Activating EGFR Mutations Research Articles

Abstract 1974: Discovery of TRX-211-399, a potent, CNS-penetrant, highly selective inhibitor of EGFR exon 20 insertion mutations

Abstract Lung cancer is the leading cause of cancer-related deaths worldwide, accounting for approximately 2 million new cases and 1.8 million deaths annually. Various types of EGFR-activating mutations are one of the most important oncogenic drivers in non-small cell lung cancer (NSCLC). Among NSCLC patients with EGFR mutations, 5-10% of patients have EGFR exon 20 insertion (ex20ins) mutations that are insensitive to clinically available EGFR tyrosine kinase inhibitors (TKIs). Recently, as mobocertinib (EXKIVITY®) failed to improve progression-free survival in Phase 3 clinical trial, there remains a high unmet medical need to develop new drugs with wider therapeutic window to treat NSCLC harboring EGFR ex20ins mutations. Herein, we report a novel EGFR-TKI, TRX-211-399, specifically designed to target ex20ins mutations. TRX-211-399 potently inhibited the proliferation of not only Ba/F3 cells overexpressing near-loop (A767dupASV, S768dupSVD) and far-loop (H773insNPH, H773dupH) mutations but also patient-derived NSCLC cell line. In particular, TRX-211-399 demonstrated high selectivity against wild-type EGFR. With favorable DMPK profiles, once-daily oral administration of TRX-211-399 showed significant tumor regression in multiple Ba/F3 xenograft models carrying different EGFR exon20ins mutations. Furthermore, in a PC-9-luc cell intracranial xenograft model, TRX-211-399 induced substantial anti-tumor effects and prolonged survival without body weight loss. TRX-211-399 is currently undergoing further preclinical evaluation as a potential candidate for clinical development for patients with EGFR exon20ins mutations. Citation Format: Kwangwoo Chun, Sumin Lim, Joohyun Lee, Seulgi Choi, Seongrak Kim, Youngil Choi, Areum Park, Bohee Kim, Yongseo Park, Eunhyun Choi, Sungwon Lee, Koo Lee. Discovery of TRX-211-399, a potent, CNS-penetrant, highly selective inhibitor of EGFR exon 20 insertion mutations [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 1974.

Abstract 5162: Tumor transcriptional identity as a key predictor of clinical outcome in EGFR-Mutant non-small cell lung cancer

Abstract Background: EGFR tyrosine-kinase inhibitors (TKIs) produce significant clinical benefit in patients (pts) harboring EGFR-activating mutations, however, patient outcomes remain heterogeneous, highlighting the need to identify novel biomarkers for treatment response prediction. We aim to investigate the association of tumor transcriptional identity with clinical outcomes in EGFR-mutant NSCLC. Methods: We used consensus classification to derive unsupervised transcriptionally distinct clusters in EGFR-mutant NSCLC from the TCGA (N= 44). Then, we built a predictive model using extreme-gradient boosting to (1) classify an additional 88 surgically resected tumors from the LCCS study and analyzed for overall survival (OS) prediction; (2) classify metastatic EGFR-mutant NSCLC from the RELAY trial with available RNAseq data (N = 106) and analyzed for progression-free survival (PFS) with erlotinib treatment. Results: Consensus clustering revealed two distinct clusters, one associated with more lineage-preserving features and one with more lineage-independent features that could transcriptionally distinguish EGFR-mutant lung cancer. No differences in primary EGFR mutations were detected across the two clusters. Ingenuity Pathway Analysis revealed TGFB1 as the most significantly enriched pathway in the lineage-independent cluster which was also significantly more mesenchymal (p = 0.0028). For surgically resectioned EGFR-mutant NSCLC, OS was consistently shorter in the lineage-independent cluster for TCGA (23.6 vs 58.3 mo; p = 0.049; HR = 0.4) and the LCCS cohort (55.7 vs not-reached; p = 0.0073; HR = 0.27). In the metastatic setting with erlotinib treatment, there was a trend for PFS to be shorter in the lineage-independent cluster (15.2 vs 19.4 mo; p = 0.12; HR = 0.61). Conclusions: Transcriptional identity in EGFR-mutant lung cancer are prognostic of clinical outcome. The lineage-independent tumors have inferior benefit to EGFR TKI as well as inferior OS, indicating that transcriptional biomarkers can be independent of oncogene biomarkers. These transcriptional biomarkers may help identify pts with poor outcome for future intensification of therapies. Citation Format: Simon Heeke, Monique Nilsson, Don Gibbons, Jianjun Zhang, Ignatio I. Wistuba, Keunchil Park, John V. Heymach, Xiuning Le. Tumor transcriptional identity as a key predictor of clinical outcome in EGFR-Mutant non-small cell lung cancer [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 5162.

