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New Drug Mix Also Prevents Hiv Growth

The fight against AIDS took another step forward Tuesday as scientists announced they had been unable to grow the human immunodeficiency virus from the blood cells of AIDS patients treated with an experimental combination of three drugs.

Researchers from Abbott Laboratories in Philadelphia said that after six months on ritonavir, the company’s experimental medication, and two other drugs, six AIDS patients showed no signs of the virus when their blood cells were cultured and grown in the laboratory.

Andre Pernet, an Abbott vice president, said the finding, along with others about the company’s new drug, represented “the light at the end of the tunnel” for HIV, the lethal virus that causes AIDS.

“We have gone one step beyond what others have done,” he said. “We have patients who are HIV negative.”

The finding was announced at the Third Conference on Retroviruses and Opportunistic Infections in Washington. It follows news on Monday from Merck & Co., which reported that its new anti-AIDS drug drove the virus down to undetectable levels in blood plasma.

The new drugs, which are expected to be approved by the federal Food and Drug Administration in the spring, are known as protease inhibitors. They work by interfering with an enzyme that allows HIV-infected cells to produce more infectious virus.

As a family, the protease inhibitors look much more promising than AZT and its chemical cousins.

The ritonavir study was conducted in France among 21 patients with advanced AIDS. The patients were given ritonavir along with two drugs already on the market - AZT and ddC.

On average, the patients had a 99 percent drop in the amount of virus in their blood plasma and a 99 percent drop in the number of infected blood cells over six months. They also doubled the number of infection-fighting white blood cells known as CD4 cells, which are the main target of the AIDS virus.

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