A Breakthrough in AIDS Prevention?

Could a pill a day prevent HIV infection? A new study suggests that taking daily HIV meds could reduce the risk of contracting HIV among gay and bisexual men.

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Years ago, when scientists predicted that someday you would be able to take a pill once a day to keep from contracting HIV, that idea sounded more Orwellian than real.

But the future is now.

The results of a large, international clinical trial published online this morning in the New England Journal of Medicine found that a daily dose of an anti-retroviral pill reduced the risk of contracting HIV by 43.8 percent. The study, known as iPrEx, found even higher rates -- 72.8 percent effectiveness -- in participants who adhered most closely to their daily drug regimen. Pre-exposure prophylaxis, or PrEP, as it's known, includes the use of tenofovir, a medication that is already effective in treating HIV infection.

In the scientific world, these findings signal a major coup. Those in the field say that this is the best news since this summer's breakthrough results of a microbicide gel that proved highly effective for preventing HIV in women. That news electrified both the scientific community and the media last summer -- Christmas in July in a 30-year pandemic that has offered up few wins.

This time the big win is for men. "The iPrEx study provides important evidence that PrEP works to reduce HIV infection risk among gay and bisexual men," says Robert Grant, M.D., M.P.H., an associate professor of medicine at the University of California, San Francisco, who chaired the study. "The need for new HIV prevention methods is critical. PrEP, in combination with other prevention methods, such as HIV testing, counseling and consistent condom use, could represent a major step forward for efforts to control the global epidemic.”

The iPrEx study involved 2,499 men who have sex with men -- called MSM, in public health circles -- and transgender women who have sex with men at 11 sites in Brazil, Ecuador, Peru, South Africa, Thailand and, within the United States, San Francisco and Boston. Between 8 percent and 9 percent of study participants described themselves as black, either from the U.S. or South Africa. Around the world, including in Africa and Asia, gay and bisexual men are often at highest risk.

IPrEx is one of the largest HIV-prevention trials to focus on men who have sex with men, the first HIV-prevention study looking at men in either Africa or Asia, and the first time a method using medication has been shown to prevent infection in MSM. MSM account for nearly half of the people living with HIV in the U.S. and 53 percent of all new infections.

Launched in 2007, the research was sponsored by the National Institute of Allergy and Infectious Diseases through a grant from the David Gladstone Institutes, a nonprofit group in San Francisco. In the study, participants were randomly assigned to receive either a daily anti-retroviral tablet containing tenofovir and emtricitabine (brand name Truvada) or a placebo.

This kind of study, known as double blind, since neither the researchers administering the study nor the participants knew who was receiving medication and who was receiving a placebo, is considered the gold standard of research. In the end, 36 HIV infections occurred among the 1,251 participants who received the anti-retroviral therapy, compared with 64 HIV infections among the 1,248 participants who received the placebo. The study also found this method to be safe.

Fauci and others are careful to temper joy with caution. Forty percent or even 70 percent effectiveness isn't the same as 100 percent. "No single HIV-prevention strategy is going to be effective for everyone," adds Fauci, "and it is important to note that the new findings pertain only to the effectiveness of PrEP among men who have sex with men and cannot at this point be extrapolated to other populations."

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