Monoclonal Antibody (96.5, ZME-018) in Detection of Human Melanoma in Athymic Mice

We compared the biodistribution of two radiolabeled, whole, tumor selective monoclonal antibodies ([111ln]96.5, [111ln]ZME-018) to 67Gain nude mice bearing a human melanoma known to express p97 antigen. Localization of gallium was determined 48 hr following i.v. injection. Localization of the radiolabeled antibodies was determined at 3 days and 7 days following i.v. injection. All agents showed more or less similar absolute tumor uptake which varied between 22 % and 36 % of the injected dose per gram of tumor. Only the tumor uptake of [111ln]96.5 antibody at 7 days was significantly lower than the 67Gauptake at 48 hr. However, uptake in normal tissues was generally higher for both antibodies at 3 and 7 days than for 67Gauptake at 48 hr. Therefore, the tumor-to-blood ratio for 67Gawas tenfold higher than that for either antibody, the tumor-to-muscle ratio was twofold higher. Bone was the only organ in which the tumor-to-organ ratio was consistently higher with radiolabeled antibody than with 67Ga.The tumor-to-liver and tumor-to-intestine ratios were comparable. Localization of the two tumor selective antibodies was greater than a nonspecific "control antibody " ([111ln]CEA) and change in specific activity from 0.17 mCi/mg to 3.3 mCi/mg did not influence localization. From these animal data it may be anticipated that tumor imaging with[I11ln]96.5 or [l11ln]ZME-018 will not be superior to imaging with 67Gafor detection o