letermovir Prophylaxis: A Real-World 1-Year Follow-Up Study

The prevention and management of cytomegalovirus (CMV) reactivation is important to improve the outcomes of allogeneic hematopoietic cell transplantation (allo-HCT) recipients. The aim of this study was to analyze real-world data regarding the incidence and characteristics of CMV infections until 1 year after allo-HCT under 100-day letermovir prophylaxis. A single-center retrospective study was conducted between November 2020 and October 2021. During the study period, 358 patients underwent allo-HCT, 306 of whom received letermovir prophylaxis. Cumulative incidence of clinically significant CMV infection (CS-CMVi) was 11.4%, 31.7%, and 36.9% at 14 weeks, 24 weeks, and 1 year post-HCT, respectively. Through multivariate analysis, the risk of CS-CMVi increased with graft-versus-host disease (GVHD) ≥ grade 2 (adjusted odds ratio 3.640 [2.036-6.510]; p < 0.001). One-year non-relapse mortality was significantly higher in letermovir breakthrough CS-CMVi patients than those with subclinical CMV reactivation who continued receiving letermovir (p = 0.002). There were 18 (15.9%) refractory CMV infection cases in this study population. In summary, letermovir prophylaxis is effective at preventing CS-CMVi until day 100, which increased after the cessation of letermovir. GVHD is still a significant risk factor in the era of letermovir prophylaxis. Further research is needed to establish individualized management strategies, especially in patients with significant GVHD or letermovir breakthrough CS-CMVi.

Effectiveness of letermovir for cytomegalovirus prophylaxis in allogeneic hematopoietic stem cell transplant recipients: A global systematic review

OBJECTIVE(S)

Letermovir (LET), a novel antiviral, has largely supplanted more traditional preemptive therapy (PET) for cytomegalovirus (CMV) prophylaxis in allogeneic hematopoietic stem cell transplant (allo-HCT) patients. Use of LET demonstrated efficacy against placebo in phase III randomized controlled trials, but is considerably more expensive than PET. This review aimed to evaluate the real-world effectiveness of LET in preventing clinically significant CMV infection (csCMVi) for allo-HCT recipients and related outcomes.

DESIGN

A systematic literature review was performed using an a priori protocol using PubMed, Scopus, and ClinicalTrials.gov from January 2010 to October 2021.

SETTING AND PARTICIPANTS

Studies were included if they met the following criteria: LET compared with PET, CMV-related outcomes, patients aged 18 years or older, and English language-only articles. Descriptive statistics were used to summarize study characteristics and outcomes.

OUTCOME MEASURES

CMV viremia, csCMVi, CMV end-organ disease, graft-versus-host-disease, all-cause mortality.

RESULTS

A total of 233 abstracts were screened, with 30 included in this review. Randomized trials demonstrated efficacy of LET prophylaxis in preventing csCMVi. Observational studies demonstrated varying degrees of effectiveness of LET prophylaxis compared with use of PET alone. All studies with a comparator group resulted in lower rates of csCMVi for patients using LET. Included studies varied widely by CMV viral load threshold cutoff and CMV test units, limiting synthesis of results owing to high heterogeneity.

CONCLUSION

LET reduces risk of csCMVi, but lack of standardized clinical definitions on how to evaluate csCMVi and related outcomes largely prevent synthesis of results. Clinicians must consider this limitation in the context of evaluating the effectiveness of LET to other antiviral therapies, especially for patients at risk of late-onset CMV. Future studies should focus on prospective data collection through registries and concordance of diagnostic definitions to mitigate study heterogeneity.

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.

CD4+ T cells are the major predictor of HCMV control in allogeneic stem cell transplant recipients on letermovir prophylaxis

Introduction

Human cytomegalovirus (HCMV) causes significant morbidity and mortality in allogeneic stem cell transplant (alloSCT) recipients. Recently, antiviral letermovir prophylaxis during the first 100 days after alloSCT replaced PCR-guided preemptive therapy as the primary standard of care for HCMV reactivations. Here, we compared NK-cell and T-cell reconstitution in alloSCT recipients receiving preemptive therapy or letermovir prophylaxis in order to identify potential biomarkers predicting prolonged and symptomatic HCMV reactivation.

