© 2003 by Oxford University Press
Journal of the National Cancer Institute, Vol. 95, No. 3, 189,
February 5, 2003
© 2003 Oxford University Press
NEWS |
ODAC Panel Gives Nod to Bexxar
The long journey of the experimental lymphoma treatment Bexxar (iodine 131 tositumomab) appears headed for a happy ending. In December, the U.S. Food and Drug Administration’s Oncologic Drugs Advisory Committee (ODAC) voted that Bexxar has demonstrated substantial "clinical benefit" for non-Hodgkin’s lymphoma patients who have failed either multiple chemotherapy or rituximab therapy.
The FDA is expected to give marketing approval to Bexxar for one or both indications by early spring. Bexxar, which is an I-131-radiolabeled monoclonal antibody, "will add considerably to what we can offer patients, with probably less toxicity" than existing treatments, said ODAC member Silvana Martino, D.O., of the John Wayne Cancer Institute in Santa Monica, Calif. (See News, Dec. 4, p. 1738.)
At the ODAC meeting in December, Bexxar’s sponsor, Corixa Corp., Seattle, stressed the drug’s record of long-term remissions. It’s "the most active agent that I have seen in patients with multiply relapsed or refractory low-grade B-cell non-Hodgkin’s lymphoma," said prominent lymphoma clinician James Armitage, M.D., of the University of Nebraska. (Armitage presented for Corixa.)
Although the ODAC panel approved the drug, some committee members expressed concern about the roughly 2% annual incidence of myelodysplastic syndrome (MDS), a suppression of the bone marrow, which may be the result of the combined effect of chemotherapy plus Bexxar. Extrapolating from trial results, "You’re talking about 12% to 18% [of Bexxar patients] at 6 years developing [MDS], which will be fatal," said ODAC member Douglas Blayney, M.D., of the Wilshire Oncology Medical Group in Pasadena, Calif. "I think that ought to give oncologists pause when they use this treatment, and not move to it first-line." However, no patient receiving Bexxar as first-line treatment has yet developed MDS.
The ODAC panel avoided comparing Bexxar to Zevalin (yttrium-90 ibritumomab tiuxetan), IDEC Pharmaceuticals’ yttrium-labeled anti-CD20 antibody approved by the FDA last February. Once Bexxar is approved, however, clinicians will have to choose between them. Both of the radiopharma-ceuticals have shown similar efficacy and safety. Some observers speculate that Zevalin, because of its longer beta-particle emission path length, may be better for bulkier tumors, whereas Bexxar would work better for small tumors, but no evidence for this yet exists. The process of administering Bexxar is slightly more involved because of its long-range gamma emissions and because dosing is based on the drug’s biodistribution rather than the patient’s body weight.
Because radioimmunotherapy is a new kind of cancer treatment, both Bexxar and Zevalin must battle for acceptance. Thus far, clinicians have been slow to embrace Zevalin, although lack of Medicare reimbursement before last October was a factor. "There could be a hill to climb before a particular institution gets its feet wet with this," said Bexxar co-inventor Mark Kaminski, M.D., of the University of Michigan. "But I think once they do, and they get good results, I think it’ll be difficult not to do this therapy."
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