Letermovir Versus Valganciclovir to Prevent Human Cytomegalovirus Disease in Kidney Transplant Recipients (MK-8228-002)

Inclusion Criteria:

- Have a documented negative serostatus for CMV within 180 days prior to randomization.

- Anticipate receiving a primary or secondary allograft kidney from a CMV IgG
seropositive (D+) donor at the time of screening AND have received a primary or
secondary allograft kidney from a documented D+ donor at the time of randomization.

- Be within 0 (i.e. day of transplantation) to 7 days (inclusive) post-kidney transplant
at the time of randomization.

- Males agree to use contraception during the treatment period, and for at least 90 days
after the last dose of study treatment, and refrain from donating sperm during this
period.

- Female is not pregnant, not breastfeeding, and is not a woman of childbearing
potential (WOCBP), OR if a WOCBP, agrees to follow the contraception guidance during
the treatment period and for at least 90 days after the last dose of study treatment.

Exclusion Criteria:

- Has received a previous solid organ transplant or hematopoietic stem cell transplant
(HSCT). Note: Participants who have received a prior primary allograft kidney may be
enrolled, provided that all other inclusion/exclusion criteria are met.

- Is a multi-organ transplant recipient (e.g. kidney-pancreas). Double kidney transplant
recipients (i.e. transplant of two kidneys from the same donor to the same recipient
simultaneously) will be excluded.

- Has a history of CMV disease or suspected CMV disease within 6 months prior to
randomization.

- Has suspected or known hypersensitivity to active or inactive ingredients of LET
formulations, VGCV, GCV, and/or ACV formulations.

- Is on dialysis at the time of randomization.

- Has Child-Pugh Class C severe hepatic insufficiency at screening.

- Has both moderate hepatic insufficiency AND moderate-to-severe renal insufficiency at
screening.

- Has any uncontrolled infection on the day of randomization.

- Has documented positive results for human immunodeficiency virus antibody (HIV-Ab)
test at any time prior to randomization, or for hepatitis C virus antibody (HCV-Ab)
and with detectable HCV ribonucleic acid (RNA) within 90 days prior to randomization,
or hepatitis B surface antigen (HBsAg) within 90 days prior to randomization.

- Requires mechanical ventilation, or is hemodynamically unstable, at the time of
randomization.

- Has a history of malignancy ≤5 years prior to signing informed consent.

- Is pregnant or expecting to conceive, is breastfeeding, or plans to breastfeed from
the time of consent through at least 90 days following cessation of study therapy.

- Is expecting to donate eggs or sperm starting from the time of consent through at
least 90 days following cessation of study therapy.

- Has received within 30 days prior to randomization or plans to receive during the
study any of the following anti-CMV IgG antibody treatment or anti-CMV drug therapy
including the following: Cidofovir, CMV hyper-immune globulin, Any investigational CMV
antiviral agent/biologic therapy.

- Has received within 7 days prior to randomization or plans to receive during the study
any of the following anti-CMV drug therapy: LET, GCV, VGCV, Foscarnet, ACV,
Valacyclovir, Famciclovir.

- Is a user of recreational or illicit drugs or has had a recent history (within the
last year) of drug or alcohol abuse or dependence.

- Is currently participating or has participated in a study with an unapproved
investigational compound or device within 28 days, or 5× half-life of the
investigational compound whichever is longer, of initial dosing on 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.