Of note, a novel ALK G1202del mutation was also identified in 8% of specimens. The authors conducted preclinical studies to determine the functional consequences of the various mutations identified in the clinical cases. Ectopic expression of the EML4–ALK G1202del mutant in Ba/F3 cells suggested that the G1202del ALK mutant confers moderate resistance to ceritinib, alectinib, and brigatinib with crizotinib potency being less affected. For 17 patients treated with alectinib (who had previously received crizotinib), 17 alectinib-resistant biopsies were analysed and ALK resistance mutations were detected in 9 (53%) specimens.