Methods

To that end, the NK-cell and T-cell repertoire of alloSCT recipients managed with preemptive therapy (n=32) or letermovir prophylaxis (n=24) was characterized by flow cytometry on days +30, +60, +90 and +120 after alloSCT. Additionally, background-corrected HCMV-specific T-helper (CD4+IFNγ+) and cytotoxic (CD8+IFNγ+CD107a+) T cells were quantified after pp65 stimulation.

Results

Compared to preemptive therapy, letermovir prophylaxis prevented HCMV reactivation and decreased HCMV peak viral loads until days +120 and +365. Letermovir prophylaxis resulted in decreased T-cell numbers but increased NK-cell numbers. Interestingly, despite the inhibition of HCMV, we found high numbers of "memory-like" (CD56dimFcεRIγ- and/or CD159c+) NK cells and an expansion of HCMV-specific CD4+ and CD8+ T cells in letermovir recipients. We further compared immunological readouts in patients on letermovir prophylaxis with non/short-term HCMV reactivation (NSTR) and prolonged/symptomatic HCMV reactivation (long-term HCMV reactivation, LTR). Median HCMV-specific CD4+ T-cell frequencies were significantly higher in NSTR patients (day +60, 0.35 % vs. 0.00 % CD4+IFNγ+/CD4+ cells, p=0.018) than in patients with LTR, whereas patients with LTR had significantly higher median regulatory T-cell (Treg) frequencies (day +90, 2.2 % vs. 6.2 % CD4+CD25+CD127dim/CD4+ cells, p=0.019). ROC analysis confirmed low HCMV specific CD4+ (AUC on day +60: 0.813, p=0.019) and high Treg frequencies (AUC on day +90: 0.847, p=0.021) as significant predictors of prolonged and symptomatic HCMV reactivation.

Discussion

Taken together, letermovir prophylaxis delays HCMV reactivation and alters NK- and T-cell reconstitution. High numbers of HCMV-specific CD4+ T cells and low numbers of Tregs seem to be pivotal to suppress post-alloSCT HCMV reactivation during letermovir prophylaxis. Administration of more advanced immunoassays that include Treg signature cytokines might contribute to the identification of patients at high-risk for long-term and symptomatic HCMV reactivation who might benefit from prolonged administration of letermovir.

Cytomegalovirus breakthrough and resistance during letermovir prophylaxis

Letermovir is a relatively new antiviral for prophylaxis against cytomegalovirus (CMV) after allogeneic hematopoietic cell transplantation (HCT). CMV-seropositive HCT recipients who received letermovir prophylaxis from 2018 to 2020 at our center were evaluated for letermovir resistance and breakthrough CMV reactivation. Two-hundred twenty-six letermovir recipients were identified and 7/15 (47%) with CMV DNAemia ≥200 IU/mL were successfully genotyped for UL56 resistance. A single C325Y resistance mutation was identified in an umbilical cord blood recipient. Ninety-five (42%), 43 (19%), and 15 (7%) patients had breakthrough CMV at any level, ≥150 IU/mL, and ≥500 IU/mL, respectively. Risk factors for breakthrough CMV reactivation at each viral threshold were examined. Cumulative steroid exposure was the strongest risk factor for CMV at all evaluated viral thresholds. Graft-versus-host disease prophylaxis with post-transplantation cyclophosphamide (aHR 2.34, 95% CI 1.28-4.28, p = 0.001) or calcineurin inhibitors plus mycophenolate (aHR 2.24, 95% CI 1.30-3.86, p = 0.004) were also associated with an increased risk of CMV reactivation at any level. De novo letermovir resistance is rare and can be successfully treated using other antivirals. Letermovir effectively prevents clinically significant CMV, however, subclinical CMV reactivation occurs frequently at our center.

