List of products in the National Drug Code with proprietary name . This medication is used to prevent disease caused by a virus called cytomegalovirus (CMV) in people who have received a bone marrow transplant. CMV disease can lead to serious infections in the body, including an infection in the eye, called CMV retinitis, that can cause blindness. Letermovir is an anti-viral drug. It works by stopping the growth of the virus.