Merck & Co., known as MSD, announced results of the pivotal Phase 3 clinical study of letermovir, an investigational antiviral medicine for the prevention of clinically-significant cytomegalovirus (CMV) infection in adult (18 years and older) CMV-seropositive recipients of an allogeneic hematopoietic stem cell transplant (HSCT), also known as bone marrow transplant (BMT). The study met its primary efficacy endpoint, showing that significantly fewer patients with undetectable CMV DNA at the start of study treatment developed clinically significant CMV infection through Week 24 post-HSCT (using a non-complete equals failure approach, in which patients who discontinued from the study prior to Week 24 post-transplant or had a missing outcome at Week 24 post-transplant were counted as failures). In the study, letermovir prophylaxis was associated with lower all-cause mortality through Week 24 post-HSCT. Based on these results, Merck plans to submit regulatory applications for the approval of letermovir in the United States and European Union in 2017.
Results from the study were presented for the first time at the BMT Tandem Meetings, the combined annual meetings of the Center for International Blood & Marrow Transplant Research (CIBMTR) and the American Society for Blood and Marrow Transplantation (ASBMT), in Orlando, Florida, USA.
“These results showed that letermovir prophylaxis beginning after HSCT and continuing through Day 100 post-transplant significantly reduced CMV infection requiring preemptive antiviral therapy through Week 24 post-transplant,” said Dr. Francisco M. Marty, associate professor of medicine at Harvard Medical School and attending physician in transplant and oncology infectious diseases at Dana-Farber Cancer Institute and Brigham and Women’s Hospital, who presented the data. “In this study, letermovir was associated with lower all-cause mortality. Based on these findings, letermovir as primary prophylaxis of CMV infection represents a potential new strategy for the prevention of CMV in this high-risk patient population.”
CMV is the most common clinically significant viral infection in allogeneic HSCT recipients. HSCT is a medical procedure in the field of hematologic oncology, most often performed for the treatment of patients with certain cancers of the blood or bone marrow, such as leukemia and lymphoma. While preemptive therapy (treatment when CMV DNA is detected in the blood) with antiviral medicines can reduce the incidence of CMV disease, CMV reactivation post-HSCT is associated with higher mortality despite the use of preemptive therapy.
“There is an unmet need for therapeutic options in the prevention of CMV infection in hematopoietic stem cell transplant recipients,” said Dr. Nicholas Kartsonis, vice president, infectious disease clinical research, Merck Research Laboratories. “As part of Merck’s long-standing commitment to developing innovative approaches in the fight against infectious diseases, we look forward to submitting regulatory applications for letermovir this year.”