The study enrolled 540 subjects who received letermovir once daily either in an oral tablet or intravenous formulation.
Therapy was begun as early as the same day as the allogeneic hematopoietic stem cell transplant and no later than 28 days post-transplant and continued for about 100 days.
The primary endpoint was the percentage of participants with clinically-significant CMV infection through 24 weeks after transplant.
Merck Research Laboratories senior vice president of clinical development Roy Baynes said: “There is an unmet need for therapeutic options in the prevention of CMV infection in high-risk allogeneic hematopoietic stem cell transplant recipients.
“Merck is pleased this pivotal Phase 3 study with letermovir met its primary endpoint.”
The company plans to present the study’s results at a future scientific conference.
Letermovir inhibits viral replication by targeting the viral terminase complex. It has orphan drug status in the US, Europe and Japan.
The US Food and Drug Administration also granted Fast Track designation to letermovir.
Merck acquired global rights to letermovir in 2012 in a deal with AiCuris GmbH & Co KG.