A novel compound called STI571, has been shown to produce responses in patients with a certain type of acute lymphoid leukemia (ALL) who are no longer responding to chemotherapy. STI571 is still undergoing clinical testing to further define its role as treatment for patients with this disease, but is emerging as a promising potential treatment strategy. (Proceedings from the American Society of Hematology, 42nd annual meeting, 2000).
Acute lymphocytic leukemia (ALL), also called acute lymphoblastic leukemia, is a cancer of the bone marrow and lymph system. The bone marrow produces early blood-forming cells, called stem cells, which grow and mature into the three blood cell types: white blood cells, which fight infection; red blood cells, which carry oxygen to the tissues; and platelets, which help the blood to clot. ALL is characterized by uncontrolled production of immature lymphocytes, or white blood cells. These immature lymphocytes never mature enough to perform their specific function of fighting infection. In addition, these rapidly dividing cells crowd out and suppress the formation of other important blood cells such as the red blood cells, platelets and other white blood cells.
Approximately 20% of ALL cases are caused by a specific genetic abnormality, referred to as the Philadelphia chromosome. The Philadelphia chromosome occurs through a switching of specific genetic information. The result of this genetic switching produces a protein called the Bcr-Abl tyrosine kinase. The Bcr-Abl tyrosine kinase protein facilitates cellular function and growth by modulating certain chemical information flow into and out of cells, and initiating growth responses to chemical stimuli. The pivotal problem with Bcr-Abl tyrosine kinase is that it performs its functions in an uncontrolled manner, leading to excessive replication and growth of cells – the hallmark trait of cancer. Patients who are Philadelphia chromosome positive typically do not respond well to standard therapies. Therefore, researchers continue to develop and explore new treatment strategies in an attempt to improve upon present treatment outcomes.
STI571 is a new type of therapy that has shown promise in producing anti-cancer responses in Philadelphia chromosome positive ALL patients who no longer respond to standard therapies. STI571 produces its effects by binding to a specific site on the Bcr-Abl tyrosine kinase. The binding of STI571 blocks the growth effects facilitated by Bcr-Abl. This, in turn, haults the excessive replication and growth of cancer cells.
Researchers from several medical centers in the United States and Europe recently conducted a clinical trial to evaluate STI571 for treatment of approximately 50 patients with Philadelphia chromosome positive ALL. All of these patients had stopped responding to chemotherapy. STI571 was orally administered as a single agent on an outpatient basis. One month following treatment, almost 60% of patients showed an anti-cancer response to STI571. Side effects from treatment were generally mild. This study is currently ongoing and additional follow up will be necessary to ascertain the true benefit of STI571.
The responses achieved by these patients are promising as they indicate the potential benefit of STI571 in the treatment of Philadelphia chromosome positive ALL that no longer responds to available therapies. Patients with this disease may wish to speak with their doctors about the risks and benefits of participating in a clinical trial further evaluating STI571 or other promising new treatment approaches. Two sources of ongoing information regarding clinical trials that can be discussed with a doctor include comprehensive, easy-to-use listing services provided by the National Cancer Institute (cancer.gov) and eCancerTrials.com. eCancerTrials.com also provides personalized clinical trial searches on behalf of patients. (Proceedings of the American Society of Hematology, 42nd Annual Meeting, Vol 96, No 11, Abstract 3580, pp 828a, 2000)
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