Evaluating the Safety and Pharmacokinetics of Maraviroc in HIV-1-Exposed Infants at Risk of Acquiring HIV-1 Infection

Inclusion Criteria: * Mother was of legal age to provide independent informed consent for research participation and was willing and able to provide written informed consent for her and her infant's participation in this study. * Mother had confirmed HIV-1 infection based on testing of two samples collected at different time points. More information on this criterion can be found in the protocol. * At entry, infant met EFV exposure requirements, based on mother's report and confirmed by medical records if available, as follows: * For Cohort 1, Stratum 1A: Infant born to a mother who did not receive EFV during the eight weeks immediately prior to delivery. Note: Breastfeeding and formula feeding infants were eligible for this stratum. * For Cohort 1, Stratum 1B: Infant born to a mother who received EFV for a minimum of two weeks immediately prior to delivery. Note: Breastfeeding and formula feeding infants were eligible for this stratum. * For Cohort 2, Stratum 2A: Infants born to a mother who did not receive EFV during the eight weeks immediately prior to delivery and if breastfeeding, mother was not receiving maternal EFV. Note: Breastfeeding and formula feeding infants were eligible for this stratum. * For Cohort 2, Stratum 2B: Breastfeeding infants born to a mother who received EFV for a minimum of two weeks immediately prior to delivery, intended to breastfeed for a minimum of six weeks and continued to receive maternal EFV while breastfeeding. Note: Only breastfeeding infants were eligible for this stratum. * At birth, infant's estimated gestational age was at least 37 weeks. Note: If gestational age at birth is not documented in the infant's available birth records, study staff may assess gestational age at the earliest possible opportunity during the screening period and use this assessment for purposes of eligibility determination. * At birth, infant's weight was at least 2 kg. Note: If weight at birth is not documented in the infant's available birth records, study staff may assess infant weight at the earliest possible opportunity during the screening period and use this assessment for purposes of eligibility determination. * At entry, infant was less than or equal to 3 days old. * At entry, infant had the following lab values: * Grade 0 alanine transaminase (ALT) (normal) * Less than or equal to Grade 1 aspartate aminotransferase (AST) and total bilirubin * Less than or equal to Grade 2 hemoglobin, white blood cell counts, platelet counts * At entry, infant had initiated antiretroviral prophylaxis that did not include a potent CYP3A4 inhibitor or inducer. See the protocol for more information. * At entry, infant was assessed by the site investigator or designee as generally healthy based on review of available medical records, other available medical history information, and physical examination findings. * Born after singleton delivery (not after multiple birth). Exclusion Criteria: * Infant had any other condition that, in the opinion of the site investigator or designee, would make participation in the study unsafe, complicate interpretation of study outcome data, or otherwise interfere with achieving the study objectives; for example, severe congenital malformation, other medical condition, or clinically significant finding from physical examination. * At entry, any positive infant HIV nucleic acid test result (results are not required to be available prior to entry but any positive results obtained prior to entry are exclusionary). * At entry, infant or breastfeeding mother was receiving any disallowed medication listed in the protocol. * Mother received maraviroc during pregnancy.