Merck Initiates Phase III Study of Letermovir, an Investigational Antiviral for Prevention of CMV Infection in High-Risk Bone Marrow Transplant Patients

Merck (MSD outside the US and Canada) has announced that the first patient has been enrolled in a global Phase III clinical study of letermovir (MK-8228), an investigational antiviral agent. The multicenter, randomised, placebo-controlled study will evaluate the efficacy and safety of letermovir for the prevention of clinically-significant cytomegalovirus (CMV) infection in adult (18 years and older) CMV-seropositive recipients of allogeneic hematopoietic stem cell transplants.

“There remains a need for additional therapeutic options in the prevention of CMV infection in high-risk patients,” said Dr Michele Trucksis, executive director, Infectious Diseases, Merck Research Laboratories. “Merck is pleased to initiate this global Phase III study with letermovir.”

“This study marks a very important step in the development of letermovir and for AiCuris as licensor of this compound,” said Prof. Helga Rübsamen-Schaeff, CEO of AiCuris. “We are very excited to have reached this stage and look forward to the results.”

In the study, letermovir will be administered once daily, either as an oral tablet or IV formulation, for 14 weeks after transplant. The dose will be 240 mg once daily for participants receiving concomitant cyclosporin A and 480 mg once daily for participants not receiving cyclosporin A. The primary outcome measure of the study will be the percentage of participants with clinically-significant CMV infection through 24 weeks after transplant who were administered letermovir compared to placebo.

Merck expects approximately 540 patients will be enrolled in the study at more than 70 centers in 20 countries, including the US. The estimated study completion date is July 2017.