Radioimmunotherapy in human colon cancer bearing nude mice with intra-tumor injection of 188Ra anti-CEA monoclonal antibody C50

Objective: The aims were to evaluate 1) the direct labelling anti-CEA monoclonal antibody (McAb) C50 with 188Re and 2) the therapeutic efficacy and specificity of radioimmunotherapy (RIT) in nude mice bearing human colon cancer with intra-tumor injection of 188Re-anti-CEA McAb C50. Methods: The antibody C50 was reduced with 4 mg Vitamin C for 0.5 h at room temperature and then mixed with 0.2 mL solution of stannous chloride and 370-740 MBq of 188Re perrhenate to proceed 2 h at room temperature for accomplishment of labelling procedure. Subcutaneous human colon cancer xenografts in nude mice were intra-tumor injected with 188Re-McAb C50 at different dosage levels (study group) and intra-tumor injected saline or intra-tumor injected 188Re-McAb C50 at different dosage levels (study group) and intra-tumor injected saline or intra-tumor injected 188ReO4 (control group). Results: Radiochemical impurities of free and colloidal 188Re left in the recovered 188Re-McAb C50 were less than 5% and 10%, respectively. The tumor growth in size was significantly inhibited or even decreased by intra-tumor injection of 188Re-McAb C50 at the dose of 14.06 MBq or more per mouse, as compared with controls. Conclusions: Direct labelling of antibody with 188Re was performed with expected result. RIT with intra-tumor injected 188Re-McAb C50 at the dose of 14.06 MBq or more per mouse has significant inhibiting effect on the tumor growth