Monkey studies paved way to successful anti-HIV gel trial

The 2010 XVIII International AIDS Conference in Vienna, Austria, was buzzing with excitement last Monday, July 19th, with the announcement of successful trial results for a vaginal microbicide gel, a recent addition to the arsenal in the fight against HIV infection in women. The phase 2 clinical trial organized by CAPRISA (Center for the AIDS Programme of Research In South Africa) tested the safety and effectiveness of the gel among nearly 900 women at two sites in South Africa.The success of the CAPRISA 004 trial is believed to be due to the addition of the anti-retroviral drug tenofovir.

Koen Van Rompay, a research scientist at the California National Primate Research Center at UC Davis, carried out the first studies showing that tenofovir was effective in treating animals that were infected with SIV (Simian Immunodeficiency Virus), laying the groundwork that led to human clinical trials including CAPRISA. Van Rompay was also attending the Vienna meeting. Also at the primate center, Professor Chris Miller tested a tenofovir gel as a vaginal microbicide in the late 1990s in the monkey model and found it to be effective. Tenofovir is now the most widely used anti-HIV drug in the world, with use in over 100 countries worldwide.

In the CAPRISA trial, almost 900 HIV negative women used either the tenofovir gel or a placebo. Over 30 months of follow up, the incidence of new HIV infections in the tenofovir group was 5.6 per 100 women-years, compared to 9.1 in the control group — a reduction of 34 percent. The gel was more effective among women who adhered strictly to the gel instructions.

Microbicidal gels could be useful for women as an extra protection in addition to condom use, or for women who cannot persuade their partners to use condoms or rely on them being monogamous.

Another ongoing trial called VOICE (funded by the U.S. National Institutes of Health), involves a daily-used tenofovir gel. Newly begun in the Fall of 2009, this study will enroll nearly 5,000 women in four African countries.

Some are calling this a historic step in the fight against HIV. Van Rompay notes how important animal research was to the early development of HIV prophylaxis regimes, and how important it continues to be as scientists develop new and more effective treatments.

More information about CAPRISA 004 here.

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