Comparative evaluation of synthetic anti-HER2 Affibody molecules site-specifically labelled with 111In using N-terminal DOTA, NOTA and NODAGA chelators in mice bearing prostate cancer xenografts.

Abstract

PURPOSE:

In disseminated prostate cancer, expression of human epidermal growth factor receptor type 2 (HER2) is one of the pathways to androgen independence. Radionuclide molecular imaging of HER2 expression in disseminated prostate cancer might identify patients for HER2-targeted therapy. Affibody molecules are small (7 kDa) targeting proteins with high potential as tracers for radionuclide imaging. The goal of this study was to develop an optimal Affibody-based tracer for visualization of HER2 expression in prostate cancer.

METHODS:

A synthetic variant of the anti-HER2 Z(HER2:342) Affibody molecule, Z(HER2:S1), was N-terminally conjugated with the chelators DOTA, NOTA and NODAGA. The conjugated proteins were biophysically characterized by electrospray ionization mass spectroscopy (ESI-MS), circular dichroism (CD) spectroscopy and surface plasmon resonance (SPR)-based biosensor analysis. After labelling with (111)In, the biodistribution was assessed in normal mice and the two most promising conjugates were further evaluated for tumour targeting in mice bearing DU-145 prostate cancer xenografts.

RESULTS:

The HER2-binding equilibrium dissociation constants were 130, 140 and 90 pM for DOTA-Z(HER2:S1), NOTA-Z(HER2:S1) and NODAGA-Z(HER2:S1), respectively. A comparative study of (111)In-labelled DOTA-Z(HER2:S1), NOTA-Z(HER2:S1) and NODAGA-Z(HER2:S1) in normal mice demonstrated a substantial influence of the chelators on the biodistribution properties of the conjugates. (111)In-NODAGA-Z(HER2:S1) had the most rapid clearance from blood and healthy tissues. (111)In-NOTA-Z(HER2:S1) showed high hepatic uptake and was excluded from further evaluation. (111)In-DOTA-Z(HER2:S1) and (111)In-NODAGA-Z(HER2:S1) demonstrated specific uptake in DU-145 prostate cancer xenografts in nude mice. The tumour uptake of (111)In-NODAGA-Z(HER2:S1), 5.6 ± 0.4%ID/g, was significantly lower than the uptake of (111)In-DOTA-Z(HER2:S1), 7.4 ± 0.5%ID/g, presumably because of lower bioavailability due to more rapid clearance. (111)In-NODAGA-Z(HER2:S1) provided higher tumour-to-blood ratio, but somewhat lower tumour-to-liver, tumour-to-spleen and tumour-to-bone ratios.

CONCLUSION:

Since distant prostate cancer metastases are situated in bone or bone marrow, the higher tumour-to-bone ratio is the most important. This renders (111)In-DOTA-Z(HER2:S1) a preferable agent for imaging of HER2 expression in disseminated prostate cancer.

• Authors: Jennie Malmberg, Anna Perols, Zohreh Varasteh, Mohamed Altai, Alexis Braun, Mattias Sandström, Ulrike Garske, Vladimir Tolmachev, Anna Orlova, Amelie Eriksson Karlström
• Journal: European journal of nuclear medicine and molecular imaging (Eur J Nucl Med Mol Imaging) Vol. 39 Issue 3 Pg. 481-92 (Mar 2012) ISSN: 1619-7089 [Electronic] Germany
• PMID: 22322933 (Publication Type: Comparative Study, Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• 1-(1,3-carboxypropyl)-4,7-carboxymethyl-1,4,7-triazacyclononane
• Acetates
• Antibodies, Monoclonal
• Chelating Agents
• Heterocyclic Compounds
• Heterocyclic Compounds, 1-Ring
• Indium Radioisotopes
• 1,4,7,10-tetraazacyclododecane- 1,4,7,10-tetraacetic acid
• 1,4,7-triazacyclononane-N,N',N''-triacetic acid
• Receptor, ErbB-2

Topics

• Acetates (chemistry)
• Amino Acid Sequence
• Animals
• Antibodies, Monoclonal (chemistry, immunology, pharmacokinetics)
• Binding Sites
• Cell Line, Tumor
• Cell Transformation, Neoplastic
• Chelating Agents (chemistry)
• Gene Expression Regulation, Neoplastic
• Heterocyclic Compounds (chemistry)
• Heterocyclic Compounds, 1-Ring (chemistry)
• Humans
• Indium Radioisotopes (chemistry)
• Isotope Labeling
• Male
• Mice
• Molecular Imaging
• Molecular Sequence Data
• Prostatic Neoplasms (genetics, metabolism, pathology)
• Receptor, ErbB-2 (immunology)
• Substrate Specificity