In vitro and in vivo studies of AT-1362, a newly synthesized and orally active inhibitor of thrombin

AT-1362 was found to be a potent, selective, and competitive inhibitor of t hrombin, with a Ki value of 6.7 nM. In a rat model of venous thrombosis ind uced by partial stasis and endothelial disruption, the ID50 values (a dose required to obtain 50% inhibition of thrombus formation over each vehicle g roup) of AT-1362 and argatroban were 0.03 mg/ kg i.v. plus 0.5 mug/kg/minut e and 0.13 mg/kg i.v. plus 8.7 mug/kg/minute, respectively, and the antithr ombotic effect of AT-1362 without prolongation of bleeding time lasted for 2 hours and disappeared 4 hours after oral administration of 30 mg/kg. In t he rat tail transection model, the BT2 values (a dose causing two-fold prol ongation of the bleeding time over each vehicle group) of AT-1362 and argat roban were 0.56 mg/kg i.v. plus 9.3 mug/kg/minute and 1.1 mg/kg i.v. plus 7 3.3 mug/kg/minute, respectively. The reduction of thrombus formation and th e prolongation of bleeding time were correlated with an ex vivo activated p artial thromboplastin time (APTT) for both drugs. AT-1362 at 0.3 mg/ kg i.v . plus 5 mug/kg/minute and argatroban at 0.6 mg/kg i.v. plus 40 mug/kg/minu te significantly (p<0.05 and p<0.01, respectively) improved the vessel pate ncy in a FeCl2-induced carotid artery thrombosis model in rats. These resul ts suggest that AT-1362 may be a potent antithrombotic agent for the treatm ent of thrombotic diseases. (C) 2000 Elsevier Science Ltd. All rights reser ved.