Mixed Results for Merck Blood Thinner

A second large study has revealed less than stellar results for an experimental Merck blood thinner. Researchers found that while it reduced cardiovascular events, it also increased the risk of major bleeding.

The drug, called vorapaxar, was designed to prevent recurrent strokes and heart attacks in patients with peripheral artery disease (PAD), which occurs when arteries in the legs harden.

Talk to your cardiologist about therapies to prevent recurrent heart events.

Dr. David Morrow of Brigham and Women's Hospital found that the drug's primary benefit mostly was lost to the higher risk of bleeding events. Merck, which funded the study, has not yet decided how it will proceed with the medication.

During the study 26,449 patients with a history of PAD, heart attacks or ischemic strokes were randomly assigned to receive 2.5 milligrams daily of vorapaxar or a placebo. All patients also took aspirin. They were then followed for a median of 30 months.

After two years the data and safety monitoring board discontinued study treatment in participants with a history of stroke because of an added risk of a brain hemorrhage.

At the three-year mark, 9.3 percent of patients taking vorapaxar had experienced a heart attack, recurrent stroke or died of a heart-related problem. In comparison, 10.5 percent of the placebo group experienced a cardiovascular event or died of a related condition.

In addition, 4.2 percent of participants receiving vorapaxar and 2.5 percent of patients taking the placebo experienced moderate or severe bleeding. Among those taking vorapaxar, there also was found to be an increased risk of intracranial hemorrhage.

The study was presented on Saturday at the American College of Cardiology Annual Scientific Session in Chicago. It also was published in the New England Journal of Medicine.