Chronic myeloid leukemia (CML) is a myeloproliferative disease characterized by the presence of BCR/ABL fusion gene in leukemic cells, which promotes uncontrolled cell proliferation. Up to 20% of CML patients show primary resistance or non-optimal response to tyrosine kinase inhibitor (TKI) therapy. We investigated the association between copy number variation (CNV) in glutathione S-transferases (GST) and cytochromes (CYP) and the response rate to TKI. We enrolled 47 patients with CML: 31 with an optimal response and 16 with failure at 6 months in accordance with European LeukemiaNet 2013 recommendations. CNV detection was performed using SALSA MLPA P128-C1 Cytochrome P450 probe mix. Patients with optimal response and with failure of TKI therapy showed different frequencies of wild type and mutated CYPs and GST (p<0.0013). Validation in the group of 15 patients proved high prognostic value (p = 0.02): positive and negative predictive value 83% and 78%; sensitivity and specificity 71% and 88%. Wild type genotypes of CYP and GST associate with a worse response to TKI treatment in CML patients. This test can be recommended for further clinical trials.

Chronic myeloid leukemia (CML) is characterized by the presence of the chimeric tyrosine kinase BCR-ABL in all leukemic cells. This non-specific enzyme promotes uncontrolled cell proliferation and genome instability. Tyrosine kinase inhibitors (TKI) help most of the people to achieve long standing remission, however up to 20% of patients develop slow response or even primary resistance to the therapy. In this work we focused on copy number variation (CNV) in glutathione transferases (GSTs) and cytochromes (CYPs) as possible predictors of the response rate to TKI. Thirty one CML patient with optimal response and 16 with therapy failure were enrolled in the study. Patient were grouped according to ELN2013 recommendations: BCR-ABL<1% and/or Ph+ 0% for optimal response and BCR-ABL>10% and/or Ph+ >35% at 6 months of TKI therapy for the failures. We found that these two groups of patients had differed frequencies of wild type and mutated genes: CYP1A2, CYP2A6, CYP2C19, CYP2C9, CYP2D6, CYP2E1, CYP3A4, CYP3A5, GSTM1, GSTP1, GSTT1 (p< 0.0013). Validation in the additional group of 15 CML patients showed that the test allows to predict failures and responders (p=0.02) with high accuracy: positive and negative predictive value 83% and 78%; sensitivity and specificity 71% and 88%. Disclosures Chelysheva: Novartis: Consultancy, Speakers Bureau; Bristol-Myers Squibb: Speakers Bureau. Shukhov:BMS: Honoraria; Novartis Pharma: Honoraria. Turkina:BMS: Honoraria; Novartis Pharma: Honoraria; Pfizer: Honoraria. Kutsev:Novartis: Speakers Bureau; Pfizer: Speakers Bureau.