New Drugs May Prevent AIDS Before It Occurs
- From: "Chim" <ChimS1@xxxxxxx>
- Date: 27 Mar 2006 20:41:56 -0800
New Drugs May Prevent AIDS Before It Occurs
By MARILYNN MARCHIONE, AP
ATLANTA (March 27) - 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.
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 practicing 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 counseling 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.
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 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, 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.
"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."
Years of previous monkey studies using tenofovir alone had shown
partial protection. The scientists thought to add the second drug, FTC,
when Gilead's combination pill, Truvada, came on the market last year.
The results, announced at a scientific meeting last month in Denver, so
electrified the field that private and government funders alike have
been looking at ways to expand human testing.
"This is an approach we've considered for a long, long time," but
didn't try sooner because AIDS drugs had side effects and risks
unacceptable for uninfected people, said Dr. Mary Fanning, director of
prevention research at the National Institute of Allergy and Infectious
Diseases.
Tenofovir changed that when it came on the market in 2001. It is
potent, safe, stays in the bloodstream long enough that it can be taken
just once a day, doesn't interact with other medicines or birth control
pills, and spurs less drug resistance than other AIDS medications.
The CDC last year launched $19 million worth of studies of it in drug
users in Thailand, heterosexual men and women in Botswana, and gay men
in Atlanta and San Francisco. A third U.S. city, not yet identified,
will be added, CDC announced last week.
Because of the exciting new monkey results, the Botswana study now will
be switched to the drug combination; the others are well under way with
tenofovir alone.
Farthest along is a study of 400 heterosexual women in Ghana by Family
Health Initiative. The Bill & Melinda Gates Foundation funded it and
others in Cambodia, Nigeria, Cameroon and Malawi, but the rest were
doomed by rumors, including fears that scientists wanted to
deliberately expose people to HIV or that study participants who got
infected might not have access to treatment. In other cases, activists
demanded better health care or clean needles for drug users as a
condition for allowing the studies to proceed.
Such problems are "part of the HIV prevention landscape" in many
foreign countries, said Dr. Helene Gayle, who formerly oversaw AIDS
research for the Gates Foundation.
Expense also 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 tenofovir study in
1,400 gay men in Peru. Private and government funders are considering
others. Tenofovir also is being tested in microbicide gels that women
could use vaginally to try 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.
And in the Atlanta labs where Heneine, Folks and others are still
minding the monkeys, "the level of enthusiasm is pretty high," Heneine
said. "This is very promising. For us to be involved in a potential
solution to the big HIV crisis and pandemic is very exciting."
03/27/06 14:12 EST
Copyright 2006 The Associated Press. The information contained in the
AP news report may not be published, broadcast, rewritten or otherwise
distributed without the prior written authority of The Associated
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