The tyrosine kinase Src and its close homolog Abl, both play important roles in chronic myelogenous leukemia (CML) progression and Imatinib resistance. No clinically approved inhibitors of the drug-resistant AblT315I exist to date. Here, we present a thorough kinetic analysis of two potent dual Src-Abl inhibitors towards wild type Src and Abl, and the AblT315I mutant. Our results show that the most potent compound BO1 shows only a modest loss of potency (fourfold) towards the AblT315I mutant in vitro and was an ATP-competitive inhibitor of wild type Abl but it acted as a non-competitive inhibitor in the case of AblT315I.