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December 14, 2009

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Major Study Finds Anti-HIV Gel Ineffective Among Women

An investigational vaginal gel that had demonstrated in earlier testing some potential for inhibiting male-to-female sexual transmission of HIV was ineffective when tested in a larger clinical trial, according to findings announced today by the Microbicides Development Programme (MDP), a not-for-profit partnership of 16 African and European research institutions.

In the earlier NIAID-funded HPTN 035 study, a Phase II/IIb clinical trial involving more than 3,000 women in Africa and the U.S., the microbicide gel PRO 2000 (Endo Pharmaceuticals, Chadds Ford, Pa.) proved to be safe and 30 percent effective at preventing HIV infection (see “Anti-HIV Gel Shows Promise in Large-scale Study in Women”). The finding, which was announced in February 2009 at the Conference on Retroviruses and Opportunistic Infection, was not statistically significant, meaning that the gel’s effect may have been the result of chance rather than a true protective effect. Further study of the investigational product was needed before PRO 2000 could be considered an effective microbicide.

In the recently concluded Phase III MDP 301 study, which enrolled 9,385 women in four African countries, PRO 2000 once again proved safe but demonstrated no evidence of reducing the risk of HIV infection compared to placebo gel (see “HIV ‘prevention’ gel PRO 2000 proven ineffective” ). The MDP study was sponsored by the Department for International Development and the Medical Research Council, both based in the United Kingdom.

Based on the combined results of both the HPTN 035 and MDP 301 studies, it can be concluded that PRO 2000 is safe but does not protect against HIV infection.

NIAID continues to explore other microbicides for HIV prevention. Most recently, NIAID launched the VOICE study, which is testing the safety and effectiveness of both an investigational microbicide gel containing the antiretroviral drug tenofovir and a pre-exposure prophylaxis strategy of providing oral antiretrovirals to women at risk for HIV infection (see “Clinical Trial of Antiretroviral-based HIV Prevention Strategies for Women Now Under Way”).

Further information on NIAID efforts in topical microbicide research can be found at the HIV/AIDS Topical Microbicides Research Activities page.

Media inquiries can be directed to the NIAID Office of Communications at 301-402-1663,

NIAID conducts and supports research—at NIH, throughout the United States, and worldwide—to study the causes of infectious and immune-mediated diseases, and to develop better means of preventing, diagnosing and treating these illnesses. News releases, fact sheets and other NIAID-related materials are available on the NIAID Web site at

About the National Institutes of Health (NIH): NIH, the nation's medical research agency, includes 27 Institutes and Centers and is a component of the U.S. Department of Health and Human Services. NIH is the primary federal agency conducting and supporting basic, clinical, and translational medical research, and is investigating the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit

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Last Updated December 14, 2009