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.

Factor VIII assay variability in postinfusion samples containing full length and B‐domain deleted FVIII

“…Both studies identified higher chromogenic assay results compared to one stage results when FVIII was in the 60-90 IU/dl range (by 12-19%) but either no difference ( 22) or lower (17) chromogenic assay results for samples containing 3-5 IU/dl FVIII.…”

“…Samples containing Advate spiked into severe haemophilic plasma have been included in multi -centre studies of FVIII assays in relation to newer concentrates (17,22). Both studies identified higher chromogenic assay results compared to one stage results when FVIII was in the 60-90 IU/dl range (by 12-19%) but either no difference ( 22) or lower (17) chromogenic assay results for samples containing 3-5 IU/dl FVIII.…”

Efficacy and safety of BAY 81‐8973, a full‐length recombinant factor VIII: results from the LEOPOLD I trial

“…Based on reports indicating that FVIII activity of full-length rFVIII products is approximately 20% lower with the one-stage assay vs. the chromogenic assay [7,8], the LEOPOLD program included an intraindividual comparison of the clinical efficacy of prophylaxis using potency labelling based on the chromogenic substrate assay per European Pharmacopoeia (CS/EP) or adjusted by a predefined factor to mimic results obtained with the one-stage assay (CS/ADJ). Results of the LEOPOLD II trial, which demonstrated the superiority of two-and three times-weekly prophylaxis dosing of BAY 81-8973 over on-demand treatment, have been published [9].…”

A world‐wide survey and field study in clinical haemostasis laboratories to evaluate FVIII:C activity assay variability of ADYNOVATE and OBIZUR in comparison with ADVATE

“…For measurement of ADVATE as a commercially available product with more than 14 years of experience in clinical use, variability seemed to be in the expected range and recent studies demonstrated no relevant discrepancies when measuring this product with different assay methods and in different laboratories [29,30]. Thus, ADVATE provided a point of comparison to determine the extent of variability between methods.…”