Prevention of carotid artery thrombosis by oral platelet GPIIb/IIIa antagonist in dogs.

BACKGROUND AND PURPOSE

Current antithrombotic therapy in acute ischemic stroke and myocardial infarction in which a combination of antiplatelet agents (aspirin) and anticoagulants (heparin) was used led to partial reduction of acute thrombotic complications. Recent advances in antiplatelet research led to the discovery of the platelet glycoprotein IIb/IIIa complex (GPIIb/IIIa), the final common pathway for platelet aggregation. The present study was undertaken to determine the oral antithrombotic efficacy of a potent and specific platelet GPIIb/ IIIa antagonist, DMP728, in an electrically induced carotid artery thrombosis model in dogs. Based on the powerful antiplatelet efficacy of this mechanism in inhibiting all agonist-induced platelet aggregation as well as in inhibiting platelet procoagulant activity (thrombin generation and hence fibrin formation), an orally active antagonist for this integrin receptor might have potential benefits in stroke.

METHODS

Anesthetized dogs were instrumented for monitoring of arterial blood pressure, heart rate, and carotid artery flow velocity. Animals were treated with saline or DMP728 (0.1 to 1.0 mg/kg PO). Thrombus formation (platelet-rich aggregate with fibrous coating and a few erythrocytes) by anodal electrolytic stimulation (300 microA) to the intimal surface of the right carotid artery was initiated 120 minutes after oral DMP728 administration and continued for 180 minutes. Whole blood cell counts, ex vivo platelet aggregation, and template bleeding time were determined at different time points throughout the study.

RESULTS

DMP728 administered at 0.1 to 1.0 mg/kg PO exhibited dose-dependent antithrombotic efficacy in this model. DMP728 was shown to be significantly effective in inhibiting ex vivo platelet aggregation and in inhibiting thrombosis at 0.3 to 1.0 mg/kg PO. The antiplatelet, antithrombotic effects of DMP728 were demonstrated without any significant changes in the different hemodynamic or coagulation parameters. These data demonstrated the oral antithrombotic efficacy of DMP728 in dogs.

CONCLUSIONS

Platelet GPIIb/IIIa blockade with an orally active antagonist was shown to be safe and effective in the prevention of carotid artery occlusive thrombosis.