ALBERT

Description: Introduction Emicizumab is a recombinant, humanized, bispecific monoclonal antibody that restores the function of missing activated factor VIII (FVIII) by bridging activated FIX and FX in persons with hemophilia A (PwHA). Prophylaxis with emicizumab once weekly or every two weeks resulted in significant reductions in bleeds, including joint bleeds, and a favorable safety profile in PwHA without FVIII inhibitors in the HAVEN 3 study (NCT02847637; Mahlangu et al. 2018). Recurrent joint bleeds in PwHA can lead to hemophilic arthropathy, and hemophilia A has been associated with decreased bone mineral density (Kempton et al. 2014). To explore the potential effect of emicizumab prophylaxis on bone and joint health beyond bleed prevention, we measured joint health scores and bone and joint biomarkers in HAVEN 3. Methods Hemophilia joint health scores (HJHS; v2.1) were evaluated at baseline and Week 49 of emicizumab prophylaxis in 107 PwHA in HAVEN 3. Biomarkers of bone formation (osteocalcin [OC], N-terminal propeptide of type I procollagen [P1NP]), bone resorption (C-terminal telopeptide of type I collagen [CTX-I]), osteoblasts (osteoprotegerin), osteoclastogenesis (soluble receptor activator of nuclear factor- kappaB Ligand [sRANKL]), cartilage turnover (cartilage oligomeric matrix protein [COMP]), and inflammation (interleukin 1 beta, interleukin 6, and tumor necrosis factor) were measured in 117 PwHA (Table 1) receiving emicizumab at baseline and after 3, 6, 12, and 18 months of treatment. In all, 94 of 117 PwHA with samples for biomarker analysis were part of the HJHS evaluation. Results PwHA previously on FVIII prophylaxis and those with no target joints at study entry had lower (indicating healthier) HJHS scores at baseline. Mean improvements from baseline of −2.25 (95% confidence interval [CI]: −4.12, −0.39) in total HJHS and −2.23 (95% CI: −4.07, −0.38) in HJHS joint-specific domain (excluding gait) were observed after 49 weeks of emicizumab prophylaxis in PwHA with one or more target joints at study entry (n=71). Improvement was consistent across HJHS for different locations (knee, ankle, elbow). No significant differences in the measured biomarkers between PwHA previously on FVIII prophylaxis or on on-demand treatment, or in those with or without target joints, were seen at baseline. Mean baseline values of most bone and joint biomarkers were within normal ranges, or similar to published levels in healthy individuals, although large variability was observed between individuals. None of the measured biomarkers changed significantly during emicizumab prophylaxis. Higher OC, P1NP, and CTX-I levels were observed in adolescent vs adult PwHA at all time points, which is consistent with reported increases of these biomarkers during skeletal growth. Data suggest a potential association of COMP levels with HJHS scores at baseline (Pearson correlation coefficient 0.46, p=0.0001). Data on two additional cartilage biomarkers, CTX-II (C-terminal telopeptide of type II collagen) and CS-846 (a chondroitin sulfate epitope) are being generated. Conclusions Reduction in joint bleeds was previously reported in HAVEN 3, including over 99% target joint resolution with long-term follow up (Callaghan et al. 2019). This analysis provides further evidence of the positive effect of emicizumab on joint health, showing significant and clinically relevant improvements in HJHS (defined as a ≥2-point reduction in HJHS joints domain [Kuijlaars et al. 2017]) after as few as 49 weeks of emicizumab prophylaxis. The biomarkers measured in blood as surrogates of bone and joint health did not show significant changes over the first 18 months of emicizumab prophylaxis. This may reflect heterogeneity between individuals, and effects on the measured biomarkers by factors other than joint health. However, improvement in bone and joint biomarkers would have been unexpected as the observed means at baseline were already similar to levels reported in healthy individuals. Although data from animal models have suggested that FVIII may play a role in bone health beyond protection against bleeds, in this study we observed no indication of worsening in any of the measured bone and joint health markers that might have resulted from reduced exposure to FVIII in PwHA who switched to emicizumab prophylaxis. Additional data are needed to better understand the long-term effect of emicizumab prophylaxis on bone and joint health. Disclosures Kiialainen: F. Hoffmann-La Roche Ltd: Employment, Equity Ownership. Niggli:F. Hoffmann-La Roche Ltd: Employment. Kempton:Novo Nordisk: Research Funding; Octapharma: Honoraria; Pfizer: Honoraria; Genentech, Inc.: Honoraria. Castaman:Sanofi: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Bayer: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Uniqure: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Kedrion: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Werfen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Takeda (SHIRE): Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Sobi: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Roche: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pfizer: Research Funding; CSL Behring: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Novo Nordisk: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Chang:Genentech/Roche: Equity Ownership; Genentech, Inc.: Employment. Paz-Priel:Genentech, Inc.: Employment. Adamkewicz:F. Hoffmann-La Roche Ltd: Equity Ownership; Genentech, Inc.: Employment. Levy:F. Hoffman La Roche: Equity Ownership; Genentech, Inc: Employment.

