Anthos Therapeutics' novel Factor XI inhibitor abelacimab significantly outperforms standard of care enoxaparin in prospective Phase 2 efficacy research published today in the New England Journal of Medicine


CAMBRIDGE, Mass., July 19, 2021 /PRNewswire/ -- Anthos Therapeutics, a clinical-stage biopharma company developing innovative therapies for cardiovascular and metabolic diseases, today announced final results from the Phase 2 ANT-005 study with its novel investigational anticoagulant abelacimab. Published today in the New England Journal of Medicine,1 and simultaneously presented as a late breaker at the International Society of Thrombosis and Haemostasis (ISTH) 2021 Congress, the data showed that a single postoperative dose of abelacimab reduced the rate of venous thromboembolism (VTE) by ~80% compared to enoxaparin (a commonly used low molecular weight heparin), following elective total knee arthroplasty, the gold standard setting for potential new anticoagulants to demonstrate efficacy.

In this parallel group study, 412 participants were randomly assigned to one of three single postoperative intravenous doses of abelacimab (150mg, 75mg or 30mg) in a blinded fashion or open-label standard of care enoxaparin given subcutaneously 40mg once daily for approximately 10 days after surgery. The primary composite efficacy outcome – which included deep vein thrombosis detected by venography of the operated leg and documented symptomatic VTE events – occurred in 4%, 5% and 13% of patients in the 150mg, 75mg and 30mg abelacimab groups respectively, compared with 22% of patients in the enoxaparin group. The 75mg and 150mg abelacimab regimens were both statistically superior to enoxaparin (p<0.001) while the 30mg dose was non-inferior. Abelacimab was well tolerated with no safety signals and bleeding was insignificant in both study arms.

"The results of this study provide exciting new evidence that inhibition of Factor XI appears an effective way to reduce the risk of pathological thrombosis – in this case, with a single post-operative dose of abelacimab. The data highlight the potential of this new approach in other clinical settings where the unmet clinical need is high," observed Jeffrey I. Weitz, MD, Professor at McMaster University, Hamilton, Ontario, and one of the study authors.

Abelacimab is a highly selective, fully human monoclonal antibody with novel dual activity against both Factor XI and its activated form, Factor XIa, achieving profound Factor XI suppression for up to 30 days following a single intravenous or subcutaneous dose.1,2

Beyond the compelling efficacy data shown in this study, Anthos' vision in developing abelacimab is to achieve 'hemostasis-sparing' anticoagulation: effective protection from thromboembolic events with a reduced risk of clinically significant bleeding. According to a recently described model of the coagulation cascade,3 Factor XI plays an important role in the development of pathological thrombosis but is hypothesized to play only a minimal role in physiological hemostasis. Factor XI inhibition thus provides a potentially significant opportunity to pharmacologically 'uncouple' the two pathways.

Dan Bloomfield, MD, Chief Medical Officer at Anthos Therapeutics, explained: "All current anticoagulants – including direct oral anticoagulants (DOACs) – impact physiological hemostasis as well as pathological thrombosis due to their action on the 'common pathway' of the coagulation cascade, thus carrying a well-documented bleeding risk which may be even greater in the real world than in clinical trials.4,5 Fear of bleeding commonly deters prescribers and patients from pursuing optimal anticoagulation6-8 so our aim in developing abelacimab is to address this major unmet need."  The ongoing Phase 2 ANT-006 study (AZALEA-TIMI 71), investigating long-term once-monthly subcutaneous administration of abelacimab for stroke prevention in patients with atrial fibrillation, is expected to provide insight on the bleeding risk with abelacimab compared to a commonly used DOAC.

Anthos Therapeutics' Chief Executive Officer, John Glasspool, commented: "More than 1 in 4 people worldwide continue to die from thromboembolic events – and yet 40-50% of high-risk individuals fail to receive optimal anticoagulation, mainly due to the prevailing fear of bleeding. Factor XI inhibition may provide a paradigm shift towards safer anticoagulation that inspires greater confidence among prescribers and patients." Mr. Glasspool added: "I am proud of the progress we have made to address unmet needs in high-risk cardiovascular and metabolic conditions since we launched two years ago with investment from Blackstone Life Sciences. The efficacy findings announced today represent the first major milestone in our development plans for abelacimab."


1.  Verhamme P et al. New Engl J Med 2021, in press
2.  Yi BA et al. ISTH 2021 poster PB0077
3.  Hsu C et al. J Am Coll Cardiol 2021, in press
4.  Buderi R et al. ISTH 2021 poster PB0047
5.  Fox, KAA et al. BMJ Open 2017; Dec 21;7(12):e017157
6.  Hsu JC et al. JAMA Cardiol. 2016; 1: 55–62.
7.  Piccini JP et al. Circulation. 2019; 139:1497–1506.
8.  Cohen AT et al. Lancet 2008; 2;371(9610):387-94

Anthos Therapeutics is a clinical-stage biopharmaceutical company focused on the development and commercialization of genetically and pharmacologically validated innovative therapies to advance care for people living with cardiovascular and metabolic (CVM) diseases. Anthos Therapeutics aims to combine the agility of a biotech with the rigor of a large pharmaceutical company. Anthos Therapeutics was launched by Blackstone Life Sciences in 2019.

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About Blackstone Life Sciences
Blackstone Life Sciences is an industry-leading private investment platform with capabilities to invest across the life cycle of companies and products within the key life science sectors. By combining scale investments and hands-on operational leadership, Blackstone Life Sciences helps bring to market promising new medicines that improve patients' lives. More information is provided at

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