Mutations were identified in 60 (60%) of these patients (all with imatinib-resistant CML-AP). Among the 60 patients with mutations, 26 unique imatinib-resistant mutations were identified, of which G250E was the most common (n = 9) (Table 5).

Conflicting evidence: Responses were seen across Bcr-Abl mutations, including those associated with dasatinib and nilotinib resistance, except T315I. Bosutinib had an acceptable safety profile; treatment-emergent adverse events were primarily manageable grade 1/2 gastrointestinal events and rash. Grade 3/4 nonhematologic adverse events (> 2% of patients) included diarrhea (8%) and rash (4%). Bosutinib may offer a new treatment option for patients with chronic-phase CML after treatment with multiple TKIs. Table 4.....

One of the 3 had a mutation (Met244Val) without evidence of acquired resistance and has achieved an MCR after receiving a dose increase from 400 to 600 mg imatinib....This finding is supported by the clinical response of a patient in our series with the Met244Val mutation who achieved a MCR with an increased dose to 600 mg of imatinib after failure to obtain a response to the initial dose of 400 mg.

Overall, these data indicate that the ENU-based assay faithfully reproduces the spectrum of mutations seen in patients with clinical resistance to imatinib mesylate...Spectrum and frequency of BCR-ABL kinase domain mutations recovered in the presence of imatinib mesylate, nilotinib, and dasatinib...Although both dasatinib and nilotinib are much more potent than imatinib mesylate and have activity against most kinase domain mutants, it is conceivable that their specific modes of binding to Abl may lead to new “vulnerable” sites that could confer drug resistance.