Article: Ibritumomab tiuxetan

Ibritumomab tiuxetan, also sold under the trade name Zevalin®, is a monoclonal antibody radioimmunotherapy treatment for some forms of B cell non-Hodgkin's lymphoma, a myeloproliferative disorder of the lymphatic system. The drug uses the monoclonal mouse IgG1 antibody ibritumomab in conjunction with the chelator tiuxetan, to which a radioactive isotope (either yttrium-90 or indium-111) is added.

Mechanism of action

The antibody binds to the CD20 antigen found on the surface of normal and malignant B cells (but not B cell precursors), allowing radiation from the attached isotope (mostly beta emission) to kill it and some nearby cells. In addition, the antibody itself may trigger cell death via antibody-dependent cell-mediated cytotoxicity (ADCC), complement-dependent cytotoxicity (CDC), and apoptosis. Together, these actions eliminate B cells from the body, allowing a new population of healthy B cells to develop from lymphoid stem cells.

Administration

Ibritumomab tiuxetan is administered by intravenous infusion which usually lasts around 10 minutes. Treatment with Zevalin showed higher response rates in clinical trials compared to treatment with only Rituxan (similar to Zevalin, but without the attached radioisotope), and showed very promising results for patients who no longer respond to Rituxan.

History

Developed by the IDEC Pharmaceuticals, which is now part of Biogen Idec, ibritumomab tiuxetan was the first radioimmunotherapy drug approved by the Food and Drug Administration (FDA) in 2002 to treat cancer.

Zevalin® is currently the most expensive drug available given in a single dose, costing over $24,000 for the average dose. However, Zevalin is essentially an entire course of lymphoma therapy which is delivered in 7-9 days, with one visit for imaging, one visit for a gamma scan, and one visit for the actual therapeutic dose. Compared to other monoclonal antibody treatments (many of which are well over $40,000 for a course of therapy) Zevalin is priced in the middle for many of these therapies.

See also

• Bexxar, an alternative radioimmunotherapy treatment for non-Hodgkin's lymphoma.