Portola Pharmaceuticals has entered into a second clinical collaboration agreement with Daiichi Sankyo to study andexanet alfa, Portola's investigational Factor Xa inhibitor antidote, in phase III registration studies with Daiichi Sankyo's Factor Xa inhibitor edoxaban. Portola's original collaboration agreement with Daiichi Sankyo, announced in June 2013, covered the conduct of a phase II proof-of-concept study, for which results are anticipated later this year.

The phase III edoxaban studies, known as ANNEXA- E (Andexanet Alfa a Novel Antidote to the Anticoagulant Effects of fXA Inhibitors—Edoxaban), are expected to start in 2015.

Portola will receive an upfront payment and is eligible to receive additional development and regulatory milestone payments. Portola retains full, worldwide commercial rights to andexanet alfa, for which Portola is pursuing an Accelerated Approval pathway.

"We now have established phase III clinical collaboration agreements with all of the manufacturers of Factor Xa inhibitors. This, combined with the FDA's designation of andexanet alfa as a Breakthrough Therapy, underscores the significant need for an antidote for the millions of patients currently being treated with these novel anticoagulants," said William Lis, CEO.