Efficacy and safety of primary letermovir prophylaxis for cytomegalovirus infection in paediatric patients undergoing allogeneic transplantation: a single-centre, retrospective, real-world analysis.

Background: Cytomegalovirus (CMV) infection is a common and life-threatening complication following allogeneic haematopoietic stem cell transplantation (allo-HSCT). Letermovir (LET) has been the standard prophylaxis for adult recipients, but studies in children remain limited.

Methods: We retrospectively analyzed children with or without LET prophylaxis after haploidentical donor (HID) for the Beijing protocol or unrelated cord blood (UCB) transplantation.

Results: Of the 151 patients, 67 received LET, including 35 HID recipients and 32 UCB recipients. During the 180 days after transplantation, we found that the LET group had a lower incidence of clinically significant CMV infection (csCMVi) than the non-LET group (13.4% vs. 56.0%, P＜0.001). In the LET group, later LET administration was identified as a risk factor for the occurrence of csCMVi (HR: 1.07, 95% CI: 1.01 - 1.14, P=0.029). Further, the HID subgroup had a lower incidence of csCMVi during follow-up than the UCB subgroup (2.9% vs. 25.0%, P=0.009). In terms of safety, the incidence and severity of adverse events, overall survival, cumulative incidence of relapse, relapse free survival, nonrelapse mortality and graft versus host disease-free, relapse-free survival were similar between the two groups.

Conclusion: LET is effective and safe in preventing csCMVi among Chinese children undergoing allo-HSCT. Compared to UCB recipients, children undergoing HID transplantation for the Beijing protocol develop less scCMVi up to 180 days post-HSCT.