Iodine I 131 tositumomab (GSK)

Iodine I 131 tositumomab (Bexxar) is a radioimmunotherapy regimen developed by GlaxoSmithKline and Corixa Corporation for the treatment of B-cell non-Hodgkin's lymphoma. The therapy consists of two components: an unlabeled murine IgG2a monoclonal antibody (tositumomab) and a version of the same antibody radiolabeled with the isotope iodine-131. Both components target the CD20 antigen, which is highly expressed on the surface of normal and malignant B-lymphocytes. The treatment protocol involves a dosimetric step to determine patient-specific clearance followed by a therapeutic dose. The unlabeled antibody is administered first to saturate non-specific binding sites and clear circulating B-cells, thereby optimizing the biodistribution of the subsequent radiolabeled dose. The iodine-131 delivers targeted beta and gamma radiation directly to the tumor sites, inducing cell death through ionizing radiation, antibody-dependent cell-mediated cytotoxicity (ADCC), and apoptosis. Although FDA-approved in 2003, the product was discontinued by the manufacturer in 2014 due to declining clinical use.

Brand names

Bexxar

Other names

Iodine-131 tositumomabIodine131 tositumomabIodine 131 tositumomab131I-tositumomabtositumomab and iodine I 131 tositumomab