To validate ENU mutagenesis screening methodology at first, we explored crizotinib or alectinib-resistant ALK mutants using Ba/F3 cells expressing EML4-ALK-wild-type clonal cells#13. As the results, C1156Y, I1171T, F1174C/I/V, L1196M, and I1268L mutations in ALK were identified as crizotinib-resistant mutants.