BackgroundMaraviroc (MVC) is a candidate drug for HIV preexposure prophylaxis (PrEP).ObjectiveTo assess the safety and tolerability of MVC-containing PrEP over 48 weeks in U.S. women at risk for HIV infection.DesignPhase 2 randomized, controlled, double-blinded study of 4 antiretroviral regimens used as PrEP. (ClinicalTrials.gov: NCT01505114).Setting12 clinical research sites of the HIV Prevention Trials Network and AIDS Clinical Trials Group.ParticipantsHIV-uninfected women reporting condomless vaginal or anal intercourse with at least 1 man with HIV infection or unknown serostatus within 90 days.InterventionMVC only, MVC-emtricitabine (FTC), MVC-tenofovir disoproxil fumarate (TDF), and TDF-FTC (control).MeasurementsAt each visit, clinical and laboratory (including HIV) assessments were done. Primary outcomes were grade 3 and 4 adverse events and time to permanent discontinuation of the study regimen. All randomly assigned participants were analyzed according to their original assignment.ResultsAmong 188 participants, 85% completed follow-up, 11% withdrew early, and 4% were lost to follow-up; 19% discontinued their regimen prematurely. The number discontinuing and the time to discontinuation did not differ among regimens. Grade 3 or 4 adverse events occurred in 5 (MVC), 13 (MVC-FTC), 9 (MVC-TDF), and 8 (TDF-FTC) participants; rates did not differ among regimens. One death (by suicide) occurred in the MVC-TDF group but was judged not to be related to study drugs. Of available plasma samples at week 48 (n = 126), 60% showed detectable drug concentrations. No new HIV infections occurred.LimitationsParticipants were not necessarily at high risk for HIV infection. The regimen comprised 3 pills taken daily. The study was not powered for efficacy.ConclusionMaraviroc-containing PrEP regimens were safe and well-tolerated compared with TDF-FTC in U.S. women. No new HIV infections occurred, although whether this was due to study drugs or low risk in the population is uncertain. Maraviroc-containing PrEP for women may warrant further study.Primary Funding SourceNational Institutes of Health.