Outcomes by Sex Following Treatment Initiation With Atazanavir Plus Ritonavir or Efavirenz With Abacavir/Lamivudine or Tenofovir/Emtricitabine

Abstract

BACKGROUND: We aimed to evaluate treatment responses to atazanavir plus ritonavir (ATV/r) or efavirenz (EFV) in initial antiretroviral regimens among women and men, and determine if treatment outcomes differ by sex. METHODS: We performed a randomized trial of open-label ATV/r or EFV combined with abacavir/lamivudine (ABC/3TC) or tenofovir/emtricitabine (TDF/FTC) in 1857 human immunodeficiency virus type 1-infected, treatment-naive persons enrolled between September 2005 and November 2007 at 59 sites in the United States and Puerto Rico. Associations of sex with 3 primary study endpoints of time to virologic failure, safety, and tolerability events were analyzed using Cox proportional hazards models. Model-based population pharmacokinetic analysis was performed using nonlinear mixed effects modeling (NONMEM version VII). RESULTS: Of 1857 participants, 322 were women. Women assigned to ATV/r had a higher risk of virologic failure with either nucleoside reverse transcriptase inhibitor backbone than women assigned to EFV, or men assigned to ATV/r. The effects of ATV/r and EFV upon safety and tolerability risk did not differ significantly by sex. With ABC/3TC, women had a significantly higher (32%) safety risk compared to men; with TDF/FTC, the safety risk was 20% larger for women compared to men, but not statistically significant. Women had slower ATV clearance and higher predose levels of ATV compared to men. Self-reported adherence did not differ significantly by sex. CONCLUSIONS: This is the first randomized clinical trial to identify a significantly earlier time to virologic failure in women randomized to ATV/r compared to women randomized to EFV. This finding has important clinical implications given that boosted protease inhibitors are often favored over EFV in women of childbearing potential. CLINICAL TRIALS REGISTRATION: NCT00118898.