Daily AIDS drug lowers risk of HIV, study finds

By David Brown
Washington Post Staff Writer
Wednesday, November 24, 2010

When gay men at high risk of becoming infected with HIV through sex take a daily dose of antiretroviral drugs, their chance of catching the virus drops by at least 40 percent, according to a new study.

The protective benefit could be as high as 95 percent if a person is extremely attentive about not missing a dose, the research on nearly 2,500 men on four continents found.

The study provides further proof that the drugs that have transformed AIDS treatment over the past 15 years might be powerful tools in preventing infection, as well. Earlier evidence of that appeared last summer, when a study testing a vaginal gel containing an AIDS drug lowered African women's risk of acquiring HIV by 40 percent.

"This study really represents what I think is a major advance in HIV prevention research," said Kevin Fenton, a physician who directs AIDS prevention activities at the Centers for Disease Control and Prevention, which was not involved in the study. The findings were published Tuesday in the New England Journal of Medicine.

This latest approach adds to a growing menu of strategies for preventing infection in ways other than by urging people to change their behavior. While globally the AIDS epidemic is starting to ebb, gay men remain a risk group in which rates of infection are growing in both rich countries and the developing world. This study offers a new tool to address that problem.

"This is an extremely important advance in our efforts to address HIV in both the United States and globally," said Chris Collins, policy director of the New York-based organization amfAR, the Foundation for AIDS Research.

"This is a great day in the fight against AIDS. It's a result that requires immediate action," said Mitchell Warren, director of AVAC, an AIDS advocacy and educational group.

The researchers running the study warned that its findings apply only to gay men and cannot be extrapolated to men and women at risk of acquiring HIV through heterosexual intercourse.

The use of antiretroviral drugs for prevention is known as "preexposure prophylaxis," or "PrEP" for short. There are about a half-dozen other studies of PrEP strategies underway around the world, testing both pills and gels in heterosexual men and women and IV drug users.

The new findings raise questions that public health authorities are already scrambling to answer.

One is whether it is ethical to use placebos in the other PrEP studies. Another is what to tell doctors and patients who want to start using the strategy now.

The two drugs in the study - emtricitabine and tenofovir - aren't officially approved for AIDS prevention. But doctors can prescribe them for that "off-label" purpose. Sold in combination under the brand name Truvada, they cost $5,000 to $14,000 a year, depending on whether they are bought at retail price or with a bulk discount. In the generic form sold to the poorest countries, however, the combination costs as little as $150 per year.

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