Description: It has now been 3 years since the von Willebrand factor (VWF)–cleaving protease implicated in thrombocytopenic purpura (TTP) pathogenesis was identified as ADAMTS13 (adisintegrin-like and metalloprotease with thrombospondin type 1 motif 13). More than 50 ADAMTS13 mutations resulting in familial TTP have been reported. Considerable progress has also been realized toward understanding the role of ADAMTS13 in normal hemostasis, as well as the mechanisms by which ADAMTS13 deficiency contributes to TTP pathogenesis. Measurement of ADAMTS13 activity in TTP and other pathologic conditions also remains a focus of a substantial clinical research effort. Building on these studies, continued investigation of ADAMTS13 and VWF holds considerable promise for advancing the understanding of TTP pathogenesis and should lead to improved diagnosis and treatment for this important hematologic disease.

Description: Background Direct factor Xa inhibitors have demonstrated compelling anticoagulant efficacy and/or safety profiles across multiple diverse patient populations. A specific antidote to reverse anticoagulation during episodes of serious uncontrolled bleeding or before urgent/emergent surgery is lacking. Andexanet alfa (proposed INN)(AnXa, PRT064445) is a modified, recombinant human fXa molecule that is catalytically inactive but retains high-affinity binding to direct fXa inhibitors. It thus acts as a decoy to reverse fXa inhibitor-mediated anticoagulation in preclinical and early clinical studies. Methods This ongoing Phase 2, double-blind, placebo-controlled study is examining the reversal by AnXa of the anticoagulant activity of rivaroxaban (riva), as well as the pharmacokinetics and safety in healthy subjects. Reversal of riva anticoagulation will be studied with up to 6 different dose cohorts/ regimens of AnXa or placebo in a 6:3 ratio (i.e., 9 subjects per cohort). Riva is administered at an oral dose of 20 mg qd for 6 days and AnXa administered intravenously on Day 6, 3 hours after the last riva dose – the approximate time of maximum riva concentration (mean ± SD: 0.64 ± 0.22 mM, n=18). Pharmacodynamic and safety data are collected through Day 48 with pharmacokinetic data through Day 10. Results We report here available data from the first 2 AnXa dose cohorts (210 mg and 420 mg, n =18). Immediately after completion of the 210 mg and 420 mg doses, anti-fXa activity decreased dose-dependently by 20% and 53%, respectively, from the pre-AnXa level and returned to placebo levels by approximately 2 hours after treatment (Figure). In parallel, the plasma concentrations of unbound riva were decreased by 32% and 51%, respectively, relative to pre-AnXa values. In addition, riva-induced inhibition of thrombin generation and prolongation of both prothrombin time and activated clotting time were also rapidly partially reversed by AnXa in a dose-dependent manner. At 2 minutes after AnXa administration, the molar ratio of AnXa to total plasma riva was 0.8 for the 210 mg dose (1.2 µM/1.6 µM, respectively) and 1.2 for the 420 mg dose (2.6 µM/2.1 µM, respectively). AnXa infusion was not associated with increases in prothrombin fragments F1+2, thrombin-antithrombin, or D-dimer (all values were within normal ranges). As expected, tissue factor pathway inhibitor activity decreased due to its binding to AnXa. AnXa was well tolerated and there were no thrombotic events, serious, or severe adverse events. Adverse events occurring in 1 or more AnXa or placebo recipients included infusion-related reactions (n = 3, all mild in severity) and post-procedural hematoma, headache, or postural dizziness (n = 2 each). Summary/Conclusions Results from this ongoing clinical trial demonstrate that AnXa is able to dose-dependently partially reverse the anticoagulant effects of rivaroxaban, as assessed by pharmacodynamic markers, in healthy subjects. These data are consistent with previously reported results with apixaban in that AnXa sequesters rivaroxaban and apixaban in a similar stoichiometric manner. Additional data with higher doses of AnXa will also be presented. AnXa is well-tolerated and a potentially promising, universal antidote for fXa inhibitors. Disclosures: Mark: Portola Pharmaceuticals: Consultancy. Off Label Use: The use of PRT064445 as an antidote for reversal of anticoagulation from direct and indirect fXa inhibitors is investigational. Vandana:Portola Pharmaceuticals: Consultancy. Michael:Portola Pharmaceuticals: Employment, Equity Ownership. Genmin:Portola Pharmaceuticals: Employment, Equity Ownership. Conley:Portola Pharmaceuticals: Employment, Equity Ownership. Stanley:Portola Pharmaceuticals: Employment, Equity Ownership. Castillo:Portola Pharmaceuticals: Employment, Equity Ownership. Hutchaleelaha:Portola Pharmaceuticals: Consultancy. Karbarz:Portola Pharmaceuticals: Employment. Lin:Portola Pharmaceuticals: Employment. Barron:Portola Pharmaceuticals: Employment. Russell:Portola Pharmaceuticals: Employment. Levy:Portola Pharmaceuticals: Employment. Connolly:Portola Pharmaceuticals: Consultancy. Curnutte:Portola Pharmaceuticals: Employment, Equity Ownership.

