Letermovir for cytomegalovirus prophylaxis in pediatric allogeneic hematopoietic stem cell transplantation: a single-center experience

Abstract Purpose Letermovir prophylaxis results in a significantly lower risk of clinically significant cytomegalovirus (CMV) infection in adult hematopoietic stem cell transplant recipients. However, studies supporting its efficacy in pediatric patients are limited. Methods We retrospectively reviewed the outcomes of ten patients who underwent allogeneic hematopoietic stem cell transplantation and received letermovir prophylaxis between November 2021 and October 2024 at our institution. Results Among the ten patients, six donors were CMV-seropositive, whereas nine recipients were CMV-seropositive. Six patients (60%) underwent transplantation from mismatched unrelated donors, and two (20%) from haploidentical donors. Five patients (50%) developed acute graft-versus-host disease (GvHD) > grade 2. Ten patients received letermovir prophylaxis for a median of 101.5 days (range, 26–279). The median daily letermovir dose was 4.6 mg/kg (range, 3.5–11.1 mg/kg), with concomitant use of cyclosporin in nine patients. Eight patients (80%) received letermovir as primary prophylaxis, and two (20%) received it as secondary prophylaxis. None of the patients treated with letermovir as primary prophylaxis had CMV reactivation even after discontinuation (median follow-up, 154 days after transplantation, range 37–850). Both patients who received letermovir as secondary prophylaxis showed CMV reactivation. None of the patients developed CMV infection. No significant adverse effects resulting from the letermovir treatment were observed. Conclusion Our data support the feasibility of letermovir prophylaxis in pediatric patients. The optimal dose of letermovir in pediatric patients has not been established. Letermovir, used as secondary prophylaxis in pediatric patients, was well tolerated.