摘要In addition to the classical resistance mechanisms,receptor tyrosine-protein kinase AXL is a main mechanism of resistance to third-generation epidermal growth factor receptor-tyrosine kinase inhibitor(EGFR-TKI)osimertinib in EGFR-mutated non-small cell lung cancer(NSCLC).Developing an effective AXL inhibitor is important to sensitize osimertinib in clinical application.In this study we assessed the efficacy of brigatinib,a second-generation of anaplastic lymphoma kinase(ALK)-TKI,as a novel AXL inhibitor,in overcoming acquired resistance to osimertinib induced by AXL activation.We established an AXL-overexpression NSCLC cell line and conducted high-throughput screening of a small molecule chemical library containing 510 anti-tumor drugs.We found that brigatinib potently inhibited AXL expression,and that brigatinib(0.5 μM)significantly enhanced the anti-tumor efficacy of osimertinib(1 μM)in AXL-mediated osimertinib-resistant NSCLC cell lines in vitro.We demonstrated that brigatinib had a potential ability to bind AXL kinase protein and further inhibit its downstream pathways in NSCLC cell lines.Furthermore,we revealed that brigatinib might decrease AXL expression through increasing K48-linked ubiquitination of AXL and promoting AXL degradation in HCC827OR cells and PC-9OR cells.In AXL-high expression osimertinib-resistant PC-9OR and HCC827OR cells derived xenograft mouse models,administration of osimertinib(10 mg·kg-1·d-1)alone for 3 weeks had no effect,and administration of brigatinib(25 mg·kg-1·d-1)alone caused a minor inhibition on the tumor growth;whereas combination of osimertinib and brigatinib caused marked tumor shrinkages.We concluded that brigatinib may be a promising clinical strategy for enhancing osimertinib efficacy in AXL-mediated osimertinib-resistant NSCLC patients.