Another class of targeted therapies includes monoclonal antibodies that deliver toxic molecules to cancer cells specifically.
- Tositumomab and 131I-tositumomab (Bexxar®) is approved to treat certain types of B-cell non-Hodgkin lymphoma. It is a mixture of monoclonal antibodies that recognize the CD20 molecule. Some of the antibodies in the mixture are linked to a radioactive substance called iodine-131. The 131I-tositumomab component delivers radioactive energy to CD20-expressing B cells specifically, reducing collateral damage to normal cells. In addition, the binding of tositumomab to the CD20-expressing B cells triggers the immune system to destroy these cells.
- Ibritumomab tiuxetan (Zevalin®) is approved to treat some patients with B-cell non-Hodgkin lymphoma. It is a monoclonal antibody directed against CD20 that is linked to a molecule that can bind radioisotopes such as indium-111 or yttrium-90. The radiolabeled forms of Zevalin deliver a high dose of radioactivity to cells that express CD20.
- Denileukin diftitox (Ontak®) is approved for the treatment of some patients with CTCL. Denileukin diftitox consists of interleukin-2 (IL-2) protein sequences fused to diphtheria toxin. The drug binds to cell surface IL-2 receptors, which are found on certain immune cells and some cancer cells, directing the cytotoxic action of the diphtheria toxin to these cells.