Abstract 14119: A Novel Antibody-Targeted Recombinant Plasminogen Activator Directed to Activated Platelets Allows Efficient Antithrombotic Prophylaxis
Introduction: Plasminogen activators such as Urokinase (scuPA) generate plasmin, which lyses fibrin and restores perfusion. However, thrombi recur due to vascular damage and inflammation. Prophylactic administration of thrombolytic drugs, especially in combination with potent platelet blockers, poses the danger of hemorrhage, leaving many patients untreated. We previously generated an antibody (SCE5) that blocks only the activated GPIIb/IIIa receptor on platelets providing targeted antithrombotic potency without bleeding time prolongation. Here we now fused SCE5 to scuPA to provide thromboprophylaxis without systemic complications.
Results: The construct was produced in HEK293 cells with high yields (4-6mg/L) and purified to a uniform 67kDa protein. Antibody binding, fibrinogen inhibition and scuPA activity of the fusion construct were on par with the parent molecules. In vitro clot lysis assays revealed significant better activity compared to control constructs. In vivo efficiency was determined in a prophylactic mouse thrombosis model. Administration of 75U/gBW SCE5-scuPA prevented occlusion after injury with 6% ferric chloride compared to saline or clinically used scuPA, and blood flow recovery was higher (e.g at 30 min it was 3.7 vs 1.5 mL/min, p<0.001) than with SCE5 alone, non-targeted scFv-scuPA and the combination of SCE5 and scuPA individually (see figure). Administration of non-targeted scuPA at the comparable effective dose (500U/gBW) caused prolonged tail bleeding times (4 min vs 1.8 min saline, p<0.01, n=5).
Conclusion: The combination of activation-specific GPIIb/IIIa blockade and plasminogen activation in one molecule allows selective platelet inhibition and targeted enrichment of fibrinolysis. These in vivo data imply that this unique anti-platelet fibrinolytic agent, in addition to providing effective thrombolysis, can be applied as a highly effective prophylactic anti-thrombotic agent without bleeding complications.
- © 2011 by American Heart Association, Inc.