T790M Resistance Mutation Research Articles

Pharmacological effects of osimertinib on a chicken chorioallantoic membrane xenograft model with the EGFR exon-19-deleted advanced NSCLC mutation.

Non-small cell lung cancer (NSCLC) affects 10-50% of patients with epidermal growth factor receptor (EGFR) mutations. Osimertinib is a third-generation EGFR tyrosine kinase inhibitor (TKI) that radically changes the outcome of patients with tumors bearing EGFR sensitizing or EGFR T790M resistance mutations. However, resistance usually occurs, and new therapeutic combinations need to be explored. The chorioallantoic membrane (CAM) xenograft model is ideal for studying aggressive tumor growth and the responses to complex therapeutic combinations due to its vascularization and complex microenvironment. This study aims to demonstrate the relevance of analyzing a complex therapeutic response to osimertinib treatment, especially through advanced transcriptomic analysis with the CAM model, which has been limited thus far. We engrafted HCC827 cells (EGFR p.E746_A750del) into the CAM model and treated them with various osimertinib doses for 7 days. The study involved supervised multivariate discrimination and ontology analysis of human transcriptional data. We found that CDX tumor growth inversely correlated with osimertinib dosage, with a notable 35% tumor weight reduction at 10 μm. Transcriptomic analysis revealed that osimertinib reduces EGFR pathway activity and its effectors, and dampens chemotaxis, immune recruitment and angiogenesis, indicating that effectiveness extends beyond cellular mechanisms to the tissue level. This was supported by a 15% reduction in blood vessels around the xenograft in osimertinib-treated cases. This study is the first to demonstrate that ontological analysis of transcriptomic data in the CAM model aligns with clinical observations, highlighting the relevance of this methodology for understanding and ameliorating the efficacy of targeted therapy in NSCLC.

Observational study of the efficacy and safety of first-line osimertinib and later treatments for uncommon epidermal growth factor receptor-activating mutation-positive advanced non-small cell lung cancer.

Osimertinib, a third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, is a first-line therapy for advanced or metastatic non-small cell lung cancer (NSCLC) with EGFR mutations, including both sensitizing and T790M resistance mutations. Its real-world efficacy against uncommon EGFR mutations remains under-researched. The REIWA study, a multicentric, prospective, observational study conducted in Japan from September 2018 to August 2020, enrolled patients with advanced or recurrent EGFR mutation-positive NSCLC receiving osimertinib. Data on clinical outcomes, safety, disease progression, and subsequent treatments were collected for patients with uncommon EGFR mutations. Of 583 patients receiving osimertinib, 39 (6.7%) had an uncommon EGFR mutation. The present study included 32 of these patients after excluding seven patients with an exon 20 insertion mutation. The overall objective response rate was 53.1% [95% confidence interval (CI): 36.4-69.1], and the disease control rate was 78.1% (95% CI: 61.0-89.3). The median progression-free survival was 9.4months (95% CI: 5.0-20.0), and the median overall survival (OS) was 21.8 (95% CI: 14.4-NA) months. Notably, patients with an exon21 L861Q mutation had a significantly longer OS than those with an exon18 G719X mutation, the respective values being 37.8 and 9.7months (hazard ratio: 0.29; 95% CI: 0.10-0.85; P=0.02). The rate of grade 3 or worse adverse events was 10.3%. Seven out of 32 (21.9%) patients showed progression involving only the central nervous system. Osimertinib demonstrated efficacy and tolerability in the clinical setting in patients with uncommon EGFR mutation-positive NSCLC.

The Resistance to EGFR-TKIs in Non-Small Cell Lung Cancer

Lung cancer has emerged as a highly aggressive malignancy posing a significant global health hazard, with a particular concern for the rising incidence and mortality of gene-altered non-small cell lung cancer (NSCLC). As the prevalence of NSCLC rises, the investigation and selection of tumor treatment techniques are gaining significance. The treatment of individuals with genetic mutations in advanced NSCLC has emphasized the application of epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs). Early and subsequent generations of EGFR-TKIs have demonstrated clinical efficacy in NSCLC patients carrying select genetic alterations. Osimertinib, a third-generation EGFR-TKI, has been sanctioned as the standard first-line therapy and is also utilized as a second-line option for individuals who develop the T790M resistance mutation following prior EGFR-TKI treatment. Approximately 10 to 30 percent of patients diagnosed with NSCLC exhibit EGFR mutations. This leads to abnormal activation of cancer genes and inactivation of tumor suppressor genes, resulting in poor prognosis for patients. This paper aims to analyze the development and resistance processes of EGFR inhibitors, thereby enhancing the comprehension of the resistance pathways to EGFR-TKIs.

Inhibition of hTERT/telomerase/telomere mediates therapeutic efficacy of osimertinib in EGFR mutant lung cancer.

