Therapeutic approaches for T790M mutation positive non-small-cell lung cancer

EGFR tyrosine kinase inhibitor ZZC4 overcomes acquired resistance to gefitinib

Despite the tremendous progress of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) development, acquired resistance mechanisms have limited their efficacy in treating non-small cell lung cancer (NSCLC). To overcome these limitations, novel EGFR-TKIs are needed. In our previous study, we presented ZZC4 as a potent EGFR-TKI. In this study, we developed NSCLC cells resistant to EGFR-TKI gefitinib and osimertinib and assessed the effect and mechanism of action of ZZC4 on those cells. HCC827 cells were cultured with gefitinib in a concentration-escalation manner to achieve HCC827 gefitinib-resistant (HCC827-GR) cells after 6 months of treatment. Then, the effect of ZZC4 was assessed at the cellular and animal levels. To understand ZZC4's mechanism of action, the proteome alteration induced by ZZC4 on the resistant cell line was compared to the parental HCC827 cells using comparative proteomics. The result showed that gefitinib's IC50 on HCC827 was 533 nM, approximately 80 times its IC50 on normal cells (7.6 nM), confirming its resistance to HCC827 cells. The obtained resistant cells were treated with ZZC4, which potently suppressed the resistant cells' proliferation with an IC50 of 0.1 nM. In tumor-bearing mice, ZZC4 also suppressed the growth of HCC827-GR cell tumors with an inhibition ratio of 82 % at ZZC4 4 mg/kg. Further, the proteomic analysis revealed that ZZC4 inhibited HCC827-GR cell growth by upregulating CDKN1B and downregulating CCNA2 and CHEK1. In conclusion, ZZC4 overcomes resistance to gefitinib by altering the cell cycle pathway.

Investigating osimertinib plus chemotherapy in EGFR-mutated advanced non-small cell lung cancer

INTRODUCTION

Worldwide, 15-40% of advanced-stage non-small cell lung cancers (NSCLCs) have an activating EGFR mutation, treatable with tyrosine-kinase inhibitors (TKIs) such as osimertinib, recommended as front-line therapy. Despite the efficacy of first-line osimertinib, most patients will experience disease progression. Therefore, combining it with chemotherapy has become an area of interest.

AREAS COVERED

Osimertinib is a third-generation EGFR-TKI that has extended survival in NSCLC patients with EGFR mutation. However, resistance eventually leads to treatment failure. This has driven the advancement of strategies to overcome resistance to osimertinib. In this setting, the FLAURA2 trial yielded positive results by combining osimertinib with chemotherapy. Additionally, a range of other approaches, including the use of bispecific antibodies and antibody-drug conjugates alongside third-generation EGFR-TKIs or chemotherapy, support the development of novel therapeutic combinations, some of which have already been approved for EGFR-mutated advanced NSCLC.

EXPERT OPINION

Next to osimertinib monotherapy, expanded upfront treatment options for patients with EGFR-mutated advanced NSCLC require patient selection considering disease extent, toxicity and tolerability, dosing schedule and what the patient can expect through shared decision-making. Further studies are needed to identify the patients who will benefit the most from combination therapies and to sequence the new drugs into the treatment algorithm.

An ultrasensitive DNA-enhanced amplification method for detecting cfDNA drug-resistant mutations in non-small cell lung cancer with selective FEN-assisted degradation of dominant somatic fragments

OBJECTIVES

Blood cell-free DNA (cfDNA) can be a new reliable tool for detecting epidermal growth factor receptor (EGFR) mutations in non-small cell lung cancer (NSCLC) patients. However, the currently reported cfDNA assays have a limited role in detecting drug-resistant mutations due to their deficiencies in sensitivity, stability, or mutation detection rate.

METHODS

We developed an Archaeoglobus fulgidus-derived flap endonuclease (Afu FEN)-based DNA-enhanced amplification system of mutated cfDNA by designing a pair of hairpin probes to anneal with wild-type cfDNA to form two 5'-flaps, allowing for the specific cleavage of wild-type cfDNA by Afu FEN. When the dominant wild-type somatic cfDNA fragments were cleaved by structure-recognition-specific Afu FEN, the proportion of mutated cfDNA in the reaction system was greatly enriched. As the amount of mutated cfDNA in the system was further increased by PCR amplification, the mutation status could be easily detected through first-generation sequencing.

