Short Communication: Bioequivalence of Tenofovir and Emtricitabine After Coencapsulation with the Proteus Ingestible Sensor.

: Adherence to tenofovir disoproxil fumarate/emtricitabine (TDF/FTC, Truvada®) is the primary determinant of HIV pre-exposure prophylaxis (PrEP) efficacy. Despite its importance, limitations exist in current methods of adherence quantification, restricting their implementation in the clinic. Proteus Discover (Proteus Digital Health®) can measure the time of each dose using an ingestible sensor that is coencapsulated with medication. In this study, the bioequivalence of coencapsulated TDF/FTC with the Proteus sensor was compared relative to unencapsulated drug. This was a 1:1 randomized cross-over study in which healthy participants received a single dose of unencapsulated and coencapsulated TDF/FTC. A 14-day washout separated each period. Blood was collected at predose and at 0.25, 0.5, 1, 2, 4, 6, 10, 24, 48, and 72 h postdose. Plasma concentrations were determined by LC-MS/MS methods, with a 10 ng/mL lower limit of quantitation (LLOQ) for both tenofovir (TFV) and FTC. Noncompartmental analysis was carried out with Phoenix® WinNonlin® for maximum concentrations (Cmax), area under the concentration-time curve from time 0 to the last measured time point (AUClast) and AUC extrapolated to infinity (AUCinf). Geometric mean ratios were calculated for each parameter and bioequivalence was defined as the 90% confidence interval (CI) of each ratio being within 80%-125%. Twenty-four participants (11 males; 19 white, 3 African American, and 2 Hispanic) completed both visits. Mean ± SD age was 28 ± 4 years and weight was 74 ± 14 kg. The 90% CIs for TFV Cmax, AUClast, and AUCinf were 89%-119%, 94%-111%, and 96%-111%, respectively. The 90% CIs for FTC Cmax, AUClast, and AUCinf were 96%-120%, 96%-108%, and 96%-108%, respectively. Bioequivalence was observed for the coencapsulation of TDF/FTC with the Proteus ingestible sensor, as assessed by a rigorously conducted pharmacokinetic study. Future studies will evaluate the utility and effectiveness of the sensor system as a tool to monitor PrEP adherence in clinical settings.