Novel Platelet Inhibitors

Platelet-inhibitory drugs are of proven benefit to individuals who suffer from atherosclerotic cardiovascular disease. Despite substantial effort to identify more potent platelet-inhibitory agents, aspirin, an irreversible inhibitor of platelet cyclooxygenase activity, remains the standard against which other drugs are judged. Drugs that appear to be at least as efficacious as aspirin in specific clinical settings include the thienopyridines ticlopidine and clopidogrel, specific inhibitors of ADP-stimulated platelet function, and the phosphodiesterase 3 inhibitor cilostazol. Ligand binding to the platelet integrin αIIbβ3 (GPIIb-IIIa), a prerequisite for platelet thrombus formation, has been a prominent target for drug development. Currently, three types of αIIbβ3 antagonists are available: the monoclonal antibody Fab fragment abciximab, cyclic peptides based on the Arg-Gly-Asp (RGD) or related amino acid motifs, and RGD-based peptidomimetics. The efficacy of each type of αIIbβ3 antagonist in the setting of acute coronary artery disease has been confirmed in multicenter clinical trials.