Synthesis, preclinical validation, dosimetry, and toxicity of 68Ga-NOTA-anti-HER2 Nanobodies for iPET imaging of HER2 receptor expression in cancer.

TitleSynthesis, preclinical validation, dosimetry, and toxicity of 68Ga-NOTA-anti-HER2 Nanobodies for iPET imaging of HER2 receptor expression in cancer.
Publication TypeJournal Article
Year of Publication2013
AuthorsXavier, C., I. Vaneycken, M. D'huyvetter, J. Heemskerk, M. Keyaerts, C. Vincke, N. Devoogdt, S. Muyldermans, T. Lahoutte, and V. Caveliers
JournalJ Nucl Med
Volume54
Issue5
Pagination776-84
Date Published2013 May
ISSN1535-5667
KeywordsAdult, Animals, Cell Line, Tumor, Chemistry Techniques, Synthetic, Drug Stability, Female, Gallium Radioisotopes, Gene Expression Regulation, Neoplastic, Heterocyclic Compounds, Humans, Mice, Multimodal Imaging, Neoplasms, Positron-Emission Tomography, Radiometry, Rats, Receptor, erbB-2, Reproducibility of Results, Single-Domain Antibodies, Tomography, X-Ray Computed
Abstract

UNLABELLED: Nanobodies are the smallest fully functional antigen-binding antibody fragments possessing ideal properties as probes for molecular imaging. In this study we labeled the anti-human epidermal growth factor receptor type 2 (HER2) Nanobody with (68)Ga via a 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA) derivative and assessed its use for HER2 iPET imaging.METHODS: The 2Rs15dHis6 Nanobody and the lead optimized current-good-manufacturing-practice grade analog 2Rs15d were conjugated with S-2-(4-isothiocyanatobenzyl)-1,4,7-triazacyclononane-1,4,7-triacetic acid (p-SCN-Bn-NOTA) to enable fast and efficient (68)Ga labeling. Biodistribution and PET/CT studies were performed on HER2-positive and -negative tumor xenografts. The effect of injected mass on biodistribution was evaluated. The biodistribution data were extrapolated to calculate radiation dose estimates for the adult female using OLINDA software. A single-dose extended-toxicity study for NOTA-2Rs15d was performed on healthy mice up to a dose of 10 mg/kg.RESULTS: Radiolabeling was quantitative (>97%) after 5 min of incubation at room temperature; specific activity was 55-200 MBq/nmol. Biodistribution studies showed fast and specific uptake (percentage injected activity [%IA]) in HER2-positive tumors (3.13 ± 0.06 and 4.34 ± 0.90 %IA/g for (68)Ga-NOTA-2Rs15dHis6 and (68)Ga-NOTA-2Rs15d, respectively, at 1 h after injection) and high tumor-to-blood and tumor-to-muscle ratios at 1 h after injection, resulting in high-contrast PET/CT images with high specific tumor uptake. A remarkable finding of the biodistribution studies was that kidney uptake was reduced by 60% for the Nanobody lacking the C-terminal His6 tag. The injected mass showed an effect on the general biodistribution: a 100-fold increase in NOTA-2Rs15d mass decreased liver uptake from 7.43 ± 1.89 to 2.90 ± 0.26 %IA/g whereas tumor uptake increased from 2.49 ± 0.68 to 4.23 ± 0.99 %IA/g. The calculated effective dose, based on extrapolation of mouse data, was 0.0218 mSv/MBq, which would yield a radiation dose of 4 mSv to a patient after injection of 185 MBq of (68)Ga-NOTA-2Rs15d. In the toxicity study, no adverse effects were observed after injection of a 10 mg/kg dose of NOTA-2Rs15d.CONCLUSION: A new anti-HER2 PET tracer, (68)Ga-NOTA-2Rs15d, was synthesized via a rapid procedure under mild conditions. Preclinical validation showed high-specific-contrast imaging of HER2-positive tumors with no observed toxicity. (68)Ga-NOTA-2Rs15d is ready for first-in-human clinical trials.

DOI10.2967/jnumed.112.111021
Alternate JournalJ. Nucl. Med.
PubMed ID23487015