BOSTON (AP) -- A variety of highly effective new AIDS drugs are on the horizon, experts say, easing worries that the fast-mutating virus will outstrip doctors' ability to treat it.

Ever since combinations of AIDS medicines transformed HIV into a manageable condition in the mid-1990s, doctors have worried that the virus would eventually mutate into forms that would elude their control. While HIV indeed has evolved into many drug-resistant forms, most patients are still able to find combinations that hold their virus in check.

At the 10th Conference on Retroviruses in Boston, experts said the outlook for potent and novel medicines to control HIV has never been brighter.

"The pipeline of new drugs has an impressive number of candidates in it. This is something we haven't seen in past years. It's a bumper crop," said Dr. John Mellors of the University of Pittsburgh.

Currently, 16 drugs are approved by the Food and Drug Administration to fight AIDS. Most of the medicines are aimed at just two targets in the virus's life cycle, proteins called protease and reverse transcriptate.

However now, doctors say, drugs are in development that are aimed at eight different points in the process by which HIV attaches itself to blood cells, enters them and finally makes new copies of the virus.

The next new drug expected to win FDA approval is T-20, being developed by Roche and Trimeris Inc., a so-called fusion inhibitor that blocks HIV from sticking to the blood cells that it attacks.

At the meeting Tuesday, doctors described encouraging results with the next generation of this drug, called T-1249, that is intended to be used when the virus grows resistant to T-20. Dr. Diego Miralles of Duke University said that even more versions are in the design stage to take over when T-1249 fails.

"I am very encouraged this year that we seem to be keeping up with the virus in terms of our ability to treat resistant virus with new drugs," Mellors said.

At least a half dozen promising drugs are in human testing, he said, and 10 or 12 more are in the pipeline.

Furthermore, AIDS medicines have gotten much easier to take. Just a few years ago, patients had to take 20 or so pills on a carefully timed daily schedule. Now that total is down to just two or three pills taken once or twice a day.

Among the new drugs in testing is one TNX-355, an antibody from Tanox Inc. Unlike other drugs, this one works by blocking the spot on blood cells where HIV normally attaches itself. Initial testing by Dr. Daniel Kuritzkes and others from Brigham and Women's Hospital in Boston found an injection once every one to three weeks dramatically reduced virus levels.

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