Improved radioimaging and tumor localization with monoclonal F(ab')₂

Monoclonal anti-tumor antibodies have great promise for radioimmunodetection and localization of tumors. Fab and F(ab')₂ fragments, which lack the Fc fragment of antibody (Ab), are cleared more rapidly from the circulation and may have less nonspecific tissue binding than intact Ab. In radioimaging studies using a murine monoclonal antibody to carcinoembryonic antigen in a human colon carcinoma xenografted into hamsters, F(ab')₂ fragments were shown superior to Fab fragments and intact antibody for scintiscanning. In double-label experiments with anti-CEA antibody and control monoclonal IgG, F(ab')₂ fragments were found to give better and more rapid specific tumor localization than intact antibody or Fab fragments. F(ab')₂ fragments offer significant promise for tumor imaging and possibly therapy.