April 29 (Bloomberg) -- Merck & Co.'s cholesterol pill Cordaptive failed to win approval from U.S. regulators, less than a week after it was recommended for marketing in the European Union.

Merck plans to submit more data to the U.S. Food and Drug Administration to demonstrate the effectiveness of the drug, known as MK-0524A, the Whitehouse Station, New Jersey-based drugmaker said in a statement. Cordaptive, the trade name for the drug, is a combination of the vitamin niacin and a new drug called laropiprant.

Niacin raises levels of HDL cholesterol, which helps ferry plaque from arteries. Laropiprant cuts down on the facial flushing caused by niacin alone, which limits its use. While the European Medicines Agency recommended approval of the drug on April 24, some doctors said there wasn't enough research on whether laropiprant is safe.

``We are tired of them saying, `Whoops, we didn't anticipate that.' This is a good example of the need to slow down,'' said Allen Taylor, a cardiologist at Walter Reed Army Medical Center in Washington. ``They've already got doctors hawking the drug, and it isn't even available.''

Merck fell $2.10, or 5.1 percent, to $39.34 at 6:56 p.m. New York time yesterday in extended trading after the announcement. The shares have dropped 20 percent on the New York Stock Exchange in the past 12 months.

$600 Million

Cordaptive could have $600 million in sales by 2011 if it wins U.S. approval, according to a report by Bear Stearns analyst John Boris.

Merck isn't publicly discussing the questions about the drug raised by the FDA, said Merck spokesman Ron Rogers in a telephone interview yesterday. The company plans to meet with the agency ``as soon as possible'' to discuss the benefits and risks of the product, although no date has been set, Rogers said.

The agency rejected the proposed trade name of Cordaptive for the treatment, and the company said it plans to suggest Tredaptive, the brand name in Europe, as an alternative, according to the statement.

Merck reaffirmed its financial forecast for 2008 and said it's confident it will hit its financial goals through 2010, the company said in a statement.

Competitors

The drug would compete with Abbott Laboratories' Niaspan, a long-acting version of niacin which had $658 million in sales last year, and Merck and Schering-Plough Corp.'s cholesterol lowering drug Zetia. Some doctors have advised that patients try older pills, including niacin, before using Zetia since results of a study raised questions about its benefits.

``We firmly believe that MK-0524A provides physicians with an important option to manage their patients' cholesterol,'' said Peter Kim, president of Merck Research Laboratories, in a company statement.

Merck-sponsored studies showed that on average, patients taking Cordaptive experienced flushing about once a month compared with once a week Niaspan, a long-acting version of niacin approved by the FDA in 1997. Those studies also showed Cordaptive raised HDL cholesterol and was similar in safety.

To contact the reporters on this story: Shannon Pettypiece in New York at spettypiece@bloomberg.net; Luke Timmerman in San Francisco at ltimmerman@bloomberg.net

Last Updated: April 29, 2008 00:01 EDT