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.