Effect of Rifampin on the Single-Dose Pharmacokinetics of Oral Cabotegravir in Healthy Subjects [PublishAheadOfPrint]

Introduction: Drug-drug interactions between antiretroviral medications and rifampin complicate the treatment of HIV and tuberculosis coinfection. This study evaluated the effect of rifampin on the pharmacokinetics of oral cabotegravir, an integrase strand transfer inhibitor being investigated for long-acting treatment and prevention of HIV-1 infection.

Methods: This was a phase I, single-center, open-label, fixed-sequence crossover study in healthy adults. The objective was to evaluate the effect of steady-state rifampin on the single-dose plasma pharmacokinetics of cabotegravir. Subjects received a single oral dose of cabotegravir 30 mg on Day 1 followed by plasma sampling on Days 1 to 8. Treatment with once-daily oral rifampin 600 mg occurred on Days 8 to 28. Subjects received a second dose of cabotegravir 30 mg on Day 21 followed by pharmacokinetic sampling on Days 21 to 28.

Results: Fifteen subjects were enrolled and completed the study. Rifampin decreased cabotegravir area under the concentration-time curve over infinite time and half-life by 59% and 57%, respectively, whereas oral clearance was increased by 2.4-fold. The maximum plasma concentration of cabotegravir was unaffected by coadministration with rifampin. All adverse events were mild in severity, with chromaturia attributed to rifampin observed in all subjects.

DISCUSSION: Rifampin induction of cabotegravir metabolism resulted in increased cabotegravir oral clearance and significantly decreased cabotegravir exposures. Rifampin is expected to increase cabotegravir clearance following long-acting injectable administration. Concomitant administration of rifampin with oral and long-acting formulations of cabotegravir is not recommended currently without further study.

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