Abstract 716: ISIS 401025, a Second Generation Antisense Oligonucleotide Targeting Prothrombin, Inhibits Plasma Prothrombin Level and Promotes Anticoagulation in Mice
The objective of the study was to evaluate the potential of antisense oligonucleotides as drugs for anticoagulation. The popularly used anticoagulants, warfarin, heparin, and low molecular weight heparin (LMWH) all possess significant drawbacks. Both warfarin and heparin require monitoring to ensure appropriate dosage level, and both heparin and LMWH require frequent subcutaneous administration. In addition, all three drugs lack the level of specificity generally desired in a drug. . Target-specific, second generation antisense oligonucleotides (ASO) are currently being evaluated in the clinic for a variety of diseases, including hyperlipidemia and type-2 diabetes. Second generation ASOs allow for less frequent (once weekly - once monthly) subcutaneous dosing due to their improved pharmacokinetic properties compared to first generation ASOs. We identified a second generation antisense oligonucleotide targeting mouse prothrombin that was capable of diminishing prothrombin transcript levels in primary mouse hepatocytes and subsequently characterized its anticoagulant effects in mice. Treatment of mice with ISIS 401025 dose-dependently inhibited prothrombin mRNA levels and activity in liver with an ED90 of approximately 20 mg/kg/week. An INR of 2.5 was achieved at a weekly dose of 50 mg/kg, corresponding to a reduction in F2 transcript of 95%. Dose-dependent inhibition of prothrombin levels in plasma was further confirmed by thrombin generation assay. The clotting times, PT and aPTT, were significantly prolonged and correlated to the degree of target inhibition. Antisense mediated depletion of prothrombin resulted in an extended PT which, unlike warfarin, was not reversed by vitamin K administration. These results demonstrate the potential utility for antisense oligonucleotide based therapeutics in regulation of coagulation pathways.