Portola Pharmaceuticals announces results from ANNEXA-4 trial

Portola Pharmaceuticals announced full results from ANNEXA-4, the company’s Phase 3b/4 trial of its Factor Xa inhibitor antidote Andexxa, in patients experiencing acute major bleeding while taking a Factor Xa inhibitor. Data are being presented as a late-breaking oral presentation at the International Stroke Conference and published simultaneously online by The New England Journal of Medicine. Full data from 352 patients showed that Andexxa rapidly and significantly reversed anti-Factor Xa activity when administered as a bolus and sustained this reversal when followed by a 120-minute infusion. Anti-Factor Xa activity is a measure of the anticoagulant activity of apixaban, rivaroxaban, edoxaban and enoxaparin, the anticoagulants studied in ANNEXA-4. Among all 352 patients, 64% were treated for intracranial hemorrhage, or ICH, and 26% were treated for a gastrointestinal bleed. Of those evaluated for efficacy 82% achieved excellent or good hemostasis over the 12-hour period following treatment with Andexxa, as determined by an independent adjudication committee. Within 30 days of enrollment, thrombotic events occurred in 34 patients and death occurred in 49 patients, consistent with previous ANNEXA-4 trial results and with the high background thrombotic risk of the enrolled patient population. The majority of thrombotic events occurred in patients who delayed or did not re-start anticoagulation therapy with a Factor Xa inhibitor during the follow-up period. Among the 100 patients who re-started oral anticoagulation therapy, no thrombotic events were observed. Two patients experienced an infusion reaction and none developed antibodies to Factor Xa or Factor X or neutralizing antibodies to Andexxa.
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