Abstract 3629: Thrombin Generation Assay: A New Biomarker for Monitoring Different Classes of Anticoagulants
Current measures to assess coagulation status are limited. For example, prothrombin time (INR; international normalized ratio) cannot predict anticoagulation in patients treated with unfractionated (UFH) and low molecular weight heparin (LMWH), or direct inhibitors of thrombin and factor Xa (fXa). As modulation of thrombin activity is common to all anticoagulants, we hypothesized that an assay based on its generation would be widely applicable to different classes of anticoagulants. Our experimental system utilized a plasma based method of tissue factor-initiated thrombin generation. Thrombin activity was quantitated by cleavage of a fluorogenic substrate. Initially, using prototype inhibitors we validated the ability of our assay to predict equivalence of anticoagulation among agents with varied mechanisms of action. Half maximal inhibition (IC50) was achieved at the listed concentrations: UFH (0.07U/ml), LMWH enoxaparin (0.23U/ml), pentasaccharide fXa inhibitor fondaparinux (160nM), thrombin inhibitor bivalirudin (2.4ug/ml), fXa inhibitors C921–78 (17nM), rivaroxaban (80nM) and razaxaban (125nM). In agreement with these in vitro results, patients treated with UFH (n16) or LMWH (n=13) demonstrated inhibition of thrombin generation ranging from 32–99% and 12–97%, respectively. Moreover, in a large cohort of patients receiving stable warfarin therapy (n=137) we observed a dose responsive relationship between thrombin generation and INR (see figure⇓). Our results show that the measurement of thrombin generation as a new biomarker has the potential to replace multiple clotting assays and permit the development of a universal test for anticoagulation.