JTV-803, 4-[(2-amidino-1,2,3,4-tetrahydroisoquinolin-7-yloxy)methyl]-1-(4-pyridinyl)piperidine-4-carboxylic acid monomethanesulfonate trihydrate showed a competitive inhibitory effect on human factor Xa, with a K(i) value of 0.019 microM. This compound was 100 times more selective in inhibiting human factor Xa as compared to its inhibitory activity against thrombin, plasmin, and trypsin. JTV-803 was also examined for its inhibitory effect on activated factor Xa obtained from plasma of various animal species. JTV-803 exerted a potent inhibitory effect on human factor Xa (IC(50): 0.081 microM). JTV-803 prolonged activated partial thromboplastin time and prothrombin time in a dose-dependent manner. Oral anticoagulant efficacy of JTV-803 was examined ex vivo for its inhibition of human factor Xa in cynomolgus monkeys. JTV-803 produced more than 20% inhibition of human factor Xa for 8 h. Taken together, the results indicate JTV-803 is a long-acting oral anticoagulant which exerts its effect via specific inhibition of human factor Xa.