Contributions
Abstract: P08
Type: Poster presentation
Presentation during EHA Scientific Conference on Bleeding Disorders:
On Friday, September 16, 2016 from 14:00 - 15:30
Location: Cristal + Coral
Background and Aims
All recombinant FVIII products commercially available so far show more or less distinct differences of the one-stage (OS) clotting and chromogenic substrate (ChS) activity assay ratios when tested against a human plasma-derived FVIII concentrate standard. A good correlation of the molar quantities of several rFVIII products with their corresponding ChS FVIII activity determinations has previously been demonstrated. The goal of the present studies was to assess which of the FVIII activity assay principles best reflects the “true” (=physiologically relevant) potency of a newly developed single-chain rFVIII concentrate (rVIII-SingleChain)as well as considering the diversity of commercially available assay reagents.
Methods
rVIII-SingleChain (Afstyla®), a product of CSL Behring, and X different rFVIII comparator products were investigated. For ChS and OS FVIII activity determinations commercially available reagents and FVIII-depleted plasma were used. Thrombin generation (TG) was performed using PPP-reagent Low (Thrombinoscope) and FVIII-depleted plasma. Blood loss was determined after application of rFVIII products in a tail clip model using FVIII deficient mice.
Results
FVIII activity determination using four ChS FVIII activity and 15 OS clotting assay reagents demonstrated similar assay reagent-dependent trends for rVIII-SingleChain and the comparator products. Further, whereas the mean OS/ChS FVIII assay ratios were in the range of 0.87 to 0.91 for the rFVIII comparator products, rVIII-SingleChain resulted in a mean ratio of about 0.5. TG investigations using an activator reagent consisting of 1 pM tissue factor and phospholipids considered to reflect the physiologic conditions of vessel injury were performed. These showed that when applied based on the ChS assay, rVIII-SingleChain and the comparator products delivered comparable time to peak and thrombin peak results whereas when applied based on the OS assay, rVIII-SingleChain showed increased potency. Comparable results were obtained in a tail clip model of FVIII deficient mice. When dosed according to the ChS FVIII assay, rVIII-SingleChain and the comparator products resulted in comparable blood loss. But when blood loss was compared based on the OS clotting activity applied, rVIII-SingleChain was associated with reduced blood loss.
Summary – Conclusion
Despite different OS/ChS assay ratios, rVIII-SingleChain and the rFVIII comparator products investigated showed comparable trends using 15 OS clotting reagents. In addition, the application of a global coagulation assay (TG) and an in vivo hemostasis model demonstrated that the ChS FVIII activity assay best reflects the “true” (= physiologically relevant) potency of rVIII-SingleChain when compared to other rFVIII products.
Abstract: P08
Type: Poster presentation
Presentation during EHA Scientific Conference on Bleeding Disorders:
On Friday, September 16, 2016 from 14:00 - 15:30
Location: Cristal + Coral
Background and Aims
All recombinant FVIII products commercially available so far show more or less distinct differences of the one-stage (OS) clotting and chromogenic substrate (ChS) activity assay ratios when tested against a human plasma-derived FVIII concentrate standard. A good correlation of the molar quantities of several rFVIII products with their corresponding ChS FVIII activity determinations has previously been demonstrated. The goal of the present studies was to assess which of the FVIII activity assay principles best reflects the “true” (=physiologically relevant) potency of a newly developed single-chain rFVIII concentrate (rVIII-SingleChain)as well as considering the diversity of commercially available assay reagents.
Methods
rVIII-SingleChain (Afstyla®), a product of CSL Behring, and X different rFVIII comparator products were investigated. For ChS and OS FVIII activity determinations commercially available reagents and FVIII-depleted plasma were used. Thrombin generation (TG) was performed using PPP-reagent Low (Thrombinoscope) and FVIII-depleted plasma. Blood loss was determined after application of rFVIII products in a tail clip model using FVIII deficient mice.
Results
FVIII activity determination using four ChS FVIII activity and 15 OS clotting assay reagents demonstrated similar assay reagent-dependent trends for rVIII-SingleChain and the comparator products. Further, whereas the mean OS/ChS FVIII assay ratios were in the range of 0.87 to 0.91 for the rFVIII comparator products, rVIII-SingleChain resulted in a mean ratio of about 0.5. TG investigations using an activator reagent consisting of 1 pM tissue factor and phospholipids considered to reflect the physiologic conditions of vessel injury were performed. These showed that when applied based on the ChS assay, rVIII-SingleChain and the comparator products delivered comparable time to peak and thrombin peak results whereas when applied based on the OS assay, rVIII-SingleChain showed increased potency. Comparable results were obtained in a tail clip model of FVIII deficient mice. When dosed according to the ChS FVIII assay, rVIII-SingleChain and the comparator products resulted in comparable blood loss. But when blood loss was compared based on the OS clotting activity applied, rVIII-SingleChain was associated with reduced blood loss.
Summary – Conclusion
Despite different OS/ChS assay ratios, rVIII-SingleChain and the rFVIII comparator products investigated showed comparable trends using 15 OS clotting reagents. In addition, the application of a global coagulation assay (TG) and an in vivo hemostasis model demonstrated that the ChS FVIII activity assay best reflects the “true” (= physiologically relevant) potency of rVIII-SingleChain when compared to other rFVIII products.