Short CommunicationA Comparison of Tenofovir Predose Concentrations in Generic Pre-exposure Prophylaxis Formulations: A Short CommunicationCattaneo, Dario PhD*; Gervasoni, Cristina MD*; Vinti, Pietro MA†,‡; Baldelli, Sara ChemD*; Fusi, Marta PharmD*; Zagato, Donatello†; De Bona, Anna MD§; Suardi, Elisa MD§; Bossolasco, Simona MD¶; Ancona, Giuseppe MD§; Rossotti, Roberto MD‖; Cernuschi, Massimo MD†,‡,¶Author Information *ASST Fatebenefratelli Sacco University Hospital, Milan, Italy; †Associazione Solidarietà AIDS Onlus, Milan, Italy; ‡Milano Checkpoint, Milan, Italy; §ASST Santi Paolo e Carlo, Milan, Italy; ¶IRCCS San Raffaele Scientific Institute, Milan, Italy; and ‖ASST Grande Ospedale Metropolitano Niguarda, Milan, Italy. Correspondence: Dario Cattaneo, PhD, Unit of Clinical Pharmacology, ASST Fatebenefratelli Sacco University Hospital, via GB Grassi 74, 20157 Milano, Italy (e-mail: firstname.lastname@example.org). The authors have not received any compensation for the present paper. Not related to the present investigation, C. Gervasoni has received educational grants from Merck Sharp & Dome, Janssen-Cilag, ViiV Healthcare, Bristol Myers Squibb, Boehringer Ingelheim, Gilead and Abbvie. D. Cattaneo has received educational grants from Janssen-Cilag and ViiV Healthcare. The remaining authors declare no conflict of interest. Dario Cattaneo and Cristina Gervasoni authors equally contributed to the work. Therapeutic Drug Monitoring: August 2020 - Volume 42 - Issue 4 - p 643-647 doi: 10.1097/FTD.0000000000000756 Buy Metrics Abstract Background: There is extensive evidence to show that pre-exposure prophylaxis (PrEP) using tenofovir disoproxil fumarate (TDF)-based formulations dramatically reduces the risk of HIV acquisition among individuals without HIV infection. Here, the authors aim to compare tenofovir plasma predose concentrations in subjects taking PrEP daily versus on demand and using different TDF-based generic formulations. Methods: Subjects providing informed signed consent for the measurement of tenofovir plasma levels were included in the study. Predose drug concentrations were stratified according to PrEP administration and the type of TDF-based formulation. The control group consisted of patients with HIV infection who were matched for renal function and were administered branded TDF that was not combined with boosted-antiretroviral drugs. Results: The study consisted of 100 subjects (mean age, 39 ± 10 years; body weight, 77 ± 11 kg). A wide distribution in tenofovir predose concentrations was observed, with values ranging from 17 to 297 ng/mL (coefficient of variation 77%). No significant differences were noted in tenofovir predose concentrations between subjects who were administered PrEP daily (n = 75) or on demand (n = 25) [94 (35–255) versus 104 (37–287) ng/mL; P = 0.476]. Comparable tenofovir predose concentrations were found between patients with HIV infection (n = 220) who were administered branded TDF and those without HIV infection who were treated with 5 different generic TDF-based formulations with generics-to-branded ratios. These were always within the range of 80%–125% and were used to define bioequivalence. Conclusions: The marketed generic formulations of TDF delivered tenofovir plasma predose concentrations comparable with those delivered by branded formulations. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.