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HIV and AIDS Current Topics in HIV and AIDS

AIDS Drug Combination May Prevent the Disease

A new drug combination, already used to treat people with HIV and AIDS, may also be effective in preventing HIV in people who don’t have the disease.

As part of an ongoing study by the Centers for Disease Control and Prevention, six monkeys were injected with tenofovir (Viread) and emtricitabine (Emtriva) before being exposed to a mix of human and monkey AIDS once a week for 14 weeks. None of the monkeys treated with the drugs became infected, while all but one of the monkeys in the control group became infected.

The monkeys then remained healthy for the next four months, proving that the drugs were preventing infection and not just delaying the onset of the virus.

Now, the drug combination, which is marketed in pill form as Truvada by Gilead Sciences Inc., will be given to HIV-negative people in Botswana to see if it works as well in humans. Meanwhile, the CDC is testing just tenofovir—which has also shown promise in preventing HIV—on homosexual men in San Francisco and Atlanta, intravenous drug users in Thailand and high risk heterosexuals in Botswana. Results won’t be available until at least late 2007 or early 2008, said Dr. Lynn Paxton, one of the study’s leaders, but researchers hope the drugs will eventually prevent at least some of the 5 million new HIV cases worldwide every year.

Based on the monkey data, the National Institute of Allergy and Infectious Diseases is also set to conduct its own Truvada trial on homosexual men in Peru.

"I’m excited about anything that can help us reduce infections." said Dr. Monica Ruiz, a NIAID behavioral scientist who is helping conduct the study. "If this is another tool we can put into our toolbox, that would be fantastic."

But all sides also cautioned that the study was preliminary, and there are no guarantees the drugs will work well in people. "Monkeys are not little humans." Paxton said.

Even in a best-case scenario, no one believes the drug will be 100 percent effective. For that reason, it would be combined with counseling, condom distribution and other methods that currently reduce the spread of HIV.

"This will never be regarded by us as a stand-alone intervention." said Paxton.

A major fear is that the drug will make people feel safer engaging in risky behavior than they otherwise would have. "I would be concerned if [the drug] was to be available broadly." said Dr. Philippe Chiliade, the medical director for the Whitman-Walker Clinic in Washington D.C., which is unaffiliated with the study. "We could end up with the HIV epidemic being fueled even more than it is now."

Also of concern is that some doctors have already begun prescribing Truvada—which was approved only for HIV treatment—to HIV-negative people who engage in extremely risky behaviors. Another small segment of the high-risk population is taking the drug illegally without a prescription.

"If people start using this, they could be putting themselves at high risk." Paxton said.