The Microbicide Trials Network (MTN) announced results of a Phase II safety and acceptability study that tested a reduced glycerin (RG) formulation of tenofovir gel developed by CONRAD to be used rectally for HIV prevention. The study, MTN-017, found that use of the rectal gel in men who have sex with men and transgender women was safe when used daily and around the time of sex. Volunteers also reported they would be as likely to use the gel before and after sex as they would take oral Truvada® to prevent HIV. Results were announced at the Conference on Retroviruses and Opportunistic Infections (CROI) held this week in Boston, MA.
The study enrolled 195 participants in Peru, South Africa, Thailand and the United States, including Puerto Rico. Volunteers participated in three eight-week study regimens: 1) RG tenofovir gel used daily, 2) RG tenofovir gel used before and after anal sex, and 3) daily use of oral Truvada. Reported side effects of gel use were minor. Adherence to the assigned products was highest during the regimens that called for rectal gel use before and after sex and daily use of oral Truvada. Volunteers were less adherent to the daily gel regimen. Additional analyses evaluating drug concentrations in blood, rectal fluid and tissue, and product effects on cell and tissue dynamics will inform continued research on the gel.
Tenofovir gel has been tested for vaginal use in women, both daily and before and after sex, but was found to cause gastrointestinal side effects when used rectally. Researchers at CONRAD and MTN found that by reducing the glycerin in the original formula, side effects were diminished. Unprotected anal sex carries a far greater risk of potential HIV infection due to the thinner lining of the rectum and men who have sex with men and transgender women are disproportionately affected.
Clinical input and study supplies of reduced glycerin tenofovir gel were provided by CONRAD, with funding from USAID. MTN-017 was funded by the National Institute of Allergy and Infectious Diseases and the National Institute of Mental Health. CONRAD received a license from Gilead Sciences, Inc. to develop tenofovir gel for HIV and herpes prevention.