Discovery, Engineering and Pre-Clinical Evaluation of an Anti-vWF A1 Domain Aptamer.

Following coronary artery damage, von Willebrand Factor (vWF) multimers adhere to exposed collagen via the vWF A3 domain. Platelets passing through damaged vessels under the conditions of high shear force associated with stenosed arteries will adhere to the vWF A1 domain via GPIb receptors. This initial platelet binding event triggers the formation of a thrombus that can limit blood flow to the myocardium and produce the symptoms of acute coronary syndrome (ACS). Through in vitro selection (SELEX) and subsequent lead optimization, we have generated a nuclease-resistant DNA aptamer that binds to the vWF A1 domain with high affinity. The anti-vWF aptamer inhibits both botrocetin-induced platelet aggregation of platelet rich plasma and shear force-induced platelet aggregation in citrated whole blood. Continuous intravenous infusion of the aptamer in cynomolgus macaques is able to effectively inhibit thrombus formation induced by electrical injury to the carotid artery. Modest effects on template bleeding are observed with the vWF-specific aptamer relative to anti-GPIIb/IIIa therapy. Based upon these results, this aptamer is an excellent candidate for treatment of ACS.