The inevitable acquired resistance to osimertinib (AZD9291), an FDA-approved third-generation EGFR tyrosine kinase inhibitor (EGFR-TKI) for the treatment of patients with advanced non-small cell lung cancer (NSCLC) harboring EGFR activating or T790M resistant mutations, limits its long-term clinical benefit. Telomere maintenance via telomerase reactivation is linked to uncontrolled cell growth and is a cancer hallmark and an attractive cancer therapeutic target. Our effort toward understanding the action mechanisms, including resistance mechanisms, of osimertinib has led to the identification of a novel and critical role in maintaining c-Myc-dependent downregulation of hTERT, a catalytic subunit of telomerase, and subsequent inhibition of telomerase/telomere and induction of telomere dysfunction in mediating therapeutic efficacy of osimertinib. Consequently, osimertinib combined with the telomere inhibitor, 6-Thio-dG, which is currently tested in a phase II trial, effectively inhibited the growth of osimertinib-resistant tumors, regressed EGFRm NSCLC patient-derived xenografts, and delayed the emergence of acquired resistance to osimertinib, warranting clinical validation of this strategy to manage osimertinib acquired resistance.

L3MBTL1, a polycomb protein, promotes Osimertinib acquired resistance through epigenetic regulation of DNA damage response in lung adenocarcinoma

Osimertinib is a third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (EGFR-TKI) approved for patients with EGFR T790M resistance mutations as first- or second-line treatment of EGFR-positive patients. Resistance to Osimertinib will inevitably develop, and the underlying mechanisms are largely unknown. In this study, we discovered that acquired resistance to Osimertinib is associated with abnormal DNA damage response (DDR) in lung adenocarcinoma cells. We discovered that the polycomb protein Lethal(3) Malignant Brain Tumor-Like Protein 1 (L3MBTL1) regulates chromatin structure, thereby contributing to DDR and Osimertinib resistance. EGFR oncogene inhibition reduced L3MBTL1 ubiquitination while stabilizing its expression in Osimertinib-resistant cells. L3MBTL1 reduction and treatment with Osimertinib significantly inhibited DDR and proliferation of Osimertinib-resistant lung cancer cells in vitro and in vivo. L3MBTL1 binds throughout the genome and plays an important role in EGFR-TKI resistance. It also competes with 53BP1 for H4K20Me2 and inhibits the development of drug resistance in Osimertinib-resistant lung cancer cells in vitro and in vivo. Our findings suggest that L3MBTL1 inhibition is a novel approach to overcoming EGFR-TKI-acquired resistance.

NUAK1-Mediated Phosphorylation of NADK Mitigates ROS Accumulation to Promote Osimertinib Resistance in Non-Small Cell Lung Carcinoma.

Osimertinib, a third-generation epidermal growth factor receptor tyrosine kinase inhibitor, is approved as a first-line therapy in advanced non-small cell lung carcinoma (NSCLC) patients with EGFR-activating mutations or the T790M resistance mutation. However, the efficacy of osimertinib is limited due to acquired resistance, highlighting the need to elucidate resistance mechanisms to facilitate the development of improved treatment strategies. Here, we screened for significantly upregulated genes encoding protein kinases in osimertinib-resistant NSCLC cells and identified NUAK1 as a pivotal regulator of osimertinib resistance. NUAK1 was highly expressed in osimertinib-resistant NSCLC and promoted the emergence of osimertinib resistance. Genetic or pharmacological blockade of NUAK1 restored the sensitivity of resistant NSCLC cells to osimertinib in vitro and in vivo. Mechanistically, NUAK1 directly interacted with and phosphorylated NADK at serine 64 (S64), which mitigated osimertinib-induced accumulation of reactive oxygen species (ROS) and contributed to the acquisition of osimertinib resistance in NSCLC. Furthermore, virtual drug screening identified T21195 as an inhibitor of NADK-S64 phosphorylation, and T21195 synergized with osimertinib to reverse acquired resistance by inducing ROS accumulation. Collectively, these findings highlight the role of the NUAK1-NADK axis in governing osimertinib resistance in NSCLC and indicate the potential of targeting this axis as a strategy for circumventing resistance.

Synergistic antitumor activity of baicalein combined with almonertinib in almonertinib-resistant non-small cell lung cancer cells through the reactive oxygen species-mediated PI3K/Akt pathway.

Almonertinib is an important third-generation epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) exhibiting high selectivity to EGFR-sensitizing and T790M-resistant mutations. Almonertinib resistance is a major obstacle in clinical use. Baicalein possesses antitumor properties, but its mechanism of antitumor action against almonertinib-resistant non-small cell lung cancer (NSCLC) remains unelucidated. CCK-8 assay was used to examine the survival rate of H1975/AR and HCC827/AR cells following treatment for 24h with different concentrations of baicalein, almonertinib or their combination. The changes in colony formation ability, apoptosis, and intracellular reactive oxygen species (ROS) levels of the treated cells were analyzed using colony formation assay and flow cytometry. Western blotting was performed to detect the changes in protein expressions in the cells. The effects of pre-treatment with NAC on proliferation, apoptosis, and PI3K/Akt signaling pathway were observed in baicalein- and/or almonertinib-treated cells. A nude mouse model bearing subcutaneous HCC827/AR cell xenograft were treated with baicalein (20mg/kg) or almonertinib (15mg/kg), and the tumor volume and body mass changes was measured. Both baicalein and almonertinib represses the viability of HCC827/AR and H1975/AR cells in a concentration-dependent manner. Compared with baicalein or almonertinib alone, the combined application of the two drugs dramatically attenuates cell proliferation; triggers apoptosis; causes cleavage of Caspase-3, PARP, and Caspase-9; downregulates the protein expressions of p-PI3K and p-Akt; and significantly inhibits tumor growth in nude mice. Furthermore, baicalein combined with almonertinib results in massive accumulation of reactive oxygen species (ROS) and preincubation with N-acetyl-L-cysteine (ROS remover) prevents proliferation as well as inhibits apoptosis induction, with partial recovery of the decline of p-PI3K and p-Akt. The combination of baicalein and almonertinib can improve the antitumor activity in almonertinib-resistant NSCLC through the ROS-mediated PI3K/Akt pathway.

