Portola Pharmaceuticals, Inc. announced the presentation of a new exploratory analysis of data from ANNEXA-4, the Company's Phase 3b/4 trial of its Factor Xa inhibitor antidote Andexxa® [coagulation factor Xa (recombinant), inactivated-zhzo], in a key subgroup of patients with acute gastrointestinal (GI) bleeding while taking a Factor Xa inhibitor. The data will be featured at the American College of Gastroenterology (ACG) 2019 Annual Scientific Meeting in San Antonio, Texas, during a plenary session on Tuesday, October 29, 2019, from 3:25 p.m. CDT to 3:35 p.m. CDT (Location: Stars at Night Ballroom – B4; Plenary Session 3B, Abstract 53). GI bleeding is a common type of anticoagulant-related bleeding that occurs in the upper or lower GI tract. Among the 352 patients in the ANNEXA-4 study, 90 (26%) were treated for acute GI bleeding and 62 (18%) were evaluable for hemostatic efficacy. Among this subset, 82% (n=51/62) achieved excellent or good hemostasis (stoppage of bleeding) over the 12-hour period following treatment with Andexxa, as determined by an independent adjudication committee. This is consistent with the 82% (n=204/249) reported in the full ANNEXA-4 study across patients with all types of bleeds (e.g., GI, intracranial hemorrhages and other sites of bleeding). Both the exploratory analysis and full study results showed that Andexxa rapidly and potently reversed anti-factor Xa activity. Patients with GI bleeding were considered efficacy evaluable if they were determined to have major bleeding, as defined by hemodynamic compromise or bleeding associated with a hemoglobin (Hb) drop = 2 g/dL or a baseline Hb = 8 g/dL, and a baseline anti-factor Xa activity = 75 ng/mL (= 0.25 IU/mL for enoxaparin patients). Among the 90 safety evaluable patients with acute GI bleeding, and within 30 days of enrollment, thrombotic events occurred in six patients (7%) and death occurred in 10 patients (11%), consistent with the full ANNEXA-4 study results and the high background thrombotic risk of the enrolled patient population. No thrombotic events were observed among the 40 (44%) patients who re-started oral anticoagulation therapy. By comparison, among the 352 safety evaluable patients in ANNEXA-4 and within 30 days of enrollment, thrombotic events occurred in 34 patients (9.7%) and death occurred in 49 patients (13.9%). All of the thrombotic events occurred in patients who delayed or did not re-start anticoagulation therapy with a Factor Xa inhibitor during the follow-up period.