Drugs to raise so-called good cholesterol may still have a future despite the widely publicized failure last year of an experimental cholesterol treatment from Pfizer, researchers said Monday at a heart conference here.

Pfizer stopped work on its drug torcetrapib last December after a 15,000-patient clinical trial showed that it raised the risk of death by 59 percent and heart problems by 25 percent. The results were a setback for Pfizer and for doctors who had hoped that torcetrapib and drugs like it would become standard treatments for heart disease.

Had it succeeded, torcetrapib would have been the first in a new class of medicines with great commercial potential -- drugs meant to raise the level of HDL cholesterol, the so-called good cholesterol that can help keep arteries clear of plaque.

On Monday, researchers at the annual scientific conference of the American Heart Association presented detailed findings from the torcetrapib trial, called Illuminate. Scientists said that they left the door at least slightly open to similar drugs in development from Merck and Roche, which are called CETP inhibitors. But the drugs, which they said would need to be developed cautiously and slowly, may be years away -- if they do not fail first.

''I think we're going to see cautious development of CETP inhibitors,'' said Dr. B. Greg Brown, professor of medicine and cardiology at the University of Washington, who has consulted for all the companies.

The stakes are high in the race to develop a drug for raising good cholesterol. Pfizer spent more than $800 million developing torcetrapib, and its research chief announced his early retirement a few months after the drug failed.

Drugs to raise levels of good cholesterol are among the last great untapped territories in the pharmaceutical industry. Heart disease is the biggest killer in the United States and Europe, and statins like Lipitor, which lower so-called bad cholesterol, are the biggest drug class worldwide, with $35 billion in annual sales. Drugs to raise good cholesterol could be just as popular, scientists and Wall Street analysts say.

Merck and Roche have not disclosed whether they intend to begin large Phase 3 trials for their CETP inhibitors. Such trials, necessary for seeking federal approval for drugs, would need to enroll 10,000 patients or more and require several years and cost at least $100 million.

Findings from the torcetrapib trial, also published in The New England Journal of Medicine, showed that the drug substantially raised good cholesterol and lowered bad cholesterol, as scientists had hoped. But it caused a sizable increase in blood pressure, a major negative effect for patients with heart disease. The effect was substantially more severe than seen in earlier-stage trials of torcetrapib and more than enough to outweigh the drug's beneficial effects on cholesterol.

The drugs from Merck and Roche have not raised blood pressure in clinical trials so far.

The problems with torcetrapib appear to be related at least in part to specific problems with the torcetrapib molecule, which the other treatments do not have, said Dr. Steven Nissen, chairman of cardiovascular medicine at the Cleveland Clinic.

Dr. Nissen was the lead investigator on a smaller clinical trial of torcetrapib. Blood tests showed that patients treated with it had an increased level of aldosterone, a hormone that regulates sodium and potassium in the blood and can affect blood pressure.

''The two trials together seem to tell us that torcetrapib had an off-target effect,'' Dr. Nissen said, referring to a negative side effect.

But the large torcetrapib trial also raised other red flags about the class of drugs in general so Merck and Roche will probably need to proceed cautiously with development. Besides having more heart problems, patients taking torcetrapib were more likely to die of cancer and infection than those on a placebo. In all, 93 patients taking torcetrapib died, compared with 59 who took a placebo.