Principal Investigator/Program Director (Last, First, Middle: Chen, Ridong ABSTRACT Adjunctive antithrombotic treatment with dual antiplatelet therapy (aspirin + P2Y12 antagonist) plus anticoagulant (heparin or bivalirudin) is an established treatment regimen for percutaneous coronary intervention (PCI) patients. Despite aggressive antithrombotic therapy, myocardial perfusion after PCI remains inadequate in many patients. Recurrent thrombosis and dose-limiting bleeding complications continue to occur in a significant number of patients. Attempts to further improve clinical outcomes have led to the development of more potent platelet P2Y12 inhibitors including prasugrel and ticagrelor, and direct factor Xa inhibitors, rivaroxaban and apixaban (not approved for PCI), but increase bleeding complications. Moreover, none of the current antithrombotics provide effective protection against coronary microvascular obstruction. This results in microinfarcts accompanied by inflammation, which is a determinant of patient prognosis, independent from infarct size. Clearly, the next milestones for acute AMI treatment are to break the link between antithrombotic potency and bleeding risk and to protect the myocardium and coronary microcirculation against reperfusion injury that causes chronic adverse left ventricle remodeling and heart failure. APT402 is a novel therapeutic fusion protein of an optimized human apyrase and annexin V that provides antiplatelet, anticoagulant, and cardioprotective activities. We hypothesize that the fusion will target the antithrombotic effect to the site of coronary thrombosis and synergistically attenuate thrombosis and reperfusion injury with minimal bleeding risk. In a rabbit carotid artery electrical injury model, APT402 preferably bound to the injured site and to the thrombus. Treatment with clopidogrel, ticagrelor, low molecular weight heparin, or bivalirudin alone failed to fully prevent occlusion with significantly increased bleeding. In contrast, APT402 maintained 100% patency without increasing bleeding time, PT, or aPTT. Strikingly, APT402 more effectively attenuated arterial thrombosis than ticagrelor plus bivalirudin. In this direct Phase II SBIR application, we propose to determine whether acute treatment with APT402 more effectively protects microvascular circulation and improves heart function in a clinically relevant model of thrombogenic myocardial infarction, while reducing bleeding risks compared to ticagrelor plus heparin, the standard-of-care treatment during PCI in the contemporary era of radial access. We have also assembled an experienced drug development team and will advance critical activities necessary to enable IND filing. Specific Aim 1. Using a porcine model of thrombogenic coronary microembolization, determine whether APT402 more effectively reduces coronary microvascular obstruction and improves LV function 60 days after reperfusion with less bleeding compared to ticagrelor plus heparin. Speci...