• Stuart J Connolly, Mark Crowther, John W Eikelboom, C Michael Gibson, John T Curnutte, John H Lawrence, Patrick Yue, Michele D Bronson, Genmin Lu, Pamela B Conley, Peter Verhamme, Jeannot Schmidt, Saskia Middeldorp, Alexander T Cohen, Jan Beyer-Westendorf, Pierre Albaladejo, Jose Lopez-Sendon, Andrew M Demchuk, Daniel J Pallin, Mauricio Concha, Shelly Goodman, Janet Leeds, Sonia Souza, Deborah M Siegal, Elena Zotova, Brandi Meeks, Sadia Ahmad, Juliet Nakamya, Truman J Milling, and ANNEXA-4 Investigators.
• From the Population Health Research Institute (S.J.C., J.W.E., D.M.S., E.Z., B.M., S.A., J.N.) and the Department of Medicine (M. Crowther), McMaster University, Hamilton, ON, and the University of Calgary, Calgary, AB (A.M.D.) - all in Canada; Harvard Medical School (C.M.G.) and Brigham and Women's Hospital (D.J.P.) - both in Boston; Portola Pharmaceuticals, South San Francisco, CA (J.T.C., J.H.L., P.Y., M.D.B., G.L., P.B.C., S.G., J.L., S.S.); University of Leuven, Leuven, Belgium (P.V.); Centre Hospitalier Universitaire de Clermont-Ferrand, Clermont-Ferrand (J.S.), and Grenoble-Alpes University Hospital, Grenoble (P.A.) - both in France; Academic Medical Center, Amsterdam (S.M.); Guy's and St. Thomas' Hospitals, King's College London, London (A.T.C.); University Hospital Carl Gustav Carus Dresden, Dresden, Germany (J.B.-W.); Instituto de Investigación Hospital Universitario La Paz, Madrid (J.L.-S.); Sarasota Memorial Hospital, Sarasota, FL (M. Concha); and Seton Dell Medical School Stroke Institute, Austin, TX (T.J.M.).
• N. Engl. J. Med. 2019 Apr 4; 380 (14): 1326-1335.

BackgroundAndexanet alfa is a modified recombinant inactive form of human factor Xa developed for reversal of factor Xa inhibitors.MethodsWe evaluated 352 patients who had acute major bleeding within 18 hours after administration of a factor Xa inhibitor. The patients received a bolus of andexanet, followed by a 2-hour infusion. The coprimary outcomes were the percent change in anti-factor Xa activity after andexanet treatment and the percentage of patients with excellent or good hemostatic efficacy at 12 hours after the end of the infusion, with hemostatic efficacy adjudicated on the basis of prespecified criteria. Efficacy was assessed in the subgroup of patients with confirmed major bleeding and baseline anti-factor Xa activity of at least 75 ng per milliliter (or ≥0.25 IU per milliliter for those receiving enoxaparin).ResultsPatients had a mean age of 77 years, and most had substantial cardiovascular disease. Bleeding was predominantly intracranial (in 227 patients [64%]) or gastrointestinal (in 90 patients [26%]). In patients who had received apixaban, the median anti-factor Xa activity decreased from 149.7 ng per milliliter at baseline to 11.1 ng per milliliter after the andexanet bolus (92% reduction; 95% confidence interval [CI], 91 to 93); in patients who had received rivaroxaban, the median value decreased from 211.8 ng per milliliter to 14.2 ng per milliliter (92% reduction; 95% CI, 88 to 94). Excellent or good hemostasis occurred in 204 of 249 patients (82%) who could be evaluated. Within 30 days, death occurred in 49 patients (14%) and a thrombotic event in 34 (10%). Reduction in anti-factor Xa activity was not predictive of hemostatic efficacy overall but was modestly predictive in patients with intracranial hemorrhage.ConclusionsIn patients with acute major bleeding associated with the use of a factor Xa inhibitor, treatment with andexanet markedly reduced anti-factor Xa activity, and 82% of patients had excellent or good hemostatic efficacy at 12 hours, as adjudicated according to prespecified criteria. (Funded by Portola Pharmaceuticals; ANNEXA-4 ClinicalTrials.gov number, NCT02329327.).Copyright © 2019 Massachusetts Medical Society.

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