Figure 1.

Radiopharmaceutical classification. Charted are key radiobiological aspects of radiopharmaceuticals of the (A) neat class (i.e., no targeting ligand) or (B) conjugated class [i.e., has targeting ligand (protein or antibody)]. (A) A neat radiopharmaceutical might act as a mineral mimetic [such as calcium in the case of radium-223 (green radionuclide)], home in on areas of tumor-related bone turnover in affected bones, incorporate and lock into mineralized bone matrix, and lethally irradiate nearby tumor cells for tumor control, as well as, osteoclasts and osteoblasts so as to mitigate abnormal tumor-related bone formation. (B) A conjugated radiopharmaceutical with a targeting ligand [like thorium-227 antibody conjugates (purple radionuclide)] might bind to cancer cell surface molecules, internalize as part of endosomes, and lethally irradiate nuclear DNA from within the cancer cell.