Portola Pharmaceuticals Inc.'s (PTLA) Andexanet alfa, which is specifically designed to reverse the anticoagulant activity of both direct and indirect Factor Xa inhibitors, is under priority review by the FDA, with a decision slated for August 17, 2016.Factor Xa inhibitors are anticoagulants used to prevent deep vein thrombosis and pulmonary embolism in patients undergoing hip or knee replacement surgery. One of the major complications of treatment with Factor Xa inhibitors is bleeding, and currently, there is no antidote or reversal agent approved for use against Factor Xa inhibitors.Portola has licensed the development and commercial rights to Andexanet alfa in Japan to Bristol-Myers Squibb Co. (BMY) and Pfizer Inc. (PFE) while retaining full commercial rights to the antidote outside of Japan.Andexanet alfa, if approved, has the long-term potential to address a total worldwide market in excess of $2.0 billion, according to the company.