JNJ-64179375 Inhibits Exosite I-Mediated Thrombin Activity While Preserving Exosite II and Active Site Function in Vitro

Anticoagulation requires a careful balance to achieve antithrombotic efficacy without disrupting normal hemostasis. Although current generation direct oral anticoagulants (DOACs) offer advantages over traditional warfarin or heparin therapy they still carry a bleeding risk, highlighting an unmet need for novel anticoagulants with improved therapeutic indices. DOACs such as apixaban and dabigatran bind to the active sites of their target proteases thereby inhibiting proteolysis of all substrates. In contrast, the recombinant antibody JNJ-64179375 (JNJ-9375) specifically binds to the exosite I region of thrombin without inhibiting active site function. Interestingly, JNJ-9375 has demonstrated an improved therapeutic index compared to apixaban in preclinical models of venous thrombosis (Chintala, M et al. Res Pract Thromb Haemost, 2017:1 (suppl 1): P201). To understand how the mechanism of action of JNJ-9375 contributes to its improved therapeutic index in preclinical models, we evaluated the impact of JNJ-9375 on the activity of thrombin toward physiological substrates in vitro. Fibrinogen is the primary in vivo substrate of thrombin and binds to it via exosite I. In a turbidimetric assay JNJ-9375 dose-dependently inhibited fibrinogen cleavage, reflecting direct competition between fibrinogen and JNJ-9375 for exosite I binding. Factor V (FV), Factor VIII (FVIII), and Factor XI (FXI) are activated by thrombin in positive feedback reactions. Exosites I and II in thrombin have bee...
Source: Blood - Category: Hematology Authors: Tags: 321. Blood Coagulation and Fibrinolytic Factors: Structural Biology of Coagulation Proteins Source Type: research