BJTJ-1837, a novel FXI activation-blocking antibody

BACKGROUND: Factor (F)XI contributes to thrombosis development while it plays a limited role in normal hemostasis. FXI targeting has the potential for preventing and treating thrombosis with little bleeding risk. OBJECTIVES: The aim of this study was to develop novel antibody therapeutics against FXI for the treatment of thrombosis-related diseases. METHODS: Mouse hybridoma technology was applied to screen for anti-FXI antibodies. Surface plasma resonance, enzyme inhibition, activated partial thromboplastin time, and prothrombin time assays were conducted to characterize the binding affinity and activity of antibodies. A cynomolgus monkey arterial venous shunt model was applied to validate the antithrombotic activities. RESULTS: A humanized antibody, BJTJ-1837, reported here bound to the protease domain of FXI and activated FXI with high affinity. BJTJ-1837 fully inhibited the activation of FXI by activated FXII and thrombin. BJTJ-1837 also demonstrated strong anticoagulant activity in human and cynomolgus monkey plasma as measured by activated partial thromboplastin time. Moreover, BJTJ-1837 showed favorable antithrombotic activity with a dose-dependent protection in an arterial venous shunt thrombosis model in cynomolgus monkeys without the bleeding adverse effect. Furthermore, BJTJ-1837 displayed favorable pharmacokinetic and pharmacodynamic properties and good developability. CONCLUSION: As a potential antithrombotic therapeutic agent with a safe profile, BJTJ-1837 is a very promising FXI activation-blocking antibody candidate.