Taking daily antiretroviral drugs greatly cuts the chances of getting infected with AIDS, researchers have found in a groundbreaking new study.
The study published today in the New England Journal of Medicine, offered the first indication of an oral method to prevent the spread of HIV among those at high risk.
"This is an important trial that further extends the growing appreciation that antiretroviral therapy can play a vital role in controlling the HIV epidemic," said Dr. Paul Volberding, co-director of the University of California San Francisco Center for AIDS Research, who was not involved with the study.
The study, which began in June 2007, followed 2,499 men and transgendered women from six countries -- including the United States -- who engaged in sex with other men and were categorized as high risk for HIV infection. Participants were randomized to either receive a combination antiretroviral drug commonly known as Truvada or a placebo.
Participants assigned to Truvada who reported taking the daily pills about half of the time they were prescribed had about a 50 percent lower risk of getting HIV. Those who reported taking the medication about 90 percent of the time had a 73 percent lower risk of infection.
"We think our results can be generalized to all communities in the world," said Dr. Javier Lama, study co-chair from Investigaciones Medicas en Salud in Peru.
In 2008, over 42,000 people in the U.S. were diagnosed with HIV. Nearly half of those infected were men who engaged in sex with other men, according to the Centers for Disease Control and Prevention.
According to Dr. Tom Coates, director of the UCLA program in global health, condom use "has already decreased due to HIV treatment being so effective."
"HIV prevention is already not working all that well among gay men," Coates said.
Surprisingly, study participants who used the new oral method, called pre-exposure prophylaxis -- or PrEP -- reported a higher compliance with other HIV prevention methods such as condom use, and also reported a decrease in the number of sexual partners, said Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, an arm of the National Institutes of Health in Bethesda, Md., which partly funded the study.
While preventative antiretroviral therapy is an innovative method, it's likely to be only a part of the larger HIV prevention effort, he said.
In fact, all study participants received additional HIV prevention, including condoms, counseling, as well as periodic HIV testing. However, the rise in HIV infections is due in large part to the failure of high-risk groups to use prevention methods.
Dr. Robert Grant, study chair from Gladstone Institute of Virology and Immunology at the University of California San Francisco warned self-reported use of medication often proves to be higher than actual use.
In fact, Grant said one of the challenges of oral PrEP may be that some may find it difficult to take the pill daily.
"Finding ways to support use of daily pill is focus of [the] next studies," said Grant, adding that future studies should determine whether more limited and shorter term use of the pill, along with other available prevention methods, may prove just as effective.
"Sustainability of treatment programs requires that something needs to be done to decrease infection [rates]," Grant said.
Truvada is commonly used as a therapy for patients already infected with HIV. In most countries, the pill costs about 40 cents a day, Grant said. However, Grant added that it's likely the price of the drug will rise if used as a prevention method. The study may prompt use of the drug in more countries.
In fact, in Peru, which is one of the countries that partook in the study, the drug is currently not available to the nearly 42,000 people infected with HIV. Fifty-five percent of study participants came from Peru, according to study co-chair Lama.
Still, researchers said it is too early to tell when the drug will be used. Researchers said it's also unlikely public health HIV prevention plans will incorporate wide use of the PrEP pill soon because there are too many questions still unanswered.
"What about women? What about heterosexual activities? What about the long term?" said Fauci, who also added that it's unclear whether taking the drug daily for longer than two years could cause complications.
Although the study was limited to one type of high-risk group, other PrEP studies are looking at other groups at risk for transmission, including heterosexual couples and intravenous drug users. Researchers also plan to conduct a longer term follow up study to iPrEx beginning 2011.
"We don't have answers to questions on public health [concerns] to determine whether and how these findings should be incorporated into ongoing HIV programs," Fauci said. "We anticipate that other PrEP studies being conducted will provide a more comprehensive view."