Liquid-based cytology specimens for next-generation sequencing in lung adenocarcinoma: challenges and evaluation of targeted therapy

BackgroundTo explore challenges of liquid-based cytology (LBC) specimens for next-generation sequencing (NGS) in lung adenocarcinoma and evaluate the efficacy of targeted therapy.MethodsA retrospective analysis was conducted on the NGS test of 357 cases of advanced lung adenocarcinoma LBC specimens and compared with results of histological specimens to assess the consistency. The impact of tumor cellularity on NGS test results was evaluated. The utility of epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) was collected. Clinical efficacy evaluation was performed and survival curve analysis was conducted using the Kaplan-Meier method.ResultsThere were 275 TKI-naive and 82 TKI-treated specimens, the mutation rates of cancer-related genes detected in both groups were similar (86.2% vs. 86.6%). The EGFR mutation rate in the TKI treated group was higher than that in the TKI-naive group (69.5% > 54.9%, P = 0.019). There was no significant difference in the EGFR mutation frequency among different tumor cellularity in the TKI-naive group. However, in the TKI treated group, the frequency of EGFR sensitizing mutation and T790M resistance mutation in specimens with < 20% tumor cellularity was significantly lower than that in specimens with ≥ 20% tumor cellularity. Among 22 cases with matched histological specimens, 72.7% (16/22) of LBC specimens were completely consistent with results of histological specimens. Among 92 patients with EGFR-mutant lung adenocarcinoma treated with EGFR-TKIs in the two cohorts, 88 cases experienced progression, and the median progression-free survival (PFS) was 12.1 months.ConclusionsCytological specimens are important sources for gene detection of advanced lung adenocarcinoma. When using LBC specimens for molecular testing, it is recommended to fully evaluate the tumor cellularity of the specimens.

Molecular residual disease (MRD) analysis from the ADAURA trial of adjuvant (adj) osimertinib in patients (pts) with resected EGFR-mutated (EGFRm) stage IB–IIIA non-small cell lung cancer (NSCLC).

8005 Background: Osimertinib (osi) is a third-generation, central nervous system-active EGFR-TKI, that potently and selectively inhibits EGFR-TKI sensitizing and EGFR T790M resistance mutations. Adj osi (3 years [yrs]) is recommended for resected EGFRm stage IB–IIIA NSCLC, based on significant improvements in disease-free survival (DFS) and overall survival (OS) in the Phase III ADAURA study (NCT02511106). A trend towards an increased DFS event rate beyond 3 yrs suggests some pts may benefit from longer adj osi treatment (tx). We explored if plasma ctDNA-based, tumor-informed MRD could predict disease recurrence. Methods: Eligible pts (≥18 yrs [≥20 in Japan/Taiwan], WHO PS 0/1 with completely resected EGFRm [Ex19del/L858R] stage IB, II or IIIA [AJCC 7th edition] NSCLC) were randomized 1:1 to osi 80 mg once daily or placebo (pbo) until disease recurrence, tx completion (up to 3 yrs), or a discontinuation criterion was met. Personalized MRD panels (RaDaR, NeoGenomics) were used, comprised of ≤50 tumor-specific variants, based on whole exome sequencing of resected tumor tissue (variants identified in germline DNA removed). Plasma sample collection: baseline (BL; at randomization surgery and adj Ctx, if received), on tx (every 12 weeks [wks]), tx discontinuation, and post-tx completion (wk 12, wk 24, then every 24 wks until 5 yrs). Plasma samples were analyzed for detection of ctDNA (MRD+). Molecular recurrence or DFS (MRD/DFS) was defined as time from randomization to post-BL MRD+, disease recurrence, or death and was compared across arms. DFS was investigator-assessed. Results: Of 682 pts randomized, 245 (36%) had samples required to produce MRD panels, which were evaluable for 220 (32%) pts across both arms. In the osi vs pbo arms, 5/112 (4%) vs 13/108 (12%) pts were MRD+ at BL; 4/5 pts became MRD– during osi tx vs 0/13 pts on pbo. On tx, MRD detection had clinical sensitivity of 65% (62 MRD+/96 DFS+), specificity of 95% (118 MRD–/124 DFS–) and preceded a DFS event by a median (95% CI) of 4.7 (2.2, 5.6) months (mos) across both arms. Median follow-up time from randomization was 44.2 (95% CI 42.4, 49.1) and 19.1 (95% CI 11.1, 28.3) mos for osi and pbo arms, respectively. Overall, 86% (95% CI 78, 92) vs 36% (95% CI 27, 45) pts in the osi vs pbo arms were MRD/DFS event free at 36 mos (HR: 0.23; 95% CI 0.15, 0.36). MRD/DFS events in the osi arm were detected at any time post-BL in 28 (25%) pts, of whom 19/28 (68%) had events post-adj osi. Most (11/19 [58%]) MRD/DFS events detected occurred within 12 mos of osi tx completion. Conclusions: MRD+ preceded DFS events in most pts with a median lead time of 4.7 mos across both arms. MRD– was maintained for most pts during adj osi tx with the majority of MRD/DFS events occurring after osi tx completion. MRD detection could potentially identify a subset of pts likely to benefit from longer adj osi. Clinical trial information: NCT02511106 .

