Idarucizumab Fully Restores Dabigatran-Induced Alterations on Platelet and Fibrin Deposition on Damaged Vessels: Studies in Vitro with Circulating Human Blood

BACKGROUND: Despite the proven efficacy and safety profile of dabigatran as compared to warfarin, bleeding remains a concern as with all anticoagulants and the reversal of dabigatran’s anticoagulant effect for emergency procedures remains controversial. Recently, idarucizumab, a specific antidote for dabigatran, has been functionally characterized and its efficacy demonstrated in animal models and healthy volunteer studies.

AIMS: We explored the effects of dabigatran on hemostasis in human blood focusing on possible interference with platelet and coagulation responses to vessel injury under flow conditions. We also compared the potential efficacy of idarucizumab with procoagulant strategies such as prothrombin complex concentrates (PCC), activated PCC (aPCC) or rFVIIa at reversing the antithrombotic action of dabigatran to better understand local processes in response to injury.

METHODS: Concentrations of dabigatran equivalent to the Cmax reported at steady state after therapy with 150 mg twice daily (184 ng/mL) were added in vitro to blood aliquots from 11 healthy donors. Whole blood samples were used to evaluate modifications in different coagulation biomarkers: 1) fibrin and platelet deposition on damaged vascular segments with whole blood under flow conditions at a shear rate of 600 s^-1, 2) dynamics of thrombin generation (TG) in plasma using a fluorogenic assay (Technothrombin TGA) and 3) viscoelastic parameters of clot formation in whole blood using by thromboelastometry (ROTEM) The efficacy of specific reversal with idarucizumab 0.3, 1 and 3 mg/mL was compared with that of non specific procoagulant concentrates such as aPCC 25 and 75 IU/kg, PCC 70 IU/kg, or rFVIIa 120 µg/kg.

RESULTS: Dabigatran (184 ng/mL) caused a pronounced 85% reduction of fibrin coverage on the damaged vessel from 67.2±9.8 to 9.5±1.3 % (p<0.01) and a moderate 35% reduction of platelet deposition from 25.9±2.7 to 16.9±2.9 % (p<0.01). Dabigatran also altered dynamics of TG with a prolongation of the lag-phase and a reductions in the maximal thrombin peak and potential of thrombin generation (p<0.01). In ROTEM, dabigatran significantly prolonged clotting time to 352±60 sec (p<0.01) and clot formation time to 312±76 sec (p<0.05). Idarucizumab completely reversed the alterations in all different biomarkers induced by dabigatran. Additionally, fibrin coverage and platelet deposition were restored to baseline values in flow studies. TG and ROTEM parameters also returned to normal values after idarucizumab. Reversal strategies with aPCC or PCC normalized and even over-compensated alterations in TG kinetics and partially improved alterations in ROTEM parameters caused by dabigatran. Interestingly, aPCC and PCC moderately improved the alteration in fibrin deposition caused by dabigatran in flow studies (15.7±8.2, 29.3±14.5, and 15.2±3.7 %, respectively for aPCCs 25, 75 or PCCs 70 IU/kg). However, levels of fibrin formation did not return to baseline values before dabigatran (67.2±32.5 %). rFVIIa showed only moderate effects on some of the biomarkers evaluated, though values were never restored to the baseline.

CONCLUSIONS: Dabigatran (184 ng/mL) added to blood from healthy volunteers caused evident alterations in hemostasis parameters related to its recognized anticoagulant action. Procoagulant concentrates significantly compensated for the overall anti-hemostastic action of dabigatran. Overall, 75 U/kg aPCC seemed the more efficient nonspecific reversal therapy. In clear contrast with non specific procoagulant strategies, idarucizumab, the specific antidote to dabigatran completely reversed all alterations in coagulation parameters evaluated in circulating human blood and in assay systems.

(Supported by SAF 2011-2814 and PI13/00517, Spanish Gov & FEDER)