Abstract 7206: Inhibition of CAD, an enzyme of de novo pyrimidine synthesis, to overcome EGFR-TKI resistance in NSCLC

Abstract Given the fast-growing cancer cells, there is an increased demand for large amounts of energy and nucleotides for DNA and RNA synthesis. Thus, targeting nucleotide metabolism, specifically de novo nucleotide biosynthesis, is a promising strategy for cancer treatment. Hyperactivation of Carbamoyl-phosphate synthetase, aspartate transcarbamylase (CAD), a key enzyme catalyzing the first three steps of de novo pyrimidine synthesis, is a common event in tumors and has been associated with chemoresistance in tumors. Our analysis, using TCGA data, revealed that increased expression of CAD is associated with poor prognosis in non-small cell lung cancer (NSCLC). Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) have demonstrated significant benefits to patients with NSCLC harboring EGFR-activating mutations; however, acquired resistance limits their long-term efficacy. Therefore, it remains urgent to discover the underlying mechanisms for discovering novel therapeutic strategies for overcoming TKI resistance. Our previous findings demonstrated that blockade of S6K1 overcomes acquired resistance to EGFR-TKIs in NSCLC. It was reported that S6K1 is involved in de novo pyrimidine biosynthesis. In this study, we aimed to investigate whether CAD mediates S6K1-induced EGFR-TKI resistance in NSCLC. Immunohistochemistry analysis on a tissue microarray of lung adenocarcinoma tissues indicated that increased co-expression of p-CAD and S6K1 proteins is associated with clinicopathological parameters and poor survival outcomes. Our in vitro results showed an increased expression level of CAD and p-CAD proteins in TKI-resistant cells compared with parental cells upon TKI treatment. Knockdown of CAD by siRNA led to sensitizing TKI-resistant cells to osimertinib, as indicated by BrdU cell proliferation assay. Inhibition of S6K1 by a siRNA or specific inhibitors PF-470867 and LY2584702 effectively reduced the phosphorylation levels of CAD protein in TKI-resistant cells, suggesting that S6K1 may serve as an upstream regulator of CAD for TKI resistance. The String database predicted a protein-protein interaction between S6K1 and CAD. Indeed, our co-immunoprecipitation (co-IP) results revealed a direct association between S6K1 and CAD proteins. Importantly, TKI treatment enhanced the binding between S6K1 and CAD. Taken together, these findings provide evidence that CAD may mediate S6K1-mediated EGFR-TKI resistance in NSCLC. Our ongoing and future work will assess whether inhibition of CAD sensitizes resistant cells to TKI in vivo and elucidate the associated mechanism. Citation Format: Leili Saeednejad Zanjani, Lei Zhao, Shaomin Wang, Margot Federoff, Xin Sun, Jun He. Inhibition of CAD, an enzyme of de novo pyrimidine synthesis, to overcome EGFR-TKI resistance in NSCLC [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 7206.

Abstract 5658: Genome-scale CRISPR screen in 3D tumor models identifies EGFR-TKI resistance mechanisms in human NSCLC

