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May 14, 2002 |
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Antibody 'truck' delivers radiation directly to cancer ROCHESTER, MINN. -- May 14, 2002 -- A new study shows that the first of a new class of drugs using an antibody to deliver radiation directly to cancer cells in patients with low-grade B cell non-Hodgkin's lymphoma may be more effective than a similar drug that uses an antibody without radiation. The study is the first large study to compare the effectiveness of the radiolabeled antibody called ibritumomab tiuxetan with a similar antibody drug, called rituximab, which carries no radiation source to kill cells. The research team led by Dr. Thomas Witzig of the Mayo Clinic compared the ability of the new drug, marketed under the name Zevalin®, to the ability of another antibody drug, marketed as Rituxan® to zero in on and kill cancerous non-Hodgkin's lymphoma B cells. They published their study results in the May 15, 2002, issue of Journal of Clinical Oncology. "Unlike chemotherapy which goes through the whole body, Zevalin carries radiation payload directly to the tumor," Witzig said in a prepared statement. "The drug radiates only about a five millimeter (.2 in.) area around the tumor." The study involved 143 patients with B cell non-Hodgkin's lymphoma who had previously failed standard chemotherapy treatments. The patients were randomly assigned to treatment with either Zevalin or Rituxan. The results showed that 80 percent of patients who received Zevalin experienced a positive response, meaning a 50 percent or more decrease in the six largest lymph nodes or nodal tumor masses. That compared to a 56 percent response rate in patients receiving only Rituxan. Most noteworthy, 30 percent of the patients receiving Zevalin achieved complete remission with no evidence of the cancer present as determined by a CT scan, compared to only 16 percent of patients taking Rituxan. Radioimmunotherapy combines monoclonal antibodies, which are engineered proteins produced in a laboratory to react against a cancer cell, with a radioactive isotope chemically bound to the antibody. The antibody then acts like a delivery truck carrying the isotope through the bloodstream to the cancer cells. Zevalin, which is made by IDEC Pharmaceutical, Corp. is the first radioimmunotherapy drug developed specifically to fight this common but usually fatal cancer of the lymph glands that, for unknown reasons, is on the increase in the United States. About 56,000 people are diagnosed with this cancer annually. IDEC also makes Rituxan in cooperation with Genentech, Inc. Along with its ability to hone in on cancer cells, Zevelin is easier on patients physically, with few serious side effects. "One treatment is required on an outpatient basis, compared to a series of treatments with chemotherapy that can last four to six months and sometimes include hospitalization because of serious side effects," says Witzig a hematolgist in the division of internal medicine. "There's no hair loss or prolonged fatigue, nausea or vomiting. The most significant side effect is a temporary decrease in the blood counts." The FDA recently approved Zevalin for treatment of patients with B cell non-Hodgkin's lymphoma that has relapsed. |
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