Optimization of Radioimmunotherapy of Renal Cell Carcinoma: Labeling of Monoclonal Antibody cG250 with 131I, 90Y, 177Lu, or 186Re

Radioimmunotherapy (RIT) can be performed with various ra-dionuclides. We tested the stability, biodistribution, and thera-peutic efficacy of various radioimmunoconjugates (131I, 88/90Y, 177Lu, and 186Re) of chimeric antirenal cell cancer monoclonal antibody G250 (mAb cG250) in nude mice with subcutaneous renal cell cancer (RCC) tumors. Methods: The 88/90Y and 177Lu labeling procedures of cG250 conjugated with cyclic diethyl-enetriaminepentaacetic acid anhydride (cDTPA), isothiocyana-tobenzyl-DTPA (SCN-Bz-DTPA), or 1,4,7,10-tetraazacyclodo-decanetetraacetic acid (DOTA) were characterized. Stability of the labeled conjugates in plasma at 37°C was assessed. Bio-distribution and therapeutic efficacy of labeled cG250 were compared in nude mice with SK-RC-52 human RCC xenografts. Results: Both SCN-Bz-DTPA and DOTA were stable in vitro (5 % release of the radiolabel during 14 and 21 d of incubation