RESULTS

In a mixture of synthetic wild-type and T790M EGFR DNA fragments, our new assay still could detect T790M mutation at the fg level with remarkably high sensitivity. We also tested its performance in detecting low variant allele frequency (VAF) mutations in clinical samples from NSCLC patients. The plasma cfDNA samples with low VAF (0.1 and 0.5 %) could be easily detected by DNA-enhanced amplification.

CONCLUSIONS

This system with enhanced amplification of mutated cfDNA is an effective tool used for the early screening and individualized targeted therapy of NSCLC by providing a rapid, sensitive, and economical way for the detection of drug-resistant mutations in tumors.

Advancements in fourth-generation EGFR TKIs in EGFR-mutant NSCLC: Bridging biological insights and therapeutic development

Third-generation EGFR tyrosine kinase inhibitor (TKIs) have revolutionized the treatment landscape for patients with non-small cell lung cancer (NSCLC) harboring EGFR activating mutations, with improved long-term outcomes compared to first-generation TKIs. Nevertheless, disease progression inevitably occurs, limiting osimertinib long-term efficacy. Indeed, the molecular biology underlying acquired resistance to first-line osimertinib is multifaceted and includes the emergence of on-target and off-target alterations. EGFR-C797S mutation represents the most frequent mechanism of on-target resistance and hinders drug binding to the target site. EGFR-independent resistance includes the activation of alternative signaling pathways, such as MET amplification and HER2 mutations, and histological transformation. In this setting, chemotherapy is the current therapeutic option, with modest clinical outcomes. Therefore, the development of novel therapeutic strategies to overcome resistance to osimertinib is a major challenge. In this setting, fourth-generation TKIs are emerging as an interesting therapeutic option to overcome on-target resistance. Preclinical drug development has led to the discovery of thiazole-amid inhibitors, which activity is mediated by the allosteric inhibition of EGFR, resulting in high specificity towards mutant-EGFR. Early phase 1/2 clinical trials are ongoing to elucidate their activity also in the clinical setting. Aim of this review is to provide a state-of-the-art analysis on preclinical development of fourth-generation EGFR-TKIs and promising preliminary clinical data.

Post-Progression Analysis of EGFR-Mutant NSCLC Following Osimertinib Therapy in Real-World Settings

BACKGROUND

Platinum-based chemotherapy is the current standard treatment option in patients with EGFR-mutant non-small-cell lung cancer (NSCLC) who progress on osimertinib. However, outcomes with chemotherapy are dismal, and the treatment of central nervous system (CNS) disease is an unmet need in this setting.

METHODS

Patients with EGFR-mutant NSCLC who were candidates to receive osimertinib in the metastatic setting at our Center from 2015 to 2022 were retrospectively evaluated to identify patients who received standard platinum-based chemotherapy post-osimertinib. Data were collected on treatment outcomes, with a focus on brain metastases and progression patterns.

RESULTS

A total of 220 patients received indication for osimertinib in the study period; n = 176 had adequate follow-up data. Overall, n = 117 patients experienced disease progression on osimertinib. The median time to osimertinib progressive disease (PD) was 15 months (95% confidence interval CI 13-18). Of them, 51 patients (45%) had no access to further treatments. Of the remaining patients, n = 8 received experimental treatments, and n = 55 received standard platinum-based chemotherapy and were considered for this study. Median duration of chemotherapy was 3 months (95% CI 2-5); the best responses among 53 evaluable patients were observed as follows: 15% partial response/complete response (PR/CR), 40% stable disease (SD), 45% PD. Median progression-free survival (PFS) and overall survival (OS) were 3 (95% CI 2-5) and 10 (95% CI 6-15) months, respectively. All patients had baseline and follow-up brain radiologic assessments, and n = 23 had brain metastases at the start of chemotherapy. With a median follow-up of 13 months, intracranial PD occurred in 47% patients, being the first site of PD in 59% of cases. The median time for intracranial (IC) PD was 2 months (95% CI 2-7). IC PD occurred as oligometastatic in 29%, whereas in 71% of cases, it was associated with systemic PD.

CONCLUSIONS

Access to subsequent treatments and CNS progression are confirmed unmet needs in EGFR-mutant NSCLC patients. Clinical and CNS-specific outcomes in patients receiving standard chemotherapy after the failure of osimertinib are dismal. Novel upfront treatment options with demonstrated prolonged PFS and better CNS outcomes may help address this important issue.

