Reagent-specific underestimation of turoctocog alfa pegol (N8-GP) clotting activity owing to decelerated activation by thrombin.

摘要: Background Factor VIII (FVIII) procoagulant activity is commonly assessed by measuring the activated partial thromboplastin time (APTT) to clot formation using one of many available but differently composed reagents. The majority APTT reagents also accurately recover extended half-life molecule N-glycoPEGylated FVIII (N8-GP; turoctocog alfa pegol), while a few silica-based give low recovery. Objective To identify cause N8-GP underestimation in presence certain Methods Development FVIIIa-dependent tenase and appearance FVIIIa from its non-PEGylated counterpart (N8) were compared clotting assays, factor Xa (FXa) assay mimic thereof, thrombin activation courses. Results A strong correlation was demonstrated between FXa assays based on similar recoveries equal responses an altered duration contact phase, validating latter as useful mimic. Contact phase influenced, could even eliminate, underestimation. Thrombin-catalyzed conversion considerably slower than that N8 despite extents adsorption silica particles APTT-SP, suggesting different modes and/or orientations adsorption. Conclusions Some activators reduce thrombin's ability cleave more native FVIII. Decelerated reflected delayed plasma, turn leading prolonged time. This forms basis for measured one-stage against standard.