Thorium-227 is an alpha-particle-emitting radionuclide with research applications in radioimmunotherapy of cancer. We produce the research medical isotope Th-227 for distribution through the National Isotope Development Center in Oak Ridge, Tennessee. Thorium-227 has a physical half-life of 18.7 days.
Thorium-227 decays to Ra-223 and other short-lived radionuclides in its decay chain to stable lead-207. Thorium-227 can be chelated (using a macrocyclic ligand "claw") and attached (using a chemical linker) to a monoclonal antibody or other protein. This radioimmunoconjugate is used to target cancer cells in the body. As thorium-227 and its daughter products decay, alpha-particles are emitted that can effectively treat cancer cells. Radioimmunoconjugates labeled with Th-227 can be particularly effective when used to target metastatic lesions in advanced cancer patients. Current research using Th-227 focuses on developing and testing new radiopharmaceutical concepts.