Influence of radiolabeled monoclonal antibody dose on tumor localization

The relationship between tumor uptake of radiolabeled monoclonal antibodies and antibody protein dose is unclear. The authors investigated the uptake of I-125-labeled 225.28S, a murine IgG2ak reactive with melanoma, into xenografts of human melanoma in nude mice after intraperitoneal injection. Groups of five to eight animals received antibody doses of 6.25, 62.5, 625, and 1,875 μg given intraperitoneally. Mean tumor uptakes 3 days after injection were nearly identical among groups at 5.45%, 6%, 5.85%, and 5.75% of the injected dose/g of tumor, respectively. Uptake in nontarget organs was also comparable. These data indicate that in the melanoma system, and using iodinated antibody, over a wide dosing range protein dose is not a major determinant of antibody uptake into tumor