STABILITY, CHARACTERIZATION, AND KINETICS OF IN-111-LABELED MONOCLONAL ANTI-TUMOR ANTIBODIES IN NORMAL ANIMALS AND NUDE MOUSE-HUMAN TUMOR-MODELS

Abstract

Monoclonal antibodies (MoAb) against carcinoembryonic antigen were successfully radiolabeled with 111In, and the radiopharmaceutical was characterized in vitro and in normal and tumor-bearing mice. The 111In-MoAb proved to be stable in vitro and in vivo under normal conditions, although instability could be induced in vitro with large quantities of Fe-free transferrin. Animal distribution studies with 111In-MoAb demonstrated tumor localization superior to 67Ga and pharmacokinetics that were highly similar to those of endogenously labeled 75Se-MoAb. The 111In-MoAb followed 1st-order kinetics and fit a 2-compartmental model when studied in nude mice bearing human colon tumors known to express carcinoembryonic antigen. Significant quantities of radiolabel appeared in tissues other than tumor, with liver and skin having the highest concentrations. Sufficient tumor/background ratios were formed for scanning purposes. 111In-MoAb may prove to be effective as a radiopharmaceutical for tumor imaging.