A gel developed to protect against HIV during vaginal sex has shown that it may also be effective in the anus, say scientists.
An early-phase study was presented this week at the 18th Conference on Retroviruses and Opportunistic Infections.
The results, based on rectal tissue biopsies sampled from HIV-negative men and women who used the product daily for one week, provide the first-ever evidence that tenofovir gel could help reduce the risk of HIV from anal sex.
According to the researchers, tenofovir gel was not especially well-liked by a majority of men and women in the study, yet most reported they would be likely to use the gel if it became available in the future as a method for preventing HIV.
Although the study found use of the gel generally safe, side effects were problematic to a few study participants. In hopes of making tenofovir gel more acceptable for rectal use, researchers have since modified the gel and are now testing it in another study.
“We are very encouraged about these findings that indicate applying tenofovir gel topically to the rectum could be a promising approach to HIV prevention,” said Peter Anton, M.D., professor of medicine and director of the Center for Prevention Research at the University of California (UCLA), who led the study with Ian McGowan, M.D., Ph.D.
“These are early results, but help set the stage for current and future trials of rectal microbicides and the development of a rectal-specific formulation of tenofovir gel,” added Dr. McGowan, who is leading the second study of the new gel formulation.
Microbicides, products applied on the inside of the rectum or vagina, are being designed and tested to help prevent or reduce the sexual transmission of HIV or other sexually transmitted infections.
The majority of microbicide research thus far has focused on products to prevent HIV during vaginal sex. Yet, the risk of becoming infected with HIV from unprotected anal sex may be at least 20 times greater than unprotected vaginal sex, in part because the rectal lining is only one-cell thick compared to the vagina’s multiple layers, making it easier for the virus to reach cells to infect.