AIDS 2010 Update: Results of CAPRISA Microbicide Gel Trial: An exciting HIV Prevention Tool for Women

AIDS 2010 Update: Results of CAPRISA Microbicide Gel Trial: An exciting HIV Prevention Tool for Women

On July 19, here in Vienna at the XVIIIth International AIDS Conference, positive results were announced from the CAPRISA 004 Phase IIb microbicide trial of 1% tenofovir gel, which was tested in 889 South African women. Overall, there were 39 percent fewer infections among women who received the gel compared to women who received the placebo –and the results showed 51% efficacy of the gel against transmission of herpes simplex virusto women.  Of note, recent vaccine trials and microbicide trials have set as a limit of efficacy 30% in order to be considered “effective”, which generally means that the FDA will approve them.  

This, of course, is great news and a real breakthrough.  There have been several previous trials of vaginal microbicides which have not shown any efficacy.  It’s also great because its potentially female controlled, i.e., women can conceivably insert it vaginally and be protected if their husbands/partners force sex upon them.  In addition, this could be a great intervention for commercial sex workers as a way to offer possible continuous protection from repeated sexual exposure.  Of note, there is an early trial of rectal microbicide (for protection during anal sex) that will probably use tenofovir, but that is likely several years away from completion.

Now the caveats.  All the vaginal microbicides to date are women controlled, BUT they are also coitally dependent.  So they MUST be inserted (up to 3-4 mls) into the vagina prior to sexual intercourse AND inserted after intercourse.  So while wonderful news, we must be cognizant of the fact that this complicated dosing schedule is unlikely to be adhered to faithfully. Next steps will be to see if other microbicides trials using tenofovir confirm the results, and a final Phase III trial to prove efficacy.

CAPRISA 004 is a Phase IIb, two-arm, double-blind, randomized, controlled microbicide trial that compared the effectiveness of a 1% tenofovir gel with a placebo gel for the prevention of HIV infection in women. Nearly 900 HIV-negative, sexually active women between the ages of 18 to 40 years were enrolled at two research sites: Durban and Vulindlela, located in KwaZulu-Natal, South Africa.

The first participant in the trial was enrolled on 23 May 2007, the data was officially presented on Tuesday, July 20) here in Vienna at a special session, “Safety and effectiveness of 1% Tenofovir Vaginal Microbicide Gel in South African Women: Results of the CAPRISA 004 Trial”.

The study was double-blinded and neither the researchers nor the participating women knew whether a woman in the study received tenofovir gel or placebo gel. Women in the study were advised to use the gel up to 12 hours before sex and soon after having sex for a maximum of two doses in 24 hours – a dosing strategy referred to as BAT24 (Before, After, Two doses in 24 hours) .  Participants used the gel for a minimum of one year and a maximum of two and a half years.  The trial team observed no substantive safety concerns from use of the gel.  Further, no increase in risky behavior was observed in the women. 

The trial was conducted by CAPRISA in partnership with the U.S.-based organizations FHI and CONRAD with funding from USAID. Gilead Sciences donated the active ingredient for the manufacture of the tenofovir gel.

MSH shares in the excitement of this news of the CAPRISA trial and congratulates the investigators and participants. We are hopeful that additional trials of tenofovir gels confirm these impressive results. As implementers of HIV and health programs throughout the world we are thrilled with the prospect of adding new tools to our prevention toolbox, particularly ones that allow women to better protect themselves against the scourge of HIV. When the time comes, we look forward to getting this product out to the people who need it most.

Scott Kellerman, MD, MPH is a Principal Technical Advisor for HIV at Management Sciences for Health.