By Liz Szabo, USA TODAY
A trio of new studies highlights the promise and challenges of preventing the spread of HIV, the virus that causes AIDS: Giving anti-AIDS drugs to healthy but high-risk patients can dramatically reduce the risk of infection.
Two studies from Africa in heterosexual patients found that the drugs reduced the rate of HIV infection by 62% to 75%, a success rate that's comparable to results from studies of gay men, according to research in today'sNew England Journal of Medicine. A third study in African women at high risk of infection, however, was ended early after researchers saw the drugs had no effect on HIV rates, largely because fewer than 40% of study participants took their pills as instructed.
Overall, though, the results bolster the notion of giving anti-AIDS drugs to healthy but high-risk people before they're exposed to HIV, says Myron Cohen, a professor at the University of North Carolina-Chapel Hill and co-author of an accompanying editorial. The strategy, known as PREP, or pre-exposure prophylaxis, is one of several powerful new tools in preventing HIV infection, he says.
An advisory panel to the Food and Drug Administration in May recommended approving the drug used in the studies, sold commercially as Truvada, for prevention. Truvada, which combines the drugs tenofovir and emtricitabine, is already approved to treat the disease. In two of the studies, patients were randomly assigned to take either a placebo or Truvada. In the third study, patients were randomly assigned to take either a placebo, Truvada or tenofovir. In that study, both tenofovir and Truvada worked about equally well.
"We're at some sort of turning point in the AIDS epidemic," says Cohen, who will speak later this month at AIDS 2012, an international conference in Washington, D.C., focusing on science and policy. "It's not a single thing going on. It's the culmination of what's happened for 30 years. … Each of them is moving the political world to start thinking about an AIDS-free generation."
About 34 million people have HIV/AIDS, including 1.1 million in the USA, according to the Centers for Disease Control and Prevention. About 50,000 Americans are newly infected with HIV each year.
A key challenge to using these drugs will be finding ways to motivate patients to take them properly, Cohen says. Researchers should find out, for example, whether women stopped taking the pills because of side effects or simply underestimated their risk of getting HIV. In the study of African women, about 3% of women became infected with HIV during the study, whether they took placebos or active drugs.
MORE: Truvada Q&A
Using pills to prevent HIV is itself controversial.
On one hand, the pills could help protect the healthy partners of HIV-positive patients, says Anthony Fauci of the National Institutes of Health. The pills could give people a way to protect themselves, even when their partners refuse to use condoms, a common problem in some countries.
But doctors have to be careful to test patients for HIV before prescribing Truvada. If someone already has HIV and doesn't take the pills faithfully, that person could develop and spread a resistant form of the AIDS virus, Cohen says.
Even AIDS activists are divided on the issue, says Guido Silvestri, a professor at theEmory University School of Medicine.
Some argue that the pills should be given to everyone at risk of HIV, especially those with high-risk lifestyles. Others worry that the pills could give people a false sense of security and lead them to stop using condoms, which reduce the risk not only of AIDS but of other sexually transmitted infections and pregnancy, Silvestri says.
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