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New AIDS Drug Holds Promise

Tipranavir might help drug-resistant patients

TUESDAY, Feb. 26, 2002 (HealthDayNews) -- Preliminary research suggests a new drug may revolutionize the treatment of people with HIV by targeting the virus in those who have developed resistance to more common AIDS medications.

The federal government has not yet approved the drug, called Tipranavir, and it may not appear on pharmacy shelves for two years or more.

"But we now have proof in patients of how Tipranavir will be effective," says Dr. Scott McCallister, associate director of virology with the Boehringer Ingelheim pharmaceutical company, which is developing the drug.

Over the past six years, a combination of drugs known as the "cocktail" has radically changed the lives of people with AIDS. Those drugs keep the virus at low or undetectable levels in the blood, although the medications aren't cures and they never eliminate HIV from the body.

However, the future doesn't look so rosy. A growing number of people with AIDS are developing resistance to drugs in one or more of the three classes of AIDS medications. When the individual medications fail, doctors must scramble to find replacements.

To make matters more challenging, some people with drug-resistant strains of HIV infect others. That means those people start out with a drug-resistant virus, instead of developing it over time.

"That makes the initial choices of therapy more complex," McCallister says.

The problem of drug resistance is growing. Slightly more than half of 1,657 AIDS patients studied had become resistant to at least one AIDS drug, according to research released in December by the University of California at San Diego.

The good news is AIDS doctors are using new tests that let them better customize the "cocktail" to individual patients who have developed resistance, says Dr. Robert Houghton, a doctor who treats people with AIDS in San Diego.

Tipranavir is designed for people with AIDS who have already developed drug resistance. In recent tests, researchers at the Aaron Diamond AIDS Research Center gave Tipranavir to 41 HIV patients who had developed resistance to AIDS drugs.

The researchers released their findings today at the annual Conference on Retroviruses and Opportunistic Infections in Seattle. They found that only 14 percent of those patients developed resistance to Tipranavir.

The drug appears to work because the AIDS virus must go through an unusually high number of mutations -- 15 or more - to defeat it, McCallister says.

"The number of patients who have a virus this resistant is very limited," he says. "For the majority of patients, it will work fine."

This spring, Boehringer Ingelheim plans to launch a study with 200 people to determine proper doses of Tipranavir. By the fall, the company hopes to launch a 1,300-person study to determine if the drug works as promised.

"If all goes well, the drug should be widely available on the market about two years after that," McCallister says.

However, Dr. Michael Horberg, who treats AIDS patients in Santa Clara, Calif., cautions there is no "magic bullet" that will help all patients who have become drug-resistant. He adds some drugs have looked good in early tests, but failed to deliver.

"There is a history of other companies that have tried to make similar claims previously, but they turned out not to be true," says Horberg, director of HIV services with the Kaiser Permanente Health Plan.

What To Do

Learn about how AIDS patients become drug-resistant by reading this fact sheet from the AIDS Treatment Data Network.

An AIDS organization known as Project Inform offers more information, including advice on how to find out if you're resistant to AIDS drugs.

SOURCES: Interviews with Scott McCallister, M.D. associate director, virology, Boehringer Ingelheim, Ridgefield, Conn.; Robert Houghton, M.D., private practice specializing in AIDS patients, San Diego; Michael Horberg, M.D., medical director, HIV services, and chairman, Northern California Pharmacy and Therapeutics Committee, Kaiser Permanente Health Plan, Santa Clara, Calif.; Feb. 26, 2002, presentation, annual Conference on Retroviruses and Opportunistic Infections, Seattle
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