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2 drugs (tenofovir+FTC) used to treat HIV may also help prevent it...
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Officials plan to expand early tests in healthy high-risk people around the world
--long before any vaccine has come close...perhaps vaccine research should be discontinued?
Studies discussed below were reported at 13th CROI Feb in Denver 2006.
Pill to prevent AIDS shows promise: Scientists
Favourable monkey studies push human trials
But high cost remains an issue for treatment
Mar. 28, 2006. 01:00 AM
By MARILYNN MARCHIONE
Associated Press
ATLANTA - Condoms and counseling have failed to stop AIDS. Scientists have long searched for a way to stop its spread, but no vaccine is in sight.
Now, 25 years after the first cases emerged, scientists think they are on the verge of proving that two drugs used to treat HIV infection also can prevent it.
The latest study was so promising that officials said they would expand early tests in healthy high-risk men and women around the world.
"This is the first thing I've seen at this point that I think really could have a prevention impact," said Thomas Folks, a scientist for the Centers for Disease Control and Prevention. "If it works, it could be distributed quickly and could blunt the epidemic."
HIV spreads to 10 people every minute, 5 million every year. Global estimates are that more than 40 million people have the virus.
If larger tests show the drugs work, they could be given to people at highest risk of HIV - from gay men in American cities to women in Africa who catch the virus from their partners.
The drugs would only be given to people along with counseling and condoms, and regular testing to make sure they haven't become infected.
"We need information about whether this approach is safe and effective" before recommending it, said Dr. Susan Buchbinder, who leads one study in San Francisco.
The drugs are tenofovir (Viread) and emtricitabine, or FTC (Emtriva), sold in combination as Truvada by Gilead Sciences Inc., a California company best known for inventing Tamiflu, a drug showing promise against bird flu.
Unlike vaccines, which work through the immune system - the very thing HIV destroys - AIDS drugs keep the virus from reproducing. They already are used to prevent infection in health care workers accidentally exposed to HIV, and in babies whose pregnant mothers receive them.
Taking them daily or weekly before exposure to the virus - the time frame isn't known yet - may keep it from taking hold, scientists think.
Tests on monkeys suggest they are right.
Six macaques were given the drugs and then challenged with a deadly combination of monkey and human AIDS viruses.
Despite 14 weekly blasts of the virus, none of the monkeys became infected. All but one of another group of monkeys that didn't get the drugs did, typically after two exposures.
"Seeing complete protection is very promising," and something never before achieved in HIV prevention experiments, said Walid Heneine, a CDC scientist working on the study.
What happened next, when scientists quit giving the drugs, was equally exciting.
"We wanted to see, was the drug holding the virus down so we didn't detect it," or was it truly preventing infection, said Folks, head of the CDC's HIV research lab. It turned out to be the latter.
"We're now four months following the animals with no drug, no virus. They're uninfected and healthy."
Peter Newman at the University of Toronto had high praise for Folks.
"It's an amazing step; he is an outstanding researcher," said Newman, who is an assistant professor in the Faculty of Social Work Centre for Applied Social Research.
But Newman cautioned that even with the exciting drug development, the results are problematical.
"Even if they say tomorrow they had discovered this pill, there would be a problem," he said. "This is because HIV/AIDS most affects the poorest people in the world...
"How do we get (a drug) to the poorest people who need it the most?" Newman asked.
"How are we going to pay for it?"
There's no doubt expense could limit use of the drugs. Gilead donated them for the studies and sells them in poor countries at cost - 57 cents (U.S.) a pill for tenofovir and 87 cents for Truvada, the combination drug. That's more than the cost of condoms, available for pennies and donated by the truckload in Africa, but often unused.
In the United States, wholesale costs are $417 for a month of tenofovir and $650 for Truvada.
There is an urgent need for new drug treatments for HIV/AIDS. Condoms and counselling alone have not been enough to halt the spread of the deadly infection. HIV spreads to 10 people every minute, or to 5 million every year. A vaccine remains the best hope but none is in sight.
If larger tests show the drugs work, they could be given to people at highest risk of HIV - from gay men in American cities to women in Africa who catch the virus from their partners.
People like Matthew Bell, a 32-year-old hotel manager in San Francisco who volunteered for a safety study of one of the drugs.
"As much as I want to make the right choices all of the time, that's not the reality of it," he said of practising safe sex. "If I thought there was a fallback parachute, a preventative, I would definitely want to add that."
Some fear that this could make things worse.
"I've had people make comments to me, `Aren't you just making the world safer for unsafe sex?'" said Dr. Lynn Paxton, team leader for the project at the Centers for Disease Control and Prevention.
The drugs would only be given to people along with counselling and condoms, and regular testing to make sure they haven't become infected. Health officials also think the strategy has potential for more people than just gay men, though they don't intend to give it "to housewives in Peoria," as Paxton puts it.
Some uninfected gay men already are getting the drugs from friends with AIDS or doctors willing to prescribe them to patients who admit not using condoms. This kind of use could lead to drug resistance and is one reason officials are rushing to expand studies.
"We need information about whether this approach is safe and effective" before recommending it, said Dr. Susan Buchbinder, who leads one study in San Francisco.
Unlike vaccines, which work through the immune system - the very thing HIV destroys - AIDS drugs simply keep the virus from reproducing. They already are used to prevent infection in health-care workers accidentally exposed to HIV, and in babies whose pregnant mothers receive them.
Taking them daily or weekly before exposure to the virus - the time frame isn't known yet - may keep it from taking hold.
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