iodine i 131 tositumomab

**Iodine i 131 tositumomab** is a radioimmunotherapeutic agent used primarily for the treatment of CD20-positive, relapsed or refractory non-Hodgkin's lymphoma. It consists of two components: * **Tositumomab**, a murine IgG2a lambda monoclonal antibody that targets the CD20 antigen on B lymphocytes, and * **Iodine‑131**, a radioactive isotope covalently linked to the antibody. The drug works by binding to CD20 on malignant B cells; this both stimulates immune-mediated cell death and delivers targeted radiation from the attached iodine‑131, resulting in direct cytotoxicity to cancer cells. The regimen involves an initial dosimetric dose followed by a therapeutic dose calculated based on patient-specific factors such as platelet count and biodistribution[2][4][5][7]. Bexxar was developed for patients whose disease is refractory to rituximab and has relapsed following chemotherapy[7]. The product was approved by the FDA but has since been discontinued.

Brand names

Bexxar

Other names

tositumomab and iodine i 131 tositumomab