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Epidermal growth factor receptor (EGFR) mutations typically occur in exons 18-21 and are established driver mutations in non-small cell lung cancer (NSCLC) 1-3 . Targeted therapies are approved for patients with 'classical' mutations and a small number of other mutations 4-6 . However, effective therapies have not been identified for additional EGFR mutations. Furthermore, the frequency and effects of atypical EGFR mutations on drug sensitivity are unknown 1,3,7-10 . Here we characterize the mutational landscape in 16,715 patients with EGFR-mutant NSCLC, and establish the structure-function relationship of EGFR mutations on drug sensitivity. We found that EGFR mutations can be separated into four distinct subgroups on the basis of sensitivity and structural changes that retrospectively predict patient outcomes following treatment with EGFR inhibitors better than traditional exon-based groups. Together, these data delineate a structure-based approach for defining functional groups of EGFR mutations that can effectively guide treatment and clinical trial choices for patients with EGFR-mutant NSCLC and suggest that a structure-function-based approach may improve the prediction of drug sensitivity to targeted therapies in oncogenes with diverse mutations., (© 2021. The Author(s).)

Purpose: Osimertinib was initially approved for T790M-positive non-small cell lung cancer (NSCLC) and, more recently, for first-line treatment of EGFR -mutant NSCLC. However, resistance mechanisms to osimertinib have been incompletely described., Experimental Design: Using cohorts from The University of Texas MD Anderson Lung Cancer Moonshot GEMINI and Moffitt Cancer Center lung cancer databases, we collected clinical data for patients treated with osimertinib. Molecular profiling analysis was performed at the time of progression in a subset of the patients., Results: In the 118 patients treated with osimertinib, 42 had molecular profiling at progression. T790M was preserved in 21 (50%) patients and lost in 21 (50%). EGFR C797 and L792 (26%) mutations were the most common resistance mechanism and were observed exclusively in T790M-preserved cases. MET amplification was the second most common alteration (14%). Recurrent alterations were observed in 22 genes/pathways, including PIK3CA, FGFR, and RET. Preclinical studies confirmed MET, PIK3CA, and epithelial-to-mesenchymal transition as potential resistance drivers. Alterations of cell-cycle genes were associated with shorter median progression-free survival (PFS, 4.4 vs. 8.8 months, P = 0.01). In 76 patients with progression, osimertinib was continued in 47 cases with a median second PFS (PFS2) of 12.6 months; 21 patients received local consolidation radiation with a median PFS of 15.5 months. Continuation of osimertinib beyond progression was associated with a longer overall survival compared with discontinuation (11.2 vs. 6.1 months, P = 0.02)., Conclusions: Osimertinib resistance is associated with diverse, predominantly EGFR-independent genomic alterations. Continuation of osimertinib after progression, alone or in conjunction with radiotherapy, may provide prolonged clinical benefit in selected patients. See related commentary by Devarakonda and Govindan, p. 6112 ., (©2018 American Association for Cancer Research.)

After sequential treatment with first- and third-generation EGFR tyrosine kinase inhibitors (TKIs), EGFR-mutant non-small cell lung cancers frequently harbor multiple resistance mutations in exon 20 of EGFR including T790M, mediating resistance to first-generation TKIs, and at codons 792, 796, or 797 mediating resistance to third-generation TKIs. However, whether these resistance mutations are in cis or trans has therapeutic implications for patients. We analyzed a cohort of 29 patients with NSCLC harboring EGFR mutations at codons 792, 796, or 797 to establish the configuration of these mutations. We performed hybrid capture-based, next-generation sequencing on formalin-fixed paraffin-embedded biopsy tissue or liquid biopsy. 27 samples had both a T790M mutation and a mutation at codons 792, 796, or 797. In all of these cases, the mutations were found in the cis configuration; the trans configuration was not observed. Two patients' samples harbored a mutation at codon 797 but no T790M mutation. In these two cases, longitudinal analysis showed earlier biopsies harbored EGFR T790M, which was undetectable following osimertinib treatment. Treatment of one these patients with both first- and third-generation EGFR TKIs resulted in a mixed response. Here we describe multiple configurations of EGFR T790M and third-generation TKI resistance mutations at codons 792, 796, and 797. These mutations are most commonly found in cis, which confers resistance to all current EGFR TKIs. We also describe two patients that exhibited T790M loss with acquisition of a mutation at codon 797. In addition, one of these patients, with an EGFR C797S in a lung biopsy was subsequently found to have EGFR C797N in a later biopsy of pleural fluid, highlighting the dynamic multiclonal nature of advanced NSCLC., Competing Interests: We have read the journal's policy and the authors of this manuscript have the following competing interests: All authors affiliated with Foundation Medicine were employees and owned FMI stock (MEG, MM, LY, JS, JG, MK, VAM, PJS, GMF, SA, LAA). JPG is an External Speaker and consultant for Foundation Medicine Inc. This affiliation does not alter our adherence to PLOS ONE policies on sharing data and materials. All other authors have no other financial conflicts to disclose.

