We report the final results of a preemptive therapy to assess the safety profile and effectiveness of letermovir for cytomegalovirus (CMV) prophylaxis for up to 48 weeks in patients undergoing allogenic hematopoietic stem cell transplantation in Japan.

Adverse drug reactions and serious adverse drug reactions occurred in 11.33% and 3.05% of the patients, respectively. At weeks 14 and 48, the rates of CMV antigen positivity were 21.34% and 38.36%, 16.57%, and 28.66% of patients required preemptive therapy, and 1.44% and 3.85% developed CMV disease, respectively.

Overall, the results of this large-scale preemptive therapy provide further evidence to support the safety profile and effectiveness of letermovir for CMV prophylaxis in real-world settings in Japan.