Accessible Unlicensed Requires Authentication Published online by De Gruyter September 20, 2021

EGFR binding Fc domain-drug conjugates: stable and highly potent cytotoxic molecules mediate selective cell killing

Sebastian Jäger, Stephan Dickgiesser, Jason Tonillo, Stefan Hecht, Harald Kolmar and Christian Schröter
From the journal Biological Chemistry


The exposition of cancer cells to cytotoxic doses of payload is fundamental for the therapeutic efficacy of antibody drug conjugates (ADCs) in solid cancers. To maximize payload exposure, tissue penetration can be increased by utilizing smaller-sized drug conjugates which distribute deeper into the tumor. Our group recently explored small human epidermal growth factor receptor 2 (HER2) targeting Fc antigen binding fragments (Fcabs) for ADC applications in a feasibility study. Here, we expand this concept using epidermal growth factor receptor (EGFR) targeting Fcabs for the generation of site-specific auristatin-based drug conjugates. In contrast to HER2-targeting Fcabs, we identified novel conjugation sites in the EGFR-targeting Fcab scaffold that allowed for higher DAR enzymatic conjugation. We demonstrate feasibility of resultant EGFR-targeting Fcab-drug conjugates that retain binding to half-life prolonging neonatal Fc receptor (FcRn) and EGFR and show high serum stability as well as target receptor mediated cell killing at sub-nanomolar concentrations. Our results emphasize the applicability of the Fcab format for the generation of drug conjugates designed for increased penetration of solid tumors and potential FcRn-driven antibody-like pharmacokinetics.

Corresponding authors: Sebastian Jäger, ADCs & Targeted NBE Therapeutics, Merck KGaA, Frankfurter Str. 250, D-64293Darmstadt, Germany; and Institute for Organic Chemistry and Biochemistry, Technical University of Darmstadt, Alarich-Weiss-Str. 4, D-64287Darmstadt, Germany, E-mail: ; and Christian Schröter, ADCs & Targeted NBE Therapeutics, Merck KGaA, Frankfurter Str. 250, D-64293 Darmstadt, Germany, E-mail:


The authors thank L. Basset for bioconjugation and analytics; S. Keller, A. Müller, C. Brunori and D. Müller-Pompalla for advice and laboratory support in protein purification; J. Schanz and R. Kellner for LC-MS measurements; J. Roßkopf for reference constructs; the manuscript anonymous reviewers for comments and suggestions.

  1. Author contributions: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.

  2. Research funding: None declared.

  3. Conflict of interest statement: The authors declare no conflicts of interest regarding this article.


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Supplementary Material

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Received: 2021-07-13
Accepted: 2021-09-07
Published Online: 2021-09-20

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