A randomized trial of safety, acceptability and adherence of three rectal microbicide placebo formulations among young sexual and gender minorities who engage in receptive anal intercourse (MTN-035)

Efforts to develop a range of HIV prevention products that can serve as behaviorally congruent viable alternatives to consistent condom use and oral pre-exposure prophylaxis (PrEP) remain crucial. MTN-035 was a randomized crossover trial seeking to evaluate the safety, acceptability, and adherence to three placebo modalities (insert, suppository, enema) prior to receptive anal intercourse (RAI). If participants had no RAI in a week, they were asked to use their assigned product without sex. We hypothesized that the modalities would be acceptable and safe for use prior to RAI, and that participants would report high adherence given their behavioral congruence with cleansing practices (e.g., douches and/or enemas) and their existing use to deliver medications (e.g., suppositories; fast-dissolving inserts) via the rectum. Participants (N = 217) were sexual and gender minorities enrolled in five different countries (Malawi, Peru, South Africa, Thailand, and the United States of America). Mean age was 24.9 years (range 18-35 years). 204 adverse events were reported by 98 participants (45.2%); 37 (18.1%) were deemed related to the study products. The proportion of participants reporting "high acceptability" was 72% (95%CI: 65% - 78%) for inserts, 66% (95%CI: 59% - 73%) for suppositories, and 73% (95%CI: 66% - 79%) for enemas. The proportion of participants reporting fully adherent per protocol (i.e., at least one use per week) was 75% (95%CI: 69% - 81%) for inserts, 74% (95%CI: 68% - 80%) for suppositories, and 83% (95%CI: 77% - 88%) for enemas. Participants fully adherent per RAI-act was similar among the three products: insert (n = 99; 58.9%), suppository (n = 101; 58.0%) and enema (n = 107; 58.8%). The efficacy and effectiveness of emerging HIV prevention drug depends on safe and acceptable delivery modalities that are easy to use consistently. Our findings demonstrate the safety and acceptability of, and adherence to, enemas, inserts, and suppositories as potential modalities through which to deliver a rectal microbicide.