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.