Refining letermovir prophylaxis strategies and CD4 + T cell-guided discontinuation in aplastic anemia patients post-allogeneic HSCT: a retrospective analysis

INTRODUCTION: Cytomegalovirus (CMV) infection is a significant complication in aplastic anemia (AA) patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT). While letermovir has shown efficacy in CMV prophylaxis, the optimal timing for discontinuing letermovir remains unclear. This study evaluates the effectiveness of letermovir prophylaxis and explores the role of CD4 + T cells in guiding the appropriate timing for stopping prophylaxis. METHODS: This retrospective cohort study included 129 AA patients who underwent allo-HSCT at Guangzhou First People's Hospital between January 2022 and January 2024. Patients were divided into three groups: Group 1 (no letermovir prophylaxis), Group 2 (letermovir prophylaxis until day 100 post-transplant), and Group 3 (letermovir prophylaxis with discontinuation based on CD4 + T cells after day 100). The primary outcomes assessed were the incidence of CMV infections, overall survival (OS), and the severity of CMV-related infections. RESULTS: The incidence of CMV infection was significantly lower in Group 2 (26.3%) and Group 3 (7.1%) compared to Group 1 (77.6%). Group 3, where letermovir discontinuation was guided by CD4 + T cells, showed no CMV infections between days 100 and 200 post-transplant, suggesting that extending prophylaxis based on immune recovery may offer additional protection. The overall survival rate was 93.0%, with no statistically significant difference observed between groups (P = 0.099). CONCLUSION: Letermovir prophylaxis significantly reduces the incidence of CMV infection in AA patients post-allo-HSCT. Discontinuing letermovir based on CD4 + T cells appears to be an effective strategy for minimizing both early and late CMV infections, indicating that immune recovery markers can guide safer and more personalized prophylaxis durations. Further studies are necessary to confirm these findings and refine the criteria for stopping letermovir prophylaxis.