A Randomized, Double Blind, Placebo-Controlled, Phase 1 Safety, and Pharmacokinetic Study of Dapivirine Gel (0.05%) Administered Rectally to HIV-1 Seronegative Adults (MTN-026)

Introduction Dapivirine (DPV), formulated as vaginal ring, demonstrated HIV risk reduction. MTN-026 explored DPV, formulated as rectal gel, for safety, pharmacokinetics, and acceptability. Methods HIV-uninfected men and women aged 18-45 years were enrolled at United States and Thailand sites and randomized 2:1 to receive DPV 0.05% or placebo gel via rectal applicator. A single dose phase was followed by 7 observed daily doses. Plasma, and fluid and tissue from both rectum and cervix were collected at baseline and after the final dose over 72 hours for pharmacokinetics, ex-vivo HIV-1 biopsy challenge, histology, and flow cytometry. Results 28 participants were randomized; 2 terminated early; 9 were female and 19 male; 12 were white, 11 Asian, 4 black and 1 other race/ethnicity. Mean age was 28.5 and 34.2 years in the DPV and placebo arms, respectively. Thirty adverse events occurred (all Grade 1 or 2, except one unrelated Grade 3) without study arm differences. DPV rectal tissue concentrations (median [interquartile range]) 0.5-1 and 2 hours after a single dose were 256 ng/gm (below limit of quantitation [BLQ], 666) and BLQ (BLQ, 600), respectively, then BLQ (BLQ, BLQ) from 24-72 hours; concentrations following multiple doses were similar. The largest median DPV plasma concentrations were 0.33 ng/mL (0.15, 0.48) after one dose and 0.40 (0.33, 0.49) after seven doses. Conclusions The DPV rectal gel was acceptable and without safety concerns. While DPV plasma concentrations were similar to the vaginal ring, rectal tissue concentrations were well below vaginal ring tissue concentrations, suggesting need for reformulation.