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A trial among women taking antiretrovirals daily to prevent sexually acquired HIV infection has been stopped early after a review suggested its data would be inconclusive. The results are surprising, as data from a large, multi-country study presented last year showed the approach - called pre-exposure prophylaxis (PrEP) - is protective against HIV for men who have sex with men. The halted FEM-PrEP trial involved 1,951 women from South Africa, Kenya and Tanzania randomized to take either Truvada or placebo daily. Fifty-six acquired HIV: exactly half in the Truvada arm and half in the placebo group.
Reasons for FEM-PrEP's inconclusive results remain speculative, but lapses in adherence could be to blame. Blood samples taken to measure adherence still must be analyzed, said researchers.
There could be a significant difference between how active orally administered Truvada is in vaginal compared to rectal tissue. When tenofovir - a Truvada component, along with emtricitabine - is taken orally, concentrations of it are higher in rectal tissue than vaginal tissue, according to unpublished research cited by Dr. Timothy Mastro, a vice president at Family Health International. FHI conducted the trial.
Also, concentrations of tenofovir are about 100 times higher in vaginal tissue when the drug is formulated as a vaginal gel rather than a pill, according to a study presented earlier this year at the Conference on Retroviruses and Opportunistic Infections. Research on this gel has shown a protective effect.
It is possible the FEM-PrEP participants had concurrent STDs or irritation in the vaginal lining, increasing their vulnerability to infection, said Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, who was not involved in the study.
Though 96 percent of participants were taking oral or injection contraceptives, there were more pregnancies in the Truvada arm. Those taking oral contraceptives showed the highest rate of pregnancy. This finding, too, surprised the researchers, who said there is no known interaction between the HIV medications and contraceptives.
At least two other African PrEP trials with female participants are continuing.
The Friends of AIDS Foundation is dedicated to enhancing the quality of life for HIV positive individuals and empowering people to make healthy choices to prevent the spread of the HIV virus. To learn more about The Friends of AIDS Foundation, please visit: http://www.friendsofaids.org.
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