Vienna 2010: CAPRISA 004 microbicide study – a turning point for HIV prevention

Findings from the CAPRISA 004 microbicide study mark a significant milestone both for the microbicide research field and HIV prevention as a whole. A breakthrough in the fight against HIV/AIDS is being announced at the VIII International AIDS Conference in Vienna. CAPRISA 004 is a vaginal gel for women that can significantly reduce the risk of infection with HIV. The gel contains the antiretroviral drug tenofovir and is the first method of HIV prevention that women at risk of the disease through sexual intercourse can control.

Anthony S. Fauci, MD, director of the National Institute of Allergy and Infectious Diseases at the National Institutes of Health said: “For years, antiretroviral medicines have been effectively used to treat HIV infection. Through the successful conduct of the CAPRISA 004 study, we now have proof that an antiretroviral drug, in this case tenofovir, can be formulated into a vaginal gel that can protect women against HIV infection.

"Given that women make up the majority of new HIV infections throughout the world this finding is an important step toward empowering an at-risk population with a safe and effective HIV prevention tool” he said.

Researchers from the Centre for the AIDS Programme of Research in South Africa (CAPRISA) who conducted a study testing a vaginal microbicide with an antiretroviral (ARV) drug called tenofovir found its use before and after sex significantly more protective against HIV infection than a placebo gel among women at high risk of HIV.

CAPRISA 004 involved 889 women from Durban and a nearby rural community in South Africa, where women are at especially high risk of acquiring HIV through sexual intercourse. Women were randomly assigned to one of two study groups – tenofovir gel or placebo gel with no active ingredient - and instructed to use the study product in a regimen timed before and after sex.

At the end of the study, there were 39 percent fewer HIV infections among women who used tenofovir gel before and after sex than among those who used the placebo gel.

Approximately half of the 33 million people in the world who are infected with HIV are women, and in Africa that number rises to 60 percent. Given that abstinence, using condoms and being faithful have not been successful in preventing HIV infection, use of a vaginal microbicide gel that women can use without a man’s knowledge is a significant and critical step forward.

Six other microbicides have been tested over the past 15 years, but none of them have proved to be protective against the virus.

The Microbicide Trials Network (MTN) is currently conducting another study called VOICE – Vaginal and Oral Interventions to Control the Epidemic – that will provide evidence about the safety and efficacy of tenofovir gel used daily, regardless of when participants have sex.

Tenofovir gel and the tablets being tested in VOICE and other per-exposure prophylaxis trials incorporate some of the same ARV medicines used successfully for treatment of HIV. The hope is that they will also be safe and effective for HIV prevention.

In most cases, women acquire HIV through sexual intercourse with an infected male partner. Women often cannot control if or when condoms are used by their male partners. Moreover, women are twice as likely as their male partners to acquire HIV during unprotected sex due to biological factors that make them more susceptible to infection.

Both the CAPRISA investigators and other researchers who were not involved with the study stress that these results do not mean that a tenofovir microbicide gel is ready for market but is a really exciting first step.

Ishdeep Kohli-CNS