AIDS Drugs Show Prevention Promise

[Guest guest]

AIDS Drugs Show Prevention Promise

By MARILYNN MARCHIONE, AP Medical Writer 40 minutes ago

ATLANTA - Scientists have long believed that a vaccine is the best way to stop

the spread of AIDS, but efforts to invent one have miserably flopped.

Now they may have found something already on pharmacy shelves that seems to

prevent infection.

It's a combination of two drugs that have shown such promise in early

experiments in monkeys that officials just expanded tests of them in people

around the world.

" This is the first thing I've seen at this point that I think really could have

a prevention impact, " said 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 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. 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. 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.

Furthest 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. "

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