Merck & Co. Inc. isn't saying why it handed betrixaban back to Portola Pharmaceuticals Inc., but the biotech still believes the oral Factor Xa inhibitor has best-in-class potential. Portola thus plans to move the compound into Phase III testing itself, but in a smaller indication than it had hoped to pursue with Merck.
Betrixaban belongs to a new wave of anticoagulants designed to block one of two individual coagulation factors: either thrombin or Factor Xa. These compounds are intended to replace warfarin, which is widely used but carries a risk of major bleeding and has complicated dosing, unpredictable kinetics and interactions with many drugs and even food.
In 2009, Merck paid $50 million up front for worldwide rights to betrixaban. The molecule had completed a Phase II trial to prevent venous thromboembolism (VTE) and was in a Phase IIb trial to prevent stroke in atrial fibrillation