A Clinical Study of Letermovir (MK-8228) in Children and Adolescents Who Receive a Kidney Transplant (KT) (MK-8228-077)

A Phase 1, Open-label, Single-arm Study to Evaluate the Pharmacokinetics and Safety of Letermovir in Pediatric Kidney Transplant (KT) Recipients Less Than 18 Years of Age and Weighing Less Than 40 Kilograms

Researchers are looking for a way to prevent cytomegalovirus (CMV) in children and adolescents who receive a kidney transplant (KT) and weigh less than 40 kilograms (88.2 pounds). The goals of the study are to:

• Learn what happens to letermovir in the body over time
• Learn about the safety of letermovir and if participants tolerate it

Inclusion Criteria:

The main inclusion criteria include but are not limited to the following:

• Is a recipient of a primary or secondary allograft kidney
• Is at least 4 weeks posttransplant and not more than 52 weeks posttransplant at the time of enrollment (Day 1) and is being managed per local standard of care
• Has stable kidney function posttransplant
• Has undetectable CMV deoxyribonucleic acid (DNA) from a plasma or whole blood sample collected within 14 days prior to enrollment
• Must be able to take (as assessed by the investigator) letermovir tablets or oral pellets by mouth, or via gastrostomy or nasogastric tube (oral pellets only)
• Does not have a condition that may interfere with the absorption of oral medication (e.g., vomiting, diarrhea, or a malabsorptive condition) from the day of enrollment (Day 1) until the intensive pharmacokinetics (IPK) sampling is completed
• Weighs ≥2.5 and <40 kg at enrollment (Day 1)

Exclusion Criteria:

The main exclusion criteria include but are not limited to the following:

• Has CMV disease or suspected CMV disease between screening and enrollment
• Is on dialysis or plasmapheresis at the time of enrollment
• Has evidence of CMV viremia at any time from screening until the time of enrollment
• Has Child-Pugh B or C hepatic insufficiency within 14 days before enrollment
• Is a multi-organ transplant recipient (e.g., kidney-pancreas)
• Has any uncontrolled infection on the day of enrollment
• Requires mechanical ventilation, or is hemodynamically unstable, at the time of enrollment
• Has received or is receiving protocol-specified prohibited medications