Letermovir for cytomegalovirus prophylaxis in hematopoietic-cell transplantation

BACKGROUND: Cytomegalovirus (CMV) infection is a leading cause of illness and death in patients who have undergone allogeneic hematopoietic-cell transplantation. Available treatments are restricted by clinically significant toxic effects and drug resistance. METHODS: In this phase 2 study, we evaluated the effect of letermovir (also known as AIC246), a new anti-CMV drug with a novel mechanism of action, on the incidence and time to onset of prophylaxis failure in CMV-seropositive recipients of allogeneic hematopoieticcell transplants from matched related or unrelated donors. From March 2010 through October 2011, we randomly assigned 131 transplant recipients in a 3:1 ratio to three sequential study cohorts according to a double-blind design. Patients received oral letermovir (at a dose of 60, 120, or 240 mg per day, or matching placebo) for 12 weeks after engraftment. The primary end point was all-cause prophylaxis failure, defined as discontinuation of the study drug because of CMV antigen or DNA detection, end-organ disease, or any other cause. Patients underwent weekly surveillance for CMV infection. RESULTS: The reduction in the incidence of all-cause prophylaxis failure was dose-dependent. The incidence of prophylaxis failure with letermovir, as compared with placebo, was 48% versus 64% at a daily letermovir dose of 60 mg (P = 0.32), 32% at a dose of 120 mg (P = 0.01), and 29% at a dose of 240 mg (P = 0.007). Kaplan-Meier time-to-onset profiles for prophylaxis failure showed a significant difference in the comparison of letermovir at a dose of 240 mg per day with placebo (P = 0.002). The safety profile of letermovir was similar to placebo, with no indication of hematologic toxicity or nephrotoxicity. CONCLUSIONS: Letermovir, as compared with placebo, was effective in reducing the incidence of CMV infection in recipients of allogeneic hematopoietic-cell transplants. The highest dose (240 mg per day) had the greatest anti-CMV activity, with an acceptable safety profile.