HALF OF AMERICAN HIV IS DRUG-RESISTANT

By Daniel Haney

AP 18 Dec. 2001

Chicago -- A disturbing new study found that at least half of all Americans under care for HIV infection carry viruses that are resistant to some of the standard AIDS drugs.

HIV's relentless ability to mutate and grow impervious to AIDS drugs is the single biggest challenge of treatment, and the new research shows the magnitude of this problem.

Often patients with viruses that are resistant to some drugs can be switched to other treatment regimens. But options are limited, because viruses that elude one medicine can often outwit others that are closely related.

Smaller studies have shown this resistance is widespread, but the latest review is the first to examine the issue nationwide. It shows that about half of the 209,000 people under physicians' care for HIV in 1999 had viruses that were resistant to at least one of the 15 AIDS medicines on the market.

"This incredibly high prevalence is a bit scary. It has important implications for treatment and for transmission of drug-resistant virus," said Dr. Douglas Richman of the University of California at San Diego.

Richman's findings were based on blood samples taken from 1,908 men and women who were patients of doctors in a randomly selected sample of U.S. physicians. He presented them Tuesday at an infectious- diseases meeting in Chicago sponsored by the American Society for Microbiology.

"These are remarkable data," said Dr. Scott Hammer of Columbia University. "This amount of drug resistance is striking. It shows why we need new treatments."

The doctors found that two-thirds of the patients surveyed had measurable levels of virus in their blood. This could occur because they were taking inadequate amounts of medicine or because their virus escaped complete suppression because it was drug-resistant.

It turned out that three-quarters of these people with measurable HIV had virus that was resistant to at least one drug.

"I must admit, none of us thought it would be this high," Richman said. "It's disappointing."

Dr. Ronald Valdiserri, deputy chief of sexually transmitted diseases at the Centers for Disease Control and Prevention, noted that these resistant viruses can spread to others, and this limits treatment possibilities for newly infected people. "It underscores the importance of prevention," he said.

Among the study's findings:

- People with the best access to care had the highest level of drug- resistant virus. This is because they had often been exposed to many different drugs.

- The highest level of drug resistance - 70 percent - was against drugs known as reverse transcriptase inhibitors. This is the oldest class of AIDS medicines and includes such drugs as AZT.

- Forty-two percent of viruses were resistant to protease inhibitors. This medicine is a key ingredient of the AIDS drug combinations that helped transform AIDS into a treatable disease in the mid-1990s.

- Resistance was highest in people whose helper cells - the primary target of the AIDS virus - had fallen to the lowest levels.

- Drug resistance was less of a problem for people treated by very experienced AIDS doctors with large numbers of patients.