Long-term biodistribution in tumored mice of murine and chimeric B72.3-IgG antibody radiolabeled with 114mIn via both DTPA and a macrocyclic chelator.

To assess the possibilities of using 114mIn as a therapeutic agent, the long-term biodistribution of 114mIn was studied, in tumor-bearing nude mice, after injection of labeled monoclonal antibody (MoAb) B72.3 IgG, either DTPA-coupled murine, DTPA-coupled chimeric, or macrocycle-coupled chimeric antibody. Although the biodistributions in all cases were similar, there were important differences. The use of DTPA-coupled chimeric antibody led to higher concentrations of radioactivity in tumor, and to lower concentrations in liver and bone, as compared to DTPA-coupled murine antibody. The use of macrocycle-coupled chimeric antibody led to higher concentrations of radioactivity in the liver and in bone as compared to the DTPA-coupled chimeric antibody. However, in this case there were no significant differences in tumor uptake or clearance. Radiation doses were calculated based on the organ retention and by neglecting source-to-target contributions. Radiation dose distribution was marginally favorable for therapy in the group injected with DTPA-coupled chimeric antibody.