Thrombin receptor peptide ligand is antagonist of the thrombin receptor (EC50s = 16-33 μM to inhibit platelet aggregation in vitro). It inhibits α-thrombin and platelet aggregation induced by thrombin receptor activating peptide in vitro when used at a concentration of 32 μM but does not affect platelet aggregation induced by ADP or collagen. It also inhibits thrombin- and TRAP-induced proliferation of vascular smooth muscle cells (VSMCs). Thrombin receptor peptide ligand (100 μmol/kg bolus, i.v., plus 900 μmol/kg infusion) inhibits arterial thrombosis in a rabbit model of partial carotid artery occlusion without increasing bleeding time.