Therapeutic Potential of Amanitin-Conjugated Anti-Epithelial Cell Adhesion Molecule Monoclonal Antibody Against Pancreatic Carci

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Therapeutic Potential of Amanitin-Conjugated Anti-Epithelial Cell Adhesion Molecule Monoclonal Antibody Against Pancreatic Carcinoma

  1. Gerhard Moldenhauer,
  2. Alexei V. Salnikov,
  3. Sandra Lüttgau,
  4. Ingrid Herr,
  5. Jan Anderl and
  6. Heinz Faulstich

+ Author Affiliations

  1. Affiliations of authors: Department of Translational Immunology, German Cancer Research Center, Heidelberg, Germany (GM, AVS, SL); National Center for Tumor Diseases, Heidelberg, Germany (GM, AVS, SL); Molecular OncoSurgery Group, Department of General Surgery, University of Heidelberg and German Cancer Research Center, Heidelberg, Germany (AVS, IH); Heidelberg Pharma GmbH, Ladenburg, Germany (JA); Bioorganic Research Group, Max Planck Institute for Medical Research, Heidelberg, Germany (HF)
  1. Correspondence to: Gerhard Moldenhauer, MD, Department of Translational Immunology (D015), German Cancer Research Center, Im Neuenheimer Feld 280, Heidelberg 69120, Germany (e-mail: g.moldenhauer@dkfz.de).
  • Received June 16, 2011.
  • Revision received February 1, 2012.
  • Accepted February 3, 2012.

Abstract

Background Human epithelial cell adhesion molecule (EpCAM) is overexpressed in many cancers. Anti-EpCAM antibodies have shown promise in preclinical studies, but showed no tumor regression in a recent phase II clinical trial. Therefore, we generated a novel anti-EpCAM antibody–drug conjugate and assessed whether it showed enhanced antitumor effects.

Methods Chemical cross-linking was conducted to covalently conjugate ?-amanitin, a toxin known to inhibit DNA transcription, with chiHEA125, a chimerized anti-EpCAM monoclonal antibody, to generate the antibody–drug conjugate ?-amanitin-glutarate-chiHEA125 (chiHEA125-Ama). Antiproliferative activity of chiHEA125-Ama was tested in human pancreatic (BxPc-3 and Capan-1), colorectal (Colo205), breast (MCF-7), and bile duct (OZ) cancer cell lines in vitro using [3H]-thymidine incorporation assay. Antitumor activity of chiHEA125-Ama was assessed in vivo in immunocompromised mice bearing subcutaneous human BxPc-3 pancreatic carcinoma xenograft tumors (n = 66 mice). Cell proliferation and apoptosis were evaluated in xenograft tumors by immunohistochemistry. All statistical tests were two-sided.

Results In all cell lines, chiHEA125-Ama reduced cell proliferation (mean half maximal inhibitory concentration [IC50] = 2.5 × 10?10 to 5.4 × 10?12 M). A single dose of chiHEA125-Ama inhibited BxPc-3 xenograft tumor growth (chiHEA125 [control, n = 4 mice] vs chiHEA125-Ama [n = 6 mice], dose of 15 mg/kg with respect to IgG and 50 ?g/kg with respect to ?-amanitin, mean relative increase in tumor volume on day 16 = 884% vs ?79%, difference = 963%, 95% CI = 582% to 1344%, P = .019). Two higher doses of chiHEA125-Ama (100 ?g/kg with respect to ?-amanitin), administered 1 week apart (n = 10 mice per group), led to complete tumor regression in nine of 10 (90%) mice compared with chiHEA125, during the observation period of 16 days; increased apoptosis and reduced cell proliferation were observed in mice treated with chiHEA125-Ama.

Conclusion This preclinical study suggests that anti-EpCAM antibody conjugates with ?-amanitin have the potential to be highly effective therapeutic agents for pancreatic carcinomas and various EpCAM-expressing malignancies.