Antithrombotic Effect of Tissue Factor Inhibition by Inactivated Factor VIIa: An Ex Vivo Human Study

Abstract

FFR-rFVIIa is an inactivated recombinant factor VIIa (rFVIIa) that inhibits the binding of factor VIIa to tissue factor (TF). It has been shown to prevent TF-induced thrombosis in animals. The present study is a substudy of the Active Site Inhibited Seven (ASIS) trial and examines the antithrombotic effect of 3 doses of FFR-rFVIIa in 24 patients undergoing percutaneous coronary intervention (PCI). Group 1 (n=9) received 400 &mgr;g/kg FFR-rFVIIa and 40 to 50 U/kg heparin, group 2 (n=7) received 200 &mgr;g/kg FFR-rFVIIa and 100 U/kg heparin, and group 3 (n=8) received 50 &mgr;g/kg FFR-rFVIIa and 100 U/kg heparin. Blood thrombogenicity was assessed as total thrombus area and fibrin deposition on the perfusion chamber at shear rate conditions typical of mild-moderate coronary stenosis. Baseline blood thrombogenicity was evaluated a day before PCI, after heparin administration. A second perfusion chamber study was performed just before PCI, 15 minutes after the administration of heparin and FFR-rFVIIa. Thrombus formation at a high shear rate was markedly reduced in groups 1 and 2 after drug administration, by 79% to 84% and 76% to 87%, respectively (P <0.004 [group 1], P <0.04 [group 2]). In group 3, moderate thrombus reduction of 46% to 48% was achieved (P <0.04). Fibrin deposition in all 3 groups was nearly eliminated after drug administration. Our data demonstrate that FFR-rFVIIa has a potent antithrombotic effect at different shear rates and severe arterial injury conditions.