Extended duration of letermovir prophylaxis: how long is long enough?

Cytomegalovirus is a common viral infection in recipients of allogeneic haematopoietic stem-cell transplantation (HSCT) and a key driver of non-relapse morbidity and mortality.1 A pivotal phase 3 trial of letermovir prophylaxis in the first 100 days following transplantation in cytomegalovirus-seropositive recipients showed a greatly reduced incidence of clinically significant cytomegalovirus infection while patients were receiving letermovir.2 However, on cessation of prophylaxis, an increased incidence from day 100 to day 200 was observed, suggesting that extended prophylaxis could be beneficial.