ATLANTA – Twenty-five years after the first AIDS cases jolted the world, scientists think they soon may have a pill that people could take to keep from getting the virus that causes the global killer.
Two drugs already used to treat HIV infection have shown such promise at preventing it in monkeys that officials last week 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 federal scientist since the earliest days of AIDS. “If it works, it could be distributed quickly and could blunt the epidemic.”
Condoms and counseling alone have not been enough – HIV spreads to 10 people every minute, 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.
The drugs would only be given to people along with counseling, 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 Dr. Lynn Paxton, team leader for the project at the Centers for Disease Control and Prevention, 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.
The drugs are tenofovir and emtricitabine, or FTC , 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 only keep the virus from reproducing. They already are used to prevent infection in health care workers 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, just as taking malaria drugs in advance can prevent that disease when someone is bitten by an infected mosquito, scientists believe.
Monkeys suggest they are right.
Specifically, six macaques were given the drugs and then challenged with a deadly combination of monkey and human AIDS viruses, administered in rectal doses to imitate how the germ spreads in gay men.
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.
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.”
Expense could limit use of the drugs. Gilead donated them for the studies and sells them in poor countries at cost – 57 cents 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.
Still, health officials are hopeful the drugs could fill an important gap.
The National Institutes of Health is starting a study in 1,400 gay men in Peru. Tenofovir also is being tested in microbicide gels that women could use vaginally to prevent catching HIV.
“If you’re in an area where there’s a really high HIV incidence, something that’s even 40 percent effective could have a huge impact,” Paxton said.
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