A recombinant immunotoxin derived from a humanized epithelial cell adhesion molecule-specific single-chain antibody fragment has potent and selective antitumor activity.

Abstract

PURPOSE:

Epithelial cell adhesion molecule (Ep-CAM) is a tumor-associated antigen overexpressed in many solid tumors but shows limited expression in normal epithelial tissues. To exploit this favorable expression pattern for targeted cancer therapy, an Ep-CAM-specific recombinant immunotoxin was developed and its antitumor activity investigated.

EXPERIMENTAL DESIGN:

The immunotoxin 4D5MOCB-ETA was developed by genetically fusing a truncated form of Pseudomonas aeruginosa exotoxin A (ETA) (ETA(252-608)KDEL) to the highly stable humanized single-chain antibody fragment (scFv) 4D5MOCB. Cytotoxicity of 4D5MOCB-ETA was measured in cell growth and leucine incorporation assays in vitro. Tumor localization and antitumor activity were assessed in athymic mice bearing established human tumor xenografts.

RESULTS:

Fusion of the toxin moiety to the scFv did neither affect its thermal stability nor its antigen-binding affinity. In vitro, 4D5MOCB-ETA potently and specifically inhibited protein synthesis and reduced the viability of Ep-CAM-positive carcinoma cells of diverse histological origins with IC(50)s ranging from 0.005 to 0.2 pM. Upon systemic administration in mice, 4D5MOCB-ETA showed similar organ distribution as the scFv 4D5MOCB and preferentially localized to Ep-CAM-positive tumor xenografts with a tumor:blood ratio of 5.4. The potent antitumor activity of 4D5MOCB-ETA was demonstrated by its ability to strongly inhibit the growth and induce regression of relatively large tumor xenografts derived from lung, colon, or squamous cell carcinomas.

CONCLUSIONS:

We describe for the first time the development of a fully recombinant Ep-CAM-specific immunotoxin and demonstrate its potent activity against solid tumors of various histological origins. 4D5MOCB-ETA is currently being evaluated in a Phase I study in patients with refractory squamous cell carcinoma of the head and neck.

• Authors: Claudio Di Paolo, Jörg Willuda, Susanne Kubetzko, Ikar Lauffer, Dominique Tschudi, Robert Waibel, Andreas Plückthun, Rolf A Stahel, Uwe Zangemeister-Wittke
• Journal: Clinical cancer research : an official journal of the American Association for Cancer Research (Clin Cancer Res) Vol. 9 Issue 7 Pg. 2837-48 (Jul 2003) ISSN: 1078-0432 [Print] United States
• PMID: 12855664 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Antineoplastic Agents
• Bacterial Toxins
• Cell Adhesion Molecules
• Exotoxins
• Immunoglobulin Fragments
• Immunotoxins
• Recombinant Proteins
• Virulence Factors
• immunotoxin 4D5MOCB-ETA
• ADP Ribose Transferases
• Pseudomonas aeruginosa exotoxin A

Topics

• ADP Ribose Transferases (chemistry)
• Animals
• Antineoplastic Agents (pharmacology)
• Bacterial Toxins (chemistry, pharmacology)
• Cell Adhesion Molecules
• Cell Division
• Cell Line, Tumor
• Chromatography, Gel
• Dose-Response Relationship, Drug
• Epithelial Cells (metabolism)
• Exotoxins (chemistry)
• Female
• Flow Cytometry
• Genetic Vectors
• Humans
• Immunoglobulin Fragments (chemistry, pharmacology)
• Immunotoxins (pharmacology)
• Inhibitory Concentration 50
• Mice
• Mice, Inbred C57BL
• Mice, Nude
• Models, Molecular
• Neoplasm Transplantation
• Protein Structure, Tertiary
• Recombinant Proteins (pharmacology)
• Time Factors
• Virulence Factors (chemistry)