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Open Access Publications from the University of California

Andexanet Alfa for Acute Major Bleeding Associated with Factor Xa Inhibitors.

  • Author(s): Connolly, Stuart J
  • Milling, Truman J
  • Eikelboom, John W
  • Gibson, C Michael
  • Curnutte, John T
  • Gold, Alex
  • Bronson, Michele D
  • Lu, Genmin
  • Conley, Pamela B
  • Verhamme, Peter
  • Schmidt, Jeannot
  • Middeldorp, Saskia
  • Cohen, Alexander T
  • Beyer-Westendorf, Jan
  • Albaladejo, Pierre
  • Lopez-Sendon, Jose
  • Goodman, Shelly
  • Leeds, Janet
  • Wiens, Brian L
  • Siegal, Deborah M
  • Zotova, Elena
  • Meeks, Brandi
  • Nakamya, Juliet
  • Lim, W Ting
  • Crowther, Mark
  • ANNEXA-4 Investigators
  • et al.

Andexanet alfa (andexanet) is a recombinant modified human factor Xa decoy protein that has been shown to reverse the inhibition of factor Xa in healthy volunteers.In this multicenter, prospective, open-label, single-group study, we evaluated 67 patients who had acute major bleeding within 18 hours after the administration of a factor Xa inhibitor. The patients all received a bolus of andexanet followed by a 2-hour infusion of the drug. Patients were evaluated for changes in measures of anti-factor Xa activity and were assessed for clinical hemostatic efficacy during a 12-hour period. All the patients were subsequently followed for 30 days. The efficacy population of 47 patients had a baseline value for anti-factor Xa activity of at least 75 ng per milliliter (or ≥0.5 IU per milliliter for those receiving enoxaparin) and had confirmed bleeding severity at adjudication.The mean age of the patients was 77 years; most of the patients had substantial cardiovascular disease. Bleeding was predominantly gastrointestinal or intracranial. The mean (±SD) time from emergency department presentation to the administration of the andexanet bolus was 4.8±1.8 hours. After the bolus administration, the median anti-factor Xa activity decreased by 89% (95% confidence interval [CI], 58 to 94) from baseline among patients receiving rivaroxaban and by 93% (95% CI, 87 to 94) among patients receiving apixaban. These levels remained similar during the 2-hour infusion. Four hours after the end of the infusion, there was a relative decrease from baseline of 39% in the measure of anti-factor Xa activity among patients receiving rivaroxaban and of 30% among those receiving apixaban. Twelve hours after the andexanet infusion, clinical hemostasis was adjudicated as excellent or good in 37 of 47 patients in the efficacy analysis (79%; 95% CI, 64 to 89). Thrombotic events occurred in 12 of 67 patients (18%) during the 30-day follow-up.On the basis of a descriptive preliminary analysis, an initial bolus and subsequent 2-hour infusion of andexanet substantially reduced anti-factor Xa activity in patients with acute major bleeding associated with factor Xa inhibitors, with effective hemostasis occurring in 79%. (Funded by Portola Pharmaceuticals; ANNEXA-4 number, NCT02329327 .).

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