Experimental Merck blood-thinner found effective

An experimental blood thinner developed by Merck and Portola Pharmaceuticals was found to be safe and effective in a mid-stage study presented Monday, with a lower incidence of serious bleeding than current drugs.

The Phase II randomized trial compared the effects of betrixaban, which is part of a new class of drugs, to the widely used warfarin in 508 patients in the United States, Canada and Germany over 12 months.

All patients suffered from atrial fibrillation, an irregular heart rhythm that significantly increases stroke risks, and at least one additional stroke risk factor, such as obesity or diabetes.

"Betrixaban appears to be safe and well-tolerated in a real-life, diverse atrial fibrillation population," said Michael Ezekowitz, lead author and vice president of the Lankanau Institute for Medical Research outside of Philadelphia, Pennsylvania.

But he noted that the study was a preliminary one and that "a definitive evaluation can only be accomplished through a large, Phase III clinical trial."

Betrixaban is part of a new class of drugs called factor Xa inhibitors that prevent blood clots and are being developed by several pharmaceutical companies.

But unlike its rival factor Xa drugs, betrixaban is not cleared by the kidneys, which gives it an advantage.

"It can be used in patients with severe kidney dysfunction... It has a rapid onset of action, permits once-daily dosing and unlike warfarin, does not require constant monitoring," Ezekowitz explained in presenting the study at the American College of Cardiology annual scientific meeting in Atlanta, Georgia.

Because it is metabolized differently, betrixaban could have less harmful interactions with other drugs, one of the drawbacks of warfarin, which also requires frequent dosage adjustments and monitoring as a harmful dose can lead to serious bleeding.

(c) 2010 AFP