自然杂志AZD9291耐药机理最新发现-2015年五月

http://www.nature.com/nm/journal/vaop/ncurrent/full/nm.3854.html
Nature Medicine 2015年5月3日发表的，翻译不好的地方包涵下

获得性EGFR C797S突变介导了AZDD9291在EGFRT790非小细胞肺癌的耐药

通过对EGFR TKI AZD9291耐药的肺癌的无细胞血清DNA (cfDNA)的研究，
利用next generation sequencing (一种基因测序技术)，发现在7个病人中有一个有EGFR C797S突变
把这种突变加入肺癌细胞系中，能导致肺癌细胞对AZD9291产生耐药。

然后我们进行了droplet digital PCR(另一种基因检测技术)，
对15个经过AZD9291治疗的病人的无细胞血清DNA (cfDNA)进行了检测，
发现他们在治疗之前全都有T790M突变，但是接受AZD9291治疗并耐药后，
6个病人产生了EGFR C797S突变， 5个病人保持了T790M突变但是没有C797S突变，
4个病人失去了T790M突变，但是依然有EGFR通路的激活。

讨论部分说， 研究提示了开发AZD与其他药物联合使用的重要性。
现在联合使用的临床实验有
AZD+PD-L1抗体(MEDI4736， 又比如Opdivo or Keytruda),
AZD+ MET inhibitor （AZD6094） or
AZD+MEK inhibitor （elumetinib）.
详情参照 https://clinicaltrials.gov/ct2/show/NCT02143466


Acquired EGFR C797S mutation mediates resistance to AZD9291 in non–small cell lung cancer harboring EGFR T790M

摘要：
Here we studied cell-free plasma DNA (cfDNA) collected from subjects with advanced lung cancer whose tumors had developed resistance to the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) AZD9291. We first performed next-generation sequencing of cfDNA from seven subjects and detected an acquired EGFR C797S mutation in one; expression of this mutant EGFR construct in a cell line rendered it resistant to AZD9291. We then performed droplet digital PCR on serial cfDNA specimens collected from
15 AZD9291-treated subjects. All were positive for the T790M mutation before treatment, but upon developing AZD9291 resistance three molecular subtypes emerged: six cases acquired the C797S mutation, five cases maintained the T790M mutation but did not acquire the C797S mutation
and four cases lost the T790M mutation despite the presence of the underlying EGFR activating mutation. Our findings provide insight into the diversity of mechanisms through
which tumors acquire resistance to AZD9291 and highlight the need for therapies that are able to overcome resistance mediated by the EGFR C797S mutation.


讨论部分：

This genomic analysis of serial cfDNA specimens from an ongoing first-in-human study of AZD9291 identified three molecular
subtypes of acquired resistance, including one defined by an EGFR C797S mutation not previously detected in patient samples.
This acquired EGFR C797S mutation is anticipated to induce resistance to all covalent EGFR TKIs, highlighting the need for
novel strategies to inhibit EGFR signaling even in the presence of this mutation. The EGFR C797S mutation mechanistically parallels the acquired Bruton tyrosine kinase (BTK) C481S mutation which can be detected in patients with chronic lymphocytic leukemia with acquired resistance to the irreversible BTK inhibitor ibrutinib14, suggesting that these cysteine point mutations that block drug binding may be a recurring vulnerability for a broad range of covalent kinase inhibitors. Although a more comprehensive
analysis of plasma and biopsy tissue collected after resistance
develops will be needed to provide greater clarity on C797S mutation incidence, the emergence of this mutation in a marked proportion
of AZD9291-resistant patients suggests that development of targeted
therapies with the ability to overcome the C797S mutation is
warranted. The C797S mutation was only identified in cases harboring an exon 19 deletion (six of nine) and not in cases harboring L858R mutations (zero of six); because our cell line data suggests that the C797S mutation induces resistance with either activating
mutation (Fig. 1b), we suspect this finding is due to the small sample size studied, although a disposition toward developing the C797S mutation in cancers with an exon 19 deletion will need to be considered going forward.

Our finding that some cancers treated with AZD9291 convert from T790M+ to T790M−, and our identification of cases harboring two concurrent acquired C797S mutations, suggests an underappreciated genomic heterogeneity associated with resistance to EGFR TKIs in NSCLC. Such heterogeneity requires further study, but it may indicate a need for combination therapies that can inhibit or prevent the emergence of multiple resistance mechanisms simultaneously. The emerging toxicity profile of AZD9291 makes it potentially suitable for such rational combinations, some of which are currently under investigation in a multi-arm phase I study (NCT02143466) combining AZD9291 with either an PD-L1–specific antibody, a MET inhibitor or a MEK inhibitor.

