3rd International AIDS Society Conference on HIV Pathogenesis and Treatment Rio de Janeiro - July 24 - 27, 2005

PHARMACOKINETIC INTERACTION BETWEEN TENOFOVIR AND ATAZANAVIR IN HEALTHY SUBJECTS

IAS Conf HIV Pathog Treat 2005 Jul 24-27;3rd: Abstract No. WePe3.3C07

Agarwala S., Eley T., Child M., Wang Y., Hughes E., Grasela D.
Bristol-Myers Squibb Pharmaceutical Research Institute, Princeton, NJ, United States of America

INTRODUCTION: Atazanavir (ATV), a potent, once-daily PI, has been extensively studied, including Phase III trials of naïve patients versus a standard of care regimen containing efavirenz and treatment experienced patients versus a standard of care regimen containing lopinavir/ritonavir. Simultaneous administration of ATV 400 and tenofovir (TDF) 300 QD in healthy subjects resulted in 25% and 40% decrease in ATV AUC and Cmin, respectively, with a 25% increase in TDF exposure. This finding was unexpected as ATV is metabolized by CYP3A4 and TDF is not. The objective was to examine alternative dosing strategies for TDF/ATV based HAART regimens.

METHODS: In an open label study, healthy subjects were randomized to receive TDF 300 QD for 7 days (d) in the AM (A) or PM (B) (N=9 each). After a washout, all subjects (N=18) received ATV 400 QD AM (C), followed by ATV 400 AM + TDF 300 PM temporally separated (D) and ATV 600 + TDF 300 simultaneously in the AM (E), each for 6d. ATV/TDF were administered with a light meal. Blood samples were collected for steady-state PK.

RESULTS: No new or unexpected adverse effects attributed to study drugs were noted. Ratios of geometric means (90% C.I.) for ATV and TDF derived from a general linear model are:

CONCLUSIONS: Neither of the dosing regimens employed in this study provided comparable exposures of either ATV or TDF, relative to either ATV 400 mg QD or TDF 300 mg QD.

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050724
Clinical | WePe3.3C07 | Sangeeta Agarwala
Drug Interactions

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