Can microbicides prevent rectal transmission in MSM?

Vaginal microbicides will be used rectally

Young minority men who have sex with men (MSM) are most at risk of HIV infection in the United States, so there needs to be more prevention options and strategies addressing their vulnerability. Microbicides may be an answer.

"There is a real need to have a comprehensive HIV prevention program for this very vulnerable population," says Ian McGowan, MD, PhD, FRCP, professor of medicine in the division of gastroenterology, hepatology, and nutrition with a joint appointment in the department of obstetrics, gynecology, and reproductive sciences at the University of Pittsburgh School of Medicine in Pennsylvania.

McGowan has led the push to develop microbicides for prevention of HIV infection through rectal intercourse and is involved in research testing rectal microbicides.

"I tell people that although the majority of microbicide research has focused on vaginal microbicides, the day they're available in communities they'll be used rectally, so we better know what the safety profile is rectally," he says.

McGowan is the protocol chair of a new phase I study, called MTN-007, which looked at the safety and acceptability of tenofovir 1% gel applied rectally. The randomized, blinded, placebo-controlled study used a vaginally formulated gel.

One of the study's main goals will be to see if its use is associated with rectal mucosal damage.

A microbicide solution for prevention of HIV transmission rectally is critically important for both men and women, especially in light of new research showing a large proportion of U.S. women having anal sex, McGowan notes.

"We basically need rectal microbicides as well as vaginal microbicides," he says. "The rectal microbicides field has not been going as long as the vaginal microbicides field, but it's gathering momentum."

To move the rectal microbicides field even further along, researchers are studying ways to adapt vaginal microbicide gels and even develop new products specifically for rectal use.

"We've already begun to study vaginal products for rectal safety," McGowan says.

"There's a new study that takes a slightly different vaginal formulation with less glycerin to make it more acceptable rectally," he adds. "And the third step is to develop a truly rectal-specific formulation, and that's going into the clinical phase next year."

A Phase II rectal safety study of tenofovir gel is being developed by the MTN with the goal of studying the safety and acceptability of oral and rectal products among MSM in the U.S., Thailand, and Peru, McGowan says.