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Three new drugs promise options for HIV patients

LOS ANGELES -- Three experimental HIV drugs with two entirely new mechanisms for attacking viruses promise to spur a change in how doctors treat the virus that causes AIDS, helping thousands of patients who have stopped responding to previous medicines.

Pfizer Inc., Merck & Co., and Gilead Sciences Inc. reported positive results from drug trials at a medical meeting in Los Angeles this week. Pfizer's maraviroc is the first drug in a new class that stops the virus from entering cells. Merck's Isentress and Gilead's GS-9137 offer a second novel therapy that stops HIV from duplicating inside the body.

The findings, presented yesterday and Tuesday at the Conference on Retroviruses and Opportunistic Infections, may give patients with drug-resistant HIV new options that will help them live longer, researchers said. About 10 percent of new patients are infected with HIV that has mutated in ways that allow it to overcome current medications.

"This is an important year because there are at least two new classes of drugs becoming available," said Harold Jaffe, a professor of public health at Oxford University in England who was formerly head of HIV prevention at the US Centers for Disease Control and Prevention. "Having the option of completely new drugs that work in different ways and can be used in different combinations is a real advance."

Maraviroc and Isentress may be cleared for sale in the United States this year. They may cost $5,000 a year each, said Deutsche Bank analyst Barbara Ryan, based on prices of current drugs.

US regulators have set a meeting in April to consider approval of maraviroc for use in patients who failed on older HIV medicines. Pfizer will apply for use by newly diagnosed patients by the end of 2007. Maraviroc is the first HIV drug to block the CCR5 receptor, a chemical doorway used by the virus to slip into human cells. The drug works by changing the shape of a protein on the surface of healthy human cells, making it impossible for HIV to get a good enough grip to enter.

Merck will seek US regulatory clearance for Isentress by July for patients resistant to older drugs.