Research Papers:
Imaging the distribution of an antibody-drug conjugate constituent targeting mesothelin with 89Zr and IRDye 800CW in mice bearing human pancreatic tumor xenografts
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Abstract
Eva J. ter Weele1,2, Anton G.T. Terwisscha van Scheltinga1,2, Jos G.W. Kosterink1,4, Linda Pot2, Silke R. Vedelaar2, Laetitia E. Lamberts2, Simon P. Williams5, Marjolijn N. Lub-de Hooge1,3, Elisabeth G.E. de Vries2
1Department of Clinical Pharmacy and Pharmacology, University of Groningen, University Medical Center Groningen, Groningen, Netherlands
2Department of Medical Oncology, University of Groningen, University Medical Center Groningen, Groningen, Netherlands
3Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen, Netherlands
4Department of Pharmacy, Section of Pharmacotherapy and Pharmaceutical Care, University of Groningen, Groningen, Netherlands
5Department of Biomedical Imaging, Genentech, Inc., South San Francisco, CA, USA
Correspondence to:
Elisabeth G.E. de Vries, e-mail: [email protected]
Keywords: mesothelin, pancreatic cancer, zirconium-89, PET imaging, IRDye 800CW
Received: August 03, 2015 Accepted: October 16, 2015 Published: October 29, 2015
ABSTRACT
Mesothelin is a tumor differentiation antigen expressed by epithelial tumors, including pancreatic cancer. Currently, mesothelin is being targeted with an antibody-drug conjugate (ADC) consisting of a mesothelin-specific antibody coupled to a highly potent chemotherapeutic drug. Considering the toxicity of the ADC and reduced accessibility of pancreatic tumors, non-invasive imaging could provide necessary information. We therefore developed a zirconium-89 (89Zr) labeled anti-mesothelin antibody (89Zr-AMA) to study its biodistribution in human pancreatic tumor bearing mice. Biodistribution and dose-finding of 89Zr-AMA were studied 144 h after tracer injection in mice with subcutaneously xenografted HPAC. MicroPET imaging was performed 24, 72 and 144 h after tracer injection in mice bearing HPAC or Capan-2. Tumor uptake and organ distribution of 89Zr-AMA were compared with nonspecific 111In-IgG. Biodistribution analyses revealed a dose-dependent 89Zr-AMA tumor uptake. Tumor uptake of 89Zr-AMA was higher than 111In-IgG using the lowest tracer dose. MicroPET showed increased tumor uptake over 6 days, whereas activity in blood pool and other tissues decreased. Immunohistochemistry showed that mesothelin was expressed by the HPAC and CAPAN-2 tumors and fluorescence microscopy revealed that AMA-800CW was present in tumor cell cytoplasm. 89Zr-AMA tumor uptake is antigen-specific in mesothelin-expressing tumors. 89Zr-AMA PET provides non-invasive, real-time information about AMA distribution and tumor targeting.
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