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, regulatory and commercialization milestones, as well as royalties on sales of betrixaban. Merck will assume all development and commercialization costs. Portola has retained an option to co-fund Phase III trials in return for additional royalties and co-promotion of the drug in the U.S.

“Betrixaban represents an important addition to our late-stage portfolio with the potential to be a significant medicine in the Factor Xa inhibitor class,” said Luciano Rossetti M.D., senior vice president and franchise head, Atherosclerosis and Cardiovascular, Merck Research Laboratories. “This agreement reinforces Merck’s focus on developing an innovative portfolio of products for the treatment and management of multiple aspects of cardiovascular disease.”

Charles Homcy, M.D., president and chief executive officer of Portola, commented, “This is the second major collaboration we have announced this year validating the high quality of our drug candidates and the expertise of our R&D team. This represents a significant milestone for the company and we now have over $175 million in cash to further advance the rest of our valuable proprietary pipeline.”