Letermovir Prophylaxis for Cytomegalovirus Reactivation in β Thalassemia Major Children after Hematopoietic Cell Transplantation

Background: Cytomegalovirus(CMV) is one of the most important infections following allogeneic haematopoietic stem cell transplantation (HSCT). Although Letermovir is licensed for prophylaxis of CMV infection in allogeneic hematopoietic cell transplant adult CMV seropositive patients. There are limited data for letermovir as primary CMV prophylaxis in pediatric patients . The objective of the study was to analyze the the use of letermovir for prophylaxis from CMV infection in β thalassemia major children undergoing allo-HSCT in a single center.

M ethods : This study was an retrospective, single-center evaluation of β thalassemia major pediatric recipients treated by allo-HSCT in the First Affiliated Hospital of Guangxi Medical University. 34 patients included in the study were CMV-seropositive, underwent allo-HSCT, and were started on letermovir for primary CMV prophylaxis between June 2022 and July 2023. CMV monitoring was performed 2 times a week until day +100 after HSCT. The primary end point was CMV reactivation on days +100.

Results: 34 patients were analyzed. 20 patients were transplanted from haploidentical donor, 9 patients were transplanted from matched-related donor, 5 patients were transplanted from matched-unrelated donor. The median followed-up was 129 days (range, 50-405 days).The median age was 9 years (range, 2-16 years). The GVHD prophylaxis for matched-related donor group was cyclosporine-based , and the GVHD prophylaxisfor haploidentical and matched-unrelated donor groups were tacrolimus-based. Letermovir start at median 21 days (range 10-35 days) after HSCT. The median weight at the initiation of letermovir was 18.8 kg (range, 12-25 kg). The dose of letermovir was 240mg and 120mg orally once daily in tacrolimus co-administration and cyclosporine co-administration, respectively. During the follow-up period , CMV reactivation was observed in 8 patients totally (23.5%). Among them, 6 patients(17.6%) were in haploidentical donor group. 1 patient (2.9%) in matched-related group and 1 patient (2.9%) in matched-unrelated donor group was CMV reactivated, respectively. Throughout letermovir prophylaxis, the median CMV DNAemia level was 1945 copies (range,526-3800 copies), and the CMV DNAemia lasting time were 17.5 days (range,15-59 days). No patients developed clinically significant CMV infection. 1 patient died because of pulmonary infection of mucor. No serious hepatotoxicity, nephrotoxicity or letermovir intolerance was described.

Conclusion: Our data support letermovir prophylaxis efficacy and safety in β thalassemia major children after allo-HSCT.