Sex differences in atazanavir pharmacokinetics and associations with time to clinical events: AIDS Clinical Trials Group Study A5202

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ObjectivesIt is uncertain whether HIV-1 antiretroviral exposure and clinical response varies between males and females or different race/ethnic groups. We describe ritonavir-enhanced atazanavir pharmacokinetics in relation to virological failure, safety and tolerability in treatment-naive individuals to investigate potential differences.MethodsPlasma samples were collected from participants in AIDS Clinical Trials Group Study A5202 for measurement of antiretroviral concentrations. Individual estimates of apparent oral clearance of atazanavir (L/h) were calculated from a one-compartment model and divided into tertiles as slow (<7), middle (7 to <9; reference group) and fast (≥9). Associations between atazanavir clearance and clinical outcomes were estimated with a hazard ratio (HR) from Cox proportional hazards models. Interactions between atazanavir clearance and sex, race/ethnicity and NRTIs were investigated for each of the outcomes.ResultsAmong 786 participants, average atazanavir clearance was slower in females (n = 131) than males (n = 655). Atazanavir clearance was associated with time to virological failure (P = 0.053) and this relationship differed significantly by sex (P = 0.003). Females in the fast atazanavir clearance group had shorter time to virological failure (HR 3.49; 95% CI 1.24–9.84) compared with the middle (reference) atazanavir clearance group. Among males, the slow atazanavir clearance group had a higher risk of virological failure (HR 2.10; 95% CI 1.16–3.77).ConclusionsAtazanavir clearance differed by sex. Females with fast clearance and males with slow clearance had increased risk of virological failure.

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