New Generations of Tyrosine Kinase Inhibitors in Treating NSCLC with Oncogene Addiction: Strengths and Limitations

Tyrosine kinase inhibitors (TKIs) revolutionized the treatment of patients with advanced or metastatic non-small cell lung cancer (NSCLC) harboring most driver gene alterations. Starting from the first generation, research rapidly moved to the development of newer, more selective generations of TKIs, obtaining improved results in terms of disease control and survival. However, the use of novel generations of TKIs is not without limitations. We reviewed the main results obtained, as well as the ongoing clinical trials with TKIs in oncogene-addicted NSCLC, together with the biology underlying their potential strengths and limitations. Across driver gene alterations, novel generations of TKIs allowed delayed resistance, prolonged survival, and improved brain penetration compared to previous generations, although with different toxicity profiles, that generally moved their use from further lines to the front-line treatment. However, the anticipated positioning of novel generation TKIs leads to abolishing the possibility of TKI treatment sequencing and any role of previous generations. In addition, under the selective pressure of such more potent drugs, resistant clones emerge harboring more complex and hard-to-target resistance mechanisms. Deeper knowledge of tumor biology and drug properties will help identify new strategies, including combinatorial treatments, to continue improving results in patients with oncogene-addicted NSCLC.

The Impact of Liquid Biopsies Positive for EGFR Mutations on Overall Survival in Non-Small Cell Lung Cancer Patients

In recent years, non-small cell lung cancer treatment has been revolutionized. EGFR tyrosine kinase inhibitors and our improved understanding of its alterations have driven new diagnostic strategies. Liquid biopsies have emerged as a useful tool in these contexts, showing potential utility in early diagnosis combined with low-dose CT scans, as well as potential in monitoring treatment response and predicting the development of patients. We studied the circulating tumor DNA (ctDNA) of 38 EGFR-mutated non-small cell lung cancer patients at diagnosis in different moments of their disease by liquid biopsy techniques. Our results show that mean overall survival was significantly lower when a liquid biopsy was positive for the detection of EGFR mutations compared with wild-type patients in their liquid biopsy in both univariate (29 ± 4 vs. 104 ± 19 months; p = 0.004) and multivariate analysis (p = 0.008). Taking this into consideration, liquid biopsies could be key to improving the control of this disease.

The Resistance to EGFR-TKIs in Non-Small Cell Lung Cancer: From Molecular Mechanisms to Clinical Application of New Therapeutic Strategies

Almost 17% of Western patients affected by non-small cell lung cancer (NSCLC) have an activating epidermal growth factor receptor (EGFR) gene mutation. Del19 and L858R are the most-common ones; they are positive predictive factors for EGFR tyrosine kinase inhibitors (TKIs). Currently, osimertinib, a third-generation TKI, is the standard first-line therapy for advanced NSCLC patients with common EGFR mutations. This drug is also administered as a second-line treatment for those patients with the T790M EGFR mutation and previously treated with first- (erlotinib, gefitinib) or second- (afatinib) generation TKIs. However, despite the high clinical efficacy, the prognosis remains severe due to intrinsic or acquired resistance to EGRF-TKIs. Various mechanisms of resistance have been reported including the activation of other signalling pathways, the development of secondary mutations, the alteration of the downstream pathways, and phenotypic transformation. However, further data are needed to achieve the goal of overcoming resistance to EGFR-TKIs, hence the necessity of discovering novel genetic targets and developing new-generation drugs. This review aimed to deepen the knowledge of intrinsic and acquired molecular mechanisms of resistance to EGFR-TKIs and the development of new therapeutic strategies to overcome TKIs' resistance.

Spotlight on Furmonertinib (Alflutinib, AST2818). The Swiss Army Knife (del19, L858R, T790M, Exon 20 Insertions, "uncommon-G719X, S768I, L861Q") Among the Third-Generation EGFR TKIs?

Osimertinib, a third-generation (3G) epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) is now considered the standard of care for the first-line (1L) treatment of advanced EGFR+ NSCLC due to statistically significant improved progression-free survival (PFS) and overall survival (OS) compared with first-generation (1G) treatment from the FLAURA trial. Recently two other 3G EGFR TKIs (aumolertinib and furmonertinib) have been approved in China for treatment of EGFR T790M+ NSCLC. Randomized Phase 3 trials of these two 3G EGFR TKIs have also demonstrated PFS over gefitinib respectively. Among these two Chinese home-grown, 3G EGFR TKIs, furmonertinib seems to most closely resemble osimertinib in terms of dosing regimen, efficacy and adverse events profile. In this article, we reviewed the clinical activity and adverse events of furmonertinib at 80 mg daily (approved dose), potential usage of 160 mg daily for CNS metastasis in EGFR+ NSCLC, and usage of 160 mg or 240 mg daily in EGFR exon20 insertion positive (EGFRex20ins+) NSCLC patients.

