Emerging Treatment Paradigms for EGFR-Mutant Lung Cancers Progressing on Osimertinib: A Review

Acquired Mechanisms of Resistance to Osimertinib-The Next Challenge

Simple Summary

Osimertinib has revolutionized the treatment of EGFR-mutated tumors. Its current applications include the first-line setting, second-line setting, as well as the adjuvant setting. Although it represents a milestone in the context of targeted therapy, inevitably all tumors develop an acquired resistance, some mechanisms involve EGFR, others do so through alternative pathways leading to a bypass in osimertinib inhibition. It is key to understand these acquired mechanisms of resistance, both in the clinical setting, as well as in preclinical models, in order to develop and contribute to the identification of possible therapeutic strategies to overcome this acquired resistance.

Abstract

EGFR-mutated tumors represent a significant percentage of non-small cell lung cancer. Despite the increasing use of osimertinib, a treatment that has demonstrated an outstanding clinical benefit with a tolerable toxicity profile, EGFR tumors eventually acquire mechanisms of resistance. In the last years, multiple mechanisms of resistance have been identified; however, after progressing on osimertinib, treatment options remain bleak. In this review, we cover the most frequent alterations and potential therapeutic strategies to overcome them.

Acquired Concurrent EGFR T790M and Driver Gene Resistance From EGFR-TKIs Hampered Osimertinib Efficacy in Advanced Lung Adenocarcinoma: Case Reports

The acquired resistance of epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) is inevitable and heterogeneous. The strategies to overcome acquired resistance are significant. For patients with secondary T790M-positive after early generation EGFR-TKIs, osimertinib is the standard second-line therapy. In patients resistant to prior early generation EGFR-TKIs, the acquired T790M mutation overlaps with other driver gene resistance, such as HER2-and MET amplification, accounting for 4–8%. The efficacy of osimertinib is unclear in patients with concurrent multiple driver gene resistance. We here report a patient who acquired EGFR T790M, STRN-ALK fusion, and EGFR amplification after gefitinib progression and subsequent MET amplification acquired from osimertinib. The other patient acquired EGFR T790M and MET amplification post-dacomitinib and acquired CCDC6-RET fusion after osimertinib treatment. Besides, subsequent new bypass activations were the possible resistance mechanisms to second-line osimertinib. Both patients had progression-free survival (PFS) less than 4 months and limited benefits from osimertinib second-line therapy. The T790M accompanying driver gene resistance will be a new subtype after EGFR-TKIs progression, needing effective treatment options.

COL8A1 Promotes NSCLC Progression Through IFIT1/IFIT3-Mediated EGFR Activation

Activation of EGFR is a major risk factor for non-small cell lung cancer (NSCLC). Understanding the molecular events promoting EGFR activation can help us gain more insights into the progression of NSCLC. In this study, we demonstrate that collagen type VIII alpha 1 chain (COL8A1), an extracellular matrix component, was overexpressed in NSCLC. In NSCLC cells, knockdown of COL8A1 suppressed cell growth, cycle progression, and migration, and induced cell apoptosis. While COL8A1 overexpression promoted cell proliferation and inhibited cell apoptosis. In addition, we found that COL8A1 depletion reduced interferon response signaling and downregulated (IFIT1) and interferon-induced proteins with tetratricopeptide repeats 3 (IFIT3). Moreover, we indicated that COL8A1 could upregulate IFIT1 and IFIT3 mediated EGFR activation in vitro and in vivo. Lastly, there was a positive correlation among COL8A1, IFIT1, and IFIT3 expression, and EGFR activity in patients with NSCLC. Overall, our data demonstrate that COL8A1 contributes to NSCLC proliferation and invasion through EGFR activation, dependent on IFIT1 and IFIT3 expression.

Overcoming acquired resistance to third-generation EGFR inhibitors by targeting activation of intrinsic apoptotic pathway through Mcl-1 inhibition, Bax activation, or both

Treatment of EGFR-mutant non-small cell lung cancer (NSCLC) with mutation-selective third-generation EGFR-tyrosine kinase inhibitors (EGFR-TKIs) such as osimertinib has achieved remarkable success in the clinic. However, the immediate challenge is the emergence of acquired resistance, limiting the long-term remission of patients. This study suggests a novel strategy to overcome acquired resistance to osimertinib and other third-generation EGFR-TKIs through directly targeting the intrinsic apoptotic pathway. We found that osimertinib, when combined with Mcl-1 inhibition or Bax activation, synergistically decreased the survival of different osimertinib-resistant cell lines, enhanced the induction of intrinsic apoptosis, and inhibited the growth of osimertinib-resistant tumor in vivo. Interestingly, the triple-combination of osimertinib with Mcl-1 inhibition and Bax activation exhibited the most potent activity in decreasing the survival and inducing apoptosis of osimertinib-resistant cells and in suppressing the growth of osimertinib-resistant tumors. These effects were associated with increased activation of the intrinsic apoptotic pathway evidenced by augmented mitochondrial cytochrome C and Smac release. Hence, this study convincingly demonstrates a novel strategy for overcoming acquired resistance to osimertinib and other 3rd generation EGFR-TKIs by targeting activation of the intrinsic apoptotic pathway through Mcl-1 inhibition, Bax activation or both, warranting further clinical validation of this strategy.

The Role of TP53 Mutations in EGFR-Mutated Non-Small-Cell Lung Cancer: Clinical Significance and Implications for Therapy

Simple Summary

Non-Small-Cell Lung Cancer (NSCLC) is the primary cause of cancer-related death worldwide. Patients carrying Epidermal Growth Factor Receptor (EGFR) mutations usually benefit from targeted therapy treatment. Nonetheless, primary or acquired resistance mechanisms lead to treatment discontinuation and disease progression. Tumor protein 53 (TP53) mutations are the most common mutations in NSCLC, and several reports highlighted a role for these mutations in influencing prognosis and responsiveness to EGFR targeted therapy. In this review, we discuss the emerging data about the role of TP53 in predicting EGFR mutated NSCLC patients’ prognosis and responsiveness to targeted therapy.

Abstract

Non-Small-Cell Lung Cancer (NSCLC) is the primary cause of cancer-related death worldwide. Oncogene-addicted patients usually benefit from targeted therapy, but primary and acquired resistance mechanisms inevitably occur. Tumor protein 53 (TP53) gene is the most frequently mutated gene in cancer, including NSCLC. TP53 mutations are able to induce carcinogenesis, tumor development and resistance to therapy, influencing patient prognosis and responsiveness to therapy. TP53 mutants present in different forms, suggesting that different gene alterations confer specific acquired protein functions. In recent years, many associations between different TP53 mutations and responses to Epidermal Growth Factor Receptor (EGFR) targeted therapy in NSCLC patients have been found. In this review, we discuss the current landscape concerning the role of TP53 mutants to guide primary and acquired resistance to Tyrosine-Kinase Inhibitors (TKIs) EGFR-directed, investigating the possible mechanisms of TP53 mutants within the cellular compartments. We also discuss the role of the TP53 mutations in predicting the response to targeted therapy with EGFR-TKIs, as a possible biomarker to guide patient stratification for treatment.

