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Clinical Trial
. 2020 Apr;42(2):162-169.
doi: 10.1111/ijlh.13133. Epub 2019 Dec 10.

Recombinant FIX Fc fusion protein activity assessment with the one-stage clotting assay: A multicenter, assessor-blinded, prospective study in Japan (J-Field Study)

Katsuyuki Fukutake  1   2 , Tomomi Kobayashi  3 , Jurg M Sommer  4 , Toshiyuki Hirakata  5
Affiliations
Clinical Trial

Recombinant FIX Fc fusion protein activity assessment with the one-stage clotting assay: A multicenter, assessor-blinded, prospective study in Japan (J-Field Study)

Katsuyuki Fukutake et al. Int J Lab Hematol. 2020 Apr.

Abstract

Introduction: The one-stage clotting assay is used to measure factor IX (FIX) activity in patients' plasma samples and in FIX products for hemophilia treatment. However, the diversity of reagents and instruments has resulted in significant FIX assay variability.

Methods: The accuracy of the one-stage clotting assay to measure recombinant FIX Fc fusion protein (rFIXFc) activity was evaluated by major Japanese hemophilia treatment centers and commercial laboratories that measure factor IX activity for a majority of hemophilia B patients in Japan. Plasma-derived FIX (pdFIX) and recombinant FIX (rFIX) products were used as comparators. FIX-deficient plasma was spiked with four levels of FIX products based on label potency and measured under blinded conditions by routine one-stage clotting assay procedures in 19 participating laboratories. Interlaboratory coefficient of variation and spike recovery were calculated.

Results: Interlaboratory coefficient of variation of rFIXFc was not significantly different from that of rFIX, but appeared larger than that of pdFIX. Mean spike recovery for rFIXFc was generally comparable to rFIX and pdFIX. However, larger discrepancies between pdFIX and rFIX were observed in three of nine laboratories using ellagic acid-based activated partial thromboplastin time reagents.

Conclusion: Recombinant FIX Fc fusion protein activity was found to be similar to that of rFIX or pdFIX by the one-stage clotting assay. However, minimizing interlaboratory variability is vital for optimizing future patient care.

Keywords: Japan; biological assay; factor IX; hemophilia B; recombinant FIX Fc fusion protein.

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Conflict of interest statement

Katsuyuki Fukutake has received grants from Baxalta, Bayer, Pfizer, CSL Behring, Novo Nordisk, Biogen, Kaketsuken, Japan Blood Products Organization, and Ortho Clinical Diagnostics; personal fees from Baxalta, Bayer, Pfizer, CSL Behring, Novo Nordisk, Biogen, Kaketsuken, SRL Inc, LSI Medience, Roche Diagnostics, Siemens, Sekisui Medical, Fujirebio Inc, Abbott, Torii Pharmaceuticals, Octapharma, Chugai Pharmaceutical Co. LTD, and BioMarin; and other fees from CIMIC outside the submitted work. Tomomi Kobayashi is a current employee of Bioverativ Japan Ltd. Jurg M. Sommer is a former employee of and current consultant for Bioverativ, a Sanofi company. Toshiyuki Hirakata is a former employee of Biogen Japan Ltd.

Figures

Figure 1
Figure 1
Percentage of factor IX (FIX) activity vs nominal label activity categorized by the FIX product. Open marks indicate the FIX activity for 19 laboratories. Closed marks and bars indicate the mean and standard deviation, respectively. pdFIX, plasma‐derived factor IX; rFIX, recombinant factor IX; rFIXFc, recombinant factor IX Fc fusion protein. Percentage of nominal (label) was calculated by the measured FIX activity divided by the label potency of the sample × 100
Figure 2
Figure 2
Percentage of FIX activity to nominal in individual laboratories at concentrations of 0.90 IU/mL (A), 0.30 IU/mL (B), 0.10 IU/mL (C), and 0.03 IU/mL (D). pdFIX, plasma‐derived factor FIX; rFIX, recombinant factor IX; rFIXFc, recombinant factor IX Fc fusion protein. The dotted line shows 100% nominal at each concentration
Figure 3
Figure 3
Scatter plot of factor IX activities between each product at 0.9 IU/mL. pdFIX, plasma‐derived factor IX; rFIX, recombinant factor IX; rFIXFc, recombinant factor IX Fc fusion protein. The diagonal line shows the positive correlation line
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