Final Study Report of Andexanet Alfa for Major Bleeding With Factor Xa Inhibitors

Area of Science:

• Pharmacology
• Hematology
• Clinical Medicine

Background:

• Andexanet alfa is a modified recombinant inactive factor Xa (FXa) designed to reverse FXa inhibitors.
• The ANNEXA-4 study evaluated andexanet alfa in patients with acute major bleeding.
• This research presents the final analyses of a multicenter, prospective, phase-3b/4 study.

Purpose of the Study:

• To evaluate the efficacy and safety of andexanet alfa in reversing FXa inhibitors in patients with acute major bleeding.
• To assess the impact of andexanet alfa on anti-FXa activity and hemostatic efficacy.
• To analyze thrombotic events and mortality in patients treated with andexanet alfa.

Main Methods:

• A single-group cohort study enrolled patients with acute major bleeding within 18 hours of FXa inhibitor administration.
• Co-primary end points included anti-FXa activity change and hemostatic efficacy at 12 hours.
• An independent adjudication committee assessed bleeding criteria, hemostasis, thrombotic events, and mortality.

Main Results:

• Andexanet alfa significantly reduced anti-FXa activity across different FXa inhibitors (apixaban, rivaroxaban, edoxaban, enoxaparin).
• Good or excellent hemostasis was achieved in 80% of evaluable patients.
• Thrombotic events occurred in 10% of the safety population; none occurred after oral anticoagulation restart.

Conclusions:

• Andexanet alfa is effective in reducing anti-FXa activity in patients with major bleeding.
• The antidote demonstrated good or excellent hemostatic efficacy in a majority of patients.
• Andexanet alfa represents a significant advancement in managing bleeding complications associated with FXa inhibitors.