Junctional Adhesion Molecule-Like Protein (JAML) Is Correlated with Prognosis and Immune Infiltrates in Lung Adenocarcinoma

BACKGROUND Junctional adhesion molecule-like protein (JAML) is a member of the junctional adhesion molecule family and mediates migration of immune cells, but its function in cancers remains unclear. This study aimed to evaluate the role of JAML in the prognosis and immune infiltrates of lung adenocarcinoma (LUAD). MATERIAL AND METHODS JAML expressions in LUAD tissues and normal tissues were compared using The Cancer Genome Atlas (TCGA) database and datasets from the Gene Expression Omnibus (GEO) database. The influence of JAML expression on prognosis was analyzed by Kaplan-Meier curve and Cox regression model. Interactive and functional analyses of JAML were performed by LinkedOmics and GeneMANIA databases. TIMER2.0, TISIDB, and GEPIA2 databases were used to investigate the correlation between JAML expression and immune infiltrates. RESULTS JAML expression was decreased in LUAD (P<0.001), and lower JAML expression was associated with worse outcomes of LUAD patients. High JAML expression was the protective factor for overall survival (OS) (HR 0.706, 95% CI 0.500-0.997, P=0.048). Interactive and functional analyses suggested that co-expressed genes with JAML have an obvious link to immune-related pathways. In addition, JAML expression was positively associated with infiltrating levels of CD8+ T cells, CD4+ T cells, B cells, dendritic cells, macrophages, and neutrophils, and had significant correlations with diverse immune marker sets in LUAD. CONCLUSIONS JAML expression was significantly correlated with prognosis and immune infiltrates. These preliminary findings suggested JAML could be considered as a potential prognostic biomarker and therapeutic target for LUAD.

Preclinical assessment of combination therapy of EGFR tyrosine kinase inhibitors in a highly heterogeneous tumor model

The development of tyrosine kinase inhibitors (TKIs) has improved the treatment of non-small cell lung cancer (NSCLC) with epidermal growth factor receptor (EGFR) mutations. The current research priority is to provide viable treatments for patients who have drug-resistant EGFR mutations. We evaluated the drug sensitivity of various EGFR mutants to monotherapies and combination therapies of EGFR-TKIs. In vitro, the transforming potential and drug sensitivity of 357 EGFR variants were assessed. In vivo, we tested the sensitivity of EGFR variants to different regimens of EGFR-TKIs by examining changes in the proportion of each variant within the tumor. Out of 357 variants thoroughly examined for transforming activities, 144 (40.3%) and 282 (79.0%) transformed 3T3 and Ba/F3 cells, respectively. Among the latter variants, 50 (17.7%) were found to be resistant or only partly resistant to osimertinib or afatinib. Four of 25 afatinib-resistant variants (16%) were sensitive to osimertinib, whereas 25 of 46 osimertinib-resistant variants (54.3%) were sensitive to afatinib. Despite the lack of a synergistic impact, TKI combination treatment effectively reduced in vivo the heterogeneous tumors composed of 3T3 cells with different EGFR variants. Regimens starting with afatinib and subsequently switched to osimertinib suppressed tumor development more efficiently than the opposite combination. Combination EGFR-TKI treatment may decrease tumor growth and prevent the development of resistant variants. This work created an experimental model of a heterogeneous tumor to find the best combination therapy regimen and proposes a basic notion of EGFR-TKI combination therapy to enhance the prognosis of NSCLC patients.

The natural product berberine synergizes with osimertinib preferentially against MET-amplified osimertinib-resistant lung cancer via direct MET inhibition

Berberine is a natural product that has long been used in traditional Chinese medicine due to its antimicrobial, anti-inflammatory and metabolism-regulatory properties. Osimertinib is the first third-generation EGFR-tyrosine kinase inhibitor (TKI) approved for the treatment of non-small cell lung cancer (NSCLC) with activating EGFR mutations and those resistant to earlier generation EGFR-TKIs due to a T790M mutation. However, emergence of acquired resistance to osimertinib limits its long-term efficacy in the clinic. One known mechanism of acquired resistance to osimertinib and other EGFR-TKIs is MET (c-MET) gene amplification. Here, we report that berberine, when combined with osimertinib, synergistically and selectively decreased the survival of several MET-amplified osimertinib-resistant EGFR mutant NSCLC cell lines with enhanced induction of apoptosis likely through Bim elevation and Mcl-1 reduction. Importantly, this combination effectively enhanced suppressive effect on the growth of MET-amplified osimertinib-resistant xenografts in nude mice and was well tolerated. Molecular modeling showed that berberine was able to bind to the kinase domain of non-phosphorylated MET, occupy the front of the binding pocket, and interact with the activation loop, in a similar way as other known MET inhibitors do. MET kinase assay showed clear concentration-dependent inhibitory effects of berberine against MET activity, confirming its kinase inhibitory activity. These findings collectively suggest that berberine can act as a naturally-existing MET inhibitor to synergize with osimertinib in overcoming osimertinib acquired resistance caused by MET amplification.

Stereotactic Ablative Radiotherapy for Oligo-Progressive Disease REfractory to Systemic Therapy in Non-Small Cell Lung Cancer: A Registry-based Phase II Randomized Trial (SUPPRESS-NSCLC)

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Treatment of NSCLC patients with oligo-progressive disease on systemic treatment remains controversial.

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This phase II trial evaluates SABR to all oligo-progressive lesions in combination to current systemic therapy.

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PFS and OS between patients treated with SABR with continuation of current systemic therapy vs standard of care will be assessed.

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Intention-to-treat analysis of SABR compared to standard of care will be evaluated.

Background

Management of Non-Small Cell Lung Cancer (NSCLC) patients with oligoprogression remains controversial. There is limited data to support the strategy of Stereotactic Ablative Radiotherapy (SABR) targeting the oligoprogressive disease in combination with ongoing systemic treatment. We aim to assess the benefit of this approach compared to standard of care in the treatment of oligoprogressive NSCLC.

Methods

This phase II study will enroll 68 patients with oligoprogressive NSCLC, defined as 1–5 progressive extracranial lesions ≤5 cm involving ≤3 organs. Patients on active systemic therapy (chemotherapy, immunotherapy, targeted therapy or a combination) will be randomized 1:1 to either continue their current systemic therapy in combination with SABR to all lesions or the standard of care (switch to the next line of treatment, continue same treatment or observation). The co-primary endpoints are progression-free survival (PFS) and overall survival (OS). Secondary endpoints include time to next systemic treatment, patient-reported quality of life, cost effectiveness as well as translational analysis to characterize both adaptive immunity and immunogenic cell death markers in the peripheral blood.

Discussion

There is an unmet need to carefully examine the efficacy, safety and quality of life impact of SABR in the context of oligoprogressive disease. The present study will provide higher level randomized evidence on the role of SABR in oligoprogressive NSCLC.

Resistance mechanisms to osimertinib and emerging therapeutic strategies in nonsmall cell lung cancer

PURPOSE OF REVIEW

This review aims to introduce the resistance mechanisms to osimertinib, discuss the therapeutic strategies, and make clinical updates in overcoming resistance to osimertinib.

RECENT FINDINGS

Osimertinib has shown favorable efficacy on second-line and first-line treatments in EGFR-mutant advanced nonsmall cell lung cancer (NSCLC). However, the presence of primary and acquired resistance to osimertinib restricts its clinical benefits. The primary resistance mainly consists of BIM deletion polymorphism and EGFR exon 20 insertions. Meanwhile, the heterogeneous mechanisms of acquired resistance include EGFR-dependent (on-target) and EGFR-independent (off-target) mechanisms. EGFR C797S mutation, MET amplification, HER2 amplification, and small cell lung cancer transformation were identified as frequent resistance mechanisms. Recently, more novel mechanisms, including rare EGFR point mutations and oncogenic fusions, were reported. With the results of completed and on-going clinical trials, the emerging therapeutic strategies of postosimertinib progression are summarized.

SUMMARY

The resistance mechanisms to osimertinib are heterogeneous and gradually perfected. The combination of osimertinib with bypass targeted therapy and other therapeutic approaches emerge as promising strategies.

