July 21 (Bloomberg) -- Merck & Co. and Schering-Plough Corp. fell in New York trading after their cholesterol drug Vytorin failed in a study to prevent complications from heart-valve disease and was linked to a higher rate of cancer.

Patients getting Vytorin were less likely to have artery- clogging plaque buildup than those on a placebo, a known benefit from Merck's Zocor, one ingredient in the drug, the study known as Seas found. The elevated number of cancer cases in Vytorin users may have been a fluke, additional researchers said today.

Vytorin prescriptions have dropped by about a third since January when an earlier study, called Enhance, found it worked no better than Zocor alone in reducing plaque buildup in the brain's main artery. The newest study, originally slated for presentation at a medical meeting in November, looked at narrowing of the heart's aortic valve, a condition known as aortic stenosis, in patients on Vytorin.

The research shows Vytorin ``does appear to reduce the risk of coronary artery disease events (as has been shown for many other types of patient in previous trials) but not the rate of progression of aortic valve disease,'' said Terje Pedersen of Ulleval University Hospital in Oslo, the study's chief investigator, in the statement.

Schering-Plough, of Kenilworth, New Jersey, fell 12 percent to $18.95 in New York Stock Exchange composite trading, while Whitehouse Station, New Jersey-based Merck slid 6.2 percent to $35.33.

Cholesterol, Complications

Vytorin slashed cholesterol levels by 61 percent compared with a placebo. Still, 333 patients getting the drug suffered a complication, compared with 355 on placebo, almost identical rates, the study found. It compared a single daily Vytorin pill with a placebo in 1,873 patients to determine whether the drug reduces deaths from heart complications; the need to replace the aortic valve; the development of heart failure, heart attack, stroke, and chest pain; or the need for surgery to clear clogged arteries.

Aortic stenosis is typically treated with blood thinners and drugs to reduce the risk of congestive heart failure, when an enlarged and weakened heart can't pump enough blood to fuel the body. Patients with mild or no symptoms are often monitored by their doctors for signs of worsening, while severe cases are typically treated with surgery to repair or replace the damaged valve.

Cancer Findings

The study found that 158 patients developed cancer. Of the patients getting Vytorin, 9.9 percent had the disease. That compared with 7 percent given a placebo. Deaths from cancer were also slightly higher in those given Vytorin, the study found.

A broader analysis of other ongoing studies showed no such risk, researchers at the University of Oxford in England said in a statement today on PR Newswire. An analysis of two larger studies involving Vytorin and Zetia, called Sharp and Improve-it, led them to conclude that the increased cancer rate in the Seas study was most likely an anomaly.

``The Seas, Sharp and Improve-It trials do not provide credible evidence of any adverse effect on cancer,'' according to the statement.

The differences in cancer rates weren't related to any specific type of malignancy, the researchers said. The risk of cancer didn't worsen with longer treatment, they said.

Vytorin combines Schering-Plough's Zetia and Merck's Zocor. Vytorin and Zetia are Schering-Plough's top-selling pills with $5 billion in sales last year. Merck and Schering-Plough split the revenue through a joint venture. The company had expected sales of the drugs to fall by about $700 million this year following the Enhance study findings.

Analysts had expected results of the Seas study in November.

To contact the reporter on this story: Shannon Pettypiece in New York at spettypiece@bloomberg.net

Last Updated: July 21, 2008 17:04 EDT