Portola Pharmaceuticals has entered into a second clinical collaboration agreement with Bristol-Myers Squibb and Pfizer to study Portola’s investigational Factor Xa inhibitor reversal agent, andexanet alfa (PRT4445), with the oral Factor Xa inhibitor Eliquis (apixaban). The original agreement from November 2012 covered the Phase II proof-of-concept study and results demonstrated andexanet alfa’s ability to produce an immediate and either temporary or sustained reversal of the anticoa...