Radiolabeled Monoclonal Antibody Therapy: Bexxar®

Bexxar® (tositumomab and iodine I 131 ) is a radiolabled monoclonal antibody for the treatment of patients with CD20 positive, follicular, non-Hodgkin’s lymphoma (NHL), with and without transformation, whose disease is resistant to Rituximab and has relapsed following chemotherapy. It received US Food and Drug Administration approval in mid-2003.

How it works

Bexxar is an antibody with radioactive iodine 131 attached. The drug attaches to a protein found only on the surface of B lymphocytes such as cancerous B-cells found in many forms of Non-Hodgkin's lymphoma. The radioactivity targets the B-cell, destroying it.

Effectiveness

The effectiveness of the BEXXAR regimen was examined in a multi-center, single-arm study of 40 patients with follicular NHL whose disease had relapsed following or had not responded to Rituximab. The median age of patients in the study was 57 (range: 35-78) and the median number of prior chemotherapies was 4 (range: 1-11). Eighty-eight percent of patients met the definition of Rituximab refractory (defined as no response or a response of less than 6 months in duration).

In patients with Rituximab refractory disease, 63 percent of patients had a response to BEXXAR, with a median duration of response of 25 months. Twenty-nine percent of patients had a complete response (no clinical signs of disease) to BEXXAR. The median duration of complete responses has not been reached after a median follow up of 26 months.

The results of this study were supported by demonstration of durable objective responses in four other single-arm studies enrolling 190 patients with Rituximab-naïve, follicular NHL, with or without transformation, who had relapsed following or were refractory to chemotherapy. In these studies, the overall response rates ranged from 47 percent to 64 percent and the median durations of response ranged from 12 to 18 months.

Treatment and Side Effects

Bexxar is given intravenously once a week for two weeks.

The most common side effects occurring in the clinical trials included neutropenia, thrombocytopenia and anemia that can be both prolonged and severe.

The most common non-hematologic side effects included asthenia (weakness), fever, nausea, infection and cough.

The BEXXAR therapeutic regimen was associated with a risk of hypothyroidism and human anti-murine antibody (HAMA) formation.

Certain chemotherapy agents and ionizing radiation have been associated with the development of myelodysplasia (MDS), secondary leukemia and solid tumors. MDS, secondary leukemia and solid tumors have also been observed in patients receiving the BEXXAR therapeutic regimen. BEXXAR carries a warning about infusion-related reactions that may be induced by the administration of foreign proteins.

Hypersensitivity reactions occurred in six percent of patients. Adjustments of the rate of infusion to control adverse reactions occurred in seven percent of patients.

Dive Deeper

Other Treatment Options

  • Zevalin®, a radiotherapeutic monoclonal antibody treatment, has been approved by the FDA as Part of First-Line Therapy in Treatment of Follicular Non-Hodgkin's Lymphoma.
  • Follow this link to identify a conveniently located cancer treatment center and begin the process of enrollment.

For more information on Non-Hodgkin's Lymphoma, please see the following pages:

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