MTN-035

Primary Objectives

• To evaluate the acceptability and tolerability of each dosage form (insert, douche, suppository) when applied rectally and used prior to receptive anal intercourse (RAI)
• To evaluate adherence to each dosage form (insert, douche, suppository) prior to RAI over a 4-week-long period
• To evaluate the safety of each study product (insert, douche, suppository) when applied rectally and used prior to RAI

Study Summary
MTN-035 was a multi-site, randomized-sequence, 1:1:1:1:1:1, three-period, open-label crossover study. The study evaluated the safety, acceptability, and tolerability of and adherence to three placebo dosage forms (insert, douche, suppository) when each is applied rectally and used prior to RAI over a 4-week-long period. The study enrolled 217 healthy, HIV-uninfected men (cisgender and transgender) and transgender women (TGW) who are 18-35 years of age and who report engaging in RAI. Participants were randomized equally across six application sequences which determine the order each dosage form was used. Each dosage form was used for approximately four weeks, and there was a 1-week washout period between each dosage form application period. It is hypothesized that the placebo rectal insert, the placebo rectal douche, and the placebo rectal suppository will be safe acceptable and tolerable to participants, and that adherence will be high.

MTN-035 completed follow-up on July 27, 2020. Primary results were presented at the annual Conference on Retroviruses and Opportunistic Infections (CROI) held virtually on March 6-10, 2021. One paper has been published. Primary and other secondary manuscripts are in development.

Primary Results
Participants identified as cisgender men (172; 79.3%), transwomen (42; 19.4%) or transmen (3; 1.3%). Mean age was 24.8 (SD=4.7 years). Product-experienced participants had heterogeneity in top-ranked product choices across scenarios (Table 1). In conjoint analyses, efficacy was the strongest determinant of stated choice overall (30.4%), followed by product delivery vehicle (18.0%), and side effects (17.2%). The most chosen combination of attributes was an enema used ~ 30 minutes before sex, with 95% efficacy, offering a 3-5 day protection window, used weekly, having no side effects, and available as an over-the-counter product. In IDIs, participants' acceptability across products were informed by the aforementioned features, RAS-related characteristics (e.g., lubricity; hygiene), personal considerations (e.g., relationship status), and social context (e.g., stigma).