Abstract

The Tissue Factor-Factor VIIa complex is the initiating protease in the extrinsic pathway of the coagulation cascade. Knockout of Factor VII in mice results in embryonic lethality. However, only humans with severe Factor VII deficiency exhibit any coagulopathy. In order to determine the potential of Factor VII as an anticoagulant target and the utility of antisense oligonucleotides (ASOs) as Factor VII inhibitors, ASOs were designed to promote RNaseH mediated degradation of Factor VII RNA and evaluated in mice. Factor VII is predominantly produced in the liver, a tissue that is tractable for antisense mediated target depletion. Following three weeks of treatment, the Factor VII ASO was well tolerated and supported significant reduction of Factor VII RNA and protein in mouse liver (ED50 of 3.5 mg/kg for RNA and 2.8 mg/kg for protein). Greater than 95% reduction in Factor VII RNA levels was observed at a dose of 25 mg/kg, administered twice weekly. Following three weeks exposure to 100 mg/kg/wk, prothrombin times (PT) from platelet poor mouse plasma was more than doubled, compared to untreated animals, while activated partial thromboplastin times (aPTT) was only increased 16%. Antithrombotic activity of Factor VII ASO was determined following ferric chloride injury to the inferior vena cava. ED50 for inhibition of thrombosis was 24 mg/kg/wk. The effects of Factor VII depletion on hemostatic control were also determined using a mouse tail nick model. No increase in blood loss was detected, compared to untreated animals, up to a weekly exposure of 80 mg/kg, the highest dose utilized in the study. Compared to warfarin, ASO mediated depletion of Factor VII promoted equivalent protection from thrombosis following ferric chloride injury while maintaining better hemostatic control. These findings support the development of an ASO drug targeting Factor VII as an anticoagulant.

Disclosures: Crosby:Isis Pharmaceuticals, Inc.: Employment. Zhao:Isis Pharmaceuticals, Inc.: Employment. Gao:Isis Pharmaceuticals, Inc.: Employment. Siwkowski:Isis Pharmaceuticals, Inc.: Employment. Zhang:Isis Pharmaceuticals, Inc.: Employment. Monia:Isis Pharmaceuticals, Inc.: Employment.

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