Anti-AIDS gel shows promise

By Dr. Ananya Mandal, MDMar 1 2011

Early research with a gel containing an anti-HIV drug has shown that it has the potential to become another weapon in the fight against AIDS when applied to the rectum before anal intercourse. This is the first time scientists have found evidence that people would tolerate using a gel form of the commonly used AIDS drug tenofovir (Viread) in the rectum.

On the flip side the trials included volunteers who were not exposed to HIV and they did not like the treatment very much. There were side effects in some people and more research is needed to figure out whether the treatment is ready for release to the public.

Dr. Ian McGowan, a professor of medicine at the University of Pittsburgh who is leading a second-phase study of the gel said, “These are early results, but [they] help set the stage for current and future trials of rectal microbicides and the development of a rectal-specific formulation of tenofovir gel.” Researchers have focused on the use of microbicides such as tenofovir, as a preventive treatment to be used in vaginal sex. However, scientists think unprotected anal sex is much more risky.

This the first phase of the trial with the gel. Usually a drug undergoes three phases before it can get approval from the U.S. Food and Drug Administration. Researchers tested tenofovir gel, the oral tenofovir pill and a placebo gel in 18 HIV-negative people who abstained from sex. The investigators took small samples of cells from the rectums of the volunteers, and sent those to a lab where they were tested to see how they defended themselves against HIV virus. A seven-day treatment with the gel performed the best; a single tenofovir pill did not have much effect at fighting HIV, they found.

Rowena Johnston, director of research at the Foundation for AIDS Research, who was not involved with the study said, “Most researchers believe the rectum is more difficult to protect from HIV than the vagina, so these findings demonstrating that it can be done will energize the search for a safe, effective and user-friendly rectal microbicide…These researchers have recognized that products like condoms or microbicides are only effective if people use them. Their plan to make what appears to be an effective product into a formulation people will want to use could be a winning combination.”

The findings were to be presented Monday at the Conference on Retroviruses and Opportunistic Infections in Boston.

Another study is under way using a formulation of tenofovir gel with less glycerin, an additive found in many gel-like products, in the hope that this will make it better tolerated. A separate mid-stage study presented at the meeting compared the oral and gel forms of the drug in American and African women. It found that daily use of tenofovir gel resulted in a more than 100-times higher concentration of active drug in vaginal tissue compared with use of an oral tablet. Compared with the gel, a daily tablet was associated with a 20-times higher active drug concentration in blood. Dr. Craig Hendrix, a professor of medicine and pharmacology at Johns Hopkins School of Medicine in Baltimore and the study’s leader said, “How the differences between the gel and the tablet will translate in terms of protective effect, we can’t say just yet.”