Efficacy and safety of aumolertinib combined with or without chemotherapy as an adjuvant treatment for stage II-IIIA non-small cell lung cancer following complete tumour resection: The first third-generation EGFR-TKI versus chemotherapy phase III clinical study (APEX).

TPS8117 Background: Patients with stage II-III A non-small cell lung cancer (NSCLC) can benefit from adjuvant targeted therapy. ADAURA study shows a remarkable advantage of disease-free survival (DFS). However, there are still unresolved clinical issues. Firstly, the control group in the trial is received placebo, making it impossible to directly compare the efficacy of adjuvant targeted therapy with the traditionally recommended adjuvant chemotherapy in guidelines. Thus, it cannot address the direct comparison of third-generation TKIs with the current standard therapy (chemotherapy). Secondly, the necessity of combining chemotherapy with adjuvant targeted therapy need to explored. Aumolertinib is a third-generation epidermal growth factor receptor- tyrosine kinase inhibitor (EGFR-TKI) that potently and selectively inhibits EGFR sensitizing and EGFR T790M resistance mutations. This study aims to evaluate the efficacy and safety of aumolertinib combined with or without chemotherapy as adjuvant treatment for EGFR-sensitive mutations stage II-III A non-squamous NSCLC patients. Methods: This is a multicenter, randomized, open label, phase III study. Patients with histologically confirmed stage II-III A non-squamous NSCLC harboring EGFR mutations without prior EGFR TKI treatment and R0 resection are eligible for this study. The performance status (Eastern Cooperative Oncology Group) is 0 or 1. This trial prepared to enroll approximately 606 patients, will be randomized (3:2:1) to receive either aumolertinib alone (110mg, po, once daily) or aumolertinib (110mg, po, once daily) plus pemetrexed (500mg/m2, iv) and cisplatin (500mg/m2, iv) or pemetrexed (500mg/m2, iv) plus cisplatin (500mg/m2, iv). The first patient was enrolled on August 2, 2021. The primary end point is DFS, The secondary endpoints include 2, 3, 4, 5-year DFS rates, 5-year overall survival (OS), OS, safety and quality of life. Adverse effects were graded per CTCAE v.4.0. This trial is registered as NCT04762459. Clinical trial information: NCT04762459 .

Abstract 4668: Characterization of fourth-generation EGFR inhibitors in binding experiments with C797S mutant EGFR and cell-based assays with osimertinib-resistant non-small cell lung cancer cell lines

Abstract Osimertinib is a third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor that inhibits the EGFR kinase domain by irreversible binding of the cysteine-797 residue (C797). Osimertinib was originally designed to target the T790M mutation, which is clinically the most frequently observed resistance mechanism to treatment with first- or second-generation EGFR inhibitors. Osimertinib has a high selectivity for the classical EGFR driver mutations (exon 19 deletion and L858R) compared to wild-type EGFR. Due to this favorable selectivity profile, osimertinib has become the standard first-line therapy for non-small cell lung cancer (NSCLC). Common resistance mechanisms following osimertinib treatment are MET oncogene amplification, and cysteine-to-serine substitution at position 797 (C797S) of EGFR, which precludes binding of osimertinib. Fourth-generation EGFR inhibitors and combinations with other targeted agents are potential strategies to overcome osimertinib resistance or to increase its efficacy. Three fourth-generation EGFR inhibitors were profiled in biochemical and cell-based assays: BDTX-1535, BLU-945, and JBJ-09-063. The binding kinetics for wild-type and C797S mutant EGFR were determined in surface plasmon resonance binding experiments on a Biacore 1S+ (Cytiva). The effect on osimertinib-resistant cells, generated using two different approaches, was studied in cell viability assays. In the first model, subclones of the NSCLC cell line PC-9, harboring an exon 19 deletion activating EGFR mutation, were selected for osimertinib resistance by in vitro drug selection [1]. In the second model, the EGFR C797S mutation was introduced into the NSCLC cell line NCI-H1975, which expresses both the L858R activating mutation and the T790M resistance mutation, by gene-editing with CRISPR-Cas9. Synergies with fourth-generation EGFR inhibitors were determined by profiling combinations in a 6-by-6 matrix, and quantifying synergistic effects using the Excess over Bliss score. We will present a detailed comparison of the binding kinetics of the three fourth-generation EGFR inhibitors on wild-type and C797S-mutant EGFR, and their ability to compete with osimertinib for binding to the kinase domain of EGFR. The different fourth-generation inhibitors show various selectivities for the various EGFR mutants and differences in their ability to spare wild-type EGFR. Profiling results of the three fourth-generation EGFR inhibitors in the osimertinib-resistant cell lines and on a panel of more than one hundred human cancer cell lines will be presented. Reference: [1] Bertran-Alamillo et al. Nature Communications 10, 1812; 2019 Citation Format: Janneke J. Melis, Kirsten Kevenaar, Jeffrey J. Kooijman, Yvonne Grobben, Jacob Ytsma, Jordi Bertran-Alamillo, Miguel-Angel Molina-Vila, Nicole Willemsen-Seegers, Guido J. Zaman. Characterization of fourth-generation EGFR inhibitors in binding experiments with C797S mutant EGFR and cell-based assays with osimertinib-resistant non-small cell lung cancer cell lines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4668.

