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Aug. 14, 2006 (Toronto) -- A pill a day to keep HIV away?
That's the concept behind an experimental approach called pre-exposure prophylaxis, or PrEP, that is showing promise for preventing infection in HIV-negative people who engage in risky behaviors.
Testing of the AIDS "prevention pill" on about 860 high-risk women in Cameroon, Ghana, and Nigeria suggests the approach is safe and feasible, researchers say.
While the numbers in the test were too small to prove effectiveness, "the data are encouraging enough to propel us ahead," says Robert M. Grant, MD, an AIDS specialist at the University of California, San Francisco, who was not involved with the work.
Joep Lange, MD, PhD, an AIDS specialist at the University of Amsterdam, agrees. Lange, who is past president of the International AIDS Society, compares the strategy to giving people malariamalaria pills before traveling to a tropical country.
"With 4 million new HIV infections this year, we need to turn this epidemic around," he tells WebMD.
With a vaccine to prevent HIV -- widely considered the best way to stem the tide -- nowhere in sight, "the greatest thing pharmaceutical companies could do is develop drugs to prevent HIV," Lange says.
Uses Existing Drug
The new study, presented here at the XVI International AIDS Conference, involved a drug already approved to treat HIV called Viread.
All the women in the study were HIV-negative but considered at high risk of contracting the virus because they were sex workers or had frequent sex with multiple partners.
Half the women were given Viread and the rest were given a placebo. The women were all counseled on HIV prevention and offered condoms at every visit.
Safe, Promising
Within six months, six of the women on placebo, but only two of the women on Viread, had tested positive for HIV.
But with only a total of eight infections, it would be premature to draw any firm conclusions, says researcher Ward Cates, MD, president of research at Family Health International.
Tests of the women's kidney and liver function showed Viread was safe. This is important in a drug to be used by people who do not have the disease.
And while there were worries the women would feel protected by the drug and fail to use condoms or take other safe-sex measures, this did not happen, he tells WebMD.
In fact, "the women had more condom use and fewer sex partners than when the study began," Cates says.
"This important new prevention tool has completed its first hurdle," he says. "The drug was safe, acceptable, and did not encourage high-risk behavior in our study."
Animal studies also offer encouraging data, Lange says. The research suggests "you can get high levels of protection" either with Viread, another anti-AIDS drug known as Emtriva, or a combination of Viread and Emtriva, Cates says.
The approach is not a free pass to risky behavior, researchers stress. The strategy is aimed at people at high risk of contracting HIV who have no other options.
Grant notes there have been reports of gay and bisexual men in San Francisco and other cities taking Viread or Emtriva as an AIDS prevention pill.
"People should not take the drug, go out, and engage in high-risk behavior," he says. "We don't know enough about it at this time."
SOURCES: XVI International AIDS Conference, Toronto, Aug. 13-18, 2006. Robert M. Grant, MD, University of California, San Francisco. Joep Lange, MD, PhD, professor of medicine, University of Amsterdam. Ward Cates, MD, president of research, Family Health International.