A vaginal gel which was intended to prevent infection from the virus that causes AIDS has proved to be useless after a long and costly scientific study.
The trial lasted four years and involved 9385 women in four African countries.
The Medical Research Council in the United Kingdom which helped fund the trial in Africa describes the outcome as disheartening.
The BBC reports the risk of HIV infection was not significantly different among women supplied with the gel, than in women given a placebo gel.
It was hoped microbicide gels would prove to be an effective way to limit the spread of HIV, as experts admit that condom promotion alone has not controlled the epidemic.
New ways of curbing the spread of HIV are badly needed, particularly in sub-Saharan Africa, where nearly 60% of those infected with the virus are women.
A previous, smaller trial suggested PRO 2000 could reduce the risk of HIV infection by 30%.