2014 AACR上另一个临床前突变机理的研究，说是ERB突变，
用阿法替尼afatinib (irreversible ErbB family blocker) + cetuximab (anti-EGFR monoclonal antibody)
http://cancerdiscovery.aacrjournals.org/content/4/9/1036.short

Dual Inhibition of EGFR with Afatinib and Cetuximab in Kinase Inhibitor–Resistant EGFR-Mutant Lung Cancer with

Abstract

EGFR-mutant lung cancers responsive to reversible EGFR inhibitors (gefitinib/erlotinib) develop acquired resistance, mediated by second-site EGFR T790M mutation in >50% of cases. Preclinically, afatinib (irreversible ErbB family blocker) plus cetuximab (anti-EGFR monoclonal antibody) overcomes T790M-mediated resistance. This phase Ib study combining afatinib and cetuximab enrolled heavily pretreated patients with advanced EGFR-mutant lung cancer and acquired resistance to erlotinib/gefitinib. Patients provided post–acquired-resistance tumor samples for profiling EGFR mutations. Among 126 patients, objective response rate (overall 29%) was comparable in T790M-positive and T790M-negative tumors (32% vs. 25%; P = 0.341). Median progression-free survival was 4.7 months (95% confidence interval, 4.3–6.4), and the median duration of confirmed objective response was 5.7 months (range, 1.8–24.4). Therapy-related grade 3/4 adverse events occurred in 44%/2% of patients. Afatinib–cetuximab demonstrated robust clinical activity and a manageable safety profile in EGFR-mutant lung cancers with acquired resistance to gefitinib or erlotinib, both with and without T790M mutations, warranting further investigation.

Significance: This article reports the results of a trial combining afatinib and cetuximab in patients with acquired resistance and details the first clinical proof-of-concept for the preclinical hypothesis that a significant proportion of tumors in patients with acquired resistance to gefitinib/erlotinib remain dependent on EGFR signaling for survival. Cancer Discov; 4(9); 1036–45. ©2014 AACR.

还有的说是MEK和EGFR抑制剂联合用药

http://cancerres.aacrjournals.or ... pplement/1832.short

Combined EGFR and MEK inhibition prevents the emergence of drug resistance in EGFR mutant non-small cell lung cancer (NSCLC)

Background: EGFR inhibitors are effective clinical therapies for EGFR mutant NSCLC, but efficacy is limited by the development of acquired drug resistance. The mechanisms of resistance include secondary mutations in EGFR (T790M) and activation of compensatory signaling pathways (MET, IGFR and AXL). Mutant selective EGFR inhibitors (WZ4002, CO-1686 and AZD9291) are effective in preclinical and clinical models of EGFR T790M. Our lab has demonstrated that reactivation of ERK signaling is a mechanism of resistance to WZ4002 (WZ) which could be reversed or prevented by using a combination of WZ and MEK inhibitors. Given the broad array of possible EGFR inhibitor resistance mechanisms, we evaluated whether WZ combined with the MEK inhibitor trametinib (TRA) can prevent the emergence of resistance in vitro and in vivo.

Methods and Results: We developed a plate based resistance assay in which 350 cells/well are plated in 96 well plates and treated weekly. This system allows for evaluation of drug efficacy over weeks of treatment and can be used to measure both time to development and frequency of drug resistance. Given that ERK reactivation can cause resistance to WZ, we evaluated WZ, TRA or the combination thereof (WZ/TRA) using PC9 cells. Single agents led to 100% resistance in 2-3 weeks, versus 5% with WZ/TRA in 24 weeks. We then tested WZ/TRA in 5 additional EGFR TKI sensitive cell lines, including several known to develop acquired resistance to gefitinib (HCC827, MET amplification; HCC4006, EMT or FGFR activation; HCC2279; FGFR activation; H3255, T790M; HCC2935). In all cases, WZ/TRA significantly reduced the emergence of drug resistant clones compared to each single agent. In models with established drug resistance mechanisms, WZ/TRA was effective in 3/3 models with T790M mutations, but not (0/5) in models with established non-T790M resistance mechanisms. In models where WZ/TRA was effective, the combination led to increased apoptosis compared to single agents and effective inhibition of ERK signaling. We also evaluated the effectiveness of the WZ/TRA combination in vivo using EGFR L858R/T790M genetically engineered mouse model and PC9GR4 (T790M+) xenografts. Combination WZ/TRA treatment prevented tumor outgrowth for 24 weeks in 5 EGFR L858R/T790M GEMM mice whereas individual treatments did not. Additionally, we found that WZ/TRA combination treatment, but not single agents, could cure 7/15 xenograft tumors as assessed by lack of tumor regrowth after treatment cessation.

Conclusion: Our studies suggest that the combination of a mutant selective EGFR inhibitor and a MEK inhibitor can prevent the emergence of both T790M and non-T790M mediated drug resistance mechanisms. This strategy is more effective at preventing (6/6) than treating (3/8) cancers with established drug resistance mechanisms and should be evaluated in clinical trials in EGFR TKI naïve EGFR mutant NSCLC patients.

9291耐药后，怎么用药，现在是关键。。。。我们要找到出路。

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感谢分享，期待打开一扇门！~

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哎，对啊 什么时候是个头