Investigation of molecular mechanism leading to gefitinib and osimertinib resistance against EGFR tyrosine kinase: molecular dynamics and binding free energy calculation

Tyrosine kinase (TK) is an important protein responsible for phosphorylation of variety of proteins that helps in signal transduction process in transferring signal to regulate various physiological and biochemical processes. Drugs inhibiting signal transduction pathways can be a very rational approach to inhibit cellular physiological and biochemical process. Tyrosine kinase inhibitors are a wide family of drugs that have been used successfully in cancer chemotherapy. Certain mutations around the catalytic cleft may cause conformational changes at binding site and leads to decrease in inhibitor sensitivity to TK mutants. EGFR^T790M mutation is the first recognized acquired resistance after tyrosine kinase inhibitor therapy that leads to resistant to first generation TKI in about 50% of non-small cell lung carcinoma patients. Third generation EGFR-TKIs bind irreversibly to the C797, which is present in the ATP-binding pocket. The present work provides a molecular mechanism for understanding the Gefitinib and Osimertinib sensitivities with the EGFR^WILD, EGFR^L858R, EGFR^T790M, EGFR^T790M+C797S mutants using molecular modelling techniques. Changes in response against Gefitinib and Osimertinib were observed with the change of amino acids at the tyrosine kinase domain of EGFR^WILD and its mutants (EGFR^L858R, EGFR^T790M, EGFR^T790M+C797S). RMSD, RMSF and binding energies calculation well correlates with the change in clinical observation.Communicated by Ramaswamy H. Sarma.

Targeting Acquired and Intrinsic Resistance Mechanisms in Epidermal Growth Factor Receptor Mutant Non-Small-Cell Lung Cancer

Over the past 2 decades, rapid advances in molecular profiling and the development of targeted therapies have dramatically improved the clinical course of advanced non-small-cell lung cancer (NSCLC). Mutations in the epidermal growth factor receptor (EGFR) gene are found in about a third of patients with advanced NSCLC, and the approval of first-generation EGFR targeted kinase inhibitors significantly improved survival when compared with platinum-based doublet chemotherapy (PBC), the previous standard of care. Inevitably, selective pressure from first-generation EGFR inhibitors led to acquired resistance mechanisms, such as the T790M mutation. The advent of third-generation EGFR inhibitors (e.g., osimertinib) successfully overcame the T790M resistance mechanism, and osimertinib subsequently became the first-line therapy for EGFR mutant NSCLC. Currently, research in EGFR mutant NSCLC is primarily focused on targeting resistance mechanisms to osimertinib. Over the past several years, many important acquired and intrinsic mechanisms of resistance to osimertinib have been identified. Acquired resistance mechanisms include C797X, mesenchymal epithelial transition factor (MET) amplification, HER2/HER3 amplification, phosphoinositide 3-kinase (PI3K) pathway mutations, RAS/mitogen-activated protein kinase (MAPK) pathway mutations, cell-cycle gene alterations, oncogenic fusions, and histologic transformations. An important intrinsic resistance mechanism to osimertinib is the EGFR exon 20 insertion mutation, which is sensitive to the newly Food and Drug Administration (FDA)-approved tyrosine kinase inhibitor mobocertinib and the EGFR/MET bispecific antibody amivantamab. This review article aims to (1) summarize the advances in the treatment of EGFR mutant NSCLC, (2) delineate known resistance mechanisms to the current first-line therapy, osimertinib, and (3) describe the development of targeted drugs that aim to overcome these resistance mechanisms.

High quality of 58-month life in lung cancer patient with brain metastases sequentially treated with gefitinib and osimertinib

Brain metastases (BMs) and bone metastases seriously affect the prognosis of lung cancer patients. How to optimize the use of existing targeted drugs is an important way to address the clinical needs of the central nervous system in the individualized treatment of non-small cell lung cancer (NSCLC). In this report, we describe an NSCLC patient with BMs who survived for 58 months, which is the longest survival case among lung cancer patients with BMs. The patient was initially diagnosed with lung cancer more than 5 years ago with simultaneous brain, bone, and lung metastases. After gefitinib resistance, she received osimertinib in sequence with no progress for 58 months in total and maintained very good quality of life.

