Influence of Different Anticoagulant Agents on Fibrinopeptide A Generation

Abstract

The purpose of this study was to determine the in vitro effects of different anticoagulant drugs on fibrinopeptide A (FPA) generation inhibition and to identify whether there is any correlation between FPA generation, Hemochron ACT, global clotting as says, and chromogenic assays. Unfractionated heparin is a conventionally used anticoagulant. New anticoagulant drugs such as low molecular weight heparins (LMWHs), pentasaccharide, and antithrombin drugs are now approved for various indications. Anti-Xa drugs are in various phases of clinical development. The influence of different anticoagulant agents has been studied on fibrinopeptide A generation, Hemochron celite ACT, global clotting assays, and chromogenic anti-Xa and anti-Ila assays. Different LMWHs (Clivarin, Dalteparin, Enoxaparin, and Tinzaparin), anti-Xa agents (Pentasaccharide, DX-9065a and unfractionated heparin), and anti-Ila agents (PEG-Hirudin, Hirudin, Efegatran and Argatroban) were studied. The blood from healthy volunteers (n=4) was drawn for each drug. Imuclone FPA enzyme-linked immunosorbent kit assay, Hemochron celite ACT assay, global clotting assays (PT, APTT, Heptest-HI, thrombin time), and Loyola chromogenic anti-Xa and anti-Ila assays were studied. Pentasaccharide demonstrated minimal effects on the whole blood clotting time such as ACT and on inhibition of FPA generation (IC₅₀ > 25 /g/mL). DX-9065a exhibited a significant prolongation of ACT and marked inhibition of FPA generation (IC50 = 4.12 Ag/mL). Unfractionated heparin showed a marked inhibition of FPA generation (IC,, = 5.16 Aog/mL). Pentasaccharide, DX-9065a and UFH showed a marked correlation between ACT and inhibition of FPA generation. LMWHs demonstrated concentrationdependent inhibition of FPA generation. LMWHs studied showed good correlation between FPA generation inhibition and ACT test. Similar correlation was seen between FPA generation inhibition and the APTT, anti Xa (heptest-HI assay) and anti-IIa activity. Anti-IIa drugs demonstrated concentration-dependent inhibition of FPA generation. Their FPA generation inhibition potency is correlated with the ACT assay. A strong correlation between Hemochron ACT and FPA generation inhibition was observed. Based on this significant correlation, the FPA generation inhibition can be predicted by point-of-care ACT assay.

Keywords

Fibrinopeptide A generation Activated clotting time Factor Xa inhibitor Low molecular weight heparin Factor Ila inhibitor

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