Factor XIIa as a Novel Target for Thrombosis: Target Engagement Requirement and Efficacy in a Rabbit Model of Microembolic Signals
| Autor: | Xinkang Wang, Dietmar Seiffert, Aimie M. Ogawa, Kim O’Neill, Xueping Zhou, Zhu Chen, Christopher M. Barbieri, David E. Gutstein, Weizhen Wu, Gino Castriota, Donald Chu |
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| Rok vydání: | 2016 |
| Předmět: |
0301 basic medicine
Factor XIIa Plasmin Recombinant Fusion Proteins Serum Albumin Human Coagulation Factor XII 030204 cardiovascular system & hematology Pharmacology 03 medical and health sciences 0302 clinical medicine Fibrinolytic Agents Zymogen medicine Potency Animals Thrombus Blood Coagulation Serum Albumin business.industry Anticoagulants medicine.disease Thrombosis 030104 developmental biology Intracranial Embolism Immunology Models Animal Molecular Medicine Insect Proteins Rabbits Intracranial Thrombosis business Ex vivo medicine.drug |
| Zdroj: | The Journal of pharmacology and experimental therapeutics. 360(3) |
| ISSN: | 1521-0103 |
| Popis: | Coagulation Factor XII (FXII) plays a critical role in thrombosis. What is unclear is the level of enzyme occupancy of FXIIa that is needed for efficacy and the impact of FXIIa inhibition on cerebral embolism. A selective activated FXII (FXIIa) inhibitor, recombinant human albumin-tagged mutant Infestin-4 (rHA-Mut-inf), was generated to address these questions. rHA-Mut-inf displayed potency comparable to the original wild-type HA-Infestin-4 (human FXIIa inhibition constant = 0.07 and 0.12 nM, respectively), with markedly improved selectivity against Factor Xa (FXa) and plasmin. rHA-Mut-inf binds FXIIa, but not FXII zymogen, and competitively inhibits FXIIa protease activity. Its mode of action is hence akin to typical small-molecule inhibitors. Plasma shift and aPTT studies with rHA-Mut-inf demonstrated that calculated enzyme occupancy for FXIIa in achieving a putative aPTT doubling target in human, nonhuman primate, and rabbit is more than 99.0%. The effects of rHA-Mut-inf in carotid arterial thrombosis and microembolic signal (MES) in middle cerebral artery were assessed simultaneously in rabbits. Dose-dependent inhibition was observed for both arterial thrombosis and MES. The ED50 of thrombus formation was 0.17 mg/kg i.v. rHA-Mut-inf for the integrated blood flow and 0.16 mg/kg for thrombus weight; the ED50 for MES was 0.06 mg/kg. Ex vivo aPTT tracked with efficacy. In summary, our findings demonstrated that very high enzyme occupancy will be required for FXIIa active site inhibitors, highlighting the high potency and exquisite selectivity necessary for achieving efficacy in humans. Our MES studies suggest that targeting FXIIa may offer a promising strategy for stroke prevention associated with thromboembolic events. |
| Databáze: | OpenAIRE |
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