Letermovir Prophylaxis for Cytomegalovirus Reactivation in Allo-HSCT A Retrospective Single Center real-world data

Background: Letermovir effectively prevents Cytomegalovirus (CMV) infection without causing bone marrow suppression, but real-world data on its use in Chinese allogeneic hematopoietic stem cell transplantation (HSCT) patients is limited. Objective: We evaluated CMV viremia rates during letermovir prophylaxis and its effects on other viral infections and patient outcomes. Study Design: In the study of 159 HSCT recipients, 74 received letermovir while 85 were in the control group. Letermovir was median initiated in 15 days post-transplant, and median continued for 84 days. Result: CMV viremia rates at 100 days were significantly lower in the letermovir group (18.92% vs 56.47%, p < 0.001). The lower plasma concentrations of letermovir, delayed initiation of prophylaxis, and high-dose steroids (≥1 mg/kg of methylprednisolone) (p = 0.020) correlated with breakthrough CMV viremia. The patients in the letermovir group experienced lower rates of acute graft-versus-host disease (aGVHD) (17.57% vs. 44.71%, p < 0.001) but higher rates of Epstein Barr viremia (31.08% vs. 14.12%, p = 0.013) and lower absolute lymphocyte counts (1.19 ± 0.99 × 10^9/L vs. 1.77 ± 1.39 × 10^9/L, p = 0.004). Conclusions: Letermovir is effective in preventing CMV viremia but potentially increases EBV viremia. Breakthrough CMV viremia may be linked to low letermovir Cmin, delayed initiation of prophylaxis, and high-dose steroid use.