Interim Data Show Andexanet Alfa Rapidly Reverses Anti-Factor Xa Activity

ANNEXA-4 is a global, single-arm, open-label clinical trial designed to evaluate andexanet alfa in patients who present with an acute major bleed while receiving apixaban, rivaroxaban, edoxaban or enoxaparin.

Late-breaking clinical data presented at ACC.18 Scientific Sessions & Expo showed that andexanet alfa (AndexXa; Portola) quickly and significantly reversed anti-Factor Xa activity when given as a bolus, and sustained this reversal when followed by a 120-minute infusion, in patients experiencing acute major bleeding while taking a Factor Xa inhibitor.

ANNEXA-4 was a multicenter, prospective, single-arm, open-label study that evaluated andexanet alfa in patients presenting with an acute major bleed while receiving apixaban, edoxaban, enoxaparin or rivaroxaban. The co-primary efficacy endpoints were the maximum percent reduction in anti-Factor Xa activity and assessment of hemostasis over 12 hours following the infusion. 

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Interim efficacy data from the Phase 3b/4 ANNEXA-4 trial included 132 of 228 patients who were confirmed to have major bleeding by the independent adjudication committee, and whose baseline anti-Factor Xa activity was substantially elevated. Anti-Factor Xa activity was reduced by a median of >90% for both apixaban and rivaroxaban following the bolus dose, and was sustained during the 2-hour infusion. In addition, 83% of patients achieved excellent or good hemostasis over a 12-hour period after receiving AndexXa. 

Consistent with previous ANNEXA-4 data, thrombotic events occurred in 11% of all study patients and 12% of those experiencing an intracranial hemorrhage during the 30-day follow-up period; mortality rate was 12% for all patients.

“The interim efficacy and safety data continue to support the promising role of AndexXa as an antidote to reverse anticoagulation in Factor Xa-associated bleeding,” said Stuart J. Connolly, MD, ANNEXA-4 Executive Committee chairman and professor in the Department of Medicine of the Faculty of Health Sciences at McMaster University in Hamilton, Ontario.

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