Merck and Schering-Plough sell Vytorin through a joint venture. It and a related drug called Zetia, with collective global annual sales of more than $4.5 billion, are Schering-Plough's biggest products and among the biggest for Merck.
Results of the Vytorin study, called SEAS, will be presented at a scientific meeting in London. They will come on the heels of data from a failed earlier trial of Vytorin, released in January, that pummeled shares of both companies.
The latest study compares the blockbuster medicine to placebo among patients with aortic stenosis, irregular thickening of the main valve to the aorta that can lead to heart failure. An estimated 2 percent of people over age 65 have the condition.
Both companies had planned to report second-quarter earnings before the market opened on Monday.
The 1,873-patient SEAS study, meant to follow subjects for a minimum of four years, is the largest formal trial ever conducted in patients with aortic stenosis.
It is designed to determine whether aggressive cholesterol lowering can prevent heart attacks and cardiac-related deaths among patients who have the underlying condition although they do not have symptoms.
Vytorin is considered one of the most potent cholesterol fighters on the market, with ability to cut levels of the "bad" LDL variety by as much as 60 percent.
Sales of the pill have suffered this year, and shares of Merck and Schering-Plough have fallen sharply, due to Vytorin's failure to cut plaque in neck arteries in a separate trial called Enhance.
Widespread unfavorable publicity followed the release of the Enhance results in mid-January and recommendations by study researchers that patients first try other cholesterol fighters before opting for Vytorin.
Image At Stake
Analysts have said if the new SEAS trial succeeds, it could help redeem Vytorin in the eyes of doctors and patients. But if it fails, they said, it could further tarnish the medicine.
Vytorin combines Merck's Zocor, or simvastatin, which cuts the body's production of LDL, with the newer Zetia (ezetimibe), which prevents the intestines from absorbing LDL. The combination drug is far more expensive than generically available forms of Zocor.
"If Vytorin is yet again characterized as an expensive agent with low effect, prescriptions could be negatively impacted," Goldman Sachs analyst James Kelly said in a research report on Monday.
Kelly said the study involved a patient population that in the past has failed to benefit from statins, the class of cholesterol drugs that includes Zocor and Pfizer Lipitor.
Whitehouse Station, New Jersey-based Merck said it was delaying its second-quarter earnings report until after the primary researcher for the SEAS trial, Dr. Terje Pedersen of Ulleval University Hospital in Oslo, Norway, presents clinical trial data from the study.
A spokesman for Kenilworth, New Jersey-based Schering-Plough declined to comment on the nature of Pedersen's update.
Pedersen, in a press release of his own on Monday, said a half dozen European and U.S. scientists would participate in his presentation.
Kelly said the study was likely to result in one of two scenarios: either no significant change in any relevant outcomes measure, or no change in cardiovascular outcomes -- such as heart attacks -- but a change in progression of aortic stenosis.
Schering-Plough shares were down $1.53, or 7.1 percent, at $19.91 in morning New York Stock Exchange trade, while Merck fell $1.33 to $36.35.