Abstract 5485: Potent Antithrombotic Activity of EP224283, a Dual Factor Xa Inhibitor and GPIIb-IIIa Antagonist, in Arterial Thrombosis in Mice

Abstract

Arterial thrombosis results from combined platelet activation and coagulation at sites of vascular injury. In acute ischemic events, the cornerstone of treatment is the association of antiplatelet drugs with anticoagulants. Here we investigated the effects of EP224283, a molecule combining antithrombin-dependent factor Xa (FXa) and GPIIb-IIIa inhibition, in several thrombosis models including systemic thromboembolism, localized laser-induced thrombosis of mesenteric arterioles and carotid thrombosis after atherosclerotic plaque rupture in ApoE−/− mice. IV infusion of EP224283 produced dose-dependent anti-FXa activity and inhibition of ADP-induced platelet aggregation (PA). Specifically, 10 nmol/kg EP224283 exhibited plasmatic anti-FXa activity of 0.61±0.01 U/ml without detectable inhibition of PA, while 300 nmol/kg EP224283 exhibited both strong anti-FXa activity (7.6±0.5 U/ml) and 90% PA inhibition, 15 min after infusion. In systemic thromboembo-lism induced by collagen+adrenaline, where thrombin generation is minimal, 85% of control mice died. EP224283 (10 nmol/kg) had no effect on mortality, while all mice receiving EP224283 (300 nmol/kg) survived. When thromboembolism was induced by tissue factor, generating high amounts of active thrombin, mice injected with EP224283 (10 nmol/kg) displayed 40% reduced mortality while all mice injected with EP224283 (300 nmol/kg) survived. These results suggest that the antithrombotic effect is due to both the antiplatelet and anticoagulant properties of EP224283. In a model of localized thrombosis of mesenteric arterioles triggered by laser injury, where both platelet activation and thrombin generation are involved, EP224283 (10 nmol/kg) reduced thrombus stability, while EP224283 (300 nmol/kg) profoundly decreased thrombosis. In this model, high dose hirudin or clopidogrel do not completely inhibit thrombus formation. Thus the dual properties of EP224283 explain its efficacy in this model. Finally, in a model of atherosclerotic plaque rupture induced by ultrasounds, EP224283 (10 nmol/kg) reduced thrombosis by 80%. These results suggest that combining antiplatelet and anticoagulant activities in a single compound is a promising strategy in treatment of acute atherothrombosis.