SBIR-STTR Award

During cardiopulmonary bypass, plasma factor XII is converted to active XIIa by contact with the surfaces of the bypass circuit, initiating a process which results in massive activation of the plasma proteases of the contact system. Products of contact activation include bradykinin from the kallikrein-kinin system and the neutrophil activators XIIa, kallikrein and complement factor C5a. Neutrophil activation can result in neutrophil-mediated lung damage and dysfunction, a significant cause of post-bypass morbidity. Our goal is to discover a potent protein inhibitor of human factor XIIa which can be used to prevent activation of the contact system during extracorporeal circulation in order to attenuate post-bypass pulmonary injury. Phagemid libraries which display variants of the Kunitz protease inhibitor domain (KPI) of human protease nexin-2/amyloid beta-protein precursor will be selected with immobilized human factor XIIa to identify KPI mutants which inhibit human-factor XIIa with high potency. In the Phase II time period, a potent KPI-derived XIIa inhibitor will be tested in vivo for its ability to inhibit the contact activation system and reduce neutrophil- mediated lung damage in an animal model of cardiopulmonary bypass.National Heart, Lung, and Blood Institute (NHLBI)

The use of cardiopulmonary bypass (CPB) in cardiothoracic surgery is associated with significant postoperative bleeding and pulmonary injury due to massive activation of plasma protease systems during extracorporeal circulation. Contact activation of the kallikrein- kinin system, intrinsic coagulation, the complement cascade and fibrinolysis during CPB all contribute to excessive post-bypass blood loss and an inflammatory response manifested by pulmonary dysfunction. The goal of this research is to discover a potent protein inhibitor of human factor XIIa and plasma kallikrein which can be used to prevent activation of the contact system during CPB in order to reduce blood loss and attenuate parameters of pulmonary dysfunction. Protein engineering techniques have been used to identify variants of the Kunitz protease inhibitor domain (KPI) of the human amyloid beta-protein precursor which are potent inhibitors of factor XIIa, plasma kallikrein and plasmin. In the Phase II portion of this research, a high yield recombinant expression system will be established to generate preclinical supplies of one KPI variant. The human KPI variant will be tested in a sheep model of cardiopulmonary bypass for its ability to significantly reduce post-operative blood loss and lung injury.Proposed commercial application:A potent recombinant human protein inhibitor of factor XIIa, plasma kallikrein and plasmin would be administered prophylactically during surgeries requiring cardiopulmonary bypass to reduce postoperative blood transfusions and improve recovery times.Thesaurus termsamyloid protein, blood coagulation, coagulation factor XII, heart /lung bypass, protease inhibitor, protein engineering blood flow measurement, disease model, genetic library, kallikrein, kininogen Saccharomyces, hemodynamics, plasmid, sheep, transfection vectorNational Heart, Lung and Blood Institute (NHLBI)