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Thromb Haemost
DOI: 10.1055/a-2800-4026
Original Article: Coagulation and Fibrinolysis

Pharmacodynamic Interaction Between Emicizumab and Coagulation Factor VIII

Authors

  • Matthias Chill

    1   Department of Hematology, Hemostasis, Oncology, and Stem Cell Transplantation, Hannover Medical School, Hannover, Germany

  • Emma L. Konarski

    1   Department of Hematology, Hemostasis, Oncology, and Stem Cell Transplantation, Hannover Medical School, Hannover, Germany

  • Annika Klingberg

    1   Department of Hematology, Hemostasis, Oncology, and Stem Cell Transplantation, Hannover Medical School, Hannover, Germany

  • Birgitt Haarmeijer

    1   Department of Hematology, Hemostasis, Oncology, and Stem Cell Transplantation, Hannover Medical School, Hannover, Germany

  • Sonja Werwitzke

    2   Institute of Clinical Chemistry and Central Laboratory, Hannover Medical School, Hannover, Germany

  • Andreas Tiede 

    1   Department of Hematology, Hemostasis, Oncology, and Stem Cell Transplantation, Hannover Medical School, Hannover, Germany
    2   Institute of Clinical Chemistry and Central Laboratory, Hannover Medical School, Hannover, Germany

  • Olga Oleshko 

    1   Department of Hematology, Hemostasis, Oncology, and Stem Cell Transplantation, Hannover Medical School, Hannover, Germany
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Graphical Abstract

Abstract

Background

Emicizumab is a bispecific monoclonal antibody that mimics the cofactor function of activated factor (F) VIIIa, facilitating the FIXa-catalyzed activation of FX. Emicizumab binds to FIX/IXa and FX with considerably lower affinity than FVIIIa, suggesting that FVIII may outcompete emicizumab when present at higher concentrations. However, the interaction between emicizumab and FVIII at low FVIII concentrations is not well characterized. The current study aimed to assess the pharmacodynamic interaction between emicizumab and FVIII using classical pharmacological concepts of additivity and synergy.

Material and Methods

Thrombin generation was used as a surrogate marker of hemostatic capacity, providing well-defined quantitative outcome parameters. Tissue factor-triggered thrombin generation was measured in FVIII-deficient plasma supplemented with variable concentrations of emicizumab and recombinant FVIII, alone or in combination.

Results

A synergistic interaction between emicizumab and FVIII was observed, resulting in enhanced endogenous thrombin potential and peak thrombin generation beyond the levels expected from either agent alone. This synergistic effect was evident at low FVIII concentrations and was no longer observed once FVIII levels exceeded 20 IU/dl.

Conclusion

These findings may provide a pharmacodynamic explanation for the pronounced hemostatic effect of emicizumab at low FVIII levels and offer a conceptual framework for evaluating synergistic interactions between novel non-factor therapies and intrinsic FVIII.

Keywords

pharmacodynamic interaction - synergy - global coagulation assay - mimetic therapy - replacement therapy

Contributors' Statement

A.T. conceived the study and guided the analysis, performed statistical analysis, and conducted the pharmacodynamic modeling. O.O. planned and supervised laboratory experiments and drafted the manuscript. M.C., E.L.K., A.K., S.W., and B.H. performed the assays and interpreted data. All authors revised the manuscript and approved the final version.




Publication History

Received: 04 December 2025

Accepted: 28 January 2026

Accepted Manuscript online:
03 February 2026

Article published online:
12 February 2026

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