Abstract 5868: Upregulation of HER3 and MET in non-small cell lung cancer cells resistant to EGFR tyrosine kinase inhibitor

Abstract Introduction: Prior research demonstrates the importance of studying epidermal growth factor receptor (EGFR) activating mutations for better understanding the biology of non-small cell lung cancer (NSCLC), which comprises the majority (~80%) of lung cancers. EGFR-targeted tyrosine kinase inhibitors (TKIs) have been used in the clinic to treat NSCLC with EGFR activating mutations. First and second-generation EGFR-TKIs are effective in NSCLC patients with the most common EGFR mutations (exon 19 deletion (Del19) and exon 21-point mutation (L858R)). A third generation EGFR-TKI, osimertinib (AZD9291), has been developed to target the T790M resistance mutation, but patients are starting to show resistance to this line of therapy as well. Our study aims to elucidate the underlying mechanism(s) of EGFR-TKI resistance in NSCLC cells. Methods: NSCLC cell lines, including PC-9 and HCC827, which have the Del19 EGFR activating mutation, were utilized for experiments. From the parental cell lines, several cell lines resistant to the EGFR-TKIs were previously established. Cell proliferation (MTS) assays were used to confirm the resistance phenotype of the established cell lines. Western blot assays and RT-qPCR were utilized to determine changes in the expression level of several membrane receptors and their downstream effectors. Results: Our preliminary analysis showed that both human epidermal growth factor 3 (HER3) and mesenchymal-epithelial transition factor (MET) were upregulated in the EGFR-TKI-resistant cell lines as compared to their parental counterparts. Further studies revealed an increased level of phosphorylated STAT3 (p-STAT3) and ERK1/2 (p-ERK1/2) in the resistant cell lines when compared to the parental cell lines, suggesting the possible involvement of HER3 and/or MET in the activation of downstream signaling pathways. Upregulation of HER3 and MET was found at both the protein and mRNA level. Conclusion: Based on our initial findings, membrane receptors, including HER3 and MET, could be working together to continue activating downstream signaling pathways to evade the effects of osimertinib, resulting in resistance. Additional work is underway to define the role of HER3 and MET in the NSCLC cells resistant to EGFR-TKIs. Citation Format: Margaret Larsen, Hui Lyu, CongCong Tan, Yakun Wu, Bolin Liu. Upregulation of HER3 and MET in non-small cell lung cancer cells resistant to EGFR tyrosine kinase inhibitor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5868.

Overall Survival From the EORTC LCG-1613 APPLE Trial of Osimertinib Versus Gefitinib Followed by Osimertinib in Advanced EGFR-Mutant Non-Small-Cell Lung Cancer.

Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned co-primary or secondary analyses are not yet available. Clinical Trial Updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported.Osimertinib has been established as a standard of care for patients with common sensitizing EGFR-mutant advanced non-small-cell lung cancer (NSCLC) although the sequential approach (first-generation inhibitor gefitinib followed by osimertinib) has not been formally compared. The phase II APPLE trial (ClinicalTrials.gov identifier: NCT02856893) enrolled 156 treatment-naïve patients, and two treatment strategies were evaluated: osimertinib up front or the sequential treatment approach with gefitinib up front followed by osimertinib at the time of progression, either molecular progression (detection of plasma T790M resistance mutation) regardless of the radiologic status or just at the time of radiologic progression. Patients' characteristics were well balanced, except for the higher proportion of baseline brain metastases in the sequential approach (29% v 19%). Per protocol, 73% of patients switched to osimertinib in the sequential arm. Up-front treatment with osimertinib was associated with a lower risk of brain progression versus the sequential approach (hazard ratio [HR], 0.54 [90% CI, 0.34 to 0.86]), but a comparable overall survival was observed between both strategies (HR, 1.01 [90% CI, 0.61 to 1.68]), with the 18-month survival probability of 84% and 82.3%, respectively. The APPLE trial suggests that a sequential treatment approach is associated with more frequent progression in the brain but a similar survival in advanced EGFR-mutant NSCLC.

Genomic heterogeneity at baseline is associated with T790M resistance mutations in EGFR-mutated lung cancer treated with the first-/second-generation tyrosine kinase inhibitors.

