AIDS drug's efficacy confirmed / Further studies on darunavir show success against resistant HIV

A new AIDS drug that received accelerated federal approval last summer is significantly better at attacking highly resistant HIV than existing drugs, according to a study of 230 patients published Wednesday.

Darunavir, part of the decade-old class of drugs known as protease inhibitors, lowered virus levels to the undetectable range in 45 percent of patients after 48 weeks.

By comparison, 10 percent of patients on other drug regimens showed similar declines.

"The results were very, very good -- in many ways, perhaps, better than anyone would've expected," said Dr. Rodger MacArthur, an infectious-diseases specialist at Wayne State University in Detroit, who was not affiliated with the study.

The results of the patient study, combined with the recent development of several new classes of AIDS medications, have opened a whole new realm of options to battle the increasing problem of drug-resistant HIV, according to Dr. Steven Johnson, director of the HIV/AIDS Clinical Program at the University of Colorado.

Darunavir, trade named Prezista, was approved last year before normal testing was completed to meet the urgent need of those patients with drug-resistant HIV.

The approval required the drug's developer, Tibotec Pharmaceuticals Ltd. of Yardley, Pa., to continue safety and efficacy testing.

The latest results, published in the medical journal Lancet, combined two international studies funded by Tibotec.

The study looked at patients who had failed to respond to at least three different kinds of AIDS drugs

All of the patients were given a standard drug regimen chosen by their doctors.

In addition, 110 patients were given 600 milligrams of darunavir boosted with 100 milligrams of the protease inhibitor ritonavir to increase effectiveness.

The drugs were taken twice a day.

The primary goal was to reduce the amount of virus in patients' blood by a factor of 10 -- a key reduction that is known to lead to better survival.

After 48 weeks, 61 percent of patients in the darunavir group had achieved that.

About 15 percent of patients in the control group saw a similar decline.

Virus levels dropped to undetectable levels in most of the darunavir patients, according to the study.

Dr. Charles Farthing, one of the study's authors and chief of medicine at the AIDS Healthcare Foundation in Los Angeles, said that he was impressed with darunavir's effect on a small subgroup of patients that had previously failed to respond to various drug therapy.

Among those patients, 20 percent saw their virus levels drop to the undetectable range.

"I was almost staggered," Farthing said, adding that one patient who had failed to respond to five other drug regimens is now "fit as a fiddle."

There appeared to be no significant difference in side effects between the darunavir and the other drug regimens, according to the study.

The researchers are now planning to investigate if darunavir also should be used for newly infected patients.