Abstract INTRODUCTION: Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) are the primary treatment for EGFR-mutated non-small-cell lung cancer (NSCLC). Despite Osimertinib, an FDA-approved EGFR-TKI, showing high selectivity for EGFR-activating mutations, resistance inevitably arises, leading to disease progression. The influence of genes within cancer on Osimertinib response remains unclear. To tackle this challenge, CRISPR screens have been extensively used. However, current CRISPR screens investigating EGFR TKI resistance heavily rely on 2D monolayer cell models, lacking the ability to replicate in vivo tumors accurately. In response, we conducted a genome-scale loss-of-function CRISPR screening employing 3D tumor models embedded in an extracellular matrix across various NSCLC cell lines. Utilizing a comprehensive panel of CRISPR screens in both 3D tumor models and 2D monolayer models, we systematically assessed how genetic alterations impact cell resistance and transformation against treatment with Osimertinib, in diverse cellular contexts. METHOD: Genome-scale CRISPR-Cas9 screens in 10 NSCLC cell lines used 3D tumor models and 2D cells to pinpoint genes pivotal for EGFR TKI resistance. Cas9-expressing cell lines were transduced with a lentivirus carrying 60,000 sgRNAs targeting ~20,000 human genes. Cells were cultured in both models and treated with optimized Osimertinib or DMSO, inducing 20-30% cell growth inhibition for 3 days. Post-treatment, cells were recovered for 4 days. This treatment cycle was repeated 3-4 times in 3D models and 2-3 times in 2D cells. The sgRNA composition in each pool was analyzed using Next Generation Sequencing after treatment cycles in both models. RESULTS: Upon analyzing CRISPR screening data across 10 distinct cell lines to assess drug phenotypes, we confirmed the enrichment of established resistance pathways like PI3K/AKT/mTOR, Hippo, and MAPK signaling pathways in both 2D monolayer cells and 3D tumor models. However, notable discrepancies in EGFR TKI resistance mechanisms were evident between these two models. Specifically, CRISPR screens conducted with 3D tumor models unveiled unique resistance mechanisms, notably the LKB1/AMPK/mTOR pathway (STK11, GSK3B), Ubiquitination (RNF7, ARIH2), and stabilization of E-cadherin adherens junction (NCKAP1, EXOC4) differing from those identified in conventional 2D monolayer model. Furthermore, the 3D tumor models exhibited significantly heightened enrichment of the MAPK and Hippo signaling pathways compared to their drug phenotype score in 2D monolayer cells. CONCLUSION: This study underscores the significance of employing the 3D tumor model in drug phenotype CRISPR screen. This approach recapitulates unique gene dependency patterns and interactions linked to EGFR-TKI resistance in a 3D tumor context, revealing potential targetable vulnerabilities context-dependent. Citation Format: Pranay Agarwal, Soon Youn Choi, Xin Liu, Jina Song, Maya Tureez, Aashka Mehta, Un Jae Baek, Kyuho Han, Hong-Pyo Lee. Genome-scale CRISPR screen in 3D tumor models identifies EGFR-TKI resistance mechanisms in human NSCLC [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 5658.

Clinical phase II trial shows that combining osimertinib and afatinib resistance EGFR recurrent mutation in EGFR-mutant lung cancer

Treatment options for patients with non-small-cell lung cancer (NSCLC) with EGFR mutations are limited due to resistance to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs). Osimertinib or afatinib alone, in a preclinical model, created drug-resistant clones with EGFR secondary mutations, but their combination inhibited the emergence of these mutations. In a Phase II trial, we looked into the alternating-dose therapy of osimertinib and afatinib in patients with EGFR-mutant NSCLC. Patients with stage IV NSCLC with an activating EGFR mutation who had never received treatment were included. Every eight weeks, osimertinib (80 mg/day) and afatinib (20 mg/day) were given in alternate cycles. Utilising circulating tumour DNA collected both before and after therapy, genomic analysis was carried out. The median progression-free survival among the 50 enrolled patients was 21.3 months. A total of 70.3% of respondents responded. Overall median survival was not attained. 35 plasma samples were acquired after the development of resistance; 5 of these samples displayed an elevated MET gene copy number and 3 displayed a BRAF mutation. However, no secondary EGFR mutation was found. The effectiveness of our approach was comparable to that of osimertinib alone, as had been observed in untreated advanced NSCLC patients with EGFR mutations in the past. The treatment may stop the emergence of EGFR secondary mutations that lead to medication resistance, despite the small sample size. To determine the importance of this treatment, more research is required.

YES1 as a potential target to overcome drug resistance in EGFR-deregulated non-small cell lung cancer.

Epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) such as gefitinib and osimertinib have primarily been used as first-line treatments for patients with EGFR-activating mutations in non-small cell lung cancer (NSCLC). Novel biomarkers are required to distinguish patients with lung cancer who are resistant to EGFR-TKIs. The aim of the study is to investigate the expression and functional role of YES1, one of the Src-family kinases, in EGFR-TKI-resistant NSCLC. YES1 expression was elevated in gefitinib-resistant HCC827 (HCC827/GR) cells, harboring EGFR mutations. Moreover, HCC827/GR cells exhibited increased reactive oxygen species (ROS) levels compared to those of the parent cells, resulting in the phosphorylation/activation of YES1 due to oxidation of the cysteine residue. HCC827/GR cells showed elevated expression levels of YES1-associated protein 1 (YAP1), NF-E2-related factor 2 (Nrf2), cancer stemness-related markers, and antioxidant proteins compared to those of the parent cells. Knockdown of YES1 in HCC827/GR cells suppressed YAP1 phosphorylation, leading to the inhibition of Bcl-2, Bcl-xL, and Cyclin D1 expression. Silencing YES1 markedly attenuated the proliferation, migration, and tumorigenicity of HCC827/GR cells. Dasatinib inhibited the proliferation of HCC827/GR cells by targeting YES1-mediated signaling pathways. Furthermore, the combination of gefitinib and dasatinib demonstrated a synergistic effect in suppressing the proliferation of HCC827/GR cells. Notably, YES1- and Nrf2-regulated genes showed a positive regulatory relationship in patients with lung cancer and in TKI-resistant NSCLC cell lines. Taken together, these findings suggest that modulation of YES1 expression and activity may be an attractive therapeutic strategy for the treatment of drug-resistant NSCLC.

Uncommon de novo EGFRT790M-Mutant NSCLC characterized with unique genetic Features: Clinical response and acquired resistance to the third-generation EGFR-TKIs treatment

IntroductionThe literature on de novo EGFRT790M-mutant patients diagnosed with lung cancer is limited, and there is currently no consensus concerning the most effective treatment protocols. This study aimed to investigate the genomic characteristics of de novoEGFRT790M-mutant non-small cell lung cancer (NSCLC) and provide insights into its clinical response and resistance mechanism to third-generation EGFR-TKIs. MethodsNext-generation sequencing was utilized to screen a substantial cohort of 4,228 treatment-naïve patients from the Mygene genomic database to identifythe de novo EGFR-T790M mutation. Meanwhile, we recruited 83 individuals diagnosed with lung cancer who harbored de novo EGFRT790M mutation in the real world. In addition, 166 patients who acquired EGFR-T790M mutation after becoming resistant to first- or second-generation EGFR-TKIs were included as a comparison cohort. ResultsDe novo EGFRT790M mutation identified by next-generation sequencing is rare (∼1.3 %) in Chinese lung cancer patients. The relative variant allele frequency (VAF) of de novo EGFRT790M mutation was either comparable to or significantly lower than those of EGFR-activating mutations. Patients with de novo-T790M mutations exhibited less favorable clinical outcomes when administered third-generation EGFR-TKIs as first-line therapy thanthose with 19del mutationsdue to a high overlap rate in EGFR p.L858R mutation. In patients with a de novo EGFRT790M mutation, no correlation was observed between T790M clonality and treatment outcomes with third-generation EGFR-TKIs. In contrast, the sub-clonality of the T790M mutation detrimentally affected the third-generation EGFR-TKI treatment efficacy in patients with acquired T790M mutation. Potential resistance mechanisms of third-generation EGFR TKIs in NSCLC patients with de novo or acquired EGFRT790M mutations included EGFR p.C797S in cis or EGFR p.E709X mutation, as well as activation of bypass pathways. ConclusionsThe present study characterized the uncommon but unique de novo EGFRT790M-mutant NSCLC and laid a foundation for designing future clinical trials in the setting of uncommon EGFR mutation.

Efficacy of bevacizumab through an indwelling pleural catheter in non-small cell lung cancer patients with symptomatic malignant pleural effusion

