In Vitro Effect of Danaparoid Sodium (Orgaran ® ) on Thrombin Generation after Minimal Tissue Factor Pathway Activation.

Introduction: Orgaran ® (Org 10172) is a low molecular weight heparinoid which consists of natural sulphated glycosaminoglycans (heparan, dermatan, chondroitin sulphate). It has a mean molecular weight of approximately 6 kDa (4–10 kDa), an excellent bioavailability following subcutaneous administration and an anti-Xa/anti-IIa activity ratio superior to 22. It is the anticoagulant of choice in patients developping Heparin-Induced Thrombocytopenia (HIT), whereas its’ use is also proposed for surgical thromboprophylaxis. Orgaran ® has no effect on routine coagulation tests (aPTT, PT, TT). Thrombin generation test(TG) is a global clotting assay proven to be sensitive to the anticoagulant effect of LMWHs and specific FXa inhibitors (i.e. fondaparinux and BAY-597939). In this in vitro study, we determined the tissue factor (TF)-induced TG inhibition potency of Orgaran ® using the Thrombogram-Thrombinoscope ® assay. Materials and Methods: TG was assessed after TF pathway activation in Platelet Rich Plasma (PRP) (1.5x10 5 platelets/μl) using diluted thromboplastin (Dade Innovin ® , 1:1000 final dilution). The clotting process is provoked by a physiologically relevant TF concentration. Orgaran ® was added to control plasma from 8 healthy volunteers at five different final concentrations (0.2, 0.4, 0.6, 0.8 and 1IU anti-Xa/ml). TG was initiated by adding the triggering solution containing CaCl 2 and the fluorogenic substrate. The analyzed TG parameters are the lag time, the maximal concentration of thrombin (Cmax), the time to reach Cmax (Tmax), the TG velocity and the endogenous thrombin potential (ETP). Results: Orgaran ® prolonged significantly the lag time and the Tmax at a concentration over 0.40 IU anti-Xa/ml (p ® inhibited ETP, Cmax and TG velocity in an almost linear dose dependent manner. A significant inhibition of ETP, Cmax and TG velocity was obtained at concentrations superior to 0.20 IU anti-Xa/ml. (p ® suppressed all TG parameters by about 80% (Table 1). Conclusion: Orgaran ® exhibited a significant inhibitory activity of in vitro TG. At concentrations achieved in clinical practice (prophylactic or therapeutic dose), Orgaran ® modified in vitro TG profile while it has no effect on routine coagulation tests. Thus, TG assay is a sensitive method for monitoring Orgaran ® and this test requires a clinical prospective evaluation.