Solid, tablet-like dosage form for dual-compartment (vaginal or rectal) on-demand use. Studies in non-human primates demonstrate proof-of-concept that a single TAF/EVG insert dosed vaginally several hours either before or after SHIV exposure provides strong protection. A Phase I study to assess the safety, pharmacokinetics, and pharmacodynamics of a single TAF/EVG insert administered vaginally (CONRAD A18-146) was completed in 2019, and a Phase 1 study to assess PK and safety after rectal administration of the TAF/EVG insert (MTN-039) was completed in April 2021 with results expected in 2022.  A placebo form of this insert was also evaluated in two international, multi-site acceptability studies, including the Quatro study, comparing four vaginal dosage forms in African women, and the MTN-035 (DESIRE) study, comparing three different rectal dosage forms. Under the USAID-funded MATRIX award, the TAF/EVG insert will be advanced into a multi-dose safety and PK clinical study.