The BCR-ABL tyrosine kinase inhibitor Imatinib is highly effective for chronic myeloid leukemia (CML). However, some patients gradually develop resistance to Imatinib, resulting in therapeutic failure. In the present study, we analyzed 192 CML patients, from which CML relapse was observed in 17 individuals with involvement of other chromosomes in addition to Philadelphia translocation and who were on treatment of Imatinib (400mg per day since last 3-4 years). Interestingly, all 17 individuals had only BCR/ABL fusion at the time of diagnosis and attained complete Cytogenetic and hematological remission (CHR) within 18 weeks of the therapy. Three individuals among these 17 were not regular in the uptake of Imatinib after attaining CHR and CCyR and could be probable reason for relapse. In addition, we have also recorded primary resistance to Imatinib in 4 individuals who were diagnosed with some complex chromosomal variants. Therefore, either involvement of other genes along with BCR/ABL fusion, or additional chromosomes and point mutation in the fusion BCR/ABL gene itself could be a reason for primary resistance and relapse to Imatinib
