OA 09.01 Characterizing the Genomic Landscape of EGFR C797S in Lung Cancer Using ctDNA Next-Generation Sequencing

Combination of Osimertinib and Anlotinib May Overcome the Resistance Mediated by in cis EGFR T790M-C797S in NSCLC: A Case Report

The emergence of epidermal growth factor receptor (EGFR) exon 20 p.C797S is one of the major resistance mechanisms for osimertinib. However, there are no standard of care for non-small cell lung cancer (NSCLC) patients after acquiring EGFR C797S currently, which brings significant challenges to post-osimertinib clinical management. In the present study, we described a 52-year-old female patient with EGFR-mutated stage IV lung adenocarcinoma, who achieved a partial response (PR) to the treatment of gefitinib and osimertinib after acquiring EGFR exon 20 p.T790M-trans-C797S at osimertinib failure. After progression on the combinatorial treatment, allelic configuration shifted to T790M-cis-C797S. The patient subsequently received a regimen of osimertinib and anlotinib combined with chemotherapy, followed by osimertinib and anlotinib maintenance treatment, and achieved a PR lasting for 9 months. At disease progression, concomitant T790M-C797S mutations both in trans and cis were identified. A combination of chemo- and anti-angiogenic therapies was administrated for two cycles and then discontinued because of the poor physical condition of the patient. She passed away soon with an overall survival of 39 months and a post-osimertinib progression survival of 20 months. Our study provides the first clinical evidence that the osimertinib and anlotinib-based regimen may be an effective therapy in overcoming resistance mediated by T790M-cis-C797S. Our case also highlights the importance of dynamically monitoring the mutation status after osimertinib failure, which may provide patients with increased opportunities for targeted therapy and improve post-osimertinib progression survivals.

Use of liquid biopsy in monitoring therapeutic resistance in EGFR oncogene addicted NSCLC

Liquid biopsy has emerged as a minimally invasive alternative to tumor tissue analysis for the management of lung cancer patients, especially for epidermal growth factor receptor (EGFR) oncogene addicted tumor. In these patients, despite the clear benefits of tyrosine kinase inhibitors therapy, the development of acquired resistance and progressive disease is inevitable in most cases and liquid biopsy is important for molecular characterization at resistance and, being non-invasive, may be useful for disease monitoring. In this review, the authors will focus on the applications of liquid biopsy in EGFR-mutated non small cells lung cancer at diagnosis, during treatment and at progression, describing available data and possible future scenarios.

Emerging drugs for EGFR-mutated non-small cell lung cancer

INTRODUCTION

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) represent the standard of care for patients with metastatic non-small-cell lung cancer (NSCLC) harboring sensitizing EGFR mutations. However, these agents are associated with inevitable treatment resistance. Newer generations of TKIs are under development that may prevent or overcome resistance and enhance intracranial activity. Areas covered: In this review, we will discuss newer generations of EGFR TKIs for EGFR-mutated NSCLC. We will also address resistance mutations and escape pathways associated with these agents such as secondary mutations, downstream signaling, bypass pathways, phenotypic transformation, anti-apoptotic signaling, immune evasion, and angiogenesis. Furthermore, this article encompasses emerging data from combination trials with next-generation TKIs that are being pursued to delay or prevent the occurrence of resistance. Expert opinion: The promise and challenge of precision oncology is encapsulated in the treatment of EGFR-mutated NSCLC with TKIs. Third generation TKIs have shown superior efficacy in the front-line setting and have become standard of care. A better understanding of mechanisms of treatment failure and disease relapse will be required to develop novel therapeutic strategies to further improve patient outcomes in the future.

EGFR L792H and G796R: Two Novel Mutations Mediating Resistance to the Third-Generation EGFR Tyrosine Kinase Inhibitor Osimertinib

BACKGROUND

The third-generation EGFR tyrosine kinase inhibitor osimertinib has been approved in many countries to treat advanced NSCLC in patients with the EGFR T790M mutation. As the development of acquired resistance is inevitable, it is urgent that the mechanisms of such resistance be clarified.