Challenge and countermeasures for EGFR targeted therapy in non-small cell lung cancer

Lung cancer causes the highest mortality compared to other cancers in the world according to the latest WHO reports. Non-small cell lung cancer (NSCLC) contributes about 85% of total lung cancer cases. An extensive number of risk factors are attributed to the progression of lung cancer. Epidermal growth factor receptor (EGFR), one of the most frequently mutant driver genes, is closely involved in the development of lung cancer through regulation of the PI3K/AKT and MAPK pathways. As a representative of precision medicine, EGFR-tyrosine kinase inhibitors (TKIs) targeted therapy significantly relieves the development of activating mutant EGFR-driven NSCLC. However, treatment with TKIs facilitates the emergence of acquired resistance that continues to pose a significant hurdle with respect to EGFR targeted therapy. In this review, the development of current approved EGFR-TKIs as well as the related supporting clinical trials are summarized and discussed. Mechanisms of action and resistance were addressed respectively, which serve as important guides to understanding acquired resistance. We also explored the corresponding combination treatment options according to different resistance mechanisms. Future challenges include more comprehensive characterization of unclear resistance mechanisms in different populations and the development of more efficient and precision synthetic therapeutic strategies.

Chemotherapy Plus Immunotherapy Versus Chemotherapy Plus Bevacizumab Versus Chemotherapy Alone in EGFR-Mutant NSCLC After Progression on Osimertinib

INTRODUCTION

Patients with EGFR-mutant lung cancer who have had disease progression on osimertinib commonly receive platinum doublet chemotherapy, but whether adding immunotherapy or bevacizumab provides additional benefit is unknown.

MATERIALS AND METHODS

This was a retrospective analysis at 2 university-affiliated institutions. Patients with EGFR-mutant lung cancer who had progression on osimertinib and received next-line therapy with platinum doublet chemotherapy (chemo), platinum doublet chemotherapy plus immunotherapy (chemo-IO), or platinum doublet chemotherapy plus bevacizumab (chemo-bev), were identified; patients who continued osimertinib with these regimens were included. Efficacy outcomes including duration on treatment (DOT) and overall survival (OS) from the start of chemotherapy were assessed. Associations of treatment regimen with outcomes were evaluated using adjusted Cox regression models, using pairwise comparisons between groups.

RESULTS

104 patients were included: 57 received chemo, 12 received chemo-IO, and 35 received chemo-bev. In adjusted models, patients who received chemo-IO had worse OS than did those who received chemo (hazard ratio (HR) 2.66, 95% CI 1.25-5.65; P= .011) or those who received chemo-bev (HR 2.37, 95% CI 1.09-5.65; P= .030). A statistically significant difference in OS could not be detected in patients who received chemo-bev versus those who received chemo (HR 1.50, 95% CI 0.84-2.69; P= .17).

CONCLUSION

In this retrospective study, giving immunotherapy with platinum doublet chemotherapy after progression on osimertinib was associated with a worse OS compared with platinum doublet chemotherapy alone. Platinum doublet chemotherapy without immunotherapy (with consideration of continuation of osimertinib, in selected cases) is a reasonable choice in this setting, while we await results of clinical trials examining optimal next-line chemotherapy-based regimens in EGFR-mutant lung cancer.

Globally Approved EGFR Inhibitors: Insights into Their Syntheses, Target Kinases, Biological Activities, Receptor Interactions, and Metabolism

Targeting the EGFR with small-molecule inhibitors is a confirmed valid strategy in cancer therapy. Since the FDA approval of the first EGFR-TKI, erlotinib, great efforts have been devoted to the discovery of new potent inhibitors. Until now, fourteen EGFR small-molecule inhibitors have been globally approved for the treatment of different types of cancers. Although these drugs showed high efficacy in cancer therapy, EGFR mutations have emerged as a big challenge for these drugs. In this review, we focus on the EGFR small-molecule inhibitors that have been approved for clinical uses in cancer therapy. These drugs are classified based on their chemical structures, target kinases, and pharmacological uses. The synthetic routes of these drugs are also discussed. The crystal structures of these drugs with their target kinases are also summarized and their bonding modes and interactions are visualized. Based on their binding interactions with the EGFR, these drugs are also classified into reversible and irreversible inhibitors. The cytotoxicity of these drugs against different types of cancer cell lines is also summarized. In addition, the proposed metabolic pathways and metabolites of the fourteen drugs are discussed, with a primary focus on the active and reactive metabolites. Taken together, this review highlights the syntheses, target kinases, crystal structures, binding interactions, cytotoxicity, and metabolism of the fourteen globally approved EGFR inhibitors. These data should greatly help in the design of new EGFR inhibitors.

The correlation of WDR76 expression with survival outcomes and immune infiltrates in lung adenocarcinoma

Background

WD repeat domain 76 (WDR76) is a predicted member of the WD40-repeat-containing domain superfamily and possibly involves in various biological processes, but its function in cancers is poorly characterized. This study aimed to evaluate the role of WDR76 in the prognosis and immune infiltrates of lung adenocarcinoma (LUAD).

Methods

WDR76 expressions in LUAD tissues and normal tissues were primarily compared by The Cancer Genome Atlas (TCGA) database, and were validated in cohorts from Gene Expression Omnibus (GEO) database. The associations between WDR76 expression and clinicopathologic characteristics were analyzed. Kaplan–Meier and Cox regression analyses were performed to determine the impact of WDR76 expression on survival outcomes. The protein interaction network of WDR76 was built using STRING website. TIMER and GEPIA databases were used to investigate the correlation between WDR76 expression and immune infiltrates.

Results

WDR76 expression was elevated in LUAD (P < 0.001) and high WDR76 expression was associated with advanced N stage, M stage and pathologic stage. Expectedly, high WDR76 expression significantly correlated with poor survival outcomes and was the independent risk factor for overall survival (OS) (HR 1.468, 95% CI [1.031–2.089], P = 0.033) and disease specific survival (DSS) (HR 1.764, 95% CI [1.095–2.842], P = 0.020). DDB1 and LSH were the important proteins interacting with WDR76. WDR76 expression correlated with CD8+ T cells presence and was also positively associated with levels of inhibitory receptors.

Conclusion

WDR76 expression was involved in the regulation of immune infiltrates and had predictive value for prognosis in LUAD.

Hsa_circ_0005576 promotes osimertinib resistance through the miR-512-5p/IGF1R axis in lung adenocarcinoma cells

Osimertinib is a third‐generation epidermal growth factor receptor tyrosine kinase inhibitor (EGFR‐TKI) for lung adenocarcinoma (LUAD) harboring activating mutations, but patients ultimately develop acquired resistance. Circular RNAs are involved in EGFR‐TKI resistance, while the role of hsa_circ_0005576 in the osimertinib resistance of LUAD remains unknown. In this study, we demonstrated that hsa_circ_0005576 could facilitate osimertinib‐resistant LUAD cells. Briefly, knockdown of hsa_circ_0005576 not only suppressed the proliferation and promoted the apoptosis of resistant LUAD cells, but also increased their sensitivity to osimertinib. Mechanistically, hsa_circ_0005576, serving as an miRNA sponge, could directly interact with miR‐512‐5p and subsequently upregulate the miR‐512‐5p‐targeted insulin‐like growth factor 1 receptor. Rescue assays indicated that miR‐512‐5p inhibition could reverse the effects of hsa_circ_0005576 knockdown in LUAD cells resistant to osimertinib. Overall, our study revealed that hsa_circ_0005576 regulates proliferation and apoptosis through miR‐512‐5p/IGF1R signaling, which contributes further to the resistance of LUAD cells to osimertinib. In addition, this study provides a novel insight into the mechanisms underlying osimertinib resistance of LUAD.

