The Nation - New medication may benefit drug-resistant AIDS patients - It works with other drugs to lower the virus count, studies show.

The studies reported that up to 18% more drug-resistant patients saw the amount of virus in their blood drop to undetectable levels after 24 weeks compared with those taking a standard drug regimen.

The results with the experimental drug etravirine give a much-needed boost in the fight against drug resistance among HIV patients, particularly those resistant to the workhorse class of drugs known as non-nucleoside reverse transcriptase inhibitors, or NNRTIs.

"There are a lot of patients out there who need salvage therapy with a new NNRTI, and it looks like we'll have one," said Dr. Mark Wainberg, director of the McGill University AIDS Centre in Montreal, who was not involved in the study.

About half of patients on antiviral medications develop resistance to a drug in this class, said Wainberg, who has consulted for the maker of etravirine, Tibotec Pharmaceuticals of Yardley, Pa.

Tibotec plans to seek Food and Drug Administration approval for etravirine in the next few months.

The drug, previously known as TMC125, blocks one of the enzymes needed for replication by the human immunodeficiency virus, which causes AIDS.

The two studies, funded by Tibotec, followed 1,203 HIV patients in 19 countries. The patients had severely compromised immune systems and were resistant to NNRTIs and another commonly used class of drugs known as protease inhibitors.

Roughly half the patients were given etravirine and a protease inhibitor from Tibotec called Prezista, which the FDA approved last year. The remainder were given Prezista and a placebo.

Patients in both groups were also given other AIDS drugs depending on the recommendation of their doctors.

Dr. William Towner, one of the study's authors and medical director for Kaiser Permanente's HIV/AIDS Research Trials Program in Southern California, said using several drugs at once had proved to be an effective strategy against the quickly mutating AIDS virus.

"Adding only one active agent to a patient experiencing drug failure usually results in the rapid, predictable development of resistance to that agent," he said.