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San Francisco AIDS Foundation
PRO 2000 Microbicide Proves Ineffective

By Liz Highleyman

Winter/Spring 2010

The experimental vaginal microbicide PRO 2000, which appeared promising in earlier studies, did not protect women from becoming infected with HIV in a large Phase III clinical trial in Africa, investigators announced in December.


PRO 2000 is a 0.5% microbicidal gel inserted into the vagina prior to sexual intercourse. An earlier study of more than 3,000 African women (HPTN 035) was the first to suggest that a microbicide might help prevent male-to-female sexual transmission of HIV, with a 30% protective effect that fell just short of statistical significance.

But the MDP 301 trial -- the largest microbicide study to date, with more than 9,000 participants -- found no evidence that PRO 2000 reduced women's risk of infection. Over 12-24 months of follow-up, the HIV incidence rate was 4.5 per 100 person-years in the PRO 2000 arm versus 4.3 per 100 person-years in the placebo arm.

Speaking at CROI, Fauci said that studies of non-antiretroviral microbicides like PRO 2000 have produced "failure after failure," and the time has come to move on to next-generation products containing antiretroviral agents such as tenofovir or maraviroc.

Liz Highleyman ( is a freelance medical writer based in San Francisco.

This article was provided by San Francisco AIDS Foundation. Copyright Body Health Resources Corporation. All rights reserved.

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