Currently, the only cure for chronic myeloid leukemia is an allogeneic bone marrow or blood stem cell transplant. In older patients and patients who do not have suitable stem cell donors, the preferred treatment is alfa interferon with or without chemotherapy. Chemotherapy can be used in patients who do not tolerate interferon. These treatments can control symptoms and prolong survival but are not curative.
Chronic myeloid leukemia is caused by an acquired deficit in an individual’s genes. A portion of chromosome 9 is transferred to chromosome 11. The causative molecular abnormality is also called Bcr-Abl. An enzyme called tyrosine kinase is responsible for the ability of this molecular abnormality to cause transformation of normal cells into chronic myeloid leukemia cells. Recently, investigators at the University of Oregon have tested a drug (STI 571) that inhibits tyrosine kinase interfering with the transformation. The doctors reported their initial experience with STI 571 at the American Society of Hematology Annual Meeting in New Orleans.
STI 571 is an easily administered oral therapy that essentially has no toxicities. STI 571 was given to 54 patients with chronic myeloid leukemia who had failed alfa interferon treatment. All patients achieved a hematologic response to treatment with STI 571. Complete hematological responses were achieved in 96% of patients treated for at least 4 weeks. Cytogenetic responses were observed in the majority of patients. No significant side effects were observed with STI 571 treatment
Additionally, this is the first demonstration that a drug can be developed based on a specific molecular abnormality and may be model for treating other cancers. STI 571 is clearly the most active drug ever tested in patients with chronic myeloid leukemia. It apparently can be given for up to one year without toxicity. It is too early to know if transformation to acute leukemia is completely prevented with STI 571. Clinical trials are ongoing to determine the optimal way to use this exciting new treatment. The results of treatment with STI 571 are very encouraging and represents a potentially exciting new treatment for patients with chronic myeloid leukemia. (Blood, Vol 94, No 10, Suppl 1, Abstract 1639, pp 368a, 1999)
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