Dual therapy could prevent HIV infection

Tue 28 Mar 2006

EBEN HARRELL

SCIENTISTS have developed a drug they believe could prevent the spread of HIV, the virus that causes AIDS.

A cocktail of two drugs already used to treat HIV infection has shown such promise at preventing it in monkeys that officials have now said they are to expand early human tests around the world.

"This is the first thing I've seen that I think could have a prevention impact," said Thomas Folks, head of the HIV research lab at the US Centre for Disease Control and Prevention.

"If it works, it could be distributed quickly and could blunt the epidemic," he added.

The drugs are tenofovir (Viread) and emtricitabine, or FTC (Emtriva), sold in combination as Truvada by Gilead Sciences.

HIV spreads to ten people every minute, five million every year, hitting the world's poorest regions hardest.

Unlike vaccines, which work to boost the immune system - the very thing HIV destroys - AIDS drugs simply keep the virus from reproducing. They are already used to prevent infection in healthcare workers accidentally exposed to HIV, and in babies whose pregnant mothers receive them.

Taking them daily or weekly before exposure to the virus may keep it from taking hold, just as taking malaria drugs in advance can prevent that disease.

Tests on monkeys suggest the researchers are right. Six macaques were given the drugs and then challenged with a deadly combination of monkey and human AIDS viruses.

Despite 14 weekly doses of the virus, none of the monkeys became infected.

What happened next, when scientists stopped giving the drugs, was equally exciting, they said.

"We wanted to see, was the drug holding the virus down so we didn't detect it, or was it truly preventing infection?" said Mr Folks. It turned out to be the latter.

But healthcare workers have warned that some uninfected gay men already are getting the anti-viral 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 a drug-resistant strain of HIV, and is one reason officials are rushing to expand studies.

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