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The anaplastic lymphoma kinase (ALK) fusion oncogene is observed in 3%–5% of non-small cell lung cancer (NSCLC). Crizotinib and ceritinib, a next-generation ALK tyrosine kinase inhibitor (TKI) active against crizotinib-refractory patients, are clinically available for the treatment of ALK-rearranged NSCLC patients, and multiple next-generation ALK-TKIs are currently under clinical evaluation. These ALK-TKIs exhibit robust clinical activity in ALK-rearranged NSCLC patients; however, the emergence of ALK-TKI resistance restricts the therapeutic effect. To date, various secondary mutations or bypass pathway activation-mediated resistance have been identified, but large parts of the resistance mechanism are yet to be identified. Here, we report the discovery of p-glycoprotein (P-gp/ABCB1) overexpression as a ceritinib resistance mechanism in ALK-rearranged NSCLC patients. P-gp exported ceritinib and its overexpression conferred ceritinib and crizotinib resistance, but not to PF-06463922 or alectinib, which are next-generation ALK inhibitors. Knockdown of ABCB1 or P-gp inhibitors sensitizes the patient-derived cancer cells to ceritinib, in vitro and in vivo. P-gp overexpression was identified in three out of 11 cases with in ALK-rearranged crizotinib or ceritinib resistant NSCLC patients. Our study suggests that alectinib, PF-06463922, or P-gp inhibitor with ceritinib could overcome the ceritinib or crizotinib resistance mediated by P-gp overexpression.

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The treatment for anaplastic lymphoma kinase (ALK)‐positive lung cancer has been rapidly evolving since the introduction of several ALK tyrosine kinase inhibitors (ALK‐TKI) in clinical practice. However, the acquired resistance to these drugs has become an important issue. In this study, we collected a total of 112 serial biopsy samples from 32 patients with ALK‐positive lung cancer during multiple ALK‐TKI treatments to reveal the resistance mechanisms to ALK‐TKI. Among 32 patients, 24 patients received more than two ALK‐TKI. Secondary mutations were observed in 8 of 12 specimens after crizotinib failure (G1202R, G1269A, I1171T, L1196M, C1156Y and F1245V). After alectinib failure, G1202R and I1171N mutations were detected in 7 of 15 specimens. G1202R, F1174V and G1202R, and P‐gp overexpression were observed in 3 of 7 samples after ceritinib treatment. L1196M + G1202R, a compound mutation, was detected in 1 specimen after lorlatinib treatment. ALK‐TKI treatment duration was longer in the on‐target treatment group than that in the off‐target group (13.0 vs 1.2 months). In conclusion, resistance to ALK‐TKI based on secondary mutation in this study was similar to that in previous reports, except for crizotinib resistance. Understanding the appropriate treatment matching resistance mechanisms contributes to the efficacy of multiple ALK‐TKI treatment strategies.

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