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| |  AACR: National Cancer Institute Develops New Drug For Hairy Cell Leukemia By Cameron Johnston Special to DG News
NEW ORLEANS, LA -- March 30, 2001 -- An experimental drug developed by investigators at the United States National Cancer Institute has proven, in an early clinical trial, to be effective in treating hairy cell leukemia. The drug, known by its experimental name, BL-22, produced a complete response in 11 subjects and a partial response in two more in a trial of 15 subjects who were resistant to other treatments for the disease. The findings were released this week at the annual meeting of the American Association for Cancer Research (AACR), in New Orleans, Louisiana. According to Dr. Robert Kreitman, chief of clinical immunology at the NCI/National Institutes of Health, Bethesda, Maryland, BL-22 is an antibody fragment loaded with a pseudomonas exotoxin that binds itself to the CD-22 receptors which are found on the outer membrane of leukemia cells. The drug delivers the toxin to the cell, causing cell death. However, BL-22 spares normal cells and is attracted only to the leukemia cells. Currently, hairy cell leukemia is treated with two drugs, pentastatin and cladribine. However, 25 percent of patients become resistant to these agents over a period of five to eight years, Dr. Kreitman said. Also, patients on these drugs are unable to manufacture their own blood cells and therefore become heavily dependent on blood transfusions, which increases their risk of infections and their use of antibiotics. "All 11 patients who completed BL-22 had complete remissions and these 11, with the two partial responders had blood return to normal levels," Dr. Kreitman said in a press conference. "BL-22 is the first treatment developed in 10 years that can give complete remission in the majority of HCL patients treated. It is also the only agent that can give complete remission in the majority of HCL patients for whom conventional chemotherapy is not effective." Furthermore, most of the subjects who were treated with it had an increase in their normal cytotoxic T-cells that helped them stay in complete remission so they did not need to rely on repeat treatments once they reached a threshold level. "They don’t appear to accumulate toxicity to BL-22 either, even after many cycles of treatment, and because hairy cells stay positive for CD-22, we can keep treating them over again until they achieve complete remission," he said. Dr. Ruth Mushel, a professor of pathology at the University of Pennsylvania Medical School and head of the AACR section on micrometastasis said development of new therapies based on the biological properties of a cancer cell is a coming trend in molecular engineering. "What we have seen is that in the very early stages of a clinical trial there seems to be considerable effectiveness in the use of this therapy against hairy cell leukemia. This will be very important for those patients who have failed chemotherapy and it holds out the potential that other lymphomas may be targeted by the same approach," she said. BL-22 has been licensed to Albapharm of Rockwell Maryland, which will attempt to bring the drug into commercial production.
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