Pharmacological Profile of JNJ-64179375: A Novel, Long Acting Exosite-1 Thrombin Inhibitor.

JNJ-64179375 (JNJ-9375) is a recombinant human IgG4 monoclonal antibody engineered to mimic an IgA antibody that was identified in a patient who exhibited markedly prolonged clotting times but without spontaneous bleeding episodes over several years of follow-up. The crystal structure of the JNJ-9375 antigen-binding fragment/thrombin complex showed an almost identical binding mode to that of the patient IgA. In the current study, we characterized the in vitro and in vivo properties of JNJ-9375. Surface plasmon resonance studies demonstrated that JNJ-9375 binds to alpha-thrombin with high affinity and specificity (K-D : 0.8 nM for human thrombin). JNJ-9375 produced concentration-dependent prolongation of in vitro clotting assays in human plasma, including thrombin time (TT), ecarin clotting time, prothrombin time, and activated partial thromboplastin time, with EC2X values of 4.4, 12.4, 172.6, and 202.7 mu g/ml, respectively. JNJ-9375 inhibited thrombin-induced platelet aggregation in human plasma with an IC50 value of 52.6 nM (7.8 mu g/ml) and produced concentration-dependent prolongation of reaction time tested by thromboelastography. JNJ-9375 pretreatment resulted in dose-dependent reduction in thrombus formation in the rat arteriovenous (AV) shunt model of thrombosis. Robust efficacy was observed at 0.3 mg/kg accompanied by 1.5x of TT. Bleeding was increased at 3 mg/kg in a rat tail transection bleeding model demonstrating a therapeutic index of 10x compared with 1 x for apixaban in the same models. Our data suggest that thrombin exosite I inhibition is efficacious against thrombosis in a pretreatment prevention animal model. SIGNIFICANCE STATEMENT JNJ-9375 is a novel, fully human monoclonal antibody that binds to the exosite I region of thrombin with high affinity and specificity. JNJ-9375 concentration dependently prolonged clotting times and inhibited thrombin-induced platelet aggregation in in vitro assays based on its mechanism of action. In an in vivo rat AV shunt model, JNJ-9375 prevented thrombus formation in a dose-dependent fashion while demonstrating reduced bleeding risk. The present study demonstrated the antithrombotic effects of inhibiting the exosite I region of thrombin when given in a prevention mode in preclinical animal models.