METHODS

DNA samples from a cohort of 340 patients with lung adenocarcinoma who were taking osimertinib were subjected to next-generation sequencing and screened in terms of the frequencies of the L792H and G796R mutations. Ba/F3 cells stably expressing the EGFR L858R/T790M mutations (in cis) with either the L792H or G796R mutation were created to investigate the impact of the two novel mutations on EGFR tyrosine kinase inhibitors and other potential drug combinations in vitro. Structural analyses were performed by using Schrödinger/Maestro software (version 11.1.012, Schrödinger LLC, Cambridge, MA).

RESULTS

L792H and G796R were detected in 1.76% (six of 340) and 0.56% (two of 340) patients with lung adenocarcinoma treated with osimertinib, respectively. The introduction of L792H or G796R mutations against an L858R/T790M background caused dramatic reductions in osimertinib sensitivity. Structural modeling showed that mutations in cis with T790M either forced the ligand (osimertinib) to rotate out (breaking the binding) or pulled the hinge loop (breaking the hinge). Various other drug combinations. including cetuximab with EAI045, failed to inhibit either cis mutant effectively.

CONCLUSIONS

The EGFR L858R/T790M/L792H and L858R/T790M/G796R mutations conferred resistance to osimertinib both in vitro and in silico. For patients in whom the two resistance mutations occur at low frequency, more precise treatment strategies and additional combinational approaches are required.

Resistance Mechanisms to Targeted Therapies in ROS1+ and ALK+ Non-small Cell Lung Cancer

Purpose: Despite initial benefit from tyrosine kinase inhibitors (TKIs), patients with advanced non-small cell lung cancer (NSCLC) harboring ALK (ALK⁺) and ROS1 (ROS1⁺) gene fusions ultimately progress. Here, we report on the potential resistance mechanisms in a series of patients with ALK⁺ and ROS1⁺ NSCLC progressing on different types and/or lines of ROS1/ALK-targeted therapy.Experimental Design: We used a combination of next-generation sequencing (NGS), multiplex mutation assay, direct DNA sequencing, RT-PCR, and FISH to identify fusion variants/partners and copy-number gain (CNG), kinase domain mutations (KDM), and copy-number variations (CNVs) in other cancer-related genes. We performed testing on 12 ROS1⁺ and 43 ALK⁺ patients.Results: One of 12 ROS1⁺ (8%) and 15 of 43 (35%) ALK ⁺ patients harbored KDM. In the ROS1⁺ cohort, we identified KIT and β-catenin mutations and HER2-mediated bypass signaling as non-ROS1-dominant resistance mechanisms. In the ALK⁺ cohort, we identified a novel NRG1 gene fusion, a RET fusion, 2 EGFR, and 3 KRAS mutations, as well as mutations in IDH1, RIT1, NOTCH, and NF1 In addition, we identified CNV in multiple proto-oncogenes genes including PDGFRA, KIT, KDR, GNAS, K/HRAS, RET, NTRK1, MAP2K1, and others.Conclusions: We identified a putative TKI resistance mechanism in six of 12 (50%) ROS1 ⁺ patients and 37 of 43 (86%) ALK⁺ patients. Our data suggest that a focus on KDMs will miss most resistance mechanisms; broader gene testing strategies and functional validation is warranted to devise new therapeutic strategies for drug resistance. Clin Cancer Res; 24(14); 3334-47. ©2018 AACR.

Third generation EGFR TKIs: current data and future directions

Acquired T790 M mutation is the commonest cause of resistance for advanced non-small cell lung cancer (NSCLC) epidermal growth factor receptor (EGFR) mutant patients who had progressed after first line EGFR TKI (tyrosine kinase inhibitor). Several third generation EGFR TKIs which are EGFR mutant selective and wild-type (WT) sparing were developed to treat these patients with T790 M acquired resistant mutation. Osimertinib is one of the third generation EGFR TKIs and is currently the most advanced in clinical development. Unfortunately, despite good initial response, patients who was treated with third generation EGFR TKI would develop acquired resistance and several mechanisms had been identified and the commonest being C797S mutation at exon 20. Several novel treatment options were being developed for patients who had progressed on third generation EGFR TKI but they are still in the early phase of development. Osimertinib under FLAURA study had been shown to have better progression-free survival over first generation EGFR TKI in the first line setting and likely will become the new standard of care.