Simplified Preformed Chelate Protein Radiolabeling with Technetium-99m Mercaptoacetamidoadipoylglycylglycine (N₃S-Adipate)

A simplified kiet has been developed for Tc-99m protein radiolabeling using an N3S triamide mercaptide bifunctional chelating agent and the preformed chelate approach. The process combined N3S chelating agent, gluconate intermediate transfer agent, stannous reducing agent, and gentisic acid stabilizer into a lyophilized formulation. With sulfur donor atom hemithioacetal protection of the ligand, delta-2,3,5,6-tetrafluorothiophenyl alpha-S-(1-ethoxyethyl)mercaptoacetamido-L-adipolyglycylglycine, optimum Tc-99m chelation was achieved in a single step. Subsequent reaction with NR-LU-10 antibody Fab fragment followed by purification via QAE Sephadex anion exchange resin filter afforded Tc-99m-N3S-NR-LU-10 Fab conjugate with retained immunoreactivity and effective tumor targeting properties.