90Y-labeled monoclonal antibodies for cancer therapy

Monoclonal antibody 17-1A, which has specificity for colorectal carcinoma, was labeled with 90Y (10–20% radiolabeling yield). Tissue distribution studies in tumor-bearing nude mice were carried out. 90Y-labeled 17-1A showed good uptake in the SW 948 colon carcinoma cell line. However, 90Y-labeled A5C3, a monoclonal antihepatitis virus antibody studied as a control, showed similar uptake in this tumor. Neither antibody was taken up well by a WM-9 melanoma. It is believed that the loss of specificity observed is due to the low specific activity of the 90Y-labeled monoclonal antibody preparations used. This hypothesis is supported by radioimmunoassay data.