Major disappointment has greeted the news that the largest international clinical trial to date into a preventative gel developed by Endo Pharmaceuticals has found no evidence that it reduces the risk of HIV infection in women.

The vaginal microbicide Pro 2000 was tested in a four-year trial involved 9,385 women at six research centres in four African countries. The study, carried out by the Microbicides Development Programme and funded by the UK’s Department for International Development and the Medical Research Council, found that the risk of HIV infection in women supplied with PRO 2000 gel before sex was not significantly different than those given placebo gel.

To date, no microbicide has been shown to be effective against HIV infection and the researchers noted that this trial “shows conclusively that PRO 2000 gel is of no added benefit, ending scientific speculation about its clinical importance”.

Chief investigator Sheena McCormack of the MRC said the result is “disheartening, particularly in light of the results of a smaller trial sponsored by the US National Institutes of Health which suggested that PRO 2000 could reduce the risk of HIV infection by 30%”. Nevertheless, she went on to say that “it shows clearly the need to undertake trials which are large enough to provide definitive evidence for whether or not a product works”.

Maureen Chisembele, principal investigator of the Zambian site, said that in sub-Saharan Africa, nearly 60% of people living with the disease are women and “many are highly vulnerable to HIV despite the fact that they are faithful to their partners”. She added that “the women will be disappointed by this result as they really liked the gel and hoped it would work."