The Prospective, Open-Label Study of Andexanet Alfa in Patients Receiving a Factor Xa Inhibitor Who Have Acute Major Bleeding ( (Eliquis) in 105 and rivaroxaban (Xarelto) in 75. The ANNEXA-4 study has not enrolled patients treated with a direct factor Xa inhibitor anticoagulant and undergoing surgery, a setting that will be the subject of a future study, Dr. Connolly said.) enrolled 227 patients at any of 60 centers, with efficacy data available from 132 of the patients. About 60% of the patients had an intracranial bleed, and about 30% had a gastrointestinal bleed, and their average age was 77 years. Roughly three-quarters of patients were on an anticoagulant for atrial fibrillation, with the rest treated for venous thromboembolism, with 4% having both conditions. The most commonly used direct factor Xa inhbitors in these patients were apixaban
Clinicians administered andexanet alfa as a bolus followed by a 2-hour continuous infusion, with hemostatic efficacy assessed 12 hours after the start of treatment. The results showed that factor Xa inhibition fell by about 75%-90% within minutes of starting the bolus and remained depressed at that level during the infusion but then began recovering by 2 hours after the stop of infusion. Andexanet is a factor Xa “decoy” molecule that acts by latching onto the inhibitor molecules and thereby preventing them from interacting with actual factor Xa, but andexanet also has a short half life and hence the effect quickly reduces once treatment stops.
“There is no doubt that andexanet rapidly decreases anti–factor Xa activity,” he said.