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HIV-prevention advocates welcome promising news on microbicides

Women who were offered PRO2000 gel plus condoms in the trial had 30% fewer HIV infections than those offered only condoms or condoms plus a placebo gel

The US National Institutes of Health (NIH) has announced promising results of a multi-site clinical trial of two candidate microbicides, topical products designed to reduce the risk of HIV when applied vaginally before sex.

Known as HPTN 035, the trial was conducted by the NIH-funded Microbicide Trials Network and led by Salim S Abdool Karim, PhD from the University of KwaZulu-Natal in Durban, South Africa. Dr Karim headed a team of leading African and US researchers working at trial sites in South Africa, Malawi, Zambia, Zimbabwe and the United States.

The trial found that women who were offered PRO2000 gel plus condoms had 30% fewer HIV infections than those offered only condoms or condoms plus a placebo gel. Reported adherence to the gel was high, at 81%. In another analysis that accounted for the time that women did not use the product because they were pregnant, the study found PRO2000 to be 36% protective against HIV compared to the control arms. The other candidate microbicide tested, BufferGel, did not reduce HIV risk among women. 

“The results on PRO2000 are a ray of hope for women,” says Lori Heise, director of the Global Campaign for Microbicides (GCM), an advocacy organisation that has been campaigning to expand women’s HIV-prevention options for over a decade. “This is the first time that we have had human data actually showing that a vaginal gel can work to reduce infection. It’s not a home run, but this ‘proof of concept’ should invigorate the field.” 

Another effectiveness trial of PRO2000, conducted by the UK-funded Microbicide Development Programme (MDP), is currently in its final stages in South Africa, Tanzania, Uganda and Zambia. This trial -- known as MDP 301 -- has enrolled over 9,000 women, three times the number enrolled in HPTN 035. 

“This second trial should help us refine our estimate of how effective PRO2000 actually is,” notes Dr Samu Dube, GCM’s Africa programme leader. “With three times the number of women, the MDP trial will yield an even more precise estimate of effectiveness. We will need such data before deciding whether it makes sense to move this product forward towards licensing and distribution.” 

The CDC (Centres for Disease Control and Prevention) has also released promising data on the ability of both oral pills and vaginal gels containing the antiretroviral drug tenofovir to fully protect monkeys from HIV infection. Significantly, the next generation of microbicide trials will focus on candidates that incorporate the same highly potent antiretroviral drugs that have been successfully used for AIDS treatment. Already, a trial evaluating a tenofovir-based microbicide is underway in South Africa. 

“Much remains to be done before we have a viable product to distribute,” says Dube. “But as an African woman, a physician, and a mother, my message is that this is a great day for women and for prevention research.” 

Sent in by Paramita Kundu, Global Campaign for Microbicides, to the AIDS-India e-forum