Potential of palladium-109-labeled antimelanoma monoclonal antibody for tumor therapy.

Palladium-109, a beta-emitting radionuclide, was chelated to the monoclonal antibody 225.28S to the high molecular weight antigen associated with human melanoma. The radiolabeled antibody maintained its specific in vitro reactivity with cultured human melanoma cells. Injection of the radiolabeled monoclonal antibody into nude mice bearing human melanoma resulted in significant accumulation of the radiolabel in the tumors: 19% injected dose/g; 38:1 and 61:1 tumor-to-blood ratios at 24 and 48 hr, respectively. The localization of the radiolabeled antibody in liver and kidney also was high, but appreciably lower than that achieved in tumor. These results suggest that Pd-109-labeled monoclonal antibody to tumor-associated antigens may have potential applications in tumor immunotherapy.