Tumor imaging with Tc-99m-labeled FC-5.01 monoclonal antibody using a single step labeling method

A lyophilized one-step kit of Mab FC-5.01, reactive with human breast cance r and malignant melanomas, was formulated. A direct method based on the red uction of protein disulphide bridges using 2-mercaptoethanol was used with methylene diphosphonate as the transchelating ligand. The labeled species w ere analyzed by ITLC thin layer chromatography and high performance liquid chromatography. Labeling efficiency was greater than 90%. Immunoreactivity was assesed on LIB-BR-G cells. Tc-99m-labeled Mab FC-5.01 biodistribution a nd tumor imaging were performed in nude mice bearing IIB-BR-G breast cancer xenografts. At 24 hs accumulation of Tc-99m increased in tumor and decreas ed in blood and most organs in agreement with results of an in vitro cystei ne challenge assay. Quality control tests demonstrated that the kit was sta ble for up to 120 days. Animal studies demonstrated good and specific in vi vo tumor targeting.