Letermovir for primary and secondary cytomegalovirus prevention in allogeneic hematopoietic cell transplant recipients: Real-world experience.

Cytomegalovirus (CMV) is associated with significant morbidity and mortality in allogeneic hematopoietic cell transplantation (HCT) patients. We evaluated the efficacy of letermovir as primary and secondary prophylaxis in 53 CMV-seropositive hematopoietic stem cell transplant recipients. 70% of patients were at high risk for CMV reactivation and disease (primarily ex vivo T-cell-depleted HCT [n = 18; 34%] or haploidentical T-replete HCT [n = 12; 23%]). This was a retrospective, single-center study which identified patients transplanted between January 2018 and June 2018. Patients were followed through September 2018. The primary outcome was the incidence of clinically significant CMV infection (CMV viremia requiring preemptive treatment or CMV disease). Primary letermovir prophylaxis started at a median of 7 days (range, 7-40) after allo-HCT. The median duration of primary letermovir prophylaxis was 116 days (range, 12-221). With primary prophylaxis in 39 patients, the observed CMV reactivation rate was 5.1%. Twenty-nine patients continued primary prophylaxis beyond 14 weeks with a reactivation rate of 3.4%. No recurrent reactivation was seen with secondary prophylaxis of an additional 14 patients. Our experience demonstrates the efficacy of letermovir in a real-world setting for CMV prevention for the first 14 weeks and continued efficacy when given longer than 14 weeks after allogeneic stem cell transplantation or as secondary prophylaxis.