Overall Treatment Strategy for Patients With Metastatic NSCLC With Activating EGFR Mutations

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (EGFR-TKIs) are standard of care in the first-line (1L) setting for patients with metastatic non-small cell lung cancer (mNSCLC) with activating EGFR mutations. EGFR-activating mutations are a predictive factor for response to EGFR-TKIs. Meta-analyses have shown that patients with exon 21_L858R mutations exhibit reduced sensitivity to EGFR-TKIs, resulting in inferior patient outcomes compared to those with exon 19 deletion mutations, with worse overall survival, progression-free survival, objective response, and disease control rates. Clinical activity observed with 1L therapy with first-generation (1G), second-generation (2G), and third-generation (3G) EGFR-TKIs is not permanent, and resistance inevitably develops in all cases, supporting the importance of overall treatment planning. The introduction of the 3G EGFR-TKI, osimertinib, provides an opportunity to overcome T790M-mediated resistance to 1G, and 2G EGFR-TKIs. Additionally, with the use of osimertinib, fewer T790M mutations are being detected as T790M is not a reported resistance mechanism to 3G EGFR-TKIs. However, there are currently no approved targeted therapies after 3G EGFR-TKIs. In order to further improve patient outcomes, there is a need to explore additional options for the overall treatment strategy for patients, including 1L and beyond. Combination of vascular endothelial growth factor (VEGF) inhibitors and EGFR-TKIs or chemotherapy and EGFR-TKIs may be a potential therapeutic approach in the 1L setting. This review discusses current treatment options for mNSCLC with activating EGFR mutations based on tumor, patient, and treatment characteristics and how an overall treatment plan may be developed.

Liquid Biopsy for Advanced NSCLC: A Consensus Statement From the International Association for the Study of Lung Cancer

Although precision medicine has had a mixed impact on the clinical management of patients with advanced-stage cancer overall, for NSCLC, and more specifically for lung adenocarcinoma, the advances have been dramatic, largely owing to the genomic complexity and growing number of druggable oncogene drivers. Furthermore, although tumor tissue is historically the "accepted standard" biospecimen for these molecular analyses, there are considerable innate limitations. Thus, liquid biopsy represents a practical alternative source for investigating tumor-derived somatic alterations. Although data are most robust in NSCLC, patients with other cancer types may also benefit from this minimally invasive approach to facilitate selection of targeted therapies. The liquid biopsy approach includes a variety of methodologies for circulating analytes. From a clinical point of view, plasma circulating tumor DNA is the most extensively studied and widely adopted alternative to tissue tumor genotyping in solid tumors, including NSCLC, first entering clinical practice for detection of EGFR mutations in NSCLC. Since the publication of the first International Association for the Study of Lung Cancer (IASLC) liquid biopsy statement in 2018, several additional advances have been made in this field, leading to changes in the therapeutic decision-making algorithm for advanced NSCLC and prompting this 2021 update. In view of the novel and impressive technological advances made in the past few years, the growing clinical application of plasma-based, next-generation sequencing, and the recent Food and Drug and Administration approval in the United States of two different assays for circulating tumor DNA analysis, IASLC revisited the role of liquid biopsy in therapeutic decision-making in a recent workshop in October 2020 and the question of "plasma first" versus "tissue first" approach toward molecular testing for advanced NSCLC. Moreover, evidence-based recommendations from IASLC provide an international perspective on when to order which test and how to interpret the results. Here, we present updates and additional considerations to the previous statement article as a consensus from a multidisciplinary and international team of experts selected by IASLC.

A Biparatopic Antibody-Drug Conjugate to Treat MET-Expressing Cancers, Including Those that Are Unresponsive to MET Pathway Blockade

Lung cancers harboring mesenchymal-to-epithelial transition factor (MET) genetic alterations, such as exon 14 skipping mutations or high-level gene amplification, respond well to MET-selective tyrosine kinase inhibitors (TKI). However, these agents benefit a relatively small group of patients (4%-5% of lung cancers), and acquired resistance limits response durability. An antibody-drug conjugate (ADC) targeting MET might enable effective treatment of MET-overexpressing tumors (approximately 25% of lung cancers) that do not respond to MET targeted therapies. Using a protease-cleavable linker, we conjugated a biparatopic METxMET antibody to a maytansinoid payload to generate a MET ADC (METxMET-M114). METxMET-M114 promotes substantial and durable tumor regression in xenografts with moderate to high MET expression, including models that exhibit innate or acquired resistance to MET blockers. Positron emission tomography (PET) studies show that tumor uptake of radiolabeled METxMET antibody correlates with MET expression levels and METxMET-M114 efficacy. In a cynomolgus monkey toxicology study, METxMET-M114 was well tolerated at a dose that provides circulating drug concentrations that are sufficient for maximal antitumor activity in mouse models. Our findings suggest that METxMET-M114, which takes advantage of the unique trafficking properties of our METxMET antibody, is a promising candidate for the treatment of MET-overexpressing tumors, with the potential to address some of the limitations faced by the MET function blockers currently in clinical use.

Iterative Upgrading of Small Molecular Tyrosine Kinase Inhibitors for EGFR Mutation in NSCLC: Necessity and Perspective

Molecular targeted therapy has been reported to have fewer adverse effects, and offer a more convenient route of administration, compared with conventional chemotherapy. With the development of sequencing technology, and research on the molecular biology of lung cancer, especially whole-genome information on non-small cell lung cancer (NSCLC), various therapeutic targets have been unveiled. Among the NSCLC-driving gene mutations, epidermal growth factor receptor (EGFR) mutations are the most common, and approximately 10% of Caucasian, and more than 50% of Asian, NSCLC patients have been found to have sensitive EGFR mutations. A variety of targeted therapeutic agents for EGFR mutations have been approved for clinical applications, or are undergoing clinical trials around the world. This review focuses on: the indications of approved small molecular kinase inhibitors for EGFR mutation-positive NSCLC; the mechanisms of drug resistance and the corresponding therapeutic strategies; the principles of reasonable and precision molecular structure; and the drug development discoveries of next-generation inhibitors for EGFR.

Triple therapy with osimertinib, bevacizumab and cetuximab in EGFR-mutant lung cancer with HIF-1α/TGF-α expression

Osimertinib, a third generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, is the standard treatment for patients with lung cancer harboring EGFR T790M; however, acquired resistance is inevitable due to genetic and epigenetic changes in cancer cells. In addition, a recent randomized clinical trial revealed that the combination of osimertinib and bevacizumab failed to exhibit superior progression-free survival compared with osimertinib alone. The present study aimed to investigate the effect of triple therapy with osimertinib, bevacizumab and cetuximab in xenograft tumors with different initial tumor volumes (conventional model, 200 mm3 and large model, 500 mm3). The results demonstrated that osimertinib significantly inhibited tumor growth in both the conventional and large models; however, maximum tumor regression was attenuated in the large model in which hypoxia-inducible factor-1α (HIF-1α) and transforming growth factor-α (TGF-α) expression levels increased. Although the combination of osimertinib and bevacizumab exerted a greater inhibitory effect on tumor growth compared with osimertinib in the conventional model, the effect of this combination therapy was attenuated in the large model. TGF-α attenuated sensitivity to osimertinib in vitro; however, this negative effect was counteracted by the combination of osimertinib and cetuximab, but not osimertinib and bevacizumab. In the large xenograft tumor model, the triple therapy induced the greatest inhibitory effect on tumor growth compared with osimertinib alone and its combination with bevacizumab. Clinical trials of the triple therapy are required for patients with lung cancer with EGFR mutations and HIF-1α/TGF-α.

