Drugs Are Found to Block HIV in Monkeys; Pills, Gel May Help Protect Women

Three studies presented Monday at the 16th Conference on Retroviruses and Opportunistic Infections in Montreal signal some progress in using pharmaceuticals to prevent HIV, particularly in women.

A study of 3,100 women in the United States, South Africa, Malawi, Zambia, and Zimbabwe showed the PRO 2000/5 microbicide gel reduced the risk of HIV infection by 30 percent over the course of roughly two years. The effect did not reach the level of statistical significance -- the participants also used condoms in about three-quarters of their sexual encounters. However, PRO 2000/5 may prove useful to women who are monogamous, are married to high-risk men, and are trying to conceive, the study's lead author noted.

"This could be a niche product for a group of women who have no other option," said Durban-based researcher Salim Abdool Karim.

In another study, led by CDC virologist J. Gerardo Garcia-Lerma, rhesus macaques were given oral doses of a compound containing the antiretroviral drugs tenofovir and emtricitabine (Truvada). The doses were administered at different intervals, both before and after the monkeys were rectally exposed to HIV once a week for three months. When the first dose was given either one or three days prior to HIV exposure, five out of six animals were protected. When it was given seven days before contact with the virus, four in six were protected. However, only three in six were protected when the dose was given two hours before exposure. Of 27 untreated monkeys, 26 became infected after an average of two exposures.

In the third study, researchers applied vaginal gels containing either Truvada and tenofovir or tenofovir alone to monkeys half an hour prior to twice-weekly vaginal HIV exposure. All six monkeys that received the two-drug gel were protected, as were the six who received the tenofovir-only gel. Ten of the 11 animals in the control group became infected after an average of four exposures to the virus.

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