INTRODUCTION Osimertinib is an effective third-generation tyrosine kinase inhibitor (TKI) for EGFR-mutant lung cancers. However, treatment for patients with acquired resistance to osimertinib remains challenging. We characterized a novel EGFR mutation in exon 20 that was acquired while on osimertinib. METHODS A 79-year-old woman had disease progression during third-line treatment with osimertinib for an EGFR L858R/T790M-mutant lung cancer. Sequencing of circulating cell-free DNA showed EGFR L858R, an acquired novel EGFR M766Q mutation in exon 20, and no evidence of EGFR T790M. Homology modeling was done to investigate the effects of M776Q on binding to osimertinib. L858R and L858R/M766Q mutations were retrovirally introduced into Ba/F3 and NIH/3T3 cells and evaluated for sensitivity to first-generation (erlotinib), second-generation (afatinib, neratinib, and poziotinib), and third-generation TKIs (osimertinib) by MTS and colony formation assays. EGFR-mediated signaling pathways were interrogated by western blotting. RESULTS Modeling suggested that EGFR M766Q could disrupt osimertinib binding. L858R/M766Q double-mutant cells were 12-fold more resistant to osimertinib, and more than 250-fold more resistant to erlotinib and afatinib, as compared to L858R-mutant cells. In contrast, double-mutant cells remained sensitive to neratinib and poziotinib at clinically relevant doses (IC50, 4.3 and 1.3 nM, respectively). This was corroborated by the effect of the TKIs on colony formation and EGFR signaling. CONCLUSIONS Acquisition of EGFR M766Q exon 20 mutation is a novel mechanism of acquired resistance to osimertinib. EGFR-mutant lung cancers with an acquired EGFR M766Q mutation in the setting of osimertinib-resistance may be sensitive to neratinib and poziotinib. ==========.

中文翻译：

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肺腺癌中一种新的获得性外显子 20 EGFR M766Q 突变介导 Osimertinib 耐药但对 Neratinib 和 Poziotinib 敏感：简要报告

简介 Osimertinib 是一种有效的第三代酪氨酸激酶抑制剂 (TKI)，用于治疗 EGFR 突变的肺癌。然而，对奥希替尼获得性耐药的患者的治疗仍然具有挑战性。我们表征了在使用奥希替尼时获得的外显子 20 中的新 EGFR 突变。方法 一名 79 岁女性在使用奥希替尼治疗 EGFR L858R/T790M 突变肺癌的三线治疗期间出现疾病进展。循环无细胞 DNA 的测序显示 EGFR L858R，一种在外显子 20 中获得的新型 EGFR M766Q 突变，并且没有 EGFR T790M 的证据。进行同源建模以研究 M776Q 对与奥希替尼结合的影响。L858R 和 L858R/M766Q 突变被逆转录病毒引入 Ba/F3 和 NIH/3T3 细胞，并评估对第一代（厄洛替尼）、第二代（阿法替尼、neratinib 和 poziotinib)，以及 MTS 和集落形成试验的第三代 TKI（奥希替尼）。通过蛋白质印迹研究EGFR介导的信号通路。结果 建模表明 EGFR M766Q 可能会破坏奥希替尼的结合。与 L858R 突变细胞相比，L858R/M766Q 双突变细胞对奥希替尼的耐药性高 12 倍，对厄洛替尼和阿法替尼的耐药性高 250 倍以上。相比之下，双突变细胞在临床相关剂量（IC50 分别为 4.3 和 1.3 nM）下仍然对来那替尼和波齐替尼敏感。TKI 对集落形成和 EGFR 信号传导的影响证实了这一点。结论 获得 EGFR M766Q 外显子 20 突变是奥希替尼获得性耐药的新机制。在奥希替尼耐药的情况下具有获得性 EGFR M766Q 突变的 EGFR 突变肺癌可能对来那替尼和波齐替尼敏感。==========。