letermovir treatment in pediatric participants following allogeneic haematopoietic stem cell transplantation (hsct) (mk-8228-030)

Conditions: Cytomegalovirus (CMV) Infection

Summary: the primary objective of this study is to evaluate the pharmacokinetics (pk) of letermovir (let) in pediatric participants. participants will be enrolled in the following 3 age groups: age group 1: from 12 to \<18 years of age (adolescents); age group 2: from 2 to \<12 years of age (children); and age group 3: from birth to \<2 years of age (neonates, infants and toddlers). all participants will receive open label let for 14 weeks (\~100 days) post-transplant, with doses based on body weight and age.


Eligibility criteria:
inclusion criteria: * all participants 12 to \<18 years old must have documented positive cmv serostatus (cmv igg seropositive) for the recipient (r+) within 90 days prior to enrollment. participants from birth to \<12 years old must have documented positive cmv serostatus (cmv igg seropositive) for the recipient (r+) within 90 days prior to enrollment and/or the donor (d+); the donor serostatus should be documented within 1 year prior to enrollment. * is the recipient of a first allogeneic hsct (bone marrow, peripheral blood stem cell, or cord blood transplant). * has undetectable cmv dna from a plasma or whole blood sample collected within 5 days prior to enrollment. * is within 28 days post-hsct at the time of enrollment. * females are not pregnant, not breastfeeding,and is not a woman of childbearing potential (wocbp); or is a wocbp who agrees to follow the contraceptive guidance during the treatment period and for at least 28 days after the last dose of study intervention. * participants from 2 to \<18 years of age must not be on concomitant cyclosporin a (csa), and must be able to take let tablets or the oral granules (either by mouth or via g tube/ng tube), provided the participant 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 until the intensive pk sampling is completed in these participants. * for participants 2 \<12 years old their weight should be at least 10 kg; for participants from birth to \<2 years old their weight should be at least 2.5 kg and less than or equal to 15 kg at the time of enrollment. exclusion criteria: * has received a previous allogeneic hsct (note: receipt of a previous autologous hsct is acceptable). * has a history of cmv end-organ disease within 6 months prior to enrollment. * has evidence of cmv viremia at any time from either signing of the icf or the hsct procedure, whichever is earlier, until the time of enrollment. * has suspected or known hypersensitivity to active or inactive ingredients of let formulations. * has severe hepatic insufficiency within 5 days prior to enrollment. * is a) on renal replacement therapy (eg, hemodialysis, peritoneal dialysis) or b) has end-stage renal impairment. * has both moderate hepatic insufficiency and moderate-to-severe renal insufficiency. * has an uncontrolled infection on the day of enrollment. * requires mechanical ventilation or is hemodynamically unstable at the time of enrollment. * has a documented positive result for a human immunodeficiency virus antibody (hivab) test at any time prior to enrollment, or for hepatitis c virus antibody (hcv-ab) with detectable hcv rna, or hepatitis b surface antigen (hbsag) within 90 days prior to enrollment. * has active solid tumor malignancies with the exception of localized basal cell or squamous cell skin cancer or the condition under treatment (e.g. lymphomas). * has a preexisting cardiac condition a) for which the patient is currently being treated or b) which required hospitalization within the last 6 months or c) that may be expected to recur during the course of the trial. * has received within 7 days prior to screening any of the following: ganciclovir; valganciclovir; foscarnet; acyclovir; valacyclovir; famciclovir. * has received within 30 days prior to screening of any of the following: cidofovir; cmv immunoglobulin; any investigational cmv antiviral agent/biologic therapy; rifampin and other strong inducers (such as phenytoin, carbamazepine, st john's wort (hypericum perforatum), rifabutin and phenobarbital) and moderate inducers such as nafcillin, thioridazine, modafinil and bosentan. * has received let at any time prior to enrollment in this study. * is currently participating or has participated in a study with an unapproved investigational compound or device within 28 days, or 5x half-life of the investigational compound (excluding monoclonal antibodies), whichever is longer, of initial dosing in this study. * has previously participated in this study or any other study involving let. * has previously participated or is currently participating in any study involving administration of a cmv vaccine or another cmv investigational agent, or is planning to participate in a study of a cmv vaccine or another cmv investigational agent during the course of this study. * is pregnant or expecting to conceive, is breastfeeding, or plans to breastfeed from the time of consent through 28 days after the last dose of study intervention. * is expecting to donate eggs starting from the time of consent through 28 days after the last dose of study intervention. * has clinically relevant drug or alcohol abuse within 12 months of screening that may interfere with participant treatment, assessment, or compliance with the protocol, as assessed by the investigator.