Merck and Portola Pharmaceuticals, Inc. have signed an exclusive global collaboration and license agreement for the development and commercialization of betrixaban, an investigational oral Factor Xa inhibitor anticoagulant currently in Phase II development for the prevention of stroke in patients with atrial fibrillation (SPAF). Portola will receive an initial payment of $50 million and is eligible to receive additional payments totaling as much as $420 million based on development, regulator...