Features of cytomegalovirus DNAemia and virus-specific T-cell responses in allogeneic hematopoietic stem-cell transplant recipients during prophylaxis with letermovir

BACKGROUND

There is scarce information on the natural kinetics of cytomegalovirus (CMV) DNAemia and dynamics of CMV-specific T-cell reconstitution in allogeneic hematopoietic transplant recipients (allo-HSCT) undergoing letermovir (LMV) prophylaxis.

METHODS

Twelve adult CMV-seropositive high-risk recipients (median age, 53 years; 9 males/3 females) undergoing LMV prophylaxis and 13 non-LMV allo-HSCT controls (median age, 58 years; 7 males/6 females) were included. CMV DNAemia in plasma was monitored by real-time polymerase chain reaction. Preemptive antiviral therapy (PET) was administered upon detection of ≥1500 IU/ml. CMV-specific interferon-gamma (IFN-γ)-producing CD8⁺ and CD4⁺ T cells were enumerated by flow cytometry around days +30, +60, and +90 after allo-HSCT. Ex vivo experiments assessing of the potential effect of LMV on CMV-specific T-cell expansion in a single CMV-seropositive donor were also conducted.

RESULTS

Five LMV patients (41.6%) developed CMV DNAemia that cleared spontaneously. Four patients (33.3%) developed CMV DNAemia after LMV cessation, of which two required PET. Nine non-LMV patients (69.2%) developed CMV DNAemia (five required PET). The percentage of LMV and non-LMV patients exhibiting detectable CMV-specific T-cell responses was comparable (7/10 vs. 10/13; p = .71). Nevertheless, median CMV-specific CD4⁺ and CD8⁺ T-cell counts were lower in LMV patients by days +60 (p = .006 and .02, respectively) and +90 (p = .08 and .02). Ex vivo, CMV-specific CD8⁺ T cells expanded to the same level either in the presence (19.8%) or in the absence of LMV (20.6%).

CONCLUSIONS

In our series, episodes of CMV DNAemia in LMV patients cleared spontaneously. A diminished degree of CMV-specific T-cell reconstitution in LMV patients compared to non-LMV patients was observed.

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.

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.

Diagnosis and treatment for the early stage of cytomegalovirus infection during hematopoietic stem cell transplantation

Cytomegalovirus (CMV) infection remains a frequent complication after hematopoietic stem cell transplantation (HSCT) and causes significant morbidity and mortality in transplantation recipients. In this review, we highlight the role of major risk factors that are associated with the incidence of CMV infection. Advances in immunosurveillance may predict CMV infection, allowing early interventions to prevent severe infection. Furthermore, numerous therapeutic strategies against CMV infection after HSCT are summarized. A comprehensive understanding of the current situation of CMV treatment may provide a hint for clinical practice and even promote the development of novel strategies for precision medicine.

Therapeutic Drug Monitoring of Orally Administered Letermovir Prophylaxis in Allogeneic Hematopoietic Stem Cell Transplant Recipients

