2 drugs could be key to preventing HIV

[TexasStooge]

Results in monkeys encouraging; studies on humans to be expanded

By MARILYNN MARCHIONE / Associated Press

ATLANTA, Georgia – 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 will expand early tests in healthy high-risk people.

"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 get the virus from their partners.

The drugs are tenofovir (Viread) and emtricitabine, or FTC (Emtriva). They are 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 – these drugs simply keep the virus from reproducing.

They are already used to prevent infection in health care workers accidentally exposed to HIV and in babies whose pregnant mothers receive them.

Signs of success

Taking the drugs 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.

The results in monkeys suggest they are right. Specifically, six macaques were given the drugs and then given a deadly combination of monkey and human AIDS viruses.

Despite 14 weekly doses of the virus, none of the monkeys became infected. In another group of monkeys, which didn't get the drugs, all but one were infected, typically after two exposures.

"Seeing complete protection is very promising," said Walid Heneine, a scientist from the Centers for Disease Control and Prevention 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 Dr. 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 funding sources have been looking at ways to expand human testing.

This approach wasn't tried 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, can be taken just once a day, doesn't interact with other medicines or birth control pills, and leads to less drug resistance than other AIDS medications.

The CDC last year launched $19 million worth of studies on 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, the CDC announced last week.

Because of the new monkey results, the Botswana study 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 and 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 participants who got infected might not have access to treatment.

Such problems are "part of the HIV-prevention landscape" in many countries, said Dr. Helene Gayle, who formerly oversaw AIDS research for the Gates Foundation.

The cost

Expense also could limit 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. In the U.S., wholesale costs are $417 for a month of tenofovir and $650 for Truvada.

Still, health officials hope the drugs could fill an important gap.

"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," said Dr. Lynn Paxton, team leader for the project at the CDC.

In the Atlanta labs where scientists are still minding the monkeys, "the level of enthusiasm is pretty high," Dr. 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."

[Terrell]

Hopefully these drugs will work in humans, and will be able to clear any hurdles in getting FDA approval. There are some that will oppose any medication that prevents an STD.