Ibritumomab

Ibritumomab is a radioimmunotherapy monoclonal antibody that targets CD20 as its antigen. The antibody itself is used in chelated form with the radioactive isotopes yttrium-90 (Y-90) or indium-111 (In-111), most commonly with tiuxetan as the chelating linker in clinical use. Y-90 is used for treatment, whereas In-111 is commonly used for biodistribution assessment and imaging. Ibritumomab specifically binds to the CD20 antigen on the surface of B cells, which is present on mature B cells and most B cell lymphoma cells. Once ibritumomab binds to CD20-positive cells, the radioactive isotope chelated to the antibody induces double-strand DNA breaks, thereby killing the cancer cells.