Dissolution of Pre-Existing Platelet Thrombus by Synergistic Administration of Low Concentrations of Bifunctional Antibodies against β3 Integrin

Most antithrombotic approaches target prevention rather than the more clinically relevant issue of resolution of an existing thrombus. In this study, we describe a novel and effective therapeutic strategy for ex vivo clearance of pre-existing platelet thrombus by the combination of two bifunctional platelet GPIIIa49-66 ligands that target different parts of the arterial thrombus. We produced an additional GPIIIa49-66 agent (named APAC), which homes to activated platelets. Like our previously described SLK (which targets newly deposited fibrin strands surrounding the platelet thrombus), APAC destroys platelet aggregates ex vivo in an identical fashion with 85% destruction of platelet aggregates at 2 hours. The combined application of APAC and SLK demonstrated a ~2 fold greater platelet thrombus dissolution than either agent alone at a low concentration (0.025 µM). Platelet-rich clot lysis experiments demonstrated the time required for 50% platelet-rich fibrin clot lysis (T(50%)) by APAC (95 ± 6.1 min) or SLK (145 ± 7.1 min) was much longer than that by combined APAC + SLK (65 ± 7.6 min) at the final concentration of 0.025 µM (APAC + SLK vs APAC, p<0.05; APAC + SLK vs SLK, p<0.01). Thus these low concentrations of a combination of both agents are likely to be more effective and less toxic when used therapeutically in vivo.