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Results of FEM-PrEP Clinical Trial Examining Pre-Exposure Prophylaxis (PrEP) for HIV Prevention Among Heterosexual Women

By Kevin A. Fenton, M.D., Ph.D., and Jonathan H. Mermin, M.D., M.P.H.

April 18, 2011

Dear Colleague,

Today, FHI announced that it will stop the FEM-PrEP study of pre-exposure prophylaxis (PrEP) for HIV prevention among heterosexual women. The decision was made after a regularly scheduled interim review of data by the trial's independent data monitoring committee determined that the trial could not demonstrate efficacy even if it continued to its originally-planned conclusion.

These preliminary results are disappointing, especially given that this approach has already been shown to be effective in reducing HIV infection among men who have sex with men (MSM). The well-conducted study included nearly 2,000 women at high risk for HIV infection in three African nations and sought to determine if a once-daily pill containing oral tenofovir and emtricitabine (FTC/TDF or Truvada®) could protect women from HIV infection.

While PrEP with FTC/TDF was not shown to be effective in preliminary analyses of these study results, it cannot yet be definitely determined whether this drug combination works, or does not work, to prevent HIV among women. FEM-PrEP study investigators will be conducting additional analyses in the coming months to better assess potential reasons for the results in this study -- including examining factors such as adherence and differential risk behavior between the two trial arms -- that may account for the lack of demonstrated efficacy in this trial. Investigators from other PrEP trials, including CDC, will be working closely with FHI to review all available data and determine any implications for ongoing research.

Given today's results, CDC cautions against women using PrEP for HIV prevention at this time. We will not know if PrEP is effective for women, couples, or injection drug users until the conclusive results of this and other trials are reported.

In the interim, CDC reiterates that daily PrEP with FTC/TDF has only been shown to be effective for HIV prevention among MSM. Interim CDC guidance on use among MSM is available here.

For more information on today's FHI announcement, visit

For CDC information on PrEP research and planning, visit


Kevin A. Fenton, M.D., Ph.D.
Director, National Center for HIV/AIDS Hepatitis, STD, and TB Prevention

Jonathan H. Mermin, M.D., M.P.H.
Director, Division of HIV/AIDS Prevention National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention

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