Comparison of the outcome between immunotherapy alone or in combination with chemotherapy in EGFR-mutant non-small cell lung cancer

Whether ICIs combined with chemotherapy can improve outcomes in EGFR-mutant non-small cell lung cancer (NSCLC) remains uncertain. Patients with EGFR-mutant NSCLC and who progressed on first-line EGFR-TKIs treatment were retrospectively collected. We reviewed the outcome of these patients treated with ICIs or ICIs combined chemotherapy (ICI + C). Total 30 patients were included. The ORR were 9.1% and 25.0% for the ICI and ICI + C groups. The ICI + C group showed the trend of longer progression-free survival and overall survival periods. Patients without the T790M mutation had a significantly longer PFS than did those without this mutation (4.23 [95% CI: 2.75–5.72] vs. 1.70 [95% CI: 0.00–3.51] months, HR:4.45, p = 0.019). ICIs combined with chemotherapy tended to be more effective than ICIs alone in pretreated EGFR-mutant NSCLC. The T790M mutation may be a potential biomarker.

PTEN/AKT upregulation of TMSB10 contributes to lung cancer cell growth and predicts poor survival of the patients

PTEN/AKT signaling cascade is frequently activated in various cancers, including lung cancer. The downstream effector of this signaling cascade is poorly understood. β-Thymosin 10 (TMSB10) functions as an oncogene or tumor suppressors in cancers, whereas its significance in lung cancer remains unknown. In this study, we showed that the activation of PTEN/AKT signaling promoted the expression of TMSB10. Based on the TCGA database, TMSB10 was upregulated in lung cancer tissues and its overexpression was correlated with poor prognosis of lung cancer patients. Functional experiments demonstrated that TMSB10 knockdown suppressed, while its overexpression promoted the proliferation, growth, and migration of lung cancer cells. Apoptosis and epithelial-mesenchymal transition were also regulated by TMSB10. We therefore suggest that TMSB10 is a novel oncogene for lung cancer. Targeting TMSB10 may benefit lung cancer patients with activated PTEN/AKT signaling.

The treatment of advanced lung adenocarcinoma with activating EGFR mutations

INTRODUCTION

Lung adenocarcinomas account for approximately 40-50% of all NSCLC (Non-Small Cell Lung Cancer) cases. In addition, lung adenocarcinomas can harbor several different genetic mutations, EGFR (Epidermal Growth Factor Receptor) being the most frequent one, accounting for approximately 5-15% of all the mutations in western patients and for approximately 40-55% in Asian patients; on the other hand, EGFR mutations are uncommon in squamous histology. Approximately 90% of EGFR mutations are represented by exon 19 in-frame deletion and by the L858R exon 21-point mutation, that confer sensitivity to EGFR TKI (Tyrosine Kinase Inhibitors) treatment.

AREAS COVERED

The authors comprehensively review the current state of the art with reference to EGFR+ NSCLC treatment and to discuss the possible future developments.

EXPERT OPINION

Osimertinib must be considered the preferred first-line agent in EGFR+ advanced NSCLC patients thanks to its superior performances. With respect to acquired resistance mechanisms to osimertinib, the currently ongoing clinical trials will surely help us to better understand and tackle them. Globally, we strongly believe that a biomarker-driven sequential treatment algorithm is key in order to provide personalized, effective and durable therapies in the increasingly complex landscape of EGFR+ advanced NSCLC.

Generation and Characterization of a New Preclinical Mouse Model of EGFR-Driven Lung Cancer with MET-Induced Osimertinib Resistance

Simple Summary

The use of targeted therapy has changed the clinical management of lung cancer patients, increasing both their life quality and expectancy. Conversely, the appearance of resistance occurs in almost all patients receiving this therapy. In this regard, new strategies combining different therapies could delay or even eliminate the appearance of resistance. However, in order to develop new therapeutic treatments, we need preclinical mouse models that recapitulate human disease. In the present study, we developed a new state-of-the-art mouse model that summarizes all features occurring in EGFR-mutated patients that relapse after osimertinib after acquisition of MET amplification.

Abstract

Despite the introduction of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) to treat advanced lung cancer harboring EGFR-activating mutations, the prognosis remains unfavorable because of intrinsic and/or acquired resistance. We generated a new state-of-the-art mouse strain harboring the human EGFR^T790M/L858R oncogene and MET overexpression (EGFR/MET strain) that mimics the MET amplification occurring in one out of five patients with EGFR-mutated lung cancer that relapsed after treatment with osimertinib, a third-generation anti-EGFR TKI. We found that survival was reduced in EGFR/MET mice compared with mice harboring only EGFR^T790M/L858R (EGFR strain). Moreover, EGFR/MET-driven lung tumors were resistant to osimertinib, recapitulating the phenotype observed in patients. Conversely, as also observed in patients, the crizotinib (anti-MET TKI) and osimertinib combination improved survival and reduced tumor burden in EGFR/MET mice, further validating the model’s value for preclinical studies. We also found that in EGFR/MET mice, MET overexpression negatively regulated EGFR activity through MIG6 induction, a compensatory mechanism that allows the coexistence of the two onco-genic events. Our data suggest that single EGFR or MET inhibition might not be a good therapeutic option for EGFR-mutated lung cancer with MET amplification, and that inhibition of both pathways should be the best clinical choice in these patients.

Inhibition of MEK5/ERK5 signaling overcomes acquired resistance to the third generation EGFR inhibitor, osimertinib, via enhancing Bim-dependent apoptosis

The promising therapeutic efficacy of the third generation EGFR inhibitor, osimertinib (AZD9291), for the treatment of patients with EGFR-mutant non-small cell lung cancer (NSCLC) has been demonstrated in the clinic both as first-line and second line therapy. However, inevitable acquired resistance limits its long-term benefit to patients and is thus a significant clinical challenge. The current study focuses on studying the potential role of targeting MEK5-ERK5 signaling in overcoming acquired resistance to osimertinib. Osimertinib and other third generation EGFR inhibitors exerted a rapid and sustained suppressive effect on ERK5 phosphorylation primarily in EGFR-mutant NSCLC cell lines and lost this activity in some osimertinib-resistant cell lines. Osimertinib combined with either ERK5 or MEK5 inhibitors synergistically decreased the survival of osimertinib-resistant cell lines with enhanced induction of apoptosis primarily via augmenting Bim expression. Moreover, the combination effectively inhibited the growth of osimertinib-resistant xenografts in vivo. Together, these findings suggest the potential role of MEK5-ERK5 signaling in modulating development of acquired resistance to osimertinib and value of targeting this signaling as a potential strategy in overcoming acquired resistance to osimertinib and possibly other third generation EGFR inhibitors.

An integrated DNA and RNA variant detector identifies a highly conserved three base exon in the MAP4K5 kinase locus

RNA variants that emerge from editing and alternative splicing form important regulatory stages in protein signalling. In this report, we apply an integrated DNA and RNA variant detection workbench to define the range of RNA variants that deviate from the reference genome in a human melanoma cell model. The RNA variants can be grouped into (i) classic ADAR-like or APOBEC-like RNA editing events and (ii) multiple-nucleotide variants (MNVs) including three and six base pair in-frame non-canonical unmapped exons. We focus on validating representative genes of these classes. First, clustered non-synonymous RNA edits (A-I) in the CDK13 gene were validated by Sanger sequencing to confirm the integrity of the RNA variant detection workbench. Second, a highly conserved RNA variant in the MAP4K5 gene was detected that results most likely from the splicing of a non-canonical three-base exon. The two RNA variants produced from the MAP4K5 locus deviate from the genomic reference sequence and produce V569E or V569del isoform variants. Low doses of splicing inhibitors demonstrated that the MAP4K5-V569E variant emerges from an SF3B1-dependent splicing event. Mass spectrometry of the recombinant SBP-tagged MAP4K5^V569E and MAP4K5^V569del proteins pull-downs in transfected cell systems was used to identify the protein-protein interactions of these two MAP4K5 isoforms and propose possible functions. Together these data highlight the utility of this integrated DNA and RNA variant detection platform to detect RNA variants in cancer cells and support future analysis of RNA variant detection in cancer tissue.

