CAPRISA Trial and 1% Tenofovir Gel in Reducing the Risk of Contracting HIV
Researchers have achieved an important scientific breakthrough in the fight against HIV and genital herpes with a vaginal gel that significantly reduces a woman’s risk of being infected with these viruses. The results of the first safety and effectiveness study of an antiretroviral microbicide were reported on JULY 20TH, 2010 by the CAPRISA 004 study team at the XVIII International AIDS Conference in Vienna, Austria.
Women who used the microbicide containing 1% tenofovir—an antiretroviral drug widely used in the treatment of HIV—had 39% fewer HIV infections and 51% fewer genital herpes infections compared to women who used a placebo gel. These results provide the first evidence that an antiretroviral drug delivered in a gel form—a microbicide—can reduce sexually transmitted infections of HIV and herpes in women.
Tenofovir works by preventing HIV from growing inside human cells. Taken in pill form, tenofovir is a common component of various three-drug cocktails that are used to treat HIV infections. The new results now indicate that tenofovir formulated as a topical gel and inserted into the female genital tract also has great promise for use in HIV and herpes prevention. Tenofovir gel could fill an important HIV prevention gap by empowering women who are unable to successfully negotiate mutual faithfulness or condom use with their male partners.
The CAPRISA 004 trial of tenofovir gel involved 889 women at high risk of HIV infection at two sites in KwaZulu-Natal, South Africa. Women in the study were advised to use the gel up to 12 hours before sex and again soon after having sex, for a maximum of two doses in a day. Participants used the gel for up to two and a half years. The trial team observed no safety concerns from use of the gel and no increase in risk-taking behavior by the participants.
The study was double-blinded so that neither the researchers nor the participants knew which gel each participant received. During monthly visits, all participants were provided with HIV risk-reduction counseling, condoms, contraceptives and treatment for sexually transmitted infections, and each was clinically examined for potential side effects and tested for HIV infection.
The CAPRISA researchers also found that the protective effect against HIV increased as use of the tenofovir gel increased. Women who used the gel in more than 80% of their sex acts had a 54% reduction in HIV infections, whereas those who used the gel in less than half of their sex acts had a 28% reduction in HIV infections.
None of the women who became infected with HIV showed resistance to tenofovir, which means that when they develop AIDS and need to receive antiretroviral treatment they can safely use tenofovir in their three-drug regimen.
Tenofovir gel could prevent new HIV infections in close to a half million women over the next decade in South Africa alone. The results from this trial are a significant first step toward establishing the effectiveness of antiretroviral drugs for HIV prevention; confirmatory studies are now urgently needed.
The CAPRISA 004 study is recognized as an important trial in a number of dimensions, not only for its promising results. CAPRISA 004 is a major victory in the field of HIV prevention research. Other important HIV prevention studies are now underway. The VOICE study, which is being conducted by the Microbicide Trials Network, is currently assessing the effectiveness of tenofovir gel as well as tenofovir and Truvada tablets in different dosing strategies with women in several African countries. Other studies are now investigating the effectiveness of oral Truvada tablets among intravenous drug users and among men who have sex with men.
Should these and other studies confirm that tenofovir gel is safe and effective for HIV prevention, the product will need to be approved by drug regulatory authorities before it can be made available to the public for HIV prevention. Since this process can take several years, the South African-based Technology Innovation Agency (TIA) and U.S.-based CONRAD are working together to address the challenges of making the gel available first to women in South Africa.
This study is the first to be jointly funded by the South African and U.S. governments. The trial was conducted by CAPRISA in partnership with the U.S.-based organizations FHI and CONRAD and funding by USAID. Gilead Sciences donated the active ingredient for the manufacture of the tenofovir gel.
research care of AIDS 2010 and the CAPRISA website
photo care of News Daily