Per Ljungman, MD, PhD, Karolinska Institutet, Stockholm, Sweden, highlights the successful use of letermovir, a DNA terminase complex inhibitor, as a new treatment option for cytomegalovirus (CMV) in bone marrow transplant patients, largely through primary prophylaxis. Prof. Ljungman explains how the mechanism of action of letermovir is different to previously used antiviral drugs for CMV and was licensed after a large Phase III randomized, double-blind, placebo-controlled clinical trial in 2018. The study published in The New England Journal of Medicine defined the secondary endpoint as mortality and primary analysis determined a significant decrease in mortality six months post-transplant. However, Prof. Ljungman explains how the benefit only became significant after 48 weeks, when compared to 26 weeks, due to the enhanced ability to control classical risk factors for CMV. This interview was recorded via an online conference call with The Video Journal of Hematological Oncology (VJHemOnc).