Potentiating Therapeutic Effects of Epidermal Growth Factor Receptor Inhibition in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is a subset of breast cancer with aggressive characteristics and few therapeutic options. The lack of an appropriate therapeutic target is a challenging issue in treating TNBC. Although a high level expression of epidermal growth factor receptor (EGFR) has been associated with a poor prognosis among patients with TNBC, targeted anti-EGFR therapies have demonstrated limited efficacy for TNBC treatment in both clinical and preclinical settings. However, with the advantage of a number of clinically approved EGFR inhibitors (EGFRis), combination strategies have been explored as a promising approach to overcome the intrinsic resistance of TNBC to EGFRis. In this review, we analyzed the literature on the combination of EGFRis with other molecularly targeted therapeutics or conventional chemotherapeutics to understand the current knowledge and to provide potential therapeutic options for TNBC treatment.

A real world analysis of first line treatment of advanced EGFR mutated non-small cell lung cancer: A multi-center, retrospective study

INTRODUCTION

The recently published FLAURA trial demonstrated that osimertinib has remarkable efficacy in front-line setting for non-small cell lung cancer (NSCLC). While this has transformed current practice, there are no effective treatments following progression on osimertinib. The aim of our study was to compare progression-free survival (PFS) and overall survival (OS) between patients initiated on osimertinib to those started on other EGFR TKIs.

METHODS

This was a multicenter, retrospective study conducted at two large academic centers. Adult patients with EGFR-mutated non-small cell lung cancer (NSCLC) who received EGFR therapy between 2014 and 2019 were included. Patients were dichotomized based on front-line TKI (osimertinib vs. other). PFS, OS, and time-to-discontinuation were evaluated.

RESULTS

One-hundred seventy-two patients were included in the final analysis. Fifty-two (30.2%) patients received osimertinib and 120 (69.8%) patients received another EGFR TKI. The PFS rates at 6, 12, and 18 months were 86.3%, 79.5%, 69.8% in the osimertinib group and 86.6%, 64.2%, 39.3% in the other EGFR TKI group, respectively (p < 0.0036).Estimated OS at 6, 12, and 18 months was similar for both groups: 94.2%, 94.2%, 80.2% and 95.7%, 93.9%, 84.1%, respectively [Adjusted HR = 0.95 (95% CI, 0.37-2.44; p < 0.9128].

CONCLUSION

Osimertinib demonstrated greater 12 and 18 month PFS compared to other EGFR TKIs. This finding is consistent with results of the FLAURA trial. However, unlike FLAURA, there were no differences in estimated OS between the two groups in our study. Further research to evaluate optimal sequencing strategies in the real world of first, second and third generation TKIs is needed.

Precision Medicine in Oncology: A Review of Multi-Tumor Actionable Molecular Targets with an Emphasis on Non-Small Cell Lung Cancer

Precision medicine is essential for the modern care of a patient with cancer. Comprehensive molecular profiling of the tumor itself is necessary to determine the presence or absence of certain targetable abnormalities or biomarkers. In particular, lung cancer is a disease for which targetable genomic alterations will soon guide therapy in the majority of cases. In this comprehensive review of solid tumor-based biomarkers, we describe the genomic alterations for which targeted agents have been approved by the United States Food and Drug Administration (FDA). While focusing on alterations leading to approvals in a tumor-agnostic fashion (MSI-h, TMB-h, NTRK) and on those alterations with approvals in multiple malignancies (BRAF, ERBB2, RET, BRCA, PD-L1), we also describe several biomarkers or indications that are likely to lead to an approved drug in the near future (e.g., KRAS G12C, PD-L1 amplification, HER2 overexpression in colon cancer, HER2 mutations in lung cancer). Finally, we detail the current landscape of additional actionable alterations (EGFR, ALK, ROS1, MET) in lung cancer, a biomarker-rich malignancy that has greatly benefitted from the precision oncology revolution.

First-Line Afatinib plus Cetuximab for EGFR-Mutant Non-Small Cell Lung Cancer: Results from the Randomized Phase II IFCT-1503 ACE-Lung Study

PURPOSE

Double inhibition of epidermal growth factor receptor (EGFR) using a tyrosine kinase inhibitor plus a monoclonal antibody may be a novel treatment strategy for non-small cell lung cancer (NSCLC). We assessed the efficacy and toxicity of afatinib + cetuximab versus afatinib alone in the first-line treatment of advanced EGFR-mutant NSCLC.

PATIENTS AND METHODS

In this phase II, randomized, open-label study, patients with stage III/IV EGFR-positive NSCLC were randomly assigned (1:1) to receive afatinib (group A) or afatinib + cetuximab (group A + C). Oral afatinib 40 mg was given once daily; cetuximab 250 mg/m² was administered intravenously on day 15 of cycle 1, then every 2 weeks at 500 mg/m² for 6 months. The primary endpoint was time to treatment failure (TTF) rate at 9 months. Exploratory analysis of EGFR circulating tumor DNA in plasma was performed.

RESULTS

Between June 2016 and November 2018, 59 patients were included in group A and 58 in group A + C. The study was ended early after a futility analysis was performed. The percentage of patients without treatment failure at 9 months was similar for both groups (59.3% for group A vs. 64.9% for group A + C), and median TTF was 11.1 (95% CI, 8.5-14.1) and 12.9 (9.2-14.5) months, respectively. Other endpoints, including progression-free survival and overall survival, also showed no improvement with the combination versus afatinib alone. There was a slight numerical increase in grade ≥3 adverse events in group A + C. Allele frequency of the EGFR gene mutation in circulating tumor DNA at baseline was associated with shorter PFS, regardless of the treatment received.

CONCLUSIONS

These results suggest that addition of cetuximab to afatinib does not warrant further investigation in treatment-naïve advanced EGFR-mutant NSCLC.

Genetic Analysis and Operative Outcomes in Patients with Oncogene-Driven Advanced NSCLC Treated with Cytoreductive Surgery as a Component of Local Consolidative Therapy

Simple Summary

The efficacy of the local consolidative therapy in lung cancer has been reported previously, however, those studies described the utility of the radiation therapy rather than of surgery. Furthermore, those studies included either no or few patients with oncogene-driven NSCLC, which has distinct biological properties and treatment options. Surgery is the most reliable method of tumor removal that allows detailed examinations of resected tissue, such as comprehensive genetic analysis. This retrospective study for the first time reports the operative outcomes and the benefit of cytoreductive surgery in TKI-treated cases of oncogene-driven locally advanced or metastatic NSCLC in parallel with the genetic analysis of the tumor.

Abstract

Most patients with oncogene-driven advanced non-small cell lung cancer (NSCLC) demonstrate recurrence because of the developing targeted therapy resistance. In this retrospective study, we assessed the efficacy of surgical local consolidative treatment by analyzing the operative outcomes and genetic data in 44 patients who underwent pulmonary resection for stage IIIB/C–IV NSCLC after targeted therapy. The initial mutations were in the EGFR (n = 32), ALK (n = 11), and ROS1 (n = 1) genes. The median interval from the initiation of tyrosine kinase inhibitor (TKI) therapy immediately before the surgery to the actual operation was 9.8 months. Operative mortality was absent. Four patients showed complete remission. The median follow-up period after TKI therapy initiation was 23.1 months. The Kaplan–Meier survival analysis showed that the 2-year failure-free survival and overall survival rates from the initiation of TKI were 70.8% and 95.0%, respectively. During the follow-up period, two patients died and 15 suffered from disease progression. Among the 32 patients with EGFR mutations, 12 showed additional mutations, and targeted agents were replaced in nine patients after the operation. We conclude that pulmonary resection for advanced NSCLC after targeted therapy is feasible, and the surgical specimens could be used for planning further targeted therapy.

