A Factor XIIa Inhibitory Antibody Provides Thromboprotection in Extracorporeal Circulation Without Increasing Bleeding Risk

Abstract

Currently used anticoagulants prevent thrombosis but increase bleeding. We show an anticoagulation therapy without bleeding risk based on a plasma protease factor XII function-neutralizing antibody. We screened for antibodies against activated factor XII (FXIIa) using phage display and demonstrated that recombinant fully human antibody 3F7 binds into the FXIIa enzymatic pocket. 3F7 interfered with FXIIa-mediated coagulation, abolished thrombus formation under flow, and blocked experimental thrombosis in mice and rabbits. We adapted an extracorporeal membrane oxygenation (ECMO) cardiopulmonary bypass system used for infant therapy to analyze clinical applicability of 3F7 in rabbits. 3F7 provided thromboprotection as efficiently as heparin, and both drugs prevented fibrin deposition and thrombosis within the extracorporeal circuit. Unlike heparin, 3F7 treatment did not impair the hemostatic capacity and did not increase bleeding from wounds. These data establish that targeting of FXIIa is a safe mode of thromboprotection in bypass systems, and provide a clinically relevant anticoagulation strategy that is not complicated by excess bleeding.

Peptide Macrocycle Inhibitor of Coagulation Factor XII with Subnanomolar Affinity and High Target Selectivity

“…4 The humanized antibody 3F7 inhibited arterial and venous thrombosis in mouse and rabbit, and prevented coagulation in extracorporeal circulation in rabbits. 7 The antibody 15H8 blocked thrombosis in mice and baboon. 14 The development of small molecule FXIIa inhibitors has been challenging.…”

“…1 FXII also constitutes a constant threat in medical procedures that depend on extracorporeal circulation such as cardiopulmonary bypass surgery, extracorporeal membrane oxygenation (ECMO), or hemodialysis. 7,8 In these procedures, contact with the materials of the medical devices, such 4 as tubing and membranes, can activate FXII and trigger the coagulation and inflammation pathways. FXII can also be activated by contact with catheters which can lead to catheter occlusion and thrombosis.…”

Update on the Role of Extracorporeal CO2 Removal as an Adjunct to Mechanical Ventilation in ARDS

“…In our opinion, alternative anticoagulation approaches, such as the work by Cardenas et al utilizing regional citrate anticoagulation, could provide a promising solution to future ECCO 2 R approaches, especially in line with the tendency for developing modular therapeutic solutions permitting concomitant lung and renal interventions [39,47]. Other novel approaches are emerging with respect to heparin-free antibody-based interventions to the coagulation cascade as a means to induce thromboprotection during extracorporeal circulation [48]. Specific anticoagulation requirements for low-flow systems must be studied systematically and will be the cornerstone of further acceptance of ECCO 2 R as well as full ECMO into daily practice, especially in patients with ARDS due to multiple trauma and burns, in whom heparinization is not desired.…”

Coagulation Factor XII –A Key Pro-Inflammatory and Pro-Coagulant Protein

“…In the preliminary treatment of the in vitro rabbit extracorporeal membrane oxygenation system, single dose of 3F7 prevented blood clot formation like heparin but didn't affect hemostasis. Compared to heparin that activate FXII and mediates inflammation, 3F7 inhibits activation of FXII by dextran sulfate and interferes activation of KKS [31]; 9A2 inhibits auto-activation of FXII by binding to the Type I domain of fibronectin or Type II domain of EGF, and inhibits fibrin deposition but doesn't affect FXIIamediated KK generation during re-calcification perfusion of collagen-coated surface. 15H8 binds to the Type II domain and Kringle domain of EGF, exerting a stronger inhibitory effect than 9A2, not only on auto-activation of FXII but also on activation of PK by FXIIa [32].…”