This study analyzed whether extended molecular profiling can predict the development of epidermal growth factor receptor (EGFR) gene T790M mutation, which is the most frequent resistance alteration in non-small cell lung cancer (NSCLC) after treatment with the first-/second-generation (1G/2G) EGFR inhibitors (tyrosine kinase inhibitors [TKIs]), but only weakly associated with clinical characteristics. Whole exome sequencing (WES) was performed on pretreatment tumor tissue with matched normal samples from NSCLC patients with (n = 25, detected in tissue or blood rebiopsies) or without (n = 14, negative tissue rebiopsies only) subsequent EGFR p.T790M mutation after treatment with 1G/2G EGFR TKI. Several complex genetic biomarkers were assessed using bioinformatic methods. After treatment with first-line afatinib (44%) or erlotinib/gefitinib (56%), median progression-free survival and overall survival were 12.1 and 33.7 months, respectively. Clinical and tumor genetic characteristics, including age (median, 66 years), sex (74% female), smoking (69% never/light smokers), EGFR mutation type (72% exon 19 deletions), and TP53 mutations (41%) were not significantly associated with T790M mutation (p > 0.05). By contrast, complex biomarkers including tumor mutational burden, the clock-like mutation signature SBS1 + 5, tumor ploidy, and markers of subclonality including mutant-allele tumor heterogeneity, subclonal copy number changes, and median tumor-adjusted variant allele frequency were significantly higher at baseline in tumors with subsequent T790M mutation (all p < 0.05). Each marker alone could predict subsequent development of T790M with an area under the curve (AUC) of 0.72-0.77, but the small number of cases did not allow confirmation of better performance for biomarker combinations in leave-one-out cross-validated logistic regression (AUC 0.69, 95% confidence interval: 0.50-0.87). Extended molecular profiling with WES at initial diagnosis reveals several complex biomarkers associated with subsequent development of T790M resistance mutation in NSCLC patients receiving first-/second-generation TKIs as the first-line therapy. Larger prospective studies will be necessary to define a forecasting model.

MiR-204 suppresses cancer stemness and enhances osimertinib sensitivity in non-small cell lung cancer by targeting CD44

Osimertinib is an effective treatment option for patients with advanced non-small cell lung cancer (NSCLC) with EGFR activation or T790M resistance mutations; however, acquired resistance to osimertinib can still develop. This study explored novel miRNA-mRNA regulatory mechanisms that contribute to osimertinib resistance in lung cancer. We found that miR-204 expression in osimertinib-resistant lung cancer cells was markedly reduced compared to that in osimertinib-sensitive parental cells. miR-204 expression levels in cancer cells isolated from treatment-naive pleural effusions were significantly higher than those in cells with acquired resistance to osimertinib. miR-204 enhanced the sensitivity of lung cancer cells to osimertinib and suppressed spheroid formation, migration, and invasion of lung cancer cells. Increased miR-204 expression in osimertinib-resistant cells reversed resistance to osimertinib and enhanced osimertinib-induced apoptosis by upregulating BIM expression levels and activating caspases. Restoration of CD44 (the direct downstream target gene of miR-204) expression reversed the effects of miR-204 on osimertinib sensitivity, recovered cancer stem cell and mesenchymal markers, and suppressed E-cadherin expression. The study demonstrates that miR-204 reduced cancer stemness and epithelial-to-mesenchymal transition, thus overcoming osimertinib resistance in lung cancer by inhibiting the CD44 signaling pathway.

Abstract B099: Targeting Non Small Cell Lung Cancer EGFR-Mutant and EGFR-Inhibitor resistant cell lines by ferroptosis induction: A potential therapeutic approach

Abstract The epidermal growth factor receptor (EGFR) is a crucial signaling protein involved in regulating cellular growth, survival, and proliferation. EGFR mutations, particularly in non-small cell lung cancer (NSCLC), have been extensively studied due to their role in driving tumor progression and resistance to conventional therapies. While EGFR-mutant tumors initially respond well to EGFR inhibitors, emergence of resistance remains a significant challenge. Ferroptosis is a recently discovered form of regulated cell death characterized by accumulation of lipid peroxides and oxidative stress. It has gained attention as a potential therapeutic strategy in combating drug resistance. However, the vulnerability of various EGFR-mutant and resistant NSCLC cells to ferroptosis induction remains poorly understood. To bridge the existing knowledge gap, we investigated the responsiveness of both EGFR-mutant and their resistant counterpart NSCLC cell lines to ferroptosis induction. Interestingly, NSCLC cell lines and patients’ tumors which harbor EGFR mutations are distinct from those carrying STK11 and KEAP1 mutations, which are known to contribute to resistance to ferroptosis. This observation prompted us to test whether ferroptosis inducers could effectively target this specific subset of NSCLC. In our experimental approach, we first utilized a panel of commercially available EGFR mutant cell lines (n=3), including one harboring T790M resistance mutation, which is a common mechanism of acquired resistance to first-generation inhibitors. We subjected the EGFR-mutant cell lines in vitro to a process of acquiring resistance against three generations of EGFR inhibitors (n=4). Subsequently, upon confirmation of resistance, we evaluated their susceptibility to our proprietary ferroptosis inducer. Exome sequencing data of EGFR-inhibitor resistant cell lines and their age-matched control cell lines revealed that the former acquired genetic alterations that have previously been found to confer resistance in EGFR-inhibitor resistant patients’ tumors, suggesting that our approach is valid for modeling relevant resistance mechanisms. Our results indicate that both EGFR-mutant and resistant cell lines exhibit sensitivity to ferroptosis induction. Furthermore, we observed that EGFR-mutant patient-derived cells, which are refractory to EGFR inhibitors of several generations, were strongly cytostatic to our ferroptosis inducer. These findings provide valuable insights into the interplay between EGFR mutations, drug resistance, and ferroptosis. Exploiting the vulnerability of EGFR-inhibitor resistant NSCLC cells to ferroptosis could offer novel therapeutic options for overcoming drug resistance in EGFR-driven cancers. Further investigations into the underlying molecular mechanisms of ferroptosis inducers in NSCLC are warranted for the development of effective therapies. Citation Format: Taronish Dubash, Maria Cristina Munteanu, Cristian Nunez, Shrouq Farah, Laurence Jadin, Branko Radetich, Francesco M Marincola, Darby Schmidt, Nadia Gurvich. Targeting Non Small Cell Lung Cancer EGFR-Mutant and EGFR-Inhibitor resistant cell lines by ferroptosis induction: A potential therapeutic approach [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr B099.

