title: Comparative field study evaluating the activity of recombinant factor VIII Fc fusion protein in plasma samples at clinical haemostasis laboratories.
abstract: Discrepancies exist for some of the modified coagulation factors when assayed with different one-stage clotting and chromogenic substrate assay reagents. The aim of this study was to evaluate the performance of a recombinant factor VIII Fc fusion protein (rFVIIIFc), currently in clinical development for the treatment of severe haemophilia A, in a variety of one-stage clotting and chromogenic substrate assays in clinical haemostasis laboratories. Haemophilic plasma samples spiked with rFVIIIFc or Advate(®) at 0.05, 0.20 or 0.80 IU mL(-1) were tested by 30 laboratories using their routine procedures and plasma standards. Data were evaluated for intra- and inter-laboratory variation, accuracy and possible rFVIIIFc-specific assay discrepancies. For the one-stage assay, mean recovery was 95% to 100% of expected for both Advate(®) and rFVIIIFc at 0.8 IU mL(-1). Intra-laboratory percent coefficient of variance (CV) ranged from 6.3% to 7.8% for Advate(®), and 6.0% to 10.3% for rFVIIIFc. Inter-laboratory CV ranged from 10% for Advate(®) and 16% for rFVIIIFc at 0.8 IU mL(-1), to over 30% at 0.05 IU mL(-1) for both products. For the chromogenic substrate assay, the average FVIII recovery was 107% ± 5% and 124% ± 8% of label potency across the three concentrations of Advate(®) and rFVIIIFc, respectively. Plasma rFVIIIFc levels can be monitored by either the one-stage or the chromogenic substrate assay routinely performed in clinical laboratories without the need for a product-specific rFVIIIFc laboratory standard. Accuracy by the one-stage assay was comparable to that of Advate(®), while marginally higher results may be observed for rFVIIIFc when using the chromogenic assay.
authors.affiliation: Biogen Idec Hemophilia, Cambridge, MA, USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Sommer
authors.forename: N
authors.initials: N
authors.lastname: Moore
authors.forename: B
authors.initials: B
authors.lastname: McGuffie-Valentine
authors.forename: S
authors.initials: S
authors.lastname: Bardan
authors.forename: Y
authors.initials: Y
authors.lastname: Buyue
authors.forename: G D
authors.initials: GD
authors.lastname: Kamphaus
authors.forename: B A
authors.initials: BA
authors.lastname: Konkle
authors.forename: G F
authors.initials: GF
authors.lastname: Pierce
mesh_terms: D001780:Blood Coagulation Tests / Q000379:methods* / Q000592:standards; D005169:Factor VIII / Q000378:metabolism* / Q000627:therapeutic use; D006467:Hemophilia A / Q000097:blood* / Q000188:drug therapy; D006801:Humans; D011933:Reagent Kits, Diagnostic; D011994:Recombinant Proteins / Q000097:blood* / Q000627:therapeutic use; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D011933:Reagent Kits, Diagnostic; D011994:Recombinant Proteins; D005169:Factor VIII
keywords: B-domain deleted; chromogenic substrate assay; factor VIII; field study; one-stage clotting assay