Pharmacokinetics of Emtricitabine, Tenofovir, and GS-9137 Following Coadministration of Emtricitabine/Tenofovir Disoproxil Fumarate and Ritonavir-Boosted GS-9137

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Abstract
To evaluate the potential for clinically relevant drug-drug interaction between emtricitabine/tenofovir disoproxil fumarate (FTC/TDF) and the ritonavir-boosted HIV integrase inhibitor GS-9137 (GS-9137/r). Healthy adults were administered FTC/TDF (200/300 mg once daily) for 7 days, followed by randomization to the order of receiving GS-9137/r (50/100 mg once daily) and GS-9137/r plus FTC/TDF in a crossover fashion under fed conditions for 10 days. Pharmacokinetic (PK) blood draws were performed on days 7, 17, and 27. Lack of PK alteration for FTC, tenofovir (TFV), and GS-9137 was defined as a 90% confidence interval (CI) for the estimated ratio of geometric least squares means (coadministration/alone) between 70% and 143% for the primary PK parameters: maximum observed plasma concentration (Cmax), area under the plasma concentration-time curve over dosing interval (AUCtau), and trough concentration (Ctau). Twenty-four of the 26 enrolled subjects completed the study with no serious adverse events or discontinuations attributable to adverse events. FTC, TFV, and GS-9137 PKs were unaffected during coadministration, with Cmax, AUCtau, and Ctau, meeting the protocol definition of equivalence and also the stricter bioequivalence criteria (90% CI: 80% to 125%). FTC and TFV PK parameters were comparable to historical values. There is no clinically relevant drug-drug interaction between FTC/TDF and GS-9137/r on their coadministration.