Researchers have halted two studies of an anti-AIDS vaginal gel in Africa and India after early results suggested it might raise the risk of HIV infection instead of lowering it.
It was "a disappointing and unexpected setback" to efforts to get a simple tool to protect women from the risk of AIDS through sex, the World Health Organization said.
More than half of all new infections with the AIDS virus in Africa involve women and girls. Scientists and groups like the Gates Foundation have long sought a method of protection women could use, even without their partners' knowledge, since many men refuse to use condoms.
The studies were testing Ushercell, a gel containing cellulose sulfate, a cotton-based compound developed by Polydex Pharmaceuticals, based in Toronto.
One study involving 1,500 women in South Africa, Benin, Uganda, and India was stopped this week after an independent safety monitoring board saw more HIV infections among women using the gel than those given a dummy medication. The study was led by CONRAD, a Virginia-based health research group, and paid for by the United States Agency for International Development, and the Bill & Melinda Gates Foundation.
"I cannot think of any biological basis for these findings, and I hope that further analysis of all of the data may shed further light on this important question," said a statement by USAID's research chief, Jeff Spieler.
The second study of Ushercell, by Family Health International, involving 1,700 women in Nigeria, was stopped as a precaution.
"We did not find any evidence of greater risk of HIV infection," said a statement from Dr. Vera Halpern, who led the Nigeria study. "But we also found no evidence that the product was effective."
Ushercell appeared safe and promising in 11 previous studies, mostly done in the United States.
Another study of a different microbicide, Carraguard, developed by the New York-based Population Council, is due to wrap up in March and to report results later this year. That product is seaweed-based, and no safety problems have been seen in three preliminary evaluations on 6,000 women in South Africa, said council spokeswoman Melissa May. The study is designed to test effectiveness.
The Gates Foundation is financing that experiment as well as research on a microbicide containing tenofovir, a drug already used to treat AIDS that is showing potential as an HIV preventive.
"We remain hopeful that a safe and effective microbicide will be developed," said a statement by Nicholas Hellmann, acting director of the Gates foundation's HIV program.