Description: In a Plenary Paper, Young et al describe impressive favorable outcomes of emicizumab prophylaxis in children with hemophilia A and factor VIII inhibitors, reporting a 99% reduction in annualized bleeding, with 77% of patients having no treated bleeding events.

Description: Introduction Emicizumab - a bispecific humanized monoclonal antibody given subcutaneously - bridges FIXa and FX to restore the function of missing FVIIIa. It is approved for routine prophylaxis in people with hemophilia A (PwHA) with inhibitors of all ages. Previous data from the HAVEN 2 study of emicizumab in pediatric PwHA with inhibitors

Description: Introduction: Preclinical studies of the Syk-mediated B-cell receptor pathway and Jak-mediated cytokine pathways have demonstrated a potential therapeutic advantage for the dual inhibition of both Syk and Jak kinases in the treatment of B-cell malignancies. Cerdulatinib (PRT062070) was identified from a chemistry screen as a potent and selective inhibitor of Syk, Jak1, Jak3, and Tyk2, with minimal activity against Jak2. Cerdulatinib is efficacious in rodent models of B-cell lymphoma and autoimmune disease (Coffey et al., ASH 2012) and has demonstrated anti-tumor activity in genetically diverse B-cell lymphoma cell lines that is greater than that of Syk- or Jak- selective inhibitors alone (Ma et al., ASH 2013). Methods: This Phase 1 3+3 dose escalation study is evaluating cerdulatinib, given continuously on either a once daily (QD) or twice daily (BID) schedule, for relapsed/refractory chronic lymphocytic leukemia (CLL) or B-cell non-Hodgkin lymphoma (NHL). The primary objective is to determine the maximum tolerated dose (MTD) of cerdulatinib in patients with CLL or NHL. Secondary objectives are to assess the safety, tolerability, pharmacokinetics, and pharmacodynamics of cerdulatinib and to make a preliminary assessment of antitumor activity. Toxicity is graded according to the National Cancer Institute - Common Terminology Criteria for Adverse Events (NCI-CTCAE) v4. Clinical response is evaluated according to published criteria (Hallek et al., Blood 2008:111:5446-5456; Cheson et al., J. Clin. Oncol. 2012: 25:579-586). The level of inhibition of Syk and Jak is determined using a variety of whole blood assays measuring signaling via receptors for the B-cell antigen, IL2, IL4, IL6, and GM-CSF. Serum markers of tumor burden, including CCL3, CCL4, and other markers of inflammation, are also being measured. Results: As of 4 August 2014, twelve patients have been enrolled in once daily dose cohorts of 15 mg QD, 30 mg QD, and 45 mg QD. No dose-limiting toxicities have been reported. Grade ≥3 adverse events (AEs), regardless of causality, were: Grade 3 anemia (n=1), Grade 3 neutropenia (n=1), Grade 3 fatigue (n=1), Grade 3 hypotension (n=1), Grade 3 AST increased (n=1), Grade 3 hematochezia (n=1), and Grade 5 Pneumocystis pneumonia (PCP; n=1). The patient who experienced PCP pneumonia was a 76 year old male with CLL who had received prior therapy with bendamustine and rituximab. Cerdulatinib is well-absorbed with an average terminal elimination half-life at steady state of 14 hours. Selective inhibition of Syk and Jak in whole blood assays was observed post-treatment, with IC25-IC50 (Cmin to Cmax at steady-state) against these targets achieved at the 15 mg dose level, and IC50-IC80 (Cmin to Cmax at steady-state) achieved at the 30 mg and 45 mg doses. Reductions of 〉50% in serum markers of inflammation, as well as in CCL3 and CCL4, were noted at all dose levels post-treatment. Two patients treated at the 15 mg dose (1 CLL, 1 follicular lymphoma [FL]) remained on study for 〉230 and 〉200 days, respectively, with stable disease (SD) prior to disease progression. One patient treated at the 30 mg dose (diffuse large B-cell lymphoma [DLBCL], who did not respond to prior R-CHOP therapy), remained on study with SD for 140 days. One patient treated at the 30 mg dose (CLL) experienced a 〉60% decrease in peripheral lymphocyte count prior to coming off study for PCP pneumonia. Another patient treated at the 30 mg dose (CLL) experienced early lymphocytosis and a 33% reduction in lymph node size at the end of Cycle 2 and remains on study in Cycle 3. One patient treated at the 45 mg dose (FL) experienced a 40% decrease in lymph node size at the end of Cycle 4 and remains on study in Cycle 5. Conclusions: Cerdulatinib has been well tolerated in the initial cohorts of this Phase 1 study, with no dose-limiting toxicities and preliminary evidence of anti-tumor