Comparing the antithrombotic efficacy of a humanized anti-factor IX(a) monoclonal antibody (SB 249417) to the low molecular weight heparin enoxaparin in a rat model of arterial thrombosis

A humanized inhibitory anti-factor IX(a) antibody (SB 249417) has been compared to enoxaparin (Lovenox) in a rat model of arterial thrombosis. Pretreatment of rats with either SE 249417 (3.0 mg/ kg, i.v.) or enoxaparin (30.0 mg/kg, i.v. or s.c.) re suited in comparable and significant reductions in thrombus formation. However, the efficacious dose of enoxaparin resulted in >30-fold increase in the aPTT over baseline, while the efficacious dose of SE 249417 prolonged the aPTT by only approximately 3-fold. Additionally, pretreatment with SE 249417 resulted in sustained blood flow and arterial patency throughout the experiment in >80% of rats treated, In contrast, <30% of rats pretreated with enoxaparin remained patent throughout the experiment. The data in this report indicate that the selective inhibition of factor IX(a) with the monoclonal antibody SE 249417 produces a superior antithrombotic profile to that of the low molecular weight heparin enoxaparin. (C) 2000 Elsevier Science Ltd. All rights reserved.