New blood thinner thrombin-receptor antagonist may work without bleeding risk

When studying a new blood thinner, one of the first signs the drug is working is seeing a slight increase in minor bleeding, nose bleeds and bruising, an inconvenient side effect of preventing the blood clots that are the leading cause of heart attack and stroke.

While potentially life-saving, the drugs can also pose a risk of major bleeding in some patients, requiring frequent monitoring of blood levels.

So when he didn't see any significant increase in those typical bleeding events when studying a new blood thinner last year, UK College of Medicine cardiovascular chief David Moliterno was surprised when, at the close of the study in September, the results showed promise of significantly reducing the risk of heart attack and death with no statistical increase in major and minor bleeding events.

The drug, called a thrombin-receptor antagonist, or TRA, works in a unique way to prevent clotting by breaking down the communication between cells and proteins involved in forming clots. TRA, which is manufactured by Schering-Plough Corporation, was given in addition to established anti-clotting drugs to 1,030 patients undergoing cardiac catheterization and related intervention at 77 sites in six countries (including the United States, Canada, Italy, Belgium, Netherlands and Germany). The University of Kentucky enrolled 32 patients between August 2005 and September 2006. Patient follow-up was completed in January 2007.

"We were surprised by the extent of benefit," Moliterno said. "These results are so noteworthy because the study demonstrated that this first-in-class TRA did not increase bleeding at all in a group of patients that is certainly at risk. And honestly, therefore, we did not expect to see a large benefit. While further study is required, we observed a 46 percent lowering in serious cardiovascular events, mainly a reduction in heart attacks. This represents an early and strong efficacy signal for this novel antiplatelet compound. This is encouraging, particularly in light of the fact that this patient population requires advanced therapies and is difficult to treat."