Bexxar (tositumomab)

Bexxar (tositumomab) refers most often to the Bexxar therapeutic regimen, a type of radioimmunotherapy: Unlike traditional chemotherapy (and much like Zevalin), Bexxar combines the powerful anti-cancer effects of radiation ("radio-") with the targeted, precision action of a monoclonal antibody ("immuno")1.

Tositumomab is a monoclonal antibody that, like rituximab (Rituxan) and ibritumomab tiuxetan (Zevalin), targets the CD20 protein found on the surface of B lymphocytes.

What it's effective for and why

The Bexxar therapeutic regimen has proven to be effective in treating indolent, CD20 positive B-cell non-Hodgkin's lymphomas. It has been FDA approved since 2003 for the treatment of follicular lymphoma when the disease is refractory to rituximab and when it has relapsed following a prior regimen of chemotherapy2. Bexxar works as a combination of two closely related monoclonal antibodies: tositumomab seeks out and finds B lymphocytes (identifying them by the protein CD20), then using the iodine 131 to kill the cell with targeted radiation.

The Bexxar therapeutic regimen features two steps, the dosimetric step, and the therapeutic step. The dosimetric step involves only an infusion of tositumomab. It is followed, 7-14 days later, by the therapeutic step: once again, the patient receives an infusion of tositumomab, but this time it is followed by an additional smaller dose of tositumomab that is attached to the radioactive isotope Iodine-131. This step delivers approximately 75 cGy of radiation to the body.

Side effects: Overview3

In general, Bexxar produces side effects similar to many other drugs: nausea, vomiting, stomach, back or neck pain, diarrhea, loss of appetite, mouth sores, headaches, and hair loss to name a few. More severe side effects that have been reported include chest pain, constipation, brittle nails, hoarse voice, or a puffy face. It is important to remind the reader that not everyone receiving the drug will develop these side effects.

Additionally, some patients given the Bexxar injection have gone on to develop other cancers, notably leukemia, skin cancer, myelodysplastic syndrome (MDS) or other cancers.

Click HERE to view ongoing clinical trials of Bexxar through the National Cancer Institute's PDQ Cancer Clinical Trials Registry.


  1. Lymphoma Information Network: Bexxar
  2. NCI: FDA approval for Tositumomab and Iodine | 131
  3. MedlinePlus: Side effects of Bexxar


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