Q: Given a context passage, generate a question from the passage such that its answer is shortest continous span from the passage.
Imatinib mesylate, a selective Bcr-Abl tyrosine kinase inhibitor, has revolutionized the treatment of Bcr-Abl positive chronic myeloid leukemia and become the standard of care for this disease. The aim of this study was evaluation and analysis of cytogenetic response in different intervals and risk groups as well as finding association between pre-treatment characteristics and later probability of achievement of major cytogenetic response. We analyzed a total of 22 adult patients with newly diagnosed Philadelphia positive early chronic phase chronic myeloid leukemia treated at our institution from June 2006 to December 2009. The median follow-up time for patients during treatment with imatinib was 25.7 months (range, 12-42 months). A complete hematologic response was achieved in all of the analyzed patients within 6 months from the start of the treatment. The major cytogenetic response rate was 81.8%, and the complete cytogenetic response rate was 72.7%. The patients with low or moderate relative risk had the rate of complementary achieving major and complete cytogenetic response of 75-90%. A multivariate analysis identified the following independent prognostic factors for achieving major cytogenetic response: the absence of splenomegaly, white blood cell count less than 10 x 10(9)/L, the platelet count less than 450 x 10(9)/L, the presence of less than 5% of bone marrow blasts and basophils, the absence of blasts in peripheral blood, the presence of less than 7% of basophils in peripheral blood. Patients who early achieve complete and major cytogenetic response as well as those with low and moderate relative risk have a higher rate of achieving and maintaining complete cytogenetic response. There are also characteristics of patients before treatment that may indicate the treatment outcome.
A:
What tyrosine kinase, involved in a Philadelphia- chromosome positive chronic myelogenous leukemia, is the target of Imatinib (Gleevec)?