BackgroundSeveral studies have indicated that intrapleural infusion of bevacizumab is an effective treatment for non-small cell lung cancer (NSCLC) with malignant pleural effusion (MPE). However, the impact of bevacizumab administered through an indwelling pleural catheter (IPC) on the prognosis of these patients is unknown.MethodsConsecutive advanced NSCLC patients with symptomatic MPE receiving an IPC alone or bevacizumab through an IPC were identified in a tertiary hospital. The patient characteristics and clinical outcomes were collected.ResultsA total of 149 patients were included, and the median age was 60.3 years. Males and nonsmokers accounted for 48.3% and 65.8%, respectively. A total of 69.8% (104/149) of patients harbored actionable mutations, including 92 EGFR-activating mutations, 11 ALK fusions, and 1 ROS1 fusion. A total of 81.9% (122/149) of patients received IPC alone, and 18.1% (27/149) received bevacizumab through an IPC. The incidence of spontaneous pleurodesis during the first 6 months was greater in the bevacizumab-treated group than in the IPC-treated group in the subgroup with actionable mutations (64.3% vs. 46.9%, P = 0.28). The median overall survival (OS) in patients with actionable mutations treated with bevacizumab through an IPC was 42.2 months, which was significantly longer than the 26.7 months in patients who received an IPC alone (P = 0.045). However, the median OS did not differ between the two arms in the subgroup without actionable mutations (10.8 vs. 41.0 months, P = 0.24). No significant difference between the bevacizumab through an IPC group and the IPC group was detected in the number of participants who had adverse events, either in patients with actionable mutations (14.3% vs. 8.4%; P = 0.42) or in patients without actionable mutations (16.7% vs. 12.8%; P = 1.00).ConclusionsBevacizumab through an IPC resulted in a significantly improved prognosis for NSCLC patients with MPE and actionable mutations. However, patients without actionable mutations do not benefit from bevacizumab through IPC.

The Epidermal Growth Factor, Anaplastic Lymphoma Kinase, and ROS Proto-oncogene 1 Mutation Profile of Non-Small Cell Lung Carcinomas in the Turkish Population: A Single-Center Analysis.

The management of non-small cell lung carcinomas (NSCLC) has changed with the identification of molecular pathways. We aimed to reveal the 3-year epidermal growth factor (EGFR), anaplastic lymphoma kinase (ALK), and ROS proto-oncogene 1 (ROS1) mutation profile in the Turkish population. The histopathological and molecular data of all NSCLC cases from our department between May 2019 and April 2022 were evaluated. Molecular testing was performed in 197 NSCLC cases, and results were obtained in 182 (92.4%) (M/F: 144/38, aged 39-86). Of these, 121 were diagnosed with adenocarcinoma, 36 with squamous cell carcinoma, and 25 with NSCLC-not otherwise specified. The EGFR mutation was seen in 21 (11.5%) cases (6 exon 19 deletions, 3 exon 18 [all codon 719], 2 exon 20, 8 exon 21 point mutations, 1 concurrent exon 19 deletion and exon 20 codon 790 M point mutation, and 1 concurrent exon 19 deletion and exon 21 point mutation). The double mutation rate of EGFR was 1.1%. The mean age of these patients was 63.4 (40-79), with 24% of all females (n = 9) and 8.3% of all males (n = 12). The ALK mutation was detected in 6 (3.3%) patients (M/F: 4/2, aged 45-82), whereas the ROS1 mutation was detected in 3 (1.7%) (M/F: 2/1, aged 40-64). It is well established in the literature that EGFR-activating mutation rates vary depending on regions and ethnic groups. We concluded that the EGFR-activating mutation rates of the Turkish population are similar to the European molecular data instead of the Asian. The ALK and ROS1 mutation rates also seem concordant with the literature.

Discovery of a Novel Potent EGFR Inhibitor Against EGFR Activating Mutations and On-Target Resistance in NSCLC.

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKI) serve as the standard first-line therapy for EGFR-mutated non-small cell lung cancer (NSCLC). Despite the sustained clinical benefits achieved through optimal EGFR-TKI treatments, including the third-generation EGFR-TKI osimertinib, resistance inevitably develops. Currently, there are no targeted therapeutic options available postprogression on osimertinib. Here, we assessed the preclinical efficacy of BI-4732, a novel fourth-generation EGFR-TKI, using patient-derived preclinical models reflecting various clinical scenarios. The antitumor activity of BI-4732 was evaluated using Ba/F3 cells and patient-derived cell/organoid/xenograft models with diverse EGFR mutations. Intracranial antitumor activity of BI-4732 was evaluated in a brain-metastasis mouse model. We demonstrated the remarkable antitumor efficacy of BI-4732 as a single agent in various patient-derived models with EGFR_C797S-mediated osimertinib resistance. Moreover, BI-4732 exhibited activity comparable to osimertinib in inhibiting EGFR-activating (E19del and L858R) and T790M mutations. In a combination treatment strategy with osimertinib, BI-4732 exhibited a synergistic effect at significantly lower concentrations than those used in monotherapy. Importantly, BI-4732 displayed potent antitumor activity in an intracranial model, with low efflux at the blood-brain barrier. Our findings highlight the potential of BI-4732, a selective EGFR-TKI with high blood-brain barrier penetration, targeting a broad range of EGFR mutations, including C797S, warranting clinical development.

