A bispecific antifibrin-antiplatelet urokinase conjugate (BAAUC) induces enhanced clot lysis and inhibits platelet aggregation

Thrombolysis is well established in the treatment of acute myocardial infar ction. However, clinical application of thrombolytic agents has limitations with respect to efficacy and specificity. To achieve highly effective and at the same time clot-selective plasminogen activation urokinase was couple d to a bispecific antibody consisting of the monovalent Fab' from the antif ibrin monoclonal antibody 59D8 and the monovalent Fab' from the anti-glycop rotein GPIIb/IIIa monoclonal antibody 7E3. The bispecific antifibrin-antipl atelet urokinase conjugate (BAAUC) was synthesized and characterized. Assay s with either immobilized platelets, GPIIb/IIIa or fibrin showed an increas e in plasminogen activation compared to uncoupled urokinase by 10-fold, 58- fold and 13-fold, respectivley (p < 0.0001 each). In vitro clot lysis was p erformed on platelet-rich and fibrin-rich clots and revealed an up to 5-fol d higher potency of BAAUC compared to uncoupled urokinase (p < 0.0001). In vitro platelet aggregation was effectively inhibited by the hybrid molecule , whereas urokinase had no effect. BAAUC and two monospecific urokinase-con jugates, UK-59D8-IgG and UK-7E3-(Fab')(2) were compared with each other wit h regard to similar tests. In vitro clot assays with platelet-rich and plat elet-poor clots were performed. BAAUC achieved a significantly higher plasm inogen activation compared to each of the monospecific conjugates (p < 0.05 , respectively). we, conclude that BAAUC, a bispecific plasminogen activato r with antifibrin and antiplatelet properties has the potency to lyse both fibrin-rich and platelet-rich thrombi with high efficacy and to effectively inhibit platelet aggregation.