With balanced safety-efficacy profile, letermovir anti-cytomegalovirus (CMV) prophylaxis is used in hematopoietic stem cell transplant recipients (HSCTR). We assessed feasibility and usefulness of letermovir therapeutic drug monitoring (TDM) in HSCTR. We performed a prospective observational study on letermovir-TDM including 40 consecutive adult CMV-seropositive allogeneic-HSCTR who received orally (PO) administered letermovir. Minimal blood concentrations of letermovir (C_trough) were measured on days 3 and 7 postletermovir initiation and weekly thereafter. Letermovir-C_trough remained stable during the first 70 days post-HSCT at a median of 286 μg/L (interquartile range, 131 to 591 μg/L), with large interpatient/intrapatient variability. No associations between breakthrough clinically significant CMV infection or detectable CMV DNAemia and letermovir-C_trough were observed. Patients with letermovir-associated adverse events had higher letermovir-C_trough than patients without (400 versus 266 μg/L, P = 0.02). Letermovir-C_trough was similar in patients with or without gastrointestinal symptoms (280 versus 300 μg/L, P = 0.49). Acute grade ≥2 GvHD was associated with higher letermovir-C_trough (479 versus 248 μg/L, P = 0.001), including gastrointestinal GvHD (499 versus 263 μg/L, P = 0.004). Concomitantly administered posaconazole and cyclosporine were associated with higher letermovir-C_trough (707 versus 259 μg/L, P < 0.001 and 437 versus 248 μg/L, P = 0.01, respectively). In multivariable analysis, both posaconazole (odds ratio [OR], 4.9; 95% confidence interval [CI], 2.4 to 9.7; P < 0.0001) and cyclosporine-adjusted letermovir dose at 240 mg daily (OR, 3.5; 95% CI, 1.4 to 9.0; P = 0.01) were independently associated with higher letermovir-C_trough. In conclusion, administration of PO letermovir led to measurable and relatively stable letermovir-C_trough, without noticeable associations with clinical efficacy. Letermovir exposure was not affected by gastrointestinal symptoms, but with posaconazole and cyclosporine administration. Associations between letermovir and concomitantly administered agents and adverse events warrant additional clinical studies.

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

Cord blood transplantation (CBT) can be complicated by a high incidence of clinically significant cytomegalovirus infection (csCMVi). We have investigated the efficacy of extended letermovir prophylaxis in seropositive adult CBT recipients. The aim was to continue prophylaxis for ≥6 months (insurance permitting). By day 100, the incidence of csCMVi was 0% in 28 patients who received letermovir prophylaxis. Moreover, of 24 patients alive at day 100, none had csCMVi by day 180, having continued prophylaxis for all (n = 20) or part (n = 4) of that period. Overall, 20 patients stopped letermovir at a median of 354 days (range, 119-455 days) posttransplant, with only 5 requiring 1 (n = 4) or 2 (n = 1) courses of valganciclovir (median total duration, 58 days; range, 12-67 days) for postprophylaxis viremia, with no subsequent csCMVi. There were no toxicities attributable to letermovir. Of the 62 historic control subjects who received acyclovir only, 51 developed csCMVi (median onset, 34 days; range, 5-74 days), for a day 100 incidence of 82% (95% confidence interval, 73-92). Seven patients developed proven/probable CMV disease, and 6 died before day 100 (3 with proven/probable CMV pneumonia). Forty-five patients required extended therapy during the first 6 months for 1 (n = 10), 2 (n = 14), or 3/persistent (n = 21) csCMVi, with 43 (84%) of 51 developing significant treatment toxicities. Letermovir is a highly effective, well-tolerated prophylaxis that mitigates CMV infection, CMV-related mortality, and antiviral therapy toxicities in CBT recipients. Our data support prophylaxis duration of at least 6 months after CBT.

Letermovir vs. high-dose valacyclovir for cytomegalovirus prophylaxis following haploidentical or mismatched unrelated donor allogeneic hematopoietic cell transplantation receiving post-transplant cyclophosphamide

Patients undergoing haploidentical or mismatched unrelated donor (haplo/MMUD) allogeneic hematopoietic cell transplantation (alloHCT) receiving post-transplant cyclophosphamide (PTCy) are at high risk of cytomegalovirus (CMV) infection. Experience with letermovir (LET) in this population is limited. This single center retrospective cohort study compared CMV and transplant outcomes between LET and a historical control with high-dose valacyclovir (HDV) prophylaxis in adults undergoing haplo/MMUD alloHCT. Thirty-eight CMV seropositive patients were included, 19 in each arm. LET reduced the incidence of CMV infection (5% vs. 53%, RR 0.01, 95% CI 0.014-0.71, p = .001) and need for CMV treatment by day +100 (5% vs. 37%, RR 0.14, 95% CI 0.18-0.99, p = .017) compared to HDV. Median CMV event-free-survival was improved with LET (not reached vs. 80 days, HR 0.114, 95% CI 0.07-0.61, p = .004). These data support the efficacy of LET in alternative donor transplants.