Molecular Mechanism of EGFR-TKI Resistance in EGFR-Mutated Non-Small Cell Lung Cancer: Application to Biological Diagnostic and Monitoring

Non-small cell lung cancer (NSCLC) is the most common cancer in the world. Activating epidermal growth factor receptor (EGFR) gene mutations are a positive predictive factor for EGFR tyrosine kinase inhibitors (TKIs). For common EGFR mutations (Del19, L858R), the standard first-line treatment is actually third-generation TKI, osimertinib. In the case of first-line treatment by first (erlotinib, gefitinib)- or second-generation (afatinib) TKIs, osimertinib is approved in second-line treatment for patients with T790M EGFR mutation. Despite the excellent disease control results with EGFR TKIs, acquired resistance inevitably occurs and remains a biological challenge. This leads to the discovery of novel biomarkers and possible drug targets, which vary among the generation/line of EGFR TKIs. Besides EGFR second/third mutations, alternative mechanisms could be involved, such as gene amplification or gene fusion, which could be detected by different molecular techniques on different types of biological samples. Histological transformation is another mechanism of resistance with some biological predictive factors that needs tumor biopsy. The place of liquid biopsy also depends on the generation/line of EGFR TKIs and should be a good candidate for molecular monitoring. This article is based on the literature and proposes actual and future directions in clinical and translational research.

Next-generation sequencing of tissue and circulating tumor DNA: Resistance mechanisms to EGFR targeted therapy in a cohort of patients with advanced non-small cell lung cancer

BACKGROUND

Epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) has been considered as an effective treatment in epidermal growth factor receptor-mutant (EGFR-mutant) advanced non-small cell lung cancer (NSCLC). However, most patients develop acquired resistance eventually. Here, we compared and analyzed the genetic alterations between tissue assay and circulating tumor DNA (ctDNA) and further explored the resistance mechanisms after EGFR-TKI treatment.

METHODS AND MATERIALS

Amplification refractory mutation system-polymerase chain reaction (ARMS-PCR), Cobas^® ARMS-PCR and next-generation sequencing (NGS) were performed on tissue samples after pathological diagnosis. Digital droplet PCR (ddPCR) and NGS were performed on plasma samples. The association between genetic alterations and clinical outcomes was analyzed retrospectively.

RESULTS

Thirty-seven patients were included. The success rate of re-biopsy was 91.89% (34/37). The total detection rate of EGFR T790M was 62.16% (23/37) and the consistency between tissue and ctDNA was 78.26% (18/23). Thirty-four patients were analyzed retrospectively. For tissue re-biopsy, 24 patients harbored concomitant mutations. Moreover, tissue re-biopsy at resistance showed 21 patients (21/34, 61.76%) had the concomitant somatic mutation. The three most frequent concomitant mutations were TP53 (18/34, 52.94%), MET (4/34, 11.76%), and PIK3CA (4/34, 11.76%). Meanwhile, 21 patients (21/34, 61.76%) with EGFR T790M mutation. Progression-free survival (PFS) and overall survival (OS) were better in patients with T790M mutation (p = 0.010 and p = 0.017) or third-generation EGFR-TKI treatment (p < 0.0001 and p = 0.073). Interestingly, concomitant genetic alterations were significantly associated with a worse prognosis for patients with EGFR T790M mutation receiving third-generation EGFR-TKIs (p = 0.037).

CONCLUSIONS

Multi-platforms are feasible and highly consistent for re-biopsy after EGFR-TKI resistance. Concomitant genetic alterations may be associated with a poor prognosis for patients with EGFR T790M mutation after third-generation EGFR-TKIs.

Overcoming therapy resistance in EGFR-mutant lung cancer

Tyrosine kinase inhibitors (TKIs) have dramatically changed the clinical prospects of patients with non-small cell lung cancer harboring epidermal growth factor receptor (EGFR)-activating mutations. Despite prolonged disease control and high tumor response rates, all patients eventually progress on EGFR TKI treatment. Here, we review the mechanisms of acquired EGFR TKI resistance, the methods for monitoring its appearance, as well as current and future efforts to define treatment strategies to overcome resistance.

