Application of a composite measure of product adherence, protocol compliance, and semen exposure to a phase III microbicide HIV prevention trial

Background Strict adherence to antiretroviral-based microbicide use is important for effective HIV prevention. We previously developed a composite measure of product adherence, protocol compliance, and semen exposure for determining vaginal use of tenofovir (TFV) 1% gel applicators through biomarkers and residual drug analyses. In this study, we tested the ability of the composite measure in vaginally used TFV gel applicators from a Phase III HIV prevention clinical trial. Methods Used vaginal gel applicators from the FACTS 001 study were swabbed for detection of vaginal bacterial markers (vaginal insertion), semen DNA markers (semen exposure), and residual TFV gel (product use). Results Of 1,098 evaluable TFV and placebo applicators, 80% had detectable vaginal insertion biomarkers and 52% had semen biomarkers. Ninety-nine percent of vaginally inserted applicators TFV applicators had detectable residual TFV as measured by liquid chromatography with tandem mass spectroscopy (LC–MS/MS). Residual TFV levels were also successfully detected using Fourier Transform Infrared (FTIR)-based spectroscopy. Conclusions Vaginal insertion and semen exposure biomarkers were detectable on used TFV 1% gel applicators. Residual TFV on these gel applicators was detectable by LC–MS/MS and FTIR-based spectroscopy, which has potential to be a more convenient and quicker method for detecting drug use. With continual improvements, this composite measure of product adherence, protocol compliance, and semen exposure has potential to assess use of not only TFV gel but also other topical microbicides or products.