Short Communication: Bioequivalence of Tenofovir Component of Tenofovir/Rilpivirine/Emtricitabine in Digital Pills.

Digital pills, gelatin capsules with radiofrequency transmitters activated by stomach chloride ions, directly measure antiretroviral therapy adherence. In individuals with substance use disorders and HIV, real-time nonadherence detected by digital pills creates a platform to deliver substance use and adherence interventions. In this study, we determined the bioequivalence of tenofovir (TFV), administered as tenofovir disoproxil fumarate (TDF) in healthy human volunteers administered a commercial drug product and a digital pill formulation. We adhered generally to the US FDA Analytical Procedures and Methods for Validation for Drugs and Biologics guidelines. Ten HIV-uninfected adults without reported allergy to TFV, emtricitabine, or rilpivirine were enrolled. Participants ingested a digital pill containing TDF/emtricitabine/rilpivirine. Peripheral venous blood samples were collected at 0.5, 1, 2, 4, 8, and 24 h postingestion. After a 14-day washout period, the same participants ingested Complera™. Serial venous blood samples were collected using the same protocol as the digital pill. Liquid chromatography/mass spectrometry was used to determine a maximum concentration (Cmax), area under curve from time zero to last measured concentration (AUCo-t), and area under curve from time zero to infinity (AUCoo) of TFV. Ten participants with an average age of 27 and body mass index of 25.4 successfully completed the study. Predose TFV was undetectable before the second administration of Complera confirming adequate washout period after ingestion of the digital pill. The geometric means of AUCo-t, AUCoo, and Cmax for test and reference products were within the 95% confidence intervals and, therefore, bioequivalent. TFV overencapsulated in digital pills are bioequivalent to TFV in commercial formulations.

Population pharmacokinetics of Rilpivirine in HIV-1-infected patients treated with the single-tablet regimen rilpivirine/tenofovir/emtricitabine.

PURPOSE: Rilpivirine, prescribed for the treatment of HIV infection, presents an important inter-individual pharmacokinetic variability. We aimed to determine population pharmacokinetic parameters of rilpivirine in adult HIV-infected patients and quantify their inter-individual variability. METHODS: We conducted a multicenter, retrospective, and observational study in patients treated with the once-daily rilpivirine/tenofovir disoproxil fumarate/emtricitabine regimen. As part of routine therapeutic drug monitoring, rilpivirine concentrations were measured by UPLC-MS/MS. Population pharmacokinetic analysis was performed using NONMEM software. Once the compartmental and random effects models were selected, covariates were tested to explain the inter-individual variability in pharmacokinetic parameters. The final model qualification was performed by both statistical and graphical methods. RESULTS: We included 379 patients, resulting in the analysis of 779 rilpivirine plasma concentrations. Of the observed trough individual plasma concentrations, 24.4% were below the 50 ng/ml minimal effective concentration. A one-compartment model with first-order absorption best described the data. The estimated fixed effect for plasma apparent clearance and distribution volume were 9 L/h and 321 L, respectively, resulting in a half-life of 25.2 h. The common inter-individual variability for both parameters was 34.1% at both the first and the second occasions. The inter-individual variability of clearance was 30.3%. CONCLUSIONS: Our results showed a terminal half-life lower than reported and a high proportion of patients with suboptimal rilpivirine concentrations, which highlights the interest of using therapeutic drug monitoring in clinical practice. The population analysis performed with data from "real-life" conditions resulted in reliable post hoc estimates of pharmacokinetic parameters, suitable for individualization of dosing regimen.