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99mTc-chelator engineering to improve tumour targeting properties of a HER2-specific Affibody molecule
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Oncology, Radiology and Clinical Immunology, Biomedical Radiation Sciences.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Oncology, Radiology and Clinical Immunology, Biomedical Radiation Sciences.ORCID iD: 0000-0001-6120-2683
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Oncology, Radiology and Clinical Immunology, Section of Medical Physics.
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2007 (English)In: European Journal of Nuclear Medicine and Molecular Imaging, ISSN 1619-7070, E-ISSN 1619-7089, Vol. 34, no 11, 1843-1853 p.Article in journal (Refereed) Published
Abstract [en]

PURPOSE: Monitoring HER2 expression is crucial for selection of breast cancer patients amenable to HER2-targeting therapy. The Affibody molecule Z(HER2:342) binds to HER2 with picomolar affinity and enables specific imaging of HER2 expression. Previously, Z(HER2:342) with the additional N-terminal mercaptoacetyl-glycyl-glycyl-glycyl (maGGG) sequence was labelled with (99m)Tc and demonstrated specific targeting of HER2-expressing xenografts. However, hepatobiliary excretion caused high radioactivity accumulation in the abdomen. We investigated whether the biodistribution of Z(HER2:342) can be improved by substituting glycyl residues in the chelating sequence with more hydrophilic seryl residues. METHODS: The Affibody molecule Z(HER2:342), carrying the chelators mercaptoacetyl-glycyl-seryl-glycyl (maGSG), mercaptoacetyl-glycyl-D: -seryl-glycyl [maG(D-S)G] and mercaptoacetyl-seryl-seryl-seryl (maSSS), were prepared by peptide synthesis and labelled with (99m)Tc. The differences in the excretion pathways were evaluated in normal mice. The tumour targeting capacity of (99m)Tc-maSSS-Z(HER2:342) was studied in nude mice bearing SKOV-3 xenografts and compared with the capacity of radioiodinated Z(HER2:342). RESULTS: A shift towards renal excretion was obtained when glycine was substituted with serine in the chelating sequence. The radioactivity in the gastrointestinal tract was reduced threefold for the maSSS conjugate in comparison with the maGGG conjugate 4 h post injection (p.i.). The tumour uptake of (99m)Tc-maSSS-Z(HER2:342) was 11.5 +/- 0.5% IA/g 4 h p.i., and the tumour-to-blood ratio was 76. The pharmacokinetics and uptake characteristics of technetium-labelled Z(HER2:342) were better than those of radioiodinated Z(HER2:342). CONCLUSION: The introduction of serine residues in the chelator results in better tumour imaging properties of the Affibody molecule Z(HER2:342) compared with glycyl-containing chelators and is favourable for imaging of tumours and metastases in the abdominal area.

Place, publisher, year, edition, pages
2007. Vol. 34, no 11, 1843-1853 p.
Keyword [en]
Animals, Chelating Agents/chemistry, Drug Delivery Systems/*methods, Female, Metabolic Clearance Rate, Mice, Inbred BALB C, Mice, Nude, Organ Specificity, Ovarian Neoplasms/*metabolism/radionuclide imaging, Radiopharmaceuticals/chemistry/diagnostic use/pharmacokinetics, Recombinant Fusion Proteins/chemistry/diagnostic use/*pharmacokinetics, Technetium/chemistry/diagnostic use/*pharmacokinetics, Tissue Distribution
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:uu:diva-17041DOI: 10.1007/s00259-007-0474-6ISI: 000250205400017PubMedID: 17565496OAI: oai:DiVA.org:uu-17041DiVA: diva2:44812
Available from: 2008-06-16 Created: 2008-06-16 Last updated: 2017-12-08Bibliographically approved
In thesis
1. Molecular Imaging of HER2 Expression using Synthetic Affibody Molecules: Design, Synthesis and Biological Evaluation
Open this publication in new window or tab >>Molecular Imaging of HER2 Expression using Synthetic Affibody Molecules: Design, Synthesis and Biological Evaluation
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Molecular imaging is an emerging multidisciplinary field that addresses the visualisation of diseases at the cellular and molecular levels. This thesis focuses on the development of a synthetic Affibody molecule-based imaging tracer for the detection of HER2 expression in malignant tumours.

Papers I-IV report the development of the HER2-specific Affibody molecule, ZHER2:342 by peptide synthesis and the use of different chelators attached to the N-terminus to allow 99mTc-labelling. Paper I described the optimisation of labelling of Affibody molecules using cysteine-based chelator sequences, in which the direct labelling method under alkaline conditions was the most suitable one. Papers II-IV report the development and optimisation of the in vivo properties of the HER2-specific Affibody molecule for high-contrast imaging. By using an array of mercaptoacetyl-based chelators, it was found that the substitution of a single amino acid in a 60 amino acid-long Affibody molecule can dramatically change the pharmacokinetics of the tracer. Strategic approaches that utilised hydrophilic amino acids, such as serine, glutamate and lysine, changed the excretion pathway from hepatobiliary to renal excretion. Problems with the high accumulation of radioactivity in the abdomen area and restricted imaging were resolved by the use of mercaptoacetyl-triglutamyl, maEEE or mercaptoacetyl-seryl-lysyl-seryl, maSKS chelators.

Paper V reports the re-engineering of the HER2-specific Affibody molecule to provide a C-terminal SECG sequence using peptide synthesis. Incorporation of this sequence provided a multifunctional platform for labelling (with technetium or trivalent radiometals) and a flexible production route (recombinant or chemical synthesis). Combination of a serine, a glutamic acid and a thiol-bearing group in the chelating sequence reduced the renal accumulation of Affibody molecules.

Altogether, the in vivo efficiency of Affibody molecules to target tumours and their biodistribution properties can be improved by strategic design and suitable chemistry. Hopefully, these observations will be applicable to other small peptide and protein scaffold-based tracers.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 53 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 445
Series
National Category
Medical and Health Sciences
Research subject
Biomedical Radiation Science
Identifiers
urn:nbn:se:uu:diva-99248 (URN)978-91-554-7489-8 (ISBN)
Public defence
2009-05-16, Rudbecksalen, Rudbecklaboratoriet, Uppsala, 09:15 (English)
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Supervisors
Available from: 2009-04-24 Created: 2009-03-10 Last updated: 2009-04-24Bibliographically approved

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Orlova, AnnaTolmachev, Vladimir

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