Merck has agreed to pay $688 million to resolve two class-action lawsuits over the company’s cholesterol drug ezetimibe/simvastatin (Vytorin).

Whitehouse Station, N.J.-based Merck reported that it reached an agreement in principle with plaintiffs who alleged that Merck and Schering-Plough delayed the release of unfavorable results from the ENHANCE trial. The ENHANCE (Ezetimibe and Simvastatin in Hypercholesterolemia Enhances Atherosclerosis Regression) trial enrolled 720 patients with heterozygous familial hypercholesterolemia who received either ezetimibe/simvastatin 10/80 mg or simvastatin 80 mg alone over a two-year period. Results showed no statistically significant difference between treatment groups on the primary endpoint, which was mean change in the intima-media thickness measured at three sites in the carotid arteries.

The plaintiffs, investors who purchased securities issued by Merck and Schering-Plough between December 2006 and March 2008, claim that they lost money when the results of the ENHANCE trial were published in early 2008. The suits are pending in the U.S. District Court for the District of New Jersey against Merck and Schering-Plough, which jointly marketed Vytorin, as well as certain of their current and former officers and directors.

Under the proposed agreement, Merck will pay $215 million to resolve the securities class action against all of the Merck defendants and $473 million to resolve the securities class action against all of the Schering-Plough defendants. The agreement contains no admission of liability or wrongdoing and is subject to court approval. In connection with the settlement, Merck recorded a pre-tax and after-tax charge of $493 million, which reflects anticipated insurance recoveries.