activity. Dose escalation continues and Phase 2 expansion cohorts are planned in CLL, DLBCL and FL. Disclosures Hamlin: Gilead, Spectrum, Seattle Genetics, Genentech: Consultancy; Spectrum, GSK, Jansen and Jansen/Pharmacyclics, Portola, Seattle Genetics: Research Funding. Strickland:SCRI Development Innovations: Employment. Pandey:Portola Pharmaceuticals, Inc.: Employment; Portola Pharmaceuticals, Inc.: Equity Ownership. Coffey:Portola Pharmaceuticals: Employment, Equity Ownership. Leeds:Portola Pharmaceuticals, Inc.: Employment. Levy:Portola Pharmaceuticals: Employment; University of Michigan: Patents & Royalties. Curnutte:Portola Pharmaceuticals, Inc.: Employment, Equity Ownership; Sea Lane Biotechnologies: Consultancy; 3-V Biosciences: Equity Ownership. Wagner-Johnston:Gilead: Consultancy; Gilead: Speakers Bureau; Celgene: Research Funding. Flinn:Portola Pharmaceuticals, Inc.: Research Funding.

Description: Introduction Despite recent efforts to standardize the definition of 'new bleeds' in hemophilia A clinical trials, most notably by Blanchette et al. (J Thromb Haemost 2014), cross-study comparisons of these endpoints are still compromised by different bleed definitions, analysis methodologies and data collection approaches. The emicizumab clinical development program included an observational, non-interventional study (NIS; NCT02476942), in which a bleed and medication questionnaire (BMQ) was used to prospectively collect data on treatment with standard-of-care with factor VIII (FVIII) or bypassing agents (BPA) in adult and adolescent people with hemophilia A (PwHA) with and without inhibitors to FVIII. The study design allowed for an examination of the differences between treated and untreated bleeds, as well as any differences in their incidence between the inhibitor and non-inhibitor populations. Participation in the study was not expected to affect the number of treated and untreated bleeds. Methods The NIS was a global prospective study designed to collect real-world data on PwHA with or without inhibitors treated with current standard-of-care therapy according to routine clinical practice. Eligible participants from the NIS subsequently could enroll in a Phase III trial of emicizumab. Adult and adolescent participants (aged ≥12 years) were prompted to complete the BMQ daily. The BMQ was developed by the sponsor to enable data collection directly by patients. In addition to treatments administered, the BMQ allowed the patient to enter all the bleeds the patient experienced, irrespective of whether they were treated or not. For the purpose of the analysis of primary and secondary endpoints, a bleed was derived from the data using the definitions outlined by Blanchette et al. (J Thromb Haemost 2014) and Oldenburg et al. (N Engl J Med 2017). The efficacy endpoints included treated bleeds, all bleeds, spontaneous bleeds, joint bleeds and target joint bleeds. Results In the inhibitor and non-inhibitor cohorts, 103 and 94 patients were enrolled, with a median efficacy period of 25.4 and 27.7 weeks, respectively. NIS data for treated and untreated bleeds, including bleed types and bleed causes, are displayed in Table 1. Of all bleeds reported in the study, 625 (40.0%) were untreated in patients with inhibitors, and 160 (13.5%) were untreated in patients without inhibitors. Conclusions The NIS was the first study to report large numbers of untreated bleeds in PwHA, particularly in those with inhibitors, where approximately 40% of all bleeds were untreated (Mahlangu et al. ASH 2016; Kruse-Jarres et al. EAHAD 2018). The design of the BMQ allowed participants to capture bleeds and bleed treatment independently and enabled granular information on untreated and treated bleeds to be derived, as opposed to only bleeds where a treatment was administered, as had previously been captured in the majority of clinical studies (Keipert et al. ISTH 2018; Clausen et al. Haemophilia 2014). The reason for the large difference in the proportion of untreated bleeds in the inhibitor population versus the non-inhibitor population is unknown and warrants further investigation, but may be at least partially due to higher confidence in the efficacy of FVIII, less treatment burden, and better drug availability compared with BPAs; this may therefore influence the patient's decision on whether or not to treat. The NIS showed that further efforts to harmonize bleed definitions, analyses methodology and data collection in hemophilia A clinical trials are warranted in order to provide transparency on treated