radioimmunotherapy radioimmunotherapy radioimmunotherapy (rit) uses an antibody labeled with a radionuclide to deliver cytotoxic radiation to a target cell. it is a form of unsealed source radiotherapy. in cancer therapy, an antibody with specificity for a tumor-associated antigen is used to deliver a lethal dose of radiation to the tumor cells. the ability for the antibody to specifically bind to a tumor-associated antigen increases the dose delivered to the tumor cells while decreasing the dose to normal tissues. by its nature, rit requires a tumor cell to express an antigen that is unique to the neoplasm or is not accessible in normal cells. radioimmunotherapyschematic of radioimmunotherapy (rit)other namesriticd-9-cm92.28meshd016499 history of available agents namedescriptionfda statusema status ibritumomab tiuxetan (zevalin)monoclonal antibody anti-cd20 conjugated to a molecule that chelates yttrium-90.approved (2002)authorised (2004) iodine (131i) tositumomab (bexxar)links a molecule containing iodine-131 to an anti-cd20 monoclonal antibodyapproved (2003) withdrawn (2014)orphan drug (2003) withdrawn (2015) lutetium (177lu) lilotomab satetraxetan (betalutin)combination of lutetium-177 and an anti-cd37 monoclonal antibodyfast track (2020)orphan drug (2020) 131i tositumomab and 90y ibritumomab tiuxetan were the first agents of radioimmunotherapy, and they were approved for the treatment of refractory non-hodgkin's lymphoma. this means they are used in patients whose lymphoma is refractory to conventional chemotherapy and the monoclonal antibody rituximab. agents in clinical development a set of radioimmunotherapy drugs that rely upon an alpha-emitting isotope (e.g., bismuth-213 or, preferably, actinium-225), rather than a beta emitter, as the killing source of radiation is being developed. several phase ii clinical trials for the treatment of acute myeloid leukemia have been carried out using alpha-emitting rits. 90y-ff-21101 is a monoclonal antibody against p-cadherin radiolabeled with yttrium-90. it is one of several rit treatments under investigation intending to treat solid tumors. a phase i clinical trial began in 2015. other applications (non-approved indications) other types of cancer for which rit has therapeutic potential include prostate cancer, metastatic melanoma, ovarian cancer, neoplastic meningitis, leukemia, high-grade brain glioma, and metastatic colorectal cancer.