The trials of the microbicide — a gel containing the antiretroviral drug tenofovir, a proven anti-HIV drug in its oral form — are being conducted in the South African province of KwaZulu-Natal.
KwaZulu-Natal has been hit hard by HIV/AIDS, with rates at ten per cent above the national average.
A total of 980 women will be enrolled at two sites — one urban and one rural — and results, which are expected in 2010, will indicate if the tenofovir gel offers protection against HIV.
Salim Abdool Karim, director of the Centre for the Aids Programme of Research in South Africa (CAPRISA), which is running the trials, is optimistic.
He said the current oral use of tenofovir is highly effective and safe, and that tenofovir microbicide differs from previous microbicides.
"Tenofovir gel is a third generation microbicide and is unique in that it works within cells to stop HIV from replicating. The second generation polymer microbicides, tried to kill off or block the HIV from entering cells."
Animal studies, he added, have shown that when given a rectal microbicide with tenofovir, monkeys were protected from simian immunodeficiency virus, a virus that is similar to HIV.
Women are at greatest risk of HIV infection. According to the South African health department, 33 per cent of South African women between 25 and 29 have HIV/AIDS. In men the rate is highest between 30 and 34 (27 per cent).
And women in many developing countries have reported finding it difficult to negotiate condom use. Microbicides in the form of gels, creams vaginal rings or foam, offer women the chance to empower themselves and to protect themselves from HIV infection.
Co-researcher Quarraisha Abdool Karim from CAPRISA said a positive aspect to the antiretroviral-based microbicide was that women would be able to use the gel for up to 12 hours before sex and within 12 hours after sex. "With the gel remaining active in the body for a longer time, women stay protected," she said.Previous microbicide candidates have not proven effective. Trials of cellulose sulphate microbicide in Benin, India, Uganda and South Africa were stopped earlier this year when some women failed to take the treatment and others became infected with HIV (see Safety concerns halt trials of HIV microbicide).