Human cytomegalovirus-specific T-cell reconstitution and late-onset cytomegalovirus infection in hematopoietic stem cell transplant recipients following letermovir prophylaxis

BACKGROUND

Letermovir (LTV), recently approved for the prophylaxis of human Citomegalovirus (HCMV) reactivation after hematopoietic stem cell transplantation (HSCT), has decreased the rate of infection in the first months post-transplant.

OBJECTIVE

The aim of this study was to evaluate the impact of LTV prophylaxis on immune reconstitution and late-onset infection.

STUDY DESIGN

We studied HCMV infection and HCMV-specific T-cell reconstitution in two matched groups of HSCT recipients receiving LTV prophylaxis (N=30, LTV group) vs pre-emptive therapy (N=31, PET group). Rate of GvHD, neutropenia, baseline disease recurrence and overall survival were analyzed.

RESULTS

Clinically significant infections requiring pre-emptive therapy showed a similar rate in the PET (21/31, 68%) vs the LTV group (17/30, 57%; P=0.434), but occurred significantly later (after prophylaxis discontinuation) in the LTV group. No difference was found in peak HCMV DNAemia levels (P=0.232). HCMV-specific T-cell recovery was delayed by about 100 days in the LTV group. HCMV-specific CD4 and CD8 T cells were significantly lower in the LTV group between days 120-360 and 90-120, respectively. A lower rate of chronic GvHD (P=0.024) was found in the LTV-group. Time to engraftment, rate of disease relapse and one-year survival were not different in the two groups, whereas a trend towards a lower occurrence of neutropenia (P=0.124) and higher occurrence of acute GvHD grade III-IV (P=0.103) was observed in the LTV group.

CONCLUSIONS

LTV prophylaxis delays HCMV infection and HCMV-specific immune reconstitution, therefore immunological and virological monitoring should be implemented post-prophylaxis discontinuation. The potential effect of LTV prophylaxis in reducing chronic GvHD should be evaluated by prospective studies.

Letermovir Prophylaxis for Cytomegalovirus Infection in Allogeneic Stem Cell Transplantation: A Real-World Experience

Despite effective treatments, cytomegalovirus (CMV) continues to have a significant impact on morbidity and mortality in allogeneic stem cell transplant (allo-SCT) recipients. This multicenter, retrospective, cohort study aimed to evaluate the reproducibility of the safety and efficacy of commercially available letermovir for CMV prophylaxis in a real-world setting. Endpoints were rates of clinically significant CMV infection (CSCI), defined as CMV disease or CMV viremia reactivation within day +100-+168. 204 adult CMV-seropositive allo-SCT recipients from 17 Italian centres (median age 52 years) were treated with LET 240 mg/day between day 0 and day +28. Overall, 28.9% of patients underwent a haploidentical, 32.4% a matched related, and 27.5% a matched unrelated donor (MUD) transplant. 65.7% were considered at high risk of CSCI and 65.2% had a CMV seropositive donor. Low to mild severe adverse events were observed in 40.7% of patients during treatment [gastrointestinal toxicity (36.3%) and skin rash (10.3%)]. Cumulative incidence of CSCI at day +100 and day +168 was 5.4% and 18.1%, respectively, whereas the Kaplan-Meier event rate was 5.8% (95% CI: 2.4-9.1) and 23.3% (95% CI: 16.3-29.7), respectively. Overall mortality was 6.4% at day +100 and 7.3% at day +168. This real-world experience confirms the efficacy and safety of CMV.

