A radioimmunoconjugate of tenatumomab, a murine monoclonal antibody targeting the tumor-associated antigen (TAA) tenascin-C (TNC), labeled with iodine I 131, with potential antineoplastic activity. The antibody moiety of iodine I 131 tenatumomab binds to TNC, thereby delivering a cytotoxic dose of iodine I 131 specifically to tumors expressing TNC. TNC, an extracellular matrix protein, is upregulated in a variety of tumor cell types; it plays a key role in invasion, tumor cell proliferation and immune evasion. or A monoclonal antibody directed against the CD20 protein expressed on the surface of B-lymphocytes and radiolabeled with the radioisotope iodine I 131 with potential antineoplastic activity. Iodine I 131 tositumomab binds to and selectively delivers cyctotoxic radiation to CD20-expressing B-lymphocytes, thereby minimizing systemic radiotoxicity. or A drug used with another drug to treat certain types of B-cell non-Hodgkin lymphoma. It is also being studied in the treatment of other types of cancer. Iodine I 131 tositumomab is a form of the monoclonal antibody tositumomab that is linked to the radioactive substance iodine I 131. It is a type of radioimmunoconjugate.