Letermovir (Prevymis™) is an orally or intravenously administered 
cytomegalovirus (CMV) DNA terminase complex inhibitor being developed by Merck & 
Co., Inc., under a global license from AiCuris Anti-infective Cures GmbH. 
Letermovir has been approved in Canada and the USA for the prophylaxis of CMV 
infection and disease in adult CMV-seropositive recipients of an allogeneic 
haematopoietic stem cell transplant (HSCT). In addition, letermovir has received 
a positive opinion from the European Medicines Agency's Committee for Medicinal 
Products for Human Use, and is under review in several countries, including 
Japan. This article summarizes the milestones in the development of letermovir 
leading to its first global approval in Canada as well as the USA for the 
prophylaxis of CMV infection and disease in adult CMV-seropositive recipients of 
an allogeneic HSCT.