Evaluation of a maleimido derivative of NOTA for site-specific labeling of affibody molecules.

Abstract

Radionuclide molecular imaging has the potential to improve cancer treatment by selection of patients for targeted therapy. Affibody molecules are a class of small (7 kDa) high-affinity targeting proteins with appreciable potential as molecular imaging probes. The NOTA chelator forms stable complexes with a number of radionuclides suitable for SPECT or PET imaging. A maleimidoethylmonoamide NOTA (MMA-NOTA) has been prepared for site-specific labeling of Affibody molecules having a unique C-terminal cysteine. Coupling of the MMA-NOTA to the anti-HER2 Affibody molecule Z(HER2:2395) resulted in a conjugate with an affinity (dissociation constant) to HER2 of 72 pM. Labeling of [MMA-NOTA-Cys(61)]-Z(HER2:2395) with (111)In gave a yield of >95% after 20 min at 60 °C. In vitro cell tests demonstrated specific binding of [(111)In-MMA-NOTA-Cys(61)]-Z(HER2:2395) to HER2-expressing cell lines. In mice bearing prostate cancer DU-145 xenografts, the tumor uptake of [(111)In-MMA-NOTA-Cys(61)]-Z(HER2:2395) was 8.2 ± 0.9% IA/g and the tumor-to-blood ratio was 31 ± 1 (4 h postinjection). DU-145 xenografts were clearly visualized by a gamma camera. Direct in vivo comparison of [(111)In-MMA-NOTA-Cys(61)]-Z(HER2:2395) and [(111)In-MMA-DOTA-Cys(61)]-Z(HER2:2395) demonstrated that both conjugates provided equal radioactivity uptake in tumors, but the tumor-to-organ ratios were better for [(111)In-MMA-NOTA-Cys(61)]-Z(HER2:2395) due to more efficient clearance from normal tissues. In conclusion, coupling of MMA-NOTA to a cysteine-containing Affibody molecule resulted in a site-specifically labeled conjugate, which retains high affinity, can be efficiently labeled, and allows for high-contrast imaging.

• Authors: Vladimir Tolmachev, Mohamed Altai, Mattias Sandström, Anna Perols, Amelie Eriksson Karlström, Frederic Boschetti, Anna Orlova
• Journal: Bioconjugate chemistry (Bioconjug Chem) Vol. 22 Issue 5 Pg. 894-902 (May 18 2011) ISSN: 1520-4812 [Electronic] United States
• PMID: 21443270 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Heterocyclic Compounds
• Heterocyclic Compounds, 1-Ring
• Maleimides
• Radiopharmaceuticals
• Recombinant Fusion Proteins
• 1,4,7-triazacyclononane-N,N',N''-triacetic acid

Topics

• Animals
• Heterocyclic Compounds (chemistry, pharmacokinetics)
• Heterocyclic Compounds, 1-Ring
• Male
• Maleimides (chemistry, pharmacokinetics)
• Mice
• Mice, Nude
• Molecular Imaging
• Molecular Structure
• Radiopharmaceuticals (chemistry, pharmacokinetics)
• Recombinant Fusion Proteins (chemistry, pharmacokinetics)
• Staining and Labeling
• Tissue Distribution
• Xenograft Model Antitumor Assays