CYP3A4 is a critical enzyme in the cytochrome P450 family, responsible for metabolizing about 50% of all clinically used drugs, including several TKIs such as imatinib, erlotinib, and gefitinib, used to treat chronic myeloid leukemia (CML) and non-small cell lung cancer (NSCLC) [20]. This evidence concerns the gene CYP3A4 and chronic myelogenous leukemia, BCR-ABL1 positive.