LAUSR

A fixed‐dose combination of tenofovir alafenamide (TAF) and emtricitabine (FTC) is available in 2 tablet strengths in Japan (FTC/TAF 200/10 mg and FTC/TAF 200/25 mg). These are used once daily in combination with other antiretroviral agents for the treatment of human immunodeficiency virus type 1 infection. The primary objective of this study was to investigate if there is any clinically relevant pharmacokinetic difference for TAF, tenofovir (TFV), and FTC between Japanese and non‐Japanese with historical data. Three treatment groups were set in the study; FTC/TAF 200/10 mg in combination with darunavir (DRV) 800 mg + ritonavir (RTV) 100 mg (treatment A) or DRV/cobicistat (COBI) 800/150 mg (treatment B) and FTC/TAF 200/25 mg alone (treatment C). Especially for treatment C, it was designated for another purpose to evaluate the pharmacokinetic boosting effects of RTV and COBI on TAF bioavailability. As a result, the mean exposure of TAF among treatment groups was 125 to 154 ng/mL for Cmax and 119 to 179 ng·h/mL for AUCinf, which were comparable with the historical data in non‐Japanese. The exposures of TFV and FTC were also consistent with the historical data. Therefore, no clinically relevant pharmacokinetic differences for TAF, TFV, and FTC were observed between Japanese and non‐Japanese. Boosting effects of RTV and COBI on TAF bioavailability were slightly lower than we expected, less than a 2.5‐fold increase, but it was within the range of exposures associated with efficacy and safety in phase 3 studies. Therefore, it was not considered clinically relevant.