PREVYMIS, known generically as letermovir, is an antiviral medication designed specifically to prevent cytomegalovirus (CMV) infection in individuals who have received an allogeneic hematopoietic stem cell transplant (HSCT). CMV is a common virus that can cause serious illness or even be life-threatening in people with weakened immune systems, including transplant recipients. PREVYMIS works by inhibiting the CMV DNA terminase complex, an essential component for viral replication, thereby preventing the multiplication of the virus in the body. It is typically administered either orally or through intravenous infusion, depending on the patient's condition and healthcare provider's recommendation. Approved by regulatory authorities such as the FDA, PREVYMIS has become a critical tool in the management of CMV risk in vulnerable patient populations.