AIDS 2012: The Latest on Rectal Microbicides
July 23, 2012
What if a lube could help prevent HIV infection during sex? Microbicide researchers and advocates are hoping to answer that question and create a new HIV prevention tool -- and a sexy one at that, if rectal microbicides advocate Jim Pickett has his way.
A microbicide is a chemical agent (such as a drug) that could be formulated as a gel, lubricant, douche, or enema and applied vaginally or rectally to reduce the risk of HIV infection during sex. One benefit of using a microbicide is that it puts the HIV-fighting drug exactly where the virus is entering the body during sex. Another is that it would offer an unobtrusive and even pleasure-enhancing HIV prevention option for people who are unable or unwilling to consistently use condoms, as well as for mixed-HIV-status couples trying to have a child.
One study to date, known as CAPRISA 004, has shown a protective effect from a vaginal microbicide. Researchers saw 39% fewer new HIV infections among women who used a gel containing the antiretroviral drug tenofovir (Viread) both before and after sex, compared with women who used a placebo gel. (Both groups of women also received free condoms, safer sex counseling, and HIV testing -- the comprehensive HIV prevention package offered in all biomedical HIV prevention trials.)
At Sunday's satellite session at AIDS 2012, Ian McGowan, co-principal investigator of the Microbicide Trials Network (MTN), outlined the development of an experimental rectal microbicide that also uses tenofovir (slides from this satellite are available here). Studies to date have focused on safety and acceptability: Will the gel be safe to use during anal sex? And will people like it enough to use it?
The answer to both questions is "yes," according to results from the MTN-007 study, a Phase I study with 65 HIV-negative men and women. Researchers saw no significant differences in side effects between three study groups, in which participants rectally applied either the tenofovir gel, a gel containing the spermicide nonoxynol-9, or a placebo gel with no drug in it. The vast majority of study volunteers (80%) reported only minor gel-related side effects over the course of the week-long study, including flatulence, diarrhea, and abdominal pain; moderate side effects were noted by 18% of participants. Among those who used the tenofovir gel, 87% said they would be likely to use it again, compared with 93% who used the placebo gel and 63% who used the gel with nonoxynol-9.
A more advanced (Phase II) study, MTN-017, is gearing up to enroll 186 HIV-negative gay men, other men who have sex with men, and transgender women at sites in the United States, Peru, South Africa, and Thailand. MTN-017 will look at the safety of this tenofovir-based rectal microbicide, as well as how well participants adhere to gel use, how well they like it, and how the drug is absorbed and concentrated in rectal tissue. Study volunteers will cycle through three eight-week interventions: tenofovir gel applied to the rectum daily, tenofovir gel applied before sex, and oral Truvada PrEP. (Click here for AVAC's peek at the microbicide research timeline.)
Jim Pickett, chair of International Rectal Microbicides Advocates (IRMA) and director of Prevention Advocacy and Gay Men's Health at the AIDS Foundation of Chicago, shared with BETA his hopes for the next International AIDS conference, to be held in Melbourne, Australia, in 2014: "We'll be preparing, hopefully, for the Phase IIb/III study or something that proves efficacy"—that is, whether the rectal microbicide gel prevents HIV infection. "I just hope that we continue to move forward."
Translating clinical trial results to real-world settings can be tricky for any new HIV prevention tool. In normal life, people aren't used to inserting highly specific "doses" of lube with a clinical-looking applicator -- they simply apply it with a finger and "a little dab'll do ya," observed Pickett. In response, investigator Ian McGowan revealed that a new study, likely involving mixed-HIV-status couples, is in development to look at just that issue: How to use a tenofovir-containing rectal microbicide in the way ordinary lubes are used in the real world, without the admittedly odd-looking applicator. "I think we can be more creative," said McGowan.
Pickett also told BETA of his hopes for more research teams to jump on the rectal microbicides bandwagon, and for studies to explore non-ARV-based agents for microbicides that could ultimately be purchased over the counter. Would needing a prescription for a drug-containing microbicide hinder some folks from using the gel? "Absolutely," he said. "Having things that are just ARV-focused is problematic. There are people who don't want to put ARVs in their body," he explained. And people who are already HIV positive could be complicating their own HIV treatment if they used an ARV-based gel to prevent transmitting the virus to their sex partners: "It would be like putting suboptimal therapy in my body, or it would mess with my current drug regimen. So having things that are over-the-counter, that are not based on ARVs, would be great."
That's actually where the microbicides field began, Pickett acknowledged, but only ARV-based products have showed any promise of efficacy to date. But it's time to think creatively again, he says, and look for additional microbicide formulations -- even ones that could be used to prevent HIV and other infections but not be contraceptive, so women could use them to safely conceive with a positive partner. "Now we have to get out of the tenofovir bubble and think about other ARV agents and other mechanisms."
To learn more about rectal microbicides and how you can advocate for them, visit IRMA here.
This article was provided by BETA. It is a part of the publication Bulletin of Experimental Treatments for AIDS. Visit their website at www.betablog.org.
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