Andexanet alfa: FXa Inhibitor Antidote


  • A recombinant protein specifically designed to reverse the anticoagulant activity of both direct and indirect Factor Xa inhibitors
  • Being developed as a universal reversal agent for patients anticoagulated with an oral or injectable Factor Xa inhibitor who experience a serious uncontrolled bleeding event or who require urgent or emergent surgery
  • Designated a Breakthrough Therapy by the U.S. Food and Drug Administration
  • Portola has commercial rights to andexanet alfa outside of Japan

Clinical Development

Phase 3b/4

  • Currently being studied in ANNEXA-4, a Phase 3b/4 single-arm, open-label confirmatory study in patients receiving apixaban, rivaroxaban, edoxaban or enoxaparin (a low molecular weight heparin and indirect Factor Xa inhibitor) who present with an acute major bleed.
  • On August 17, 2016, we received a Complete Response Letter, or CRL, regarding our BLA for andexanet alfa from the FDA, which raised questions regarding manufacturing and clinical data. We continue to have discussions with the FDA and plan to submit the BLA after we have addressed the deficiencies identified in the CRL.