American Society for Transplantation and Cellular Therapy Series: #3-Prevention of Cytomegalovirus Infection and Disease After Hematopoietic Cell Transplantation

The Practice Guidelines Committee of the American Society for Transplantation and Cellular Therapy partnered with its Transplant Infectious Disease Special Interest Group to update its 2009 compendium-style infectious diseases guidelines for the care of hematopoietic cell transplant (HCT) recipients. A new approach was taken with the goal of better serving clinical providers by publishing each standalone topic in the infectious disease series as a concise format of frequently asked questions (FAQ), tables, and figures. Adult and pediatric infectious disease and HCT content experts developed and answered FAQs. Topics were finalized with harmonized recommendations that were made by assigning an A through E strength of recommendation paired with a level of supporting evidence graded I through III. The third topic in the series focuses on the prevention of cytomegalovirus infection and disease in HCT recipients by reviewing prophylaxis and preemptive therapy approaches; key definitions, relevant risk factors, and diagnostic monitoring considerations are also reviewed.

Predictors of breakthrough clinically significant cytomegalovirus infection during letermovir prophylaxis in high-risk hematopoietic cell transplant recipients

Letermovir prophylaxis in allogeneic hematopoietic cell transplant recipients significantly reduces the incidence of clinically significant cytomegalovirus infection. However, breakthrough infections still occur despite adequate prophylaxis. In the present retrospective cohort study, we identified clinically relevant predictive factors for clinically significant CMV breakthrough infection during letermovir prophylaxis. Low‐grade CMV replication (21–149 IU/ml), both at the time of letermovir initiation or during prophylaxis, was a significant risk factor for breakthrough clinically significant CMV infection. In addition, development of acute gastrointestinal graft‐versus‐host disease was significantly associated with breakthrough infection. Altogether these findings could call clinicians' attention to closer CMV monitoring and allow for prompt preemptive treatment initiation.

Letermovir for Cytomegalovirus Prophylaxis in Lung Transplant Patients with Valganciclovir-Induced Leukopenia

Cytomegalovirus (CMV) prophylaxis with valganciclovir is the standard of practice in most transplant centers, but treatment-related leukopenia can limit valganciclovir’s use. Therefore, we evaluated letermovir, a novel antiviral agent recently approved for use in hematopoietic cell transplant patients as CMV prophylaxis, in lung transplant recipients unable to tolerate valganciclovir due to severe leukopenia. We performed a retrospective analysis of all lung transplant patients at our center who received letermovir for CMV prophylaxis between 1 December 2018 and 1 January 2020. A repeated measures mixed model was used to analyze white blood cell (WBC) trends, and descriptive statistics were used to analyze secondary endpoints, including CMV DNAemia, renal function, immunosuppression dosing, and allograft function. Seventeen patients were administered letermovir during the study period due to valganciclovir-induced leukopenia (median WBC nadir 1.1 K/uL, range <0.30–2.19 K/uL). Median WBC improvement was noted in 15 (88.2%) patients after starting letermovir. Breakthrough CMV DNAemia necessitating treatment occurred in two patients, with one of the two cases being due to patient noncompliance. CMV resistance to letermovir was detected in two patients, necessitating a change to an alternative agent in one of these patients. No major side effects were reported in any patient. Letermovir is a generally safe and effective alternative for CMV prophylaxis in lung transplant recipients unable to tolerate valganciclovir due to leukopenia.

Off-Label Use of Letermovir as Preemptive Anti-Cytomegalovirus Therapy in a Pediatric Allogeneic Peripheral Blood Stem Cell Transplant

Despite the effectiveness of the currently available antiviral drugs in treating cytomegalovirus (CMV) infection, high rates of adverse effects are associated with their use. Moreover, a problem of increasing importance is the emergence of drug-resistant CMV infection. Here, we describe the first case of off-label use of letermovir (LMV) as preemptive antiviral therapy, in a pediatric allogeneic peripheral blood stem cell transplant recipient with ganciclovir-resistant CMV infection who was intolerant to foscarnet and unable to achieve viral clearance after seven doses of cidofovir. After the administration of LMV, a gradual reduction in viral load was observed and within 6 weeks of LMV treatment, after more than 6 months of positive CMV-DNAemia, the patient cleared the infection. No adverse effects associated with LMV were observed during treatment. In this pediatric study case, the off-label use of LMV for the treatment of CMV infection has been well tolerated and proved to be effective in leading to the suppression of viral replication.