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Minimal interference of concizumab with standard clinical coagulation laboratory assays - An in vitro study
Cecilia Augustsson1, Karin Strandberg1, Marianne Kjalke2
1Department of Clinical Chemistry and Pharmacology, Division of Laboratory Medicine, Coagulation Laboratory Malmö, Regional Laboratories Region Skåne, Malmö, Sweden.
Introduction:
Non-factor replacement therapies are emerging as prophylactic treatment options in haemophilia A or B (HA/HB) with and without inhibitors. Concizumab is an anti-tissue factor pathway inhibitor (TFPI) monoclonal antibody preventing factor (F)Xa inhibition and enhancing thrombin generation. Based on experience with other non-factor therapies and extended half-life products, there is a focus on potential interference with common clinical coagulation assays used to monitor patients treated with concizumab.
Aim:
To evaluate the impact of concizumab on standard clinical coagulation assays.
Methods:
Plasma samples (normal, HA/HB with/without inhibitors) in the presence/absence of added concizumab (250-16,000 ng/mL) were analysed in clinical assays including activated partial thromboplastin time (aPTT), prothrombin time (PT), FVIII and FIX one-stage clot and chromogenic substrate assay, assays for detecting FVIII or FIX inhibitors and other assays for coagulation factors.
Results:
Concizumab did not impact PT assays, but resulted in a small shortening of aPTT (up to 5 s in haemophilia plasma and 0.4 s in normal plasma). Concizumab had no, or only a minor impact on FVIII and FIX activity assays or Bethesda inhibitor assays. FXI and FXII activity in normal plasma, as measured by single factor aPTT-based assay, was significantly increased in the presence of concizumab (+11% each). This was also the case for FVII and FX measured by PT-based assays using plasma with 25% of FVII or FX (+64% and +22%, respectively).
Conclusion:
The presence of concizumab did not, or only slightly, influence the outcome of standard clinical coagulation assays relevant for HA and HB.