Real-world data on treatment outcomes in EGFR-mutant non-small-cell lung cancer patients receiving osimertinib in second or further lines

Aims: This study describes real-world outcomes of pretreated EGFR T790M-positive (T790M⁺) advanced non-small-cell lung cancer patients progressing after first- or second-generation tyrosine kinase inhibitors and receiving osimertinib, compared with T790M-negative (T790M^-) patients. We have also described progression patterns and treatment sequences. Patients & methods: This is a retrospective multicenter Italian observational study including consecutive Caucasian patients referred between 2014 and 2018. Results: 167 patients were included. Median progression-free survival was 9.8 months (95% CI: 8.3-13.3) for T790M⁺ and 6.0 months (95% CI: 4.9-7.2) for T790M^- patients, respectively. Median overall survival was 20.7 months (95% CI: 18.9-28.4) for T790M⁺ and 10.6 months (95% CI: 8.6-23.6) for T790M^- patients, respectively. The T790M mutation correlated with absence of new sites of disease. After progression, most T790M⁺ patients continued osimertinib, whereas most T790M^- patients received a different treatment line. Conclusion: Better outcomes were shown in patients receiving osimertinib. A more limited progression pattern for T790M⁺ was suggested.

Small Cell Lung Cancer Transformation as a Resistance Mechanism to Osimertinib in Epidermal Growth Factor Receptor-Mutated Lung Adenocarcinoma: Case Report and Literature Review

Introduction: Small cell lung cancer (SCLC) transformation represents a mechanism of resistance to osimertinib in EGFR-mutated lung adenocarcinoma, which dramatically impacts patients' prognosis due to high refractoriness to conventional treatments. Case Description: We present the case of a patient who developed a SCLC phenotypic transformation as resistance mechanism to second-line osimertinib for T790M-positive EGFR-mutated NSCLC. Our patient received platinum-etoposide doublet following SCLC switch and achieved a modest clinical benefit which lasted 4 months. NGS and IHC analyses for p53 and Rb were performed on subsequent liver biopsies, revealing baseline TP53 mutation and complete absence of p53 and Rb expression. Primary cell cultures were established following a liver biopsy at the time of SCLC transformation, and drug sensitivity assays showed meaningful cell growth inhibition when osimertinib was added to platinum-etoposide compared with control (p < 0.05). A review of the current literature regarding SCLC transformation after failure of osimertinib was performed. Conclusions: Based on retrospective data available to date, platinum-etoposide chemotherapy is the preferred treatment choice in the occurrence of SCLC transformation after osimertinib failure. The extension of osimertinib in combination with chemotherapy in the occurrence of SCLC transformation as resistance mechanism to osimertinib is a matter of debate. The combination of osimertinib and platinum-etoposide was effective in inhibiting cell growth in our primary cell cultures. Clinical studies are needed to further explore this combination in the occurrence of SCLC transformation as a resistance mechanism to osimertinib.

An update of new small-molecule anticancer drugs approved from 2015 to 2020

A high incidence of cancer has given rise to the development of more anti-tumor drugs. From 2015 to 2020, fifty-six new small-molecule anticancer drugs, divided into ten categories according to their anti-tumor target activities, have been approved. These include TKIs (30 drugs), MAPK inhibitors (3 drugs), CDK inhibitors (3 drugs), PARP inhibitors (3 drugs), PI3K inhibitors (3 drugs), SMO receptor antagonists (2 drugs), AR antagonists (2 drugs), SSTR inhibitors (2 drugs), IDH inhibitors (2 drugs) and others (6 drugs). Among them, PTK inhibitors (30/56) have led to a paradigm shift in cancer treatment with less toxicity and more potency. Each of their structures, approval statuses, applications, SAR analyses, and original research synthesis routes have been summarized, giving us a more comprehensive map for further efforts to design more specific targeted agents for reducing cancer in the future. We believe this review will help further research of potential antitumor agents in clinical usage.

Downregulation of death receptor 4 is tightly associated with positive response of EGFR mutant lung cancer to EGFR-targeted therapy and improved prognosis

Death receptor 4 (DR4), a cell surface receptor, mediates apoptosis or induces inflammatory cytokine secretion upon binding to its ligand depending on cell contexts. Its prognostic impact in lung cancer and connection between EGFR-targeted therapy and DR4 modulation has not been reported and thus was the focus of this study. Methods: Intracellular protein alterations were measured by Western blotting. Cell surface protein was detected with antibody staining and flow cytometry. mRNA expression was monitored with qRT-PCR. Gene transactivation was analyzed with promoter reporter assay. Drug dynamic effects in vivo were evaluated using xenografts. Gene modulations were achieved with gene overexpression and knockdown. Proteins in human archived tissues were stained with immunohistochemistry. Results: EGFR inhibitors (e.g., osimertinib) decreased DR4 levels only in EGFR mutant NSCLC cells and tumors, being tightly associated with induction of apoptosis. This modulation was lost once cells became resistant to these inhibitors. Increased levels of DR4 were detected in cell lines with acquired osimertinib resistance and in NSCLC tissues relapsed from EGFR-targeted therapy. DR4 knockdown induced apoptosis and augmented apoptosis when combined with osimertinib in both sensitive and resistant cell lines, whereas enforced DR4 expression significantly attenuated osimertinib-induced apoptosis. Mechanistically, osimertinib induced MARCH8-mediated DR4 proteasomal degradation and suppressed MEK/ERK/AP-1-dependent DR4 transcription, resulting in DR4 downregulation. Moreover, we found that DR4 positive expression in human lung adenocarcinoma was significantly associated with poor patient survival. Conclusions: Collectively, we suggest that DR4 downregulation is coupled to therapeutic efficacy of EGFR-targeted therapy and predicts improved prognosis, revealing a previously undiscovered connection between EGFR-targeted therapy and DR4 modulation.

Managing Acquired Resistance to Third-Generation EGFR Tyrosine Kinase Inhibitors Through Co-Targeting MEK/ERK Signaling

Although epidermal growth factor receptor (EGFR)-targeted therapy has improved clinical outcomes of patients with advanced non-small-cell lung cancer (NSCLC) carrying activating EGFR mutations, the development of acquired resistance to EGFR tyrosine kinase inhibitors (EGFR-TKIs), including the promising third-generation ones, results in disease progression and has become an unavoidable problem that limits patient long-term benefit. The third-generation EGFR-TKIs, osimertinib and almonertinib, are now approved for the treatment of advanced NSCLC patients harboring activating EGFR mutations (first-line) and/or the resistant T790M mutation (second-line). Clinically, appropriate management of acquired resistance to third-generation EGFR-TKIs will substantially improve their long-term efficacy against EGFR-mutant NSCLC. Recent preclinical and clinical studies suggest that activation of the Ras/Raf/MEK/ERK signaling pathway may be an important resistance mechanism and accordingly co-targeting this pathway effectively overcomes and abrogates acquired resistance to third-generation EGFR-TKIs. This review focuses on discussing the scientific rationale for and potential of co-targeting MEK/ERK signaling in delaying and overcoming acquired resistance to third-generation EGFR-TKIs, particularly osimertinib.

