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First Responses Seen in Cancer Patients To a Recombinant Immunotoxin

Bob Kuska

Over the last decade, scientists have produced many recombinant immunotoxins — small, bioengineered antibodies linked to a toxin — as part of an experimental strategy to directly target and deliver deadly poisons to tumor cells. However, despite the great promise of this approach, there have been no published reports of cancer patients responding to a recombinant immunotoxin.

That is, until now. In the November 15 issue of the journal Blood, a team of scientists from the National Cancer Institute reports that four out of four patients with hairy cell leukemia, an uncommon cancer of immune B cells, had "major responses" to a recombinant immunotoxin called LMB-2. All of the patients previously had not responded to standard treatments for the cancer, including chemotherapy and removal of the spleen.

Robert Kreitman, M.D., lead author on the study, said one patient in this early stage clinical trial had a complete remission after treatment with the immunotoxin and has not relapsed 16 months later. For the three other patients, Kreitman and colleagues observed partial responses, detecting a 98% to 99.8% reduction in malignant circulating cells. All of the side effects were reversible and usually lasted less than a week. These included fever, nausea, vomiting, and rash.

"This offers a proof of principle that recombinant immunotoxins will one day have an important role in treating cancer," said Ira Pastan, M.D., senior author on the paper. "But there is still much work to be done to maximize their potential for cancer patients."



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Dr. Ira Pastan

 


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