ABL1 and acute lymphoblastic leukemia: According to the recommendation of NCCN Guidelines of Acute Lymphoblastic Leukemia (Version 2, 2019), bosutinib is considered a good option for relapsed or refractory Ph+ ALL with E255 V/K, F317L/V/I/C, F359 V/C/I, T351A, or Y253H mutations,[4] which matched the ABL mutation profile at the third relapse in our patient well.