Osimertinib with or without Chemotherapy in EGFR-Mutated Advanced NSCLC

BackgroundOsimertinib is a third-generation epidermal growth factor receptor–tyrosine kinase inhibitor (EGFR-TKI) that is selective for EGFR-TKI–sensitizing and EGFR T790M resistance mutations. Evidence suggests that the addition of chemotherapy may extend the benefits of EGFR-TKI therapy.MethodsIn this phase 3, international, open-label trial, we randomly assigned in a 1:1 ratio patients with EGFR-mutated (exon 19 deletion or L858R mutation) advanced non–small-cell lung cancer (NSCLC) who had not previously received treatment for advanced disease to receive osimertinib (80 mg once daily) with chemotherapy (pemetrexed [500 mg per square meter of body-surface area] plus either cisplatin [75 mg per square meter] or carboplatin [pharmacologically guided dose]) or to receive osimertinib monotherapy (80 mg once daily). The primary end point was investigator-assessed progression-free survival. Response and safety were also assessed.ResultsA total of 557 patients underwent randomization. Investigator-assessed progression-free survival was significantly longer in the osimertinib–chemotherapy group than in the osimertinib group (hazard ratio for disease progression or death, 0.62; 95% confidence interval [CI], 0.49 to 0.79; P<0.001). At 24 months, 57% (95% CI, 50 to 63) of the patients in the osimertinib–chemotherapy group and 41% (95% CI, 35 to 47) of those in the osimertinib group were alive and progression-free. Progression-free survival as assessed according to blinded independent central review was consistent with the primary analysis (hazard ratio, 0.62; 95% CI, 0.48 to 0.80). An objective (complete or partial) response was observed in 83% of the patients in the osimertinib–chemotherapy group and in 76% of those in the osimertinib group; the median response duration was 24.0 months (95% CI, 20.9 to 27.8) and 15.3 months (95% CI, 12.7 to 19.4), respectively. The incidence of grade 3 or higher adverse events from any cause was higher with the combination than with monotherapy — a finding driven by known chemotherapy-related adverse events. The safety profile of osimertinib plus pemetrexed and a platinum-based agent was consistent with the established profiles of the individual agents.ConclusionsFirst-line treatment with osimertinib–chemotherapy led to significantly longer progression-free survival than osimertinib monotherapy among patients with EGFR-mutated advanced NSCLC. (Funded by AstraZeneca; FLAURA2 ClinicalTrials.gov number, NCT04035486.)

CT-based nomogram for early identification of T790M resistance in metastatic non-small cell lung cancer before first-line epidermal growth factor receptor-tyrosine kinase inhibitors therapy

BackgroundTo evaluate the value of computed tomography (CT) radiomics in predicting the risk of developing epidermal growth factor receptor (EGFR) T790M resistance mutation for metastatic non-small lung cancer (NSCLC) patients before first-line EGFR-tyrosine kinase inhibitors (EGFR-TKIs) therapy.MethodsA total of 162 metastatic NSCLC patients were recruited and split into training and testing cohort. Radiomics features were extracted from tumor lesions on nonenhanced CT (NECT) and contrast-enhanced CT (CECT). Radiomics score (rad-score) of two CT scans was calculated respectively. A nomogram combining two CT scans was developed to evaluate T790M resistance within up to 14 months. Patients were followed up to calculate the time of T790M occurrence. Models were evaluated by area under the curve at receiver operating characteristic analysis (ROC-AUC), calibration curve, and decision curve analysis (DCA). The association of the nomogram with the time of T790M occurrence was evaluated by Kaplan–Meier survival analysis.ResultsThe nomogram constructed with the rad-score of NECT and CECT for predicting T790M resistance within 14 months achieved the highest ROC-AUCs of 0.828 and 0.853 in training and testing cohorts, respectively. The DCA showed that the nomogram was clinically useful. The Kaplan–Meier analysis showed that the occurrence time of T790M difference between the high- and low-risk groups distinguished by the rad-score was significant (p < 0.001).ConclusionsThe CT-based radiomics signature may provide prognostic information and improve pretreatment risk stratification in EGFR NSCLC patients before EGFR-TKIs therapy. The multimodal radiomics nomogram further improved the capability.Relevance statementRadiomics based on NECT and CECT images can effectively identify and stratify the risk of T790M resistance before the first-line TKIs treatment in metastatic non-small cell lung cancer patients.Key points• Early identification of the risk of T790M resistance before TKIs treatment is clinically relevant.• Multimodel radiomics nomogram holds potential to be a diagnostic tool.• It provided an imaging surrogate for identifying the pretreatment risk of T790M.Graphical

