BACKGROUND: Chronic myelogenous leukemia (CML) is caused by the BCR-ABL tyrosine 
kinase, the product of the Philadelphia chromosome. Imatinib mesylate, formerly 
STI571, is a selective inhibitor of this kinase.
METHODS: A total of 532 patients with late--chronic-phase CML in whom previous 
therapy with interferon alfa had failed were treated with 400 mg of oral 
imatinib daily. Patients were evaluated for cytogenetic and hematologic 
responses. Time to progression, survival, and toxic effects were also evaluated.
RESULTS: Imatinib induced major cytogenetic responses in 60 percent of the 454 
patients with confirmed chronic-phase CML and complete hematologic responses in 
95 percent. After a median follow-up of 18 months, CML had not progressed to the 
accelerated or blast phases in an estimated 89 percent of patients, and 95 
percent of the patients were alive. Grade 3 or 4 nonhematologic toxic effects 
were infrequent, and hematologic toxic effects were manageable. Only 2 percent 
of patients discontinued treatment because of drug-related adverse events, and 
no treatment-related deaths occurred.
CONCLUSIONS: Imatinib induced high rates of cytogenetic and hematologic 
responses in patients with chronic-phase CML in whom previous interferon therapy 
had failed.