Next Generation Sequencing-Based Profiling of Cell Free DNA in Patients with Advanced Non-Small Cell Lung Cancer: Advantages and Pitfalls

Lung cancer (LC) is the main cause of death for cancer worldwide and non-small cell lung cancer (NSCLC) represents the most common histology. The discovery of genomic alterations in driver genes that offer the possibility of therapeutic intervention has completely changed the approach to the diagnosis and therapy of advanced NSCLC patients, and tumor molecular profiling has become mandatory for the choice of the most appropriate therapeutic strategy. However, in approximately 30% of NSCLC patients tumor tissue is inadequate for biomarker analysis. The development of highly sensitive next generation sequencing (NGS) technologies for the analysis of circulating cell-free DNA (cfDNA) is emerging as a valuable alternative to assess tumor molecular landscape in case of tissue unavailability. Additionally, cfDNA NGS testing can better recapitulate NSCLC heterogeneity as compared with tissue testing. In this review we describe the main advantages and limits of using NGS-based cfDNA analysis to guide the therapeutic decision-making process in advanced NSCLC patients, to monitor the response to therapy and to identify mechanisms of resistance early. Therefore, we provide evidence that the implementation of cfDNA NGS testing in clinical research and in the clinical practice can significantly improve precision medicine approaches in patients with advanced NSCLC.

Mutational spectrum of acquired resistance to reversible versus irreversible EGFR tyrosine kinase inhibitors

Background

Over the past years, EGFR tyrosine kinase inhibitors (TKI) revolutionized treatment response. 1st-generation (reversible) EGFR TKI and later the 2nd –generation irreversible EGFR TKI Afatinib were aimed to improve treatment response. Nevertheless, diverse resistance mechanisms develop within the first year of therapy. Here, we evaluate the prevalence of acquired resistance mechanisms towards reversible and irreversible EGFR TKI.

Methods

Rebiopsies of patients after progression to EGFR TKI therapy (> 6 months) were targeted to histological and molecular analysis. Multiplexed targeted sequencing (NGS) was conducted to identify acquired resistance mutations (e.g. EGFR p.T790M). Further, Fluorescence in situ hybridisation (FISH) was applied to investigate the status of bypass mechanisms like, MET or HER2 amplification.

Results

One hundred twenty-three rebiopsy samples of patients that underwent first-line EGFR TKI therapy (PFS ≥6 months) were histologically and molecularly profiled upon clinical progression. The EGFR p.T790M mutation is the major mechanism of acquired resistance in patients treated with reversible as well as irreversible EGFR TKI. Nevertheless a statistically significant difference for the acquisition of T790M mutation has been identified: 45% of afatinib- vs 65% of reversible EGFR TKI treated patients developed a T790M mutation (p-value 0.02). Progression free survival (PFS) was comparable in patients treated with irreversible EGFR irrespective of the sensitising primary mutation or the acquisition of p.T790M.

Conclusions

The EGFR p.T790M mutation is the most prominent mechanism of resistance to reversible and irreversible EGFR TKI therapy. Nevertheless there is a statistically significant difference of p.T790M acquisition between the two types of TKI, which might be of importance for clinical therapy decision.

A review on progression of epidermal growth factor receptor (EGFR) inhibitors as an efficient approach in cancer targeted therapy

The identification of molecular agents inhibiting specific functions in cancer cells progression is considered as one of the most successful plans in cancer treatment. The epidermal growth factor receptor (EGFR) over-activation is observed in a vast number of cancers, so, targeting EGFR and its downstream signaling cascades are regarded as a rational and valuable approach in cancer therapy. Several synthetic EGFR tyrosine kinase inhibitors (TKIs) have been evaluated in recent years, mostly exhibited clinical efficacy in relevant models and categorized into first, second, third and fourth-generation. However, studies are still ongoing to find more efficient EGFR inhibitors in light of the resistance to the current inhibitors. In this review, the importance of targeting EGFR signaling pathway in cancer therapy and related epigenetic mutations are highlighted. The recent advances on the discovery and development of different EGFR inhibitors and the use of various therapeutic strategies such as multi-targeting agents and combination therapies have also been reviewed.