and untreated bleeds, as the latter might have been under-reported in clinical studies to date. Capturing untreated bleeds in future trials could provide useful insights to physicians as, while the long-term sequelae of untreated bleeds are as yet unknown, they are expected to be, at the very least, distressing for patients. Acknowledgments: Editorial assistance under the direction of the authors was provided by Maria Alfaradhi, PhD, of Gardiner-Caldwell Communications, and was funded by F. Hoffmann-La Roche Ltd. Disclosures Callaghan: Sancilio Pharmaceuticals Company: Employment; Hema Pharmaceuticals: Honoraria; Alnylam Pharmaceuticals: Equity Ownership; Amgen: Employment; Roche/Genentech: Employment, Honoraria, Membership on an entity's Board of Directors or advisory committees; Global Blood Therepeutics: Employment; Novo Nordisk: Employment, Membership on an entity's Board of Directors or advisory committees; Pfizer: Employment, Honoraria, Research Funding; Bioverativ: Honoraria; Octapharma: Honoraria; Shire: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Grifols: Honoraria; Bayer: Honoraria, Membership on an entity's Board of Directors or advisory committees. Asikanius:Roche: Employment, Equity Ownership. Lehle:F. Hoffmann-La Roche: Employment. Oldenburg:Biotest: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Biogen Idec: Honoraria, Membership on an entity's Board of Directors or advisory committees; Chugai: Honoraria, Membership on an entity's Board of Directors or advisory committees; Grifols: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees; Swedish Orphan Biovitrum: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; CSL Behring: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novo Nordisk: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Octapharma: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Shire: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Bayer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Mahlangu:Novo Nordisk: Honoraria, Research Funding; Pfizer: Research Funding; Spark: Honoraria; Bayer: Research Funding; Roche: Honoraria, Research Funding; Chugai: Honoraria; CSL Berhing: Honoraria; Alnylam: Research Funding; Shire: Honoraria; CLS: Research Funding. Uguen:F.Hoffmann-LaRoche: Employment. Chebon:F. Hoffmann-La Roche: Employment. Kruse-Jarres:Roche/Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; CSL Behring: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Membership on an entity's Board of Directors or advisory committees, Research Funding; Grifols: Membership on an entity's Board of Directors or advisory committees; Novo Nordisk: Consultancy, Membership on an entity's Board of Directors or advisory committees. Jimenez-Yuste:Grifols: Consultancy, Research Funding; Octapharma: Consultancy, Research Funding; NovoNordisk: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Sobi: Consultancy, Research Funding; Shire: Consultancy, Research Funding; Roche: Consultancy, Research Funding; Bayer: Consultancy, Research Funding; CSL Behring: Consultancy. Shima:F. Hoffmann-La Roche Ltd: Membership on an entity's Board of Directors or advisory committees; Chugai Pharmaceutical Co., Ltd: Consultancy, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties: Anti-FIXa/X bispecific antibodies , Research Funding, Speakers Bureau. Trask:Roche: Employment, Equity Ownership. Kessler:Genentech: Research Funding; Sangamo: Research Funding; Bayer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Biomarin: Research Funding; Dimension Advisory boards: Membership on an entity's Board of Directors or advisory committees; Octapharma: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novo Nordisk: Honoraria, Research Funding; DSMB: Membership on an entity's Board of Directors or advisory committees. Levy:Roche: Employment, Equity Ownership. Santagostino:Shire: Membership on an entity's Board of Directors or advisory committees; Octapharma: Membership on an entity's Board of Directors or advisory committees; Grifols: Membership on an entity's Board of Directors or advisory committees; CSL Behring: Membership on an entity's Board of Directors or advisory committees; Novo Nordisk: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees; Kedrion: Membership on an entity's Board of Directors or advisory committees; Sobi: Membership on an entity's Board of Directors or advisory committees; Bioverativ: Membership on an entity's Board of Directors or advisory committees; Bayer: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees.

