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内容記述 |
Objective: The chelator is introduced by reacting an active ester or acid anhydride with the ε-amino group of the Lys residue in the antibody. However, because these reactions are random, it is not known which Lys residue in the antibody has been introduced with a chelator. In addition, the number of chelating agents introduced into the antibody varies from preparation to preparation. In other words, if it is possible to prepare antibodies in which the introduction of a chelator is site-specific and the number of introductions is clear, it is believed that the above problem can be improved. In the field of radiopharmaceutical chemistry, click chemistry is used in a variety of applications, including bioconjugation, radiolabeling, probe purification, and in vivo pre-targeting [1]. Thus, by performing a click reaction between an azide group and a DBCO group, it is possible to combine different radionuclides, i.e. to introduce radionuclides for diagnosis or treatment using a common chelating structure. Various methods have been reported for the introduction of site-specific azide groups into amino acid residues in antibodies, and the synthesis is relatively straightforward. We report the radiolabeling of the DBCO-containing DOTA derivative group using copper-64 and zirconium-89.Method: The copper-64 and zirconium-89 radioactivity were produced using a remotely controlled versatile system developed in our house [2, 3]. The conversion of 89Zr(Ox)x to 89ZrCl4 was carried out with reference to the literature [4]. Results: The labeling reaction was performed at room temperature for 10 min with DOTA-DBCO/DMSO (50 μL, 2 mg/mL) and 64CuCl2 (300 μL, acetate buffer, 0.1 mol/L, pH 5.0). The radiochemical yield of 64Cu-DOTA-DBCO was very low (<5%). There was no improvement in yield even when the labeling reaction was performed at 70°C. When the solubility of DBCO-DOTA was investigated using various buffer solutions, it was found that DBCO-DOTA at a concentration of 10 mg/mL could be prepared using acetate buffer (3 mol/L, pH 5.2). Accordingly, a labeling reaction was conducted at 70 °C for 10 minutes using DBCO-DOTA/acetate buffer (30 μL, 10 mg/mL, 3 moL/L, pH 5.2) and 64CuCl2 (300 μL, acetate buffer, 0.1 mol/L, pH 5.0). The radiochemical yield of 64Cu-DOTA-DBCO was greatly improved (>98%). It was found that the yield of the labeling reaction between DBCO-DOTA and copper-64 was significantly affected by the organic solvent. Next, we used the above labeling reaction conditions in a reaction with 89ZrCl4, but the yield was low (<20%). We are currently investigating conditions to improve the yield. We also report on the radiolabeling of DOTA derivatives that can be used as substrates for click reactions.Summary: We successfully radiosynthesized 64Cu-DOTA-DBCO for application in click reaction for the radiolabeling of antibodies.Reference: [1] Bauer, D., et al, Bioconjugate Chem., 2023, 34, 1925-1950. [2] Ohya, T., et al. Nucl. Med. Biol., 2016, 43, 685-691. [3] Nagatsu, K., et al Nucl. Med. Biol., 2012, 39, 1281-1285. [4] Holland J. P., et al Nucl. Med. Biol., 2009, 36, 729-739.Acknowledgements: This work was supported by AMED under Grant Number 21zf0127003h001. |