Current Approaches in NSCLC Targeting K-RAS and EGFR

The research and treatment of non-small cell lung cancer (NSCLC) have achieved some important advances in recent years. Nonetheless, the overall survival rates for NSCLC remain low, indicating the importance to effectively develop new therapies and improve current approaches. The understanding of the function of different biomarkers involved in NSCLC progression, survival and response to therapy are important for the development of early detection tools and treatment options. Epidermal growth factor receptor (EGFR) and Kirsten rat sarcoma viral oncogene homolog (K-RAS) are two of the main significant biomarkers for the management of NSCLC. Mutations in these genes were associated with development and response to therapies. For example, the use of small molecule tyrosine kinase (TK) inhibitors and immunotherapy has led to benefits in some, but not all patients with altered EGFR. In contrast, there is still no effective approved drug to act upon patients harbouring K-RAS mutations. In addition, K-RAS mutations have been associated with lack of activity of TK inhibitors. However, promising approaches aimed to inhibit mutant K-RAS are currently under study. Therefore, this review will discuss these approaches and also EGFR therapies, and hopefully, it will draw attention to the need of continued research in the field in order to improve the outcomes in NSCLC patients.

Poor Prognosis With Coexistence Of EGFR T790M Mutation And Common EGFR-Activating Mutation In Non- Small Cell Lung Cancer

Purpose

Previous studies have shown that the presence of EGFR T790M mutation may reduce the treatment efficacy of tyrosine kinase inhibitors (TKIs) in EGFR-mutant lung cancer. However, little is known about the clinical features and outcomes of EGFR T790M mutation in pretreated patients with NSCLC.

Patients and methods

The clinical features of EGFR-activating and T790M mutations were assessed in a large cohort of patients with EGFR-TKI-naïve NSCLC (all/EGFR mutations, n=16,347/7,687). The correlation between the pretreatment T790M mutation status and clinical outcomes was evaluated using univariate and multivariate analyses.

Results

Pretreatment T790M mutation was reported in 1.39% of the patients and coexisted with an EGFR-activating or uncommon mutation. The dual EGFR T790M and common EGFR-activating mutations were more likely to be detected in lung adenocarcinoma, whereas single T790M mutation was more prevalent in non-adenocarcinomas. The presence of de novo T790M mutation correlated with reduced recurrence-free survival (RFS) in patients with NSCLC (odds ratio [OR] 3.37, 95% confidence interval [CI] 1.67-6.79, P = 0.001). After molecular stratification, T790M mutation was shown to exert adverse effects on the RFS of EGFR 19-del group (OR 2.89, 95% CI 1.10-7.91, P = 0.028) and EGFR L858R group (OR 3.43, 95% CI 1.33-8.88, P = 0.013). Furthermore, pretreatment T790M mutation promoted tumor metastasis to different sites.

Conclusion

T790M-positive tumors presented special clinical features, and the coexistence of T790M and common EGFR-activating mutations was associated with poor prognosis in patients with NSCLC.

Resistances to EGFR tyrosine kinase inhibitors in lung cancer-how to routinely track them in a molecular pathology laboratory?

Patients with advanced or metastatic forms of lung cancer with an activating mutation in epidermal growth factor receptor (EGFR) are given tyrosine kinase inhibitors (TKIs) targeted therapies that are more efficient than chemotherapy. These patients are excluded from first-line immunotherapy. After a phase of regression these tumors develop systematically resistance requiring a rapid change in therapy. At present two strategies are being discussed. The first strategy, so called "historical' sequential treatment strategy, is based on the administration of first- or second-generation TKIs until the emergence of therapeutic resistance and, in the case of a EGFR T790M mutation, on the administration of third-generation TKIs. The recently proposed second strategy, so called the "next-generation" TKIs strategy, concerns initial treatment with third-generation TKIs. This latter strategy appears to be promising but needs to be confirmed by data comparing survival curves of patients treated in a sequential manner. Several criteria influence the choice of these strategies, in particular the presence of brain metastases, the potential toxicity and the economic model. The selected therapeutic algorithm has certainly an impact on the activity of laboratories. The sequential approach requires investigation into EGFR T790M resistance mutations, using blood and then possibly a tissue biopsy, or into other mechanisms of resistance in the absence of this mutation. In the case of tumor progression under treatment with third-generation TKIs the EGFR C797S mutation in the cis or trans positions is looked for. In the absence of this latter mutation other mechanisms of resistance are then investigated. We describe here the different methodological approaches used to identify resistance mechanisms linked to treatment with TKIs targeting mutations in EGFR.