Each year, more than 2.7 million people become newly infected with HIV. The majority of new infections worldwide occur in women and girls, and unprotected sex is the single greatest factor in the “feminization” of the AIDS epidemic. Women are biologically more vulnerable to HIV infection in any single act of intercourse, and their risks are heightened by bias, discrimination, poverty, violence and other conditions that reduce their ability to control when and with whom they have sex, or to negotiate safer sex. Stemming the spread of new infections is critical to ending the AIDS epidemic, and relies in part on increasing access to effective, women-controlled HIV prevention technologies.
Results of a new clinical study conducted in South Africa suggest, for the first time, that a vaginal microbicide–in the form of a gel containing the anti-retroviral drug (ARV) tenofovir which is widely used in treatment of AIDS–can help prevent sexual transmission of HIV.
In the study, funded in part by the U.S. Agency for International Development (USAID) and the Government of South Africa, and conducted by the Centre for the AIDS Programme of Research in South Africa (CAPRISA), tested efficacy of the gel in 889 HIV-negative, sexually active South African women who were considered to be at high risk of HIV infection. PLUS News reports that half of the women were given vaginal applicators containing a 1 percent concentration of tenofovir gel, while the other half were given a placebo gel. The women were asked to insert a dose of the gel 12 hours before sexual intercourse and a second dose within 12 hours after intercourse.
The gel itself was created by CONRAD, a nonprofit organization based in Arlington, Virginia long involved in publicly-funded research on contraception and other sexual and reproductive health technologies, under a royalty-free license from Foster City, California-based Gilead, the world’s biggest maker of AIDS medicines
The study found a 39 percent reduction in HIV transmission among women who used the gel 70 percent of the time, and a 59 percent reduction among women who used it in over 80 percent of all acts of sexual intercourse.
Overall, according to CAPRISA, “98 women out of the 889 became HIV positive during
the trial—with 38 in the tenofovir gel group and 60 in the placebo gel group.”
Out of the 434 women who tested negative for herpes at the start of the trial, 29 became infected in the tenofovir group and 58 became infected in the placebo group. The reduced rates of HIV and herpes infections among the women who used the tenofovir gel are statistically significant.
“Tenofovir gel has a potential dual effect in preventing HIV. Since women with genital herpes are much more likely to become infected with HIV, the additional protection of tenofovir gel against herpes creates a second mechanism whereby the gel may have a bigger impact in preventing HIV,” said study co-principal investigator, Dr Salim S. Abdool Karim, Director of CAPRISA and Pro Vice-Chancellor (Research) of the University of KwaZulu-Natal, South Africa
During monthly visits, all participants were provided with HIV risk-reduction counseling, condoms and treatment for sexually transmitted infections, and each was clinically examined for potential side effects and tested for HIV infection. 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. 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 CAPRISA researchers also found that the protective effect against HIV and genital herpes increased as use of the tenofovir gel increased. Women who used the gel in more than 80 percent of their sex acts had a 54 percent reduction in HIV infections, whereas those who used the gel in less than half of their sex acts had a 28 percent reduction in HIV infections. Among those women who became infected, tenofovir gel had no effect on
the amount of HIV in their bloodstream at the time of infection. Also, none of the women who became infected with HIV showed resistance to tenofovir.
“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,” Karim told PLUS News.
“This new technology has the potential to alter the course of the HIV epidemic, especially in southern Africa where young women bear the brunt of this devastating disease.”
The next step is to replicate these results in other studies to confirm the findings. Researchers estimate that, if the results are confirmed, widespread use of the gel at the same level of efficacy could prevent over half a million new HIV infections in South Africa alone over the next decade.
At least one major donor, the United States government, promised ongoing support for the research, development and distribution of a successful product.
“After these results are confirmed in an ongoing and similar study supported by the National Institutes of Health in the U.S. Department of Health and Human Services, as well as other studies, we will work with partners at the global and country levels to integrate this product into programs,” said USAID Administrator Rajiv Shah in a statement.
But much work remains to be done. In reality, bringing a successful microbicide to market will take at least a few years. “As exciting as this result is – and as important as it is to follow it up without delay – the reality is that this product will not be available for widespread introduction tomorrow,” cautioned Mitchell Warren, Executive Director of the AIDS Vaccine Advocacy Coalition, in an interview with PLUS News.
“We believe that the most responsible plan of action now is to quickly and efficiently articulate the sequence of steps necessary for confirmation and follow-up of these results, while also aggressively planning for potential roll-out of a licensable product,” Warren said.
“It is critical to manage expectations while maintaining urgency.”