Description: Background: Direct fXa inhibitors appear to have similar or superior anticoagulant efficacy and safety relative to warfarin (and in some cases low molecular weight heparin) in the management of venous thromboembolism and stroke prevention in atrial fibrillation. However, they are limited by the lack of a specific antidote to reverse anticoagulation in cases of major bleeding episodes or prior to urgent/emergency surgery. Andexanet alfa (AnXa, PRT064445) is a modified, recombinant human fXa molecule that is catalytically inactive but retains high-affinity binding to direct and indirect fXa inhibitors, therefore acting as a decoy to bind and sequester fXa inhibitors. We previously reported Phase 2 data with apixaban, rivaroxaban and enoxaparin in healthy subjects and demonstrated that AnXa was able to rapidly and extensively reverse pharmacodynamic (PD) markers of anticoagulation. Here we report new clinical data demonstrating that AnXa rapidly reverses the PD markers of edoxaban-mediated anticoagulation – anti-fXa activity and inhibition of thrombin generation. Methods: This ongoing Phase 2, double-blind, placebo-controlled study is examining the reversal by AnXa of the anticoagulant activity of edoxaban (edox, the most recent fXa inhibitor for which an NDA/MAA was submitted) as well as its pharmacokinetics (PK) and safety profile in healthy subjects. Reversal of edox anticoagulation is being studied with up to 3 different dose cohorts/regimens of AnXa or placebo in a 6:3 ratio (i.e., 9 subjects per cohort). Edox is administered at an oral dose of 60 mg qd for 6 days and AnXa administered intravenously on Day 6, 3 hours after the last edox dose. PD and safety data are collected through Day 48 with PK data through Day 10. Results and Conclusions: We report here available data from the first 2 AnXa dose cohorts (600 mg bolus, n=9; 800 mg bolus followed by 8 mg/min infusion for 1 hr, n=9). Immediately after completion of the 600 mg or 800 mg bolus, anti-fXa activity decreased dose-dependently by 52% and 73%, respectively, from the pre-AnXa level, remained constant during the infusion, and returned to placebo levels by approximately 2 hours after treatment. In addition, edox-induced inhibition of thrombin generation and prolongation of clotting times were also reversed by AnXa in a dose-dependent manner. AnXa was well tolerated and there were no thrombotic events, serious, or severe adverse events. One subject was discontinued on Day 5 prior to AnXa dosing due to a vasovagal reaction. These data are consistent with previously reported results for other fXa inhibitors in that AnXa rapidly reverses PD markers of anticoagulation, restores normal thrombin generation, and is well tolerated. Disclosures Crowther: CSL Behring: Honoraria; Shire: Honoraria; Celgene: Honoraria; Bayer: Honoraria; AKP America: Consultancy; Leo Pharma: Consultancy, Honoraria, Research Funding; Janssen: Consultancy; Portola Pharmaceuticals, Inc.: Consultancy; The Heart and Stroke Foundation of Ontario: Career Investigator Award, Career Investigator Award Other. Levy:Portola Pharmaceuticals: Employment; University of Michigan: Patents & Royalties. Lu:Portola Pharmaceuticals Inc: Employment. Leeds:Portola Pharmaceuticals, Inc: Employment. Lin:Portola Pharmaceuticals, Inc.: Employment. Pratikhya:Portola Pharmaceuticals, Inc.: Employment. Conley:Portola Pharmaceuticals Inc: Employment; Portola Pharmaceuticals Inc: Equity Ownership. Connolly:Portola Pharmaceuticals Inc: Consultancy. Curnutte:Portola Pharmaceuticals, Inc.: Employment, Equity Ownership; Sea Lane Biotechnologies: Consultancy; 3-V Biosciences: Equity Ownership.