DX-9065a, an Orally Active, Specific Inhibitor of Factor Xa, Inhibits Thrombosis without Affecting Bleeding Time in Rats

We evaluated the antithrombotic effects of DX-9065a, a specific factor Xa inhibitor, using tissue thromboplastin-induced DIC (TP-DIC) and the arterio-venous shunt (AV shunt) in rats. Intravenous TP injection reduced the platelet counts and fibrinogen concentrations in blood. In the TP-DIC model, an intravenous dose of DX-9065a 0.23 mg/kg 1 min before TP injection suppressed the consumption of platelets and fibrinogen to 57% and 66%, respectively, and the production of FDP almost completely. In the AV shunt model, DX-9065a inhibited thrombus formation to 51% on intravenous administration of 0.23 mg/kg and to 60% when given orally at 23.3 mg/kg. Intravenous administration of 2.33 mg/kg of DX-9065a did not affect the bleeding time. These results suggest that Xa inhibition may be an appropriate approach for suppressing thrombosis without impairing haemostasis.