Comparison of the immunoreactivity of rituximab antibody labeled with either I-125 or Re-188 for radioimmunotherapy

Monoclonal antibodies against tumor-associated antigens can be applied as delivery vehicles for radionuclides to treat tumors. The specificity of MAbs for tumor-associated antigens can be exploited to direct radionuclides selectively to tumor cells after systemic administration. In radioimmunotherapy, therapeutic efficacy depends on the choice of the radionuclide. The chemical characteristics of radioiodine and radiometals (Re-188) differ significantly with respect to labeling procedure and consequently the specificity of monoclonal antibody can be affected due to discrepancy of labeling condition. Rituximab is a genetically engineered, chimeric anti-CD20 monoclonal antibody with mouse variable and human constant region. The CD-20 itself plays an important role in human B-cell proliferation and is an effective target for immunotherapy. In the present study, we compared the immunoreactivity of I-125-labeled Rituximab with Re-188-labeled Rituximab according to radionuclide-optimized labeling condition in cell binding assay of Lindmo method