Triepitopic antibody fusions inhibit cetuximab-resistant BRAF and KRAS mutant tumors via EGFR signal repression

J Mol Biol. 2012 Sep 28;422(4):532-44. doi: 10.1016/j.jmb.2012.06.014. Epub 2012 Jun 15.

Abstract

Dysregulation of epidermal growth factor receptor (EGFR) is a hallmark of many epithelial cancers, rendering this receptor an attractive target for cancer therapy. Much effort has been focused on the development of EGFR-directed antibody-based therapeutics, culminating in the clinical approval of the drugs cetuximab and panitumumab. Unfortunately, the clinical efficacy of these drugs has been disappointingly low, and a particular challenge to targeting EGFR with antibody therapeutics has been resistance, resulting from mutations in the downstream raf and ras effector proteins. Recent work demonstrating antibody cocktail-induced synergistic downregulation of EGFR motivated our design of cetuximab-based antibody-fibronectin domain fusion proteins that exploit downregulation-based EGFR inhibition by simultaneously targeting multiple receptor epitopes. We establish that, among our engineered multiepitopic formats, trans-triepitopic antibody fusions demonstrate optimal efficacy, inducing rapid EGFR clustering and internalization and consequently ablating downstream signaling. The combined effects of EGFR downregulation, ligand competition, and immune effector function conspire to inhibit tumor growth in xenograft models of cetuximab-resistant BRAF and KRAS mutant cancers. Our designed triepitopic constructs have the potential to enhance the efficacy and expand the scope of EGFR-directed therapies, and our multiepitopic may be readily applied to other receptor targets to formulate a new class of antibody-based therapeutics.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Antibodies, Monoclonal / immunology
  • Antibodies, Monoclonal / pharmacology*
  • Antibodies, Monoclonal, Humanized
  • Antineoplastic Agents / immunology
  • Antineoplastic Agents / pharmacology*
  • Cell Line, Tumor
  • Cetuximab
  • Down-Regulation / drug effects
  • Drug Resistance, Neoplasm
  • ErbB Receptors / genetics
  • ErbB Receptors / metabolism*
  • Female
  • Fibronectins / immunology
  • Fibronectins / pharmacology
  • HCT116 Cells
  • HEK293 Cells
  • HT29 Cells
  • Humans
  • Mice
  • Mutation
  • Neoplasms / drug therapy*
  • Neoplasms / genetics
  • Neoplasms / immunology
  • Proto-Oncogene Proteins / genetics*
  • Proto-Oncogene Proteins / metabolism
  • Proto-Oncogene Proteins B-raf / genetics*
  • Proto-Oncogene Proteins B-raf / metabolism
  • Proto-Oncogene Proteins p21(ras)
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / immunology
  • Recombinant Fusion Proteins / pharmacology
  • Signal Transduction
  • ras Proteins / genetics*
  • ras Proteins / metabolism

Substances

  • Antibodies, Monoclonal
  • Antibodies, Monoclonal, Humanized
  • Antineoplastic Agents
  • Fibronectins
  • KRAS protein, human
  • Proto-Oncogene Proteins
  • Recombinant Fusion Proteins
  • EGFR protein, human
  • ErbB Receptors
  • BRAF protein, human
  • Proto-Oncogene Proteins B-raf
  • Proto-Oncogene Proteins p21(ras)
  • ras Proteins
  • Cetuximab