DEVELOPMENT OF NEW INHIBITORS OF PLATELET AGGREGATION

PLATELETS IN CIRCULATION ADHERE TO SITES OF VASCULAR INJURY,BECOME ACTIVATED BY AGONISTS SUCH AS THROMBIN, AND AGGREGATEPRIMARILY BY BINDING. INHIBITORS OF PLATELET AGGREGATION INCLUDE CERTAIN MURINE MONOCLONAL ANTIBODIES DIRECTED AGAINST THE MEMBRANE GLYCOPROTEIN (GP) IIB-IIIA. PLATELET AGGREGATION IS IMPORTANT IN PATHOLOGIC STATES CHARACTERIZED BY VASCULAR OCCLUSION, SUCH AS MYOCARDIAL INFARCTION, STROKE, AND RESTENOSIS OF ARTERIES FOLLOWING ANGIOPLASTY OR THROMBOLYTIC THERAPY. THE OBJECTIVE OF THIS RESEARCH IS TO DEVELOP AN ANTITHROMBOTIC AGENT THAT WILL INHIBIT PLATELET AGGREGATION. THE PRIMARY AMINO ACID SEQUENCES OF REGIONS OFGPIIB-IIIA INVOLVED IN FIBRINOGEN BINDING WILL BE IDENTIFIED. SOLUBLE FORMS OF GPIIB OR GPIIIA THAT BIND FIBRINOGEN WILL THEN EITHER BE USED DIRECTLY AS INHIBITORS OF PLATELET AGGREGATION, OR AS THE BASIS FOR THE DESIGN OF NOVEL INHIBITORS, SUCH AS NONHYDROLYZABLE PEPTIDES. RECENTLY, THE AMINO ACID SEQUENCES OF GPIIB AND GPIIIA HAVE BECOME AVAILABLE. THUS, IT IS POSSIBLE TO UTILIZE SYNTHETICPEPTIDES AND EXPRESSION OF RECOMBINANT FRAGMENTS OF THE PROTEINS TO ANALYZE PUTATIVE BINDING SITES. IN PHASE I, NOVEL MONOCLONAL ANTIBODIES AGAINST GPIIB-IIIA WILL BE GENERATED TO IDENTIFY FIBRINOGEN-BINDING SITES AND EVALUATE THESE ANTIBODIES IN A MICROTITER PLATE ASSAY USING PURIFIED GPIIB-IIIA COMPLEX AND RADIOLABELED FIBRINOGEN.