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% of patients after 48 weeks. \"The results were very, very good - in many ways, perhaps, better than anyone would\'ve expected,\" said Dr. Rodger D. MacArthur, an infectious disease specialist at Wayne State University, who was not affiliated with the study.