Friday August 31, 2001

Researchers Say Drug-Resistant HIV on the Rise

By Deena Beasley

LOS ANGELES (Reuters) - By 2005, nearly half of all HIV patients in San Francisco will not respond to drugs now used to treat the disease, due mostly to inaccurate use of those drug regimens by doctors, a study reported on Thursday.

Researchers at the San Francisco and Los Angeles campuses of the University of California used a mathematical model to understand the evolution of drug-resistant HIV strains in the San Francisco gay community from 1996 to 2001.

Drug-resistant HIV arises when people who are already infected fail to respond to their treatment, and may be spread when they have unprotected sex with others. "We found that the vast majority of new cases come from acquired drug resistance, not sexual transmission,'' Sally Blower, lead author of the study and UCLA professor of biomathematics, told Reuters.

Many AIDS patients have had great success with so-called drug cocktails using highly active antiretroviral therapies, but HIV can develop resistance to these drugs and their long-term effectiveness is not known.

The drug cocktails are also less effective when complicated treatment schedules are not followed, and failure to adhere to these schedules can increase the potential for future drug resistance.

"The glib answer to the trend is noncompliance on the part of patients, but there are many other factors,'' Blower said. She noted that some AIDS patients have access to state-of-the-art specialty treatment centers, while many others look to general practitioners or other medical centers for care.

"It is because of the way the healthcare system is set up in this country,'' she said.

In a report published in the September issue of Nature Medicine, her team found that the number of drug-resistant HIV cases has already reached epidemic proportions in San Francisco, rising from some 3% of overall cases in 1997 to a projected 42% in 2005.

They estimate that transmission from one person to another accounted for just 8% of new drug-resistant infections last year, and that percentage will rise to 16% in 2005. The researchers conclude that transmission of drug-resistant strains has not increased, and will not increase, the overall number of new HIV infections.

"You can decrease the amount of acquired drug resistance if you have experts dealing with AIDS patients,'' Blower said. ''These are very complicated medicines and the guidelines for using them are changing all the time.''

She said the results of the theoretical model can be extrapolated to other regions. The model included variables such as the number of drug-sensitive cases, the treatment rates, increases in risky sexual behavior and the rate at which drug resistance emerges during treatment to predict the evolution of 1,000 different strains of drug-resistant HIV.

Blower recommended several ways to minimize the prevalence and transmission of drug-resistant HIV including delaying drug treatment as long as possible in order to maximize the medical benefit and delay side effects.

She also suggested creating centralized specialty clinics for treatment, developing more effective treatments and reducing the amount of time a drug-resistant patient is on ineffective therapy.