Thrombin-Generierung durch Asparaginase

The bacterial enzyme asparaginase is an important antineoplastic drug used for the treatment of a variety of lymphoproliferative disorders and lymphomas, in particular acute lymphoblastic leukemia. Its capacity to modulate the plasmatic coagulation is a known clinical complication. As a side effect the asparaginase might pathologically activate or inactivate the intrinsic coagulation. The aim of the present research work is to analyze the action of different asparaginase drugs on the plasmatic thrombin generation in 118 individual normal plasma samples using the new ultra specific, ultra-sensitive and precise thrombin generation test recalcified coagulation activity assay (RECA). Three different asparaginases were utilized for the laboratory analytical experiments; two native Escherichia coli (E. coli) asparaginases and an E. coli asparaginase coupled to polyethylene glycol (PEG-asparaginase). The two native E. coli asparaginases only differed in their time of production (the first lot produced would be referred to as the old lot, whereas the second lot produced would be called the new lot). The RECA diagnosed the coagulation modulating (especially the prothrombotic) power of the present asparaginases. Therefore, the approximate (approx.) 200 % stimulatory concentration (SC200) or the approx. 50 % inhibitory concentration (IC50) was determined. The SC200 is the plasmatic asparaginase concentration that results in 200 % of the original thrombin generation. The IC50 is the asparaginase concentration that results in only 50 % of the original thrombin generation. The supplemented plasmas became procoagulant or anticoagulant, or stayed resistant to hemostasis modulation by asparaginase. The old lot asparaginase was procoagulant in every plasma sample with approx. SC200-values of 5.8 ± 5.4 unit per milliliter (U/ml) (mean value ± 1 standard deviation) [MV ± 1 SD]. By contrast, only 51 % of the plasma samples that were supplemented with the new lot asparaginase became procoagulant, 24.5 % of the supplemented plasmas had a combination of SC200 and IC50 (depending on coagulation reaction time), 21 % had just an IC50 (MV = 6 U/ml) and 3,5 % of the plasmas were resistant towards modulation of coagulation. This means that the new lot has less thrombotic potential compared to the old one. In contrast the analyzed IC50-values point out that it could have an anticoagulant effect on the plasmatic blood coagulation of the individual patient, which could lead to bleeding complications. The PEG-asparaginase has been described as a modified molecule of asparaginase with less side effects than unmodified native asparaginase. The comparative plasma samples supplemented with both asparaginase preparations demonstrated no difference between the native E. coli asparaginase and the PEG-asparaginase with regard to the blood coagulation. The approx. SC200-values of both asparaginases correlated with a correlation coefficient greater than 0.9 . This high correlation and the similar mean values indicated, that respective plasmatic thrombin generation the rather expensive modified PEG-asparaginase behaved similar as the native asparaginase. Thus the hemostatic system of every patient responds individually to certain asparaginase preparations. Using the RECA, the patient’s individual coagulation triggering response to asparaginase can be previewed and the drug dosage could be adjusted: it is suggested to diagnose the patient´s individual coagulation response to bacterial asparaginase prior to and during the administration of the drug. Patients with an increased risk for asparaginase-induced thrombosis should be treated with prophylactic to therapeutic concentrations of low molecular weight heparin (LMWH).