A competitive purinergic P2Y1 receptor antagonist (Kb = 102 nM); selective for P2Y1 over P2Y2, P2Y4, P2Y6, P2Y12, and P2Y13, as well as P2X1-4, receptors at 10 µM; reduces 2-MeSADP-induced PLC activity (IC50 = 331 nM in turkey erythrocyte membranes); inhibits ADP-induced platelet shape change and aggregation in washed isolated human platelets at 10 µM; prolongs the length of tail bleeding time in mice, as well as decreases platelet thrombus formation in a mouse model of iron chloride-induced arterial thrombosis at 50 mg/kg