Letermovir for Secondary Prophylaxis in Solid Organ Transplant Recipients

This is a research study to test the tolerability and clinical effectiveness of the study drug, Letermovir (LET), when used as secondary prophylaxis following treatment of Cytomegalovirus (CMV) infection and disease in a solid organ transplant recipient. This study is an open label trial in which Letermovir will be prescribed to prevent the recurrence of CMV infection and disease in a solid organ transplant recipient following treatment of CMV infection or disease.

Inclusion Criteria: 1. Adult (\> 18 years old) solid organ transplant recipients (heart, kidney or liver patients) recovering from treated CMV disease in whom the clinician deems that the patient need secondary prophylaxis and in whom written informed consent is obtained. 2. Patient able to participate with follow up for 6 months 3. Not enrolled in competing clinical trials Exclusion Criteria: 1. Patients with creatinine clearance less than 10 ml per min at time of enrollment 2. Hypersensitivity to letermovir or has a CMV isolate which is known to be resistant to letermovir based on prior testing 3. On CVVH or renal dialysis at the time of enrollment 4. Has Child Pugh Class C severe hepatic insufficiency at screening. 5. Has both moderate hepatic insufficiency AND moderate to severe renal insufficiency at screening. Note: Moderate hepatic insufficiency is defined as Child Pugh Class B (Appendix 8); moderate to severe renal insufficiency is defined as CrCl \