TARGET: A Phase II, Open-Label, Single-Arm Study of 5-Year Adjuvant Osimertinib in Completely Resected EGFR-Mutated Stage II to IIIB NSCLC Post Complete Surgical Resection

IntroductionOsimertinib is a central nervous system (CNS)-active, third generation, irreversible, epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) that potently and selectively inhibits EGFR-TKI sensitizing and EGFR T790M resistance mutations, with demonstrated efficacy in EGFR-mutated (EGFRm) non-small cell lung cancer (NSCLC). We present the rationale and design for TARGET (NCT05526755), which will evaluate the efficacy and safety of 5 years of adjuvant osimertinib in patients with completely resected EGFRm stage II to IIIB NSCLC. Materials and MethodsTARGET is a phase II, multinational, open-label, single-arm study. Adults aged ≥18 years (Taiwan ≥20 years), with resected stage II to IIIB NSCLC are eligible; prior adjuvant chemotherapy is allowed. Eligible patients must have locally confirmed common (exon 19 deletion or L858R) or uncommon (G719X, L861Q, and/or S768I) EGFR-TKI sensitizing mutations, alone or in combination. Patients will receive osimertinib 80 mg once daily for 5 years or until disease recurrence, discontinuation or death. The primary endpoint is investigator-assessed disease-free survival (DFS) at 5 years (common EGFR mutations cohort). Secondary endpoints include: investigator-assessed DFS at 3 and 4 years; overall survival at 3, 4, and 5 years (common EGFR mutations cohort); DFS at 3, 4, and 5 years (uncommon EGFR mutations cohort); safety and tolerability, type of recurrence and CNS metastases (both cohorts). Exploratory endpoints include: tissue/plasma concordance; analysis of circulating molecules in plasma samples using different profiling approaches to detect minimal residual disease; incidence and change over time of incidental pulmonary nodules. ResultsTARGET is currently recruiting, and completion is expected in 2029.

Furmonertinib as adjuvant therapy in postoperative EGFR-mutated stage IA2-IIIA non-small cell lung cancer (NSCLC) with high-risk pathological factors.

150 Background: NSCLC patients with high-risk pathological factors such as micropapillary (MP), solid (S), spread through air spaces (STAS), and visceral pleural invasion (VPI) have shown poor prognosis in previous studies. Furmonertinib (AST2818) is a novel, promising oral third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI), which has demonstrated efficacy in tumours harbouring sensitive EGFR mutations and T790M resistance mutation. Here, we investigated the efficacy and safety of furmonertinib as adjuvant therapy in postoperative EGFR-mutated NSCLC patients with high-risk pathological factors. Methods: Patients who underwent radical lung cancer surgery with both EGFR mutations and MP/S/STAS/VPI were enrolled and received furmonertinib 80mg daily. The adjuvant therapy time (6-36months) depended on patients’ pathologic stage and physical conditions. The disease-free survival (DFS), safety and tolerability were evaluated. Results: This study retrospectively analyzed 69 patients who were pathologically confirmed adenocarcinoma, EGFR mutation positive (exon 19 deletion/L858R/exon 20ins), stage IA2-IIIA NSCLC. All of them had at least one high-risk pathological factor. There were 44 (63.8%) patients with MP, 14 (20.3%) with S, 10 (14.5%) with STAS and 33 (47.8%) with VPI. All patients were followed at least 13 months, and 24 (34.8%) of them have been followed up for over 21 months, median follow-up time was 18.5 months. By the cut-off date of March 1, 2023, all patients were alive and with no radiographic recurrence, including 3 (4.3%) with exon 20ins. During therapy, 26 (37.7%) patients had treatment-related adverse events (TRAEs) of any grade. The most common TRAEs were rash (12/69, 17.4%), mouth ulcer (6/69, 8.7%), diarrhea (5/69, 7.2%) and transaminase elevation (4/69, 5.8%). Only 2 (2.9%) patients had TRAEs of grade 3 or higher and 1(1.4%) of the two discontinued therapy. Conclusions: This is the first study to demonstrate that furmonertinib has good efficacy and a tolerable safety profile as adjuvant therapy in EGFR-mutated NSCLC patients with high-risk pathological factors who underwent radical lung cancer surgery.[Table: see text]