The influence of monoclonal antibody dose on tumor uptake of radiolabeled antibody.

The impact of antibody protein dose on tumor accumulation of radiolabeled monoclonal antibody was studied in nude mice with xenografts of human melanomas. 225.28S, a murine monoclonal antibody reactive with a high-molecular weight antigen of melanoma, was radiolabeled with I-125 and administered intraperitoneally to nude mice with human melanoma xenografts. Three days later, the animals were sacrificed, and tumor and normal tissue uptake of I-125 antibody was determined. At doses of 6.25, 62.5, 625 and 1875 ug of monoclonal antibody, there were no significant differences in percent of injected dose reaching the tumor/g of tumor or in the non-tumor uptakes achieved. These findings indicate that in the melanoma system, antibody dose is not a critical determinant of tumor uptake, and additionally indicate that low doses of antibody protein are appropriate for studies involving radioiodinated antibody localization.