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Optimized synthesis and indium complex formation with the bifunctional chelator NODIA-Me


Weinmann, Christian; Holland, Jason P; Läppchen, Tilman; Scherer, Harald; Maus, Stephan; Stemler, Tobias; Bohnenberger, Hendrik; Ezziddin, Samer; Kurz, Philipp; Bartholomä, Mark D (2018). Optimized synthesis and indium complex formation with the bifunctional chelator NODIA-Me. Organic & Biomolecular Chemistry, 16(40):7503-7512.

Abstract

The bifunctional chelator NODIA-Me holds promise for radiopharmaceutical development. NODIA-Me is based on the macrocycle TACN (1,4,7-triazacyclononane) and incorporates two additional methylimidazole arms for metal chelation and an acetic acid residue for bioconjugation. The original two step synthesis was less than optimal due to low yields and the requirement of semi-preparative RP-HPLC purifications. Here, the overall yield for the preparation of NODIA-Me was improved two- to five-fold via two synthetic routes using different protection/deprotection techniques. This way, it was possible (1) to prepare of NODIA-Me on multi-gram scale and (2) to avoid time-consuming HPLC purifications. Inspired by recent results with nat/68Ga3+, preliminary studies on the radiolabeling properties and complex formation of NODIA-Me with nat/111In3+ were performed. Quantitative radiochemical yields were achieved at ambient temperature providing molar activities of ∼30 MBq nmol−1, which could be increased to ∼240 MBq nmol−1 at 95 °C. At r.t., pH 5.5 was optimal for 111In-labeling, but quantitative yields were also achieved in the pH range from 5.5 to 8.2, when the reaction temperature was increased. Stability tests of 111In complexes in vitro revealed high kinetic stabilities in serum and ligand challenge experiments, which is a consequence of the formation of rigid 1 : 1 indium chelates as shown by NMR studies in solution. In summary, the new synthetic routes afford the BFC NODIA-Me in high yields and on large scale. Further, 111In complexation experiments broaden the scope of our chelating system for radiopharmaceutical applications.

Abstract

The bifunctional chelator NODIA-Me holds promise for radiopharmaceutical development. NODIA-Me is based on the macrocycle TACN (1,4,7-triazacyclononane) and incorporates two additional methylimidazole arms for metal chelation and an acetic acid residue for bioconjugation. The original two step synthesis was less than optimal due to low yields and the requirement of semi-preparative RP-HPLC purifications. Here, the overall yield for the preparation of NODIA-Me was improved two- to five-fold via two synthetic routes using different protection/deprotection techniques. This way, it was possible (1) to prepare of NODIA-Me on multi-gram scale and (2) to avoid time-consuming HPLC purifications. Inspired by recent results with nat/68Ga3+, preliminary studies on the radiolabeling properties and complex formation of NODIA-Me with nat/111In3+ were performed. Quantitative radiochemical yields were achieved at ambient temperature providing molar activities of ∼30 MBq nmol−1, which could be increased to ∼240 MBq nmol−1 at 95 °C. At r.t., pH 5.5 was optimal for 111In-labeling, but quantitative yields were also achieved in the pH range from 5.5 to 8.2, when the reaction temperature was increased. Stability tests of 111In complexes in vitro revealed high kinetic stabilities in serum and ligand challenge experiments, which is a consequence of the formation of rigid 1 : 1 indium chelates as shown by NMR studies in solution. In summary, the new synthetic routes afford the BFC NODIA-Me in high yields and on large scale. Further, 111In complexation experiments broaden the scope of our chelating system for radiopharmaceutical applications.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Uncontrolled Keywords:Physical and Theoretical Chemistry, Organic Chemistry, Biochemistry
Language:English
Date:1 January 2018
Deposited On:07 Mar 2019 08:24
Last Modified:25 Sep 2019 00:24
Publisher:Royal Society of Chemistry
ISSN:1477-0520
OA Status:Green
Publisher DOI:https://doi.org/10.1039/c8ob01981a
Project Information:
  • : FunderSNSF
  • : Grant IDPP00P2_163683
  • : Project TitleAdvanced radiochemical methods for multi-modal imaging with nanomedicines
  • : FunderH2020
  • : Grant ID676904
  • : Project TitleNanoSCAN - Developing multi-modality nanomedicines for targeted annotation of oncogenic signaling pathways
  • : FunderKrebsliga Schweiz
  • : Grant IDKLS-4257-08-201
  • : Project Title

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