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Hamostaseologie
DOI: 10.1055/a-2717-3413
Original Article

On Factor VIII Assay Discrepancies in Post-infusion Samples Obtained from Patients Treated with Efanesoctocog Alfa

Authors

  • Jens Müller

    1   Institute of Experimental Hematology and Transfusion Medicine, University Clinic Bonn, University of Bonn, Bonn, Germany

  • Martin Büchsel

    2   Institute for Clinical Chemistry and Laboratory Medicine, Medical Center and Faculty of Medicine, University of Freiburg, Freiburg, Germany

  • Behnaz Pezeshkpoor 

    1   Institute of Experimental Hematology and Transfusion Medicine, University Clinic Bonn, University of Bonn, Bonn, Germany

  • Heiko Rühl

    1   Institute of Experimental Hematology and Transfusion Medicine, University Clinic Bonn, University of Bonn, Bonn, Germany

  • Bernd Pötzsch

    1   Institute of Experimental Hematology and Transfusion Medicine, University Clinic Bonn, University of Bonn, Bonn, Germany

  • Claudia Klein

    1   Institute of Experimental Hematology and Transfusion Medicine, University Clinic Bonn, University of Bonn, Bonn, Germany

  • Georg Goldmann

    1   Institute of Experimental Hematology and Transfusion Medicine, University Clinic Bonn, University of Bonn, Bonn, Germany

  • Natascha Marquardt

    1   Institute of Experimental Hematology and Transfusion Medicine, University Clinic Bonn, University of Bonn, Bonn, Germany

  • Thilo Albert

    1   Institute of Experimental Hematology and Transfusion Medicine, University Clinic Bonn, University of Bonn, Bonn, Germany

  • Kerstin Herbst

    1   Institute of Experimental Hematology and Transfusion Medicine, University Clinic Bonn, University of Bonn, Bonn, Germany

  • Johannes Oldenburg

    1   Institute of Experimental Hematology and Transfusion Medicine, University Clinic Bonn, University of Bonn, Bonn, Germany

Funding There was no funding for this retrospective study.
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Abstract

Efanesoctocog alfa (efa) is a recombinant coagulation factor VIII (FVIII) concentrate, engineered for improved extended half-life in hemophilia A treatment. Its design results in discrepancies in FVIII diagnostic tests, as has so far been demonstrated using spiked sample material (efa added to FVIII-deficient plasma). The aim of the present study was to evaluate FVIII assay discrepancies in post-infusion samples obtained from patients treated with efa. This retrospective analysis included 43 male patients on efa prophylaxis (26 on once weekly and 17 on twice weekly treatment scheme) summoned for determination of incremental recoveries. FVIII activity was measured at trough (3.5 or 7 days post-infusion) and peak levels (30 minutes post-infusion) using three diagnostic tests: two one-stage clotting assays (OSCAs) based on Actin FSL (AFSL) or Actin FS (AFS), and a chromogenic substrate assay (FVIII CSA). Incremental recoveries as determined by the recommended AFSL-based OSCA were found to be comparable between patient groups. At peak levels (64 to 214 IU/dL), comparable overestimation (1.9-fold) of plasma efa activity relative to Actin FSL-based OSCA was observed for both, the AFS-based OSCA and the FVIII CSA. In contrast, at trough levels (5 to 64 IU/dL), rate of overestimation relative to the AFSL-based OSCA results was found to be lower for the FVIII CSA (1.3-fold) when compared with the AFS-based OSCA (1.9-fold). Further analysis demonstrated different behavior of spiked and post-infusion samples within the FVIII CSA. Future studies will reveal underlying mechanisms and assess if drug-specific calibration will sufficiently correct for this phenomenon.

Keywords

coagulation factor VIII - diagnostic tests - efanesoctocog alfa - hemophilia A - reproducibility of results

Ethics Statement

For this retrospective analysis, no approval by the local Ethics Committee was required.


Authors' Contributions

J.M. and J.O.: designed the concept of this retrospective analysis; J.M., C.K., G.G., N.M., T.A., K.H., and J.O.: performed data curation and data analysis; M.B., B.Pe., H.R., and B.Pö.: analyzed the data and provided critical expertise; J.M.: wrote the manuscript. All authors reviewed, revised, and finally agreed on the final version of the manuscript.


Supplementary Material



Publication History

Received: 18 August 2025

Accepted: 06 October 2025

Article published online:
19 January 2026

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