Tumor imaging with 99mTc-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 cancer and malignant melanomas, was formulated. A direct method based on the reduction of protein disulphide bridges using 2-mercaptoethanol was used with methylene diphosphonate as the transchelating ligand. The labeled species were analyzed by ITLC thin layer chromatography and high performance liquid chromatography. Labeling efficiency was greater than 90%. Immunoreactivity was assessed on IIB-BR-G cells. 99mTc-labeled Mab FC-5.01 biodistribution and tumor imaging were performed in nude mice bearing IIB-BR-G breast cancer xenografts. At 24 hs accumulation of 99mTc increased in tumor and decreased in blood and most organs in agreement with results of an in vitro cysteine challenge assay. Quality control tests demonstrated that the kit was stable for up to 120 days. Animal studies demonstrated good and specific in vivo tumor targeting.