Introduction: Moffitt Cancer Center's Personalized Medicine Clinical Service (PMCS) reviews somatic next-generation sequencing (NGS) assay results, provides interpretations, and identifies potential therapeutic options. The number of individuals reviewed by our clinical service who are eligible for on-label or off-label drug therapy based on genetic test results has previously not been quantitated. We determined the number of patients harboring an actionable mutation that would qualify a patient for an on-label drug or consideration for off-label drug treatment., Methods: The Food and Drug Administration (FDA) Table of Pharmacogenomic Biomarkers in Drug Labeling was utilized to identify anticancer agents containing genomic markers in the Indications and Usage section of the drug label. A database containing discrete NGS patient data was queried retrospectively for those drugs and associated genomic mutations included in this study. On-label was defined as those patients who were eligible for a drug based on harboring a targetable mutation in the FDA-approved cancer type. Off-label was defined as those patients who may be considered for a drug based on harboring a targetable mutation in a non-FDA-approved cancer type., Results: A total of 1072 patients and 1131 NGS results were eligible for study inclusion. Fifty-two patients (4.9%) had results for more than one NGS assay. Seventeen drugs targeting ALK, BRAF, BRCA1/BRCA2, EGFR, or ERBB2 mutations met the study inclusion criteria. Of the entire patient population, 92 (8.6%) unique patients were eligible for at least one on-label drug; off-label use of at least one drug could be considered in 103 (9.6%) unique patients., Conclusion: Combining both on-label and off-label opportunities, 175 (16.3%) unique patients had actionable mutations in six genes. Because most patients reviewed by our PMCS have previously treated advanced disease with limited treatment options, identifying additional lines of therapy is of clinical utility., (© 2017 Pharmacotherapy Publications, Inc.)

The nucleoside analog ganciclovir (GCV) elicits cytotoxicity in tumor cells via a novel mechanism in which drug incorporation into DNA produces minimal disruption of replication, but numerous DNA double strand breaks occur during the second S-phase after drug exposure. We propose that homologous recombination (HR), a major repair pathway for DNA double strand breaks, can prevent GCV-induced DNA damage, and that inhibition of HR will enhance cytotoxicity with GCV. Survival after GCV treatment in cells expressing a herpes simplex virus thymidine kinase was strongly dependent on HR (>14-fold decrease in IC50 in HR-deficient vs. HR-proficient CHO cells). In a homologous recombination reporter assay, the histone deacetylase inhibitor, suberoylanilide hydroxamic acid (SAHA; vorinostat), decreased HR repair events up to 85%. SAHA plus GCV produced synergistic cytotoxicity in U251tk human glioblastoma cells. Elucidation of the synergistic mechanism demonstrated that SAHA produced a concentration-dependent decrease in the HR proteins Rad51 and CtIP. GCV alone produced numerous Rad51 foci, demonstrating activation of HR. However, the addition of SAHA blocked GCV-induced Rad51 foci formation completely and increased γH2AX, a marker of DNA double strand breaks. SAHA plus GCV also produced synergistic cytotoxicity in HR-proficient CHO cells, but the combination was antagonistic or additive in HR-deficient CHO cells. Collectively, these data demonstrate that HR promotes survival with GCV and compromise of HR by SAHA results in synergistic cytotoxicity, revealing a new mechanism for enhancing anticancer activity with GCV., (Copyright © 2013 Elsevier B.V. All rights reserved.)