BJTJ-1837, a novel FXI activation-blocking antibody

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.

The aim of this study was to develop novel antibody therapeutics against FXI for the treatment of thrombosis-related diseases.

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.

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.

As a potential antithrombotic therapeutic agent with a safe profile, BJTJ-1837 is a very promising FXI activation-blocking antibody candidate.