An experimental cholesterol treatment touted by drugmaker Merck & Co. significantly reduced artery-clogging fats in late-stage testing, but it got a mixed reception from Wall Street analysts Tuesday.

The drug, called Cordaptive, can both raise good cholesterol and lower bad cholesterol. It combines an extended-release form of the B vitamin niacin with a chemical to inhibit an often intolerable niacin side effect called flushing — redness, burning and tingling of the face.

At a European cardiology conference Sunday, Merck for the first time reported results of a major study of Cordaptive. The 24-week study, which included about 1,600 patients, found that compared with dummy pills, Cordaptive produced an 18 percent drop in levels of LDL-C, or "bad" cholesterol; a 26 percent drop in another type of blood fat called triglycerides, and a 20 percent increase in levels of HDL-C, or "good" cholesterol.

Those results were about the same whether or not patients were also taking cholesterol-lowering drugs called statins. Among study patients taking Cordaptive, 29 percent had moderate flushing or worse, versus 56 percent of patients taking just extended-release niacin and 6 percent of those taking a dummy pill.

Analyst Steve Brozak of WBB Securities said the safety profile for Cordaptive, which is awaiting Food and Drug Administration approval, wasn't perfect but is "not problematic."

"I think that the FDA will be predisposed to approve it," Brozak said, given the many people with heart disease or uncontrolled cholesterol, which contributes to hardening of the arteries.

Joseph Tooley, an analyst at A.G. Edwards Pharmaceutical Group, wrote that Cordaptive appears as safe as niacin and that its reduced flushing differentiates it from existing products.

But Cowen and Co. analyst Steve Scala wrote that Cordaptive's safety profile "trended less favorably" than extended-release niacin, with measures of substances in the blood that can indicate potential liver damage, muscle damage and blood-sugar problems a little worse for Cordaptive than the extended-release niacin.

"We think there's no difference between those, especially given the size of the trial," responded Dr. John Paolini, head of the Cordaptive product development team at Merck. "Most importantly, there were no cases of hepatitis" or symptoms of liver damage in the patients.

Any worrisome changes in blood levels of enzymes were temporary and ended when patients stopped taking Cordaptive, he said.

Niacin has been used to control cholesterol for decades, and an extended release version, called Niaspan, has been on sale for years. The flushing problem, however, has prevented many patients from reaching the most effective dose and caused many others to stop taking niacin or Niaspan altogether, Paolini said in a telephone interview from the conference in Vienna.

In a statement Tuesday, Abbott Labs, maker of Niaspan, countered that facial flushing is generally a temporary side effect, which can be easily managed with aspirin.

Cordaptive would beef up Merck's cholesterol franchise, a key area because its statin drug Zocor, which had been Merck's top seller, has seen sales plunge since it got generic competition a year ago. Merck and partner Schering-Plough Corp. jointly market two other cholesterol drugs, Zetia and Vytorin.

Scala forecast $150 million in Cordaptive sales in 2008, with revenue growing to $700 million in 2012. Banc of America Securities analyst Chris Schott predicted $665 million in 2011 sales.

Morgan Stanley analyst Jami Rubin agreed that sales could top $700 million by 2011, but noted that Abbott Labs is developing a concentrated version of its niacin drug.