JTV-803, 4-[(2-amidino-1,2,3,4-tetrahydroisoquinolin-7-yloxy)methyl]-1-(4-pyridinyl)piperidine-4-carboxylic acid monomethanesulfonate trihydrate, at > or = 0.1 mg/kg/h inhibited the increase in plasma thrombin-antithrombin III complex in response to continuous infusion of thromboplastin in rats. JTV-803 inhibited thrombus formation in an arteriovenous shunt model by intravenous infusion at > or = 0.3 mg/kg/h and prolonged the occlusion time of photochemically induced arterial thrombus in the middle cerebral artery at >1.5 mg/kg/0.5 h. Activated partial thromboplastin time was prolonged at 10 mg/kg/h. Intravenous administration of JTV-803 prolonged bleeding time at 30 mg/kg/h, a dose 10-100 times higher than the dose that inhibited thrombus formation. Compared with thrombin inhibitor, JTV-803 had less of an effect on the bleeding time. In the arteriovenous shunt model in cynomolgus monkey, JTV-803 prolonged the occlusion time when administered by continuous infusion at 0.3 mg/kg/h or orally at 10 mg/kg. These results suggest that the human factor Xa inhibitor JTV-803 is an orally active anticoagulant that does not affect bleeding time and is useful for the prevention of thrombus.