Impressive response to dabrafenib, trametinib, and osimertinib in a metastatic EGFR-mutant/BRAF V600E lung adenocarcinoma patient

The survival outcomes of the FLAURA trial support osimertinib as the new standard of care for untreated patients harboring activating mutations in the epidermal growth factor receptor (EGFR). Despite the initial response, disease progression invariably occurs. Although uncommon, BRAF V600E mutation arises as a unique mechanism of resistance, and thus far, no prospective studies are available to support concurrent EGFR/BRAF blockade. We report a case of impressive radiological and ctDNA response under dabrafenib, trametinib, and osimertinib in an advanced EGFR-mutant lung adenocarcinoma patient who developed BRAF V600E as one of the acquired resistance mechanisms to second-line osimertinib. Moreover, the patient experienced remarkable clinical improvement and good tolerance to combination therapy. The present case suggests the importance of prospective studies evaluating both efficacy and safety of the combination in later line settings and points towards the potential of ctDNA to monitor resistance mechanisms and treatment benefit in clinical practice.

Distinct profile of cell-free DNA in malignant pleural effusion of non-small cell lung cancer and its impact on clinical genetic testing

Cell-free DNA (cfDNA) in supernatant of pleural effusion from advanced NSCLC patients has been proved as surrogate sample detecting therapeutic targets as well as tumor mutation burden (TMB). As recently reported, cfDNA in pleural effusion supernatant is superior to plasma in TMB evaluation. It is reasonable to hypothesize that cfDNA profile in pleural effusion (PE) and plasma might be different. It remains to be elucidated why cfDNA in PE supernatant impacts on genetic analysis. Consequently, the approach dealing with cfDNA from PE supernatant might need to be different from that for plasma cfDNA in order to obtain accurate clinical genetic testing result. Methods: Pleural effusion samples from 32 patients with stage IV lung adenocarcinoma were collected. Supernatant and sediment were processed separately to extract Cell-free DNA as well as sediment DNA (PE-S). cfDNA from pleural effusion was analyzed by Agilent 2100 bioanalyzer. Libraries were prepared by 1) direct use of the total cfDNA without fragmentation step (PE-FL) or 2) use of full-length cfDNA fragmented to 150-250bp (PE-F), 3) use of cfDNA fragments enriched to ~167bp (PE-E167) as well as 4) use of cfDNA fragments larger than 500bp enriched (PE-E500). All samples were subjected to targeted next-generation sequencing (NGS) with a panel of 448 cancer-related genes as well as a panel of 10 NSCLC driver genes. Results: cfDNA were successfully extracted from 30 MPE samples. cfDNA displayed distinct profile in supernatant of malignant pleural effusion from that of plasma cfDNA. No statistical difference in detection of hotspot variations between PE-E167 and PE-F by 448-gene or 10-gene panel. While TMB from PE-F samples was significantly higher than that from PE-E167 and PE-FL. Higher TMB from PE-F was resulted from cancer-unspecific variants with low allele frequency (0.1%-1%) which were mainly introduced by long-fragment cfDNA. Similar genetic profile was observed between paired cfDNA of PE-FL and cfDNA of PE-E167. Conclusion: Long-fragment cfDNA in the PE supernatant will introduce low abundant cancer unrelated variants which leads overestimation of TMB. Paired PE-FL and PE-E167 gave comparable outcomes. Direct use of the total cfDNA without fragmentation step (PE-FL) is recommended for library preparation of NGS testing in clinical practice to exclude interference from long fragments of the cfDNA.

Combining Osimertinib With Chemotherapy in EGFR-Mutant NSCLC at Progression

BACKGROUND

Osimertinib is a third-generation EGFR tyrosine kinase inhibitor that has improved survival and central nervous system (CNS) outcomes in patients with non-small cell lung cancer (NSCLC) with activating EGFR mutations. However, little is known about the efficacy and safety of combining osimertinib with chemotherapy.

METHODS

This was a retrospective study performed at 3 institutions. Patients with advanced EGFR-mutated NSCLC who received concurrent osimertinib with chemotherapy in the third-line or beyond were identified by chart review. Efficacy outcomes including duration on treatment (DOT), overall survival (OS), and CNS outcomes were assessed. Safety outcomes were also evaluated.

RESULTS

A total of 44 patients met inclusion criteria. Median DOT with osimertinib plus platinum doublet (n = 28) was 6.1 months (95% CI 4.1 months-not reached), and with osimertinib plus single-agent chemotherapy (n = 29) was 2.6 months (95% CI 1.8-4.8 months). Median OS from the start of osimertinib plus chemotherapy was 10.4 months (95% CI 7.0-13.2 months). At initiation of osimertinib plus chemotherapy, 37 patients (84%) had CNS metastases; 9 of these (24%) had CNS disease progression on osimertinib plus chemotherapy. Chemotherapy was delayed or dose reduced due to toxicity in 8 patients (18%); osimertinib was discontinued in 1 patient (2%) for reduced cardiac ejection fraction, and dose reduced in 2 patients (5%).

CONCLUSIONS

The combination of osimertinib plus chemotherapy appeared safe and showed favorable control of CNS disease in this cohort of patients who had progressed systemically with multiple prior lines of therapy, with DOT and survival outcomes similar to historical chemotherapy controls.

Tolerant/Persister Cancer Cells and the Path to Resistance to Targeted Therapy

The capacity of cancer to adapt to treatment and evolve is a major limitation for targeted therapies. While the role of new acquired mutations is well-established, recent findings indicate that resistance can also arise from subpopulations of tolerant/persister cells that survive in the presence of the treatment. Different processes contribute to the emergence of these cells, including pathway rebound through the release of negative feedback loops, transcriptional rewiring mediated by chromatin remodeling and autocrine/paracrine communication among tumor cells and within the tumor microenvironment. In this review, we discuss the non-genetic mechanisms that eventually result in cancer resistance to targeted therapies, with a special focus on those involving changes in gene expression.

Genotyping of Cerebrospinal Fluid Associated With Osimertinib Response and Resistance for Leptomeningeal Metastases in EGFR-Mutated NSCLC

INTRODUCTION

Patients with NSCLC with leptomeningeal metastases (LM) presented dismal prognosis. Cerebrospinal fluid (CSF) is suggested as a medium of liquid biopsy of LM. However, the clinical implications of CSF genotyping on treatment outcomes remained elusive.

METHODS

Patients with EGFR-mutated advanced NSCLC with LM were included: cohort 1, patients with LM who were treated with osimertinib with CSF and plasma genotyping performed before the first dosing of osimertinib (baseline, n = 45); cohort 2, CSF genotyping on progression on osimertinib and development of LM (the progression event on osimertinib is the diagnosis of LM, n = 35). Circulating tumor DNA in CSF underwent next-generation sequencing.

RESULTS

Sensitivity of CSF genotyping for EGFR-sensitizing mutations was 93.3% (42 of 45) and 97.1% (34 of 35) in cohorts 1 and 2, respectively. In cohort 1, patients with EGFR exon 19 deletion had higher median intracranial progression free survival (iPFS) than those with EGFR exon 21 L858R mutation (11.9 versus 2.8 mo; p = 0.02). Median iPFS was significantly longer in patients with T790M-positive CSF genotyping (15.6 mo) than T790M-negative CSF (7.0 mo, p = 0.04). Concurrent CDK4 (2.8 versus 11.6 mo, p = 0.002) and CDKN2A (2.5 versus 9.6 mo, p = 0.04) mutation with EGFR-sensitizing mutations indicated lower median iPFS. Patients with T790M-negative CSF, EGFR exon 21 L858R mutation, concurrent FGF3 alteration, and over first-line osimertinib had shortened iPFS. In cohort 2, possible EGFR-related and EGFR-independent resistance mechanisms were found including C797S mutation, MET dysregulation, and TP53 plus RB1 co-occurrence. Patients with loss of T790M in CSF had a shorter median iPFS (7.4 mo) compared with those with reserved T790M (13.6 mo, p = 0.01).

CONCLUSIONS

Genotyping of CSF indicated heterogeneous response to osimertinib and revealed the genetic characteristic of LM on osimertinib failure in patients with EGFR-mutated NSCLC diagnosed with LM.