A Phase 3 Study of Brincidofovir Versus Valganciclovir for the Prevention of Cytomegalovirus

Inclusion Criteria Subjects must have met all of the following criteria, as applicable, to be eligible to participate in this study: 1. Were male or female kidney transplant recipients who were ≥18 years of age (subject to local law/practice for clinical trial participation) and ≤14 days following their first or second renal allograft. 2. Were at high risk of cytomegalovirus (CMV) infection, which for the purposes of this study, was defined as CMV-seropositive recipients who received lymphocyte depleting induction treatment with antithymocyte globulin (Thymoglobulin® or Atgam®) prior to or during the qualifying transplant. 3. Had an estimated glomerular filtration rate of \>10 mL/min (Cockcroft-Gault equation) at screening based on local laboratory results. 4. Were CMV viremia negative (i.e., "not detected") as measured by the designated central virology laboratory using the Roche COBAS® AmpliPrep/COBAS® TaqMan® CMV Test no more than 5 days prior to subject randomization, and at all prior assessments performed since transplant under local standard of care. 5. Were able to ingest, absorb, and tolerate tablets. 6. If male, was willing to use an acceptable contraceptive method(s) throughout the duration of his participation in the study, i.e., through Week 24. 7. If female of childbearing potential, i.e., not postmenopausal or surgically sterile, was willing to use 2 acceptable contraceptive methods, 1 of which must have been a barrier method, throughout the duration of her participation in the study, i.e., through Week 24. 8. Were willing and able to provide informed consent. 9. Were willing and able to participate in all required study activities for the entire duration of the study (i.e., through Week 24). Exclusion Criteria Subjects who met any of the following criteria were not eligible to participate in this study: 1. Weighed ≤50 kg (110 lbs) or ≥120 kg (265 lbs). 2. Were pregnant or breastfeeding or intended to conceive during the study period (i.e., through Week 24). 3. Received a stem cell transplant or solid organ transplant other than a kidney transplant. 4. Had suspected CMV disease (either syndrome or tissue-invasive disease) or detectable CMV viremia by the central virology laboratory prior to the first dose of study drug. 5. Had a history of CMV disease (either syndrome or tissue-invasive disease) within 6 months prior to the first dose of study drug. 6. Had an absolute neutrophil count of \< 500 cells/μL, platelet count of \< 25,000 platelets/μL, or hemoglobin of \< 8 g/dL at screening. 7. Had hypersensitivity (not including renal dysfunction or an eye disorder) to valganciclovir (vGCV), ganciclovir (GCV), cidofovir (CDV), or brincidofovir (BCV) or their excipients. 8. Had received (or who are anticipated to need treatment with) any of the following: * GCV, vGCV, foscarnet, intravenous CDV, or any other anti-CMV therapy (including CMV immune globulin, cell-based therapies, and investigational anti-CMV drugs, e.g., leflunomide, letermovir \[previously AIC246\], or maribavir) at any time posttransplant; * Any anti-CMV vaccine at any time; * Any other investigational drug within 14 days prior to the first dose of study drug (unless prior approval had been received from the Chimerix Medical Monitor or designee); or * Prior treatment with BCV at any time. \[Note: An "investigational drug" was defined as any drug that was not approved for any indication by the FDA (or appropriate regulatory authority).\] 9. Received acyclovir (ACV) orally at \>2000 mg total daily dose (TDD) or intravenously at \>15 mg/kg TDD, valacyclovir (vACV) at \> 3000 mg TDD on the first dose of study drug or were anticipated to receive any of these drugs at the doses described after the first dose of study drug. 10. Were infected with HIV, hepatitis B virus (HBV), and/or hepatitis C virus (HCV), had evidence of active viral replication within 6 months prior to screening, as demonstrated by detectable HIV or HCV RNA, or detectable HBV DNA in blood, plasma or serum. 11. Had severe vomiting, diarrhea or malabsorption syndrome on or prior to the first dose of study drug. 12. Had gastrointestinal (GI) disease that would have, in the judgment of the investigator, precluded the subject from taking or absorbing oral medication (e.g., gastroparesis, diabetic autonomic neuropathy affecting the GI tract, clinically active Crohn's disease, ischemic colitis, moderate or severe ulcerative colitis, small bowel resection, ileus, or any condition expected to require abdominal surgery during the course of study participation). 13. Had serum alanine aminotransferase or aspartate aminotransferase concentrations \>5 x the upper limit of normal (ULN). 14. Had total serum bilirubin \>2 x the ULN and direct bilirubin \>1.5 x the ULN. 15. Had moderate (Class B) to severe (Class C) hepatic dysfunction according to the Child-Pugh Turcotte scoring system. 16. Received or would require digoxin or ketoconazole therapy (other than topical formulations) during the treatment phase of the study. 17. Had active malignancies (with the exception of basal cell carcinoma). 18. Had a serious psychiatric, medical disorder, including abnormal laboratory values, that would have, in the judgment of the investigator, put the subject at increased risk by participating in the study, or would have interfered with the conduct of study.