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  4th IAS (Intl AIDS Society) Conference on HIV Pathogenesis, Treatment and Prevention
Sydney, Australia
22-25 July 2007
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HIV-Drug Tenofovir Tested on Virus-Free People for Prevention PreP
  By Simeon Bennett
July 22 (Bloomberg) -- HIV drugs will be given to people who don't have the virus by U.S. scientists to determine whether the medicines can protect those at greatest risk of catching the AIDS-causing disease.
The Centers for Disease Control and Prevention in Atlanta are recruiting volunteers in Thailand, Botswana and the U.S. to test so-called pre-exposure prophylaxis as a means of prevention. The National Institutes of Health is planning a trial for Peru and Ecuador, researchers told an AIDS conference in Sydney today.
The theory suggests that taking anti-HIV drugs before potential exposure to the virus can protect a person against acquiring it through risky sex or intravenous drug use. It's controversial because of concern it may raise resistance to the drugs, making them less effective when infection happens.
``We don't yet have definitive proof this is effective,'' Dawn Smith, the CDC's associate chief for science, told the conference.
Unlike other experimental approaches to fighting HIV such as vaccines and microbicides, the technique uses drugs that are already in use, such as Gilead Sciences Inc.'s Viread and Truvada. The regime has been shown to lower the risk of infection in monkeys, according to the AIDS Vaccine Advocacy Coalition.
U.S. Trial
The U.S. trial will target young black males who have sex with men because they are statistically more at risk of contracting HIV than their white peers, Smith said. The Thai trial will target as many as 2,000 injecting drug users, and the trial in Botswana will recruit as many as 1,200 heterosexual men and women. The CDC expects its first set of results by mid-next year, Smith said.
As many as 1,400 men who have sex with men may be enrolled in the study in Peru and Ecuador. Participants will take one tablet a day of Truvada, said Robert Grant, associate professor of medicine at the University of California, San Francisco, who is heading the study in Peru and Ecuador.
Gilead's sales of Truvada rose 29 percent to $385.4 million in the second quarter from a year earlier, the Foster City, California-based company said last week. It sells wholesale for about $770 a month.
``Even at the current price, there are several models indicating that it could be a cost effective means of prevention,'' Grant said in an interview in Sydney today.
Truvada was chosen because it has ``an excellent track record'' for safety, as confirmed by an initial pre-exposure prophylaxis study in 936 women in West Africa, he said.
`Weigh the Risk'
``This intervention would be appropriate only for people who are at imminent risk of acquiring HIV and, in that setting, you have to weigh the risk of getting a deadly infection versus taking an antiviral drug potentially for a long period of time,'' Grant said.
The numbers of people who have to be treated to prevent every infection will help determine whether pre-exposure prophylaxis is adopted, said Professor Sharon Lewin, head of infectious diseases at Melbourne's Alfred Hospital.
``It may be relevant in countries with much higher prevalence rates and where there is a much higher risk of acquiring HIV,'' Lewin said in an interview. ``I doubt it will have any role in Australia.''
If proven effective, so-called pre-exposure prophylaxis would be used to enhance the protective effects of condoms, counseling and other methods of prevention, Grant said.
``We have to be very broad in our thinking'' about prevention, said Pedro Cahn, president of the International AIDS Society and assistant professor of infectious diseases at the Buenos Aires Medical School, in an interview in Sydney. ``Prevention certainly works if you use condoms, but you need to have access to condoms and use them consistently.'' The technique might provide some women better control over their ability to prevent infection since the use of a condom sometimes depends on the willingness of their male partner to use one, he said.
To contact the reporter on this story: Simeon Bennett in Sydney or
Last Updated: July 22, 2007 09:51 EDT