Tyrosine kinase inhibitors (TKIs) approved for the treatment of chronic myeloid leukemia. (a) The crystal structure of the ABL1 kinase domain is shown in complex with the indicated TKI. Highlighted residues indicate mutations that confer resistance to the indicated TKI in vitro. Orange (moderate) and red (severe) spheres indicate the level of TKI resistance. (b) The chemical structures of the TKIs. Adapted with permission from O’Hare et al. .