Germline USP36 Mutation Confers Resistance to EGFR-TKIs by Upregulating MLLT3 Expression in Patients with Non-Small Cell Lung Cancer.

Although somatic mutations were explored in depth, limited biomarkers were found to predict the resistance of EGFR tyrosine kinase inhibitors (EGFR-TKI). Previous studies reported N6-methyladenosine (m6A) levels regulated response of EGFR-TKIs; whether the germline variants located in m6A sites affected resistance of EGFR-TKIs is still unknown. Patients with non-small cell lung cancer (NSCLC) with EGFR-activating mutation were enrolled to investigate predictors for response of EGFR-TKIs using a genome-wide-variant-m6A analysis. Bioinformatics analysis and series of molecular biology assays were used to uncover the underlying mechanism. We identified the germline mutation USP36 rs3744797 (C > A, K814N) was associated with survival of patients with NSCLC treated with gefitinib [median progression-free survival (PFS): CC vs. CA, 16.30 vs. 10.50 months, P < 0.0001, HR = 2.45] and erlotinib (median PFS: CC vs. CA, 14.13 vs. 9.47 months, P = 0.041, HR = 2.63). Functionally, the C > A change significantly upregulated USP36 expression by reducing its m6A level. Meanwhile, rs3744797_A (USP36 MUT) was found to facilitate proliferation, migration, and resistance to EGFR-TKIs via upregulating MLLT3 expression in vitro and in vivo. More importantly, MLLT3 and USP36 levels are tightly correlated in patients with NSCLC, which were associated with prognosis of patients. Mechanistically, USP36 MUT stabilized MLLT3 by deubiquitinating MLLT3 in nucleoli and consequently activating its downstream signaling (HIF1α and Snai). Furthermore, inhibition of MLLT3 alleviated USP36 variant-induced EGFR-TKIs resistance in EGFR-mutant NSCLC. These findings characterized rs3744797 as an oncogenic variant in mediating EGFR-TKI resistance and tumor aggressiveness through deubiquitinating MLLT3, highlighting the variant as a predictive biomarker for EGFR-TKI response in NSCLC.

Effects of H2-Receptor Antagonists on the Exposure of Dacomitinib.

Dacomitinib is an irreversible epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor indicated for the treatment of patients with advanced non-small-cell lung cancer (NSCLC) and EGFR-activating mutations. Proton-pump inhibitors decreased dacomitinib exposure. This analysis summarizes the effect of Histamine-2 receptor antagonists (H2RAs) on dacomitinib exposure. A within-patient comparison of the steady-state trough concentrations (Ctrough,ss) of dacomitinib and its active metabolite and active moiety with and without concomitant use of H2RAs was conducted using a linear mixed effects model with pooled data from 11 clinical studies in patients with NSCLC. An oral absorption physiologically based pharmacokinetic (PBPK) model was constructed and verified using clinical pharmacokinetic (PK) data after a single dose of dacomitinib in healthy volunteers to estimate the effect of gastric pH altered by an H2RA on dacomitinib's PKs. The adjusted geometric mean of the dacomitinib Ctrough,ss of the dacomitinib parent, metabolite and active moiety following co-administration with an H2RA was approximately 86%, 104% and 100% relative to that following dacomitinib 45 mg administration without an H2RA (p > 0.05). The PBPK modeling showed negligible change in dacomitinib maximum concentration (Cmax) and area under the drug concentration-time curve (AUC) over 0-24 h after H2RA administration when compared with those administered dacomitinib alone. Co-administration of an H2RA with dacomitinib is not expected to have any clinically relevant effect on dacomitinib exposure.

BLU-945, a potent and selective next-generation EGFR TKI, has antitumor activity in models of osimertinib-resistant non-small-cell lung cancer.

Despite the availability of several epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs), most patients with non-small-cell lung cancer (NSCLC) eventually develop resistance to these agents. Notably, EGFR_C797S mutations confer resistance to the third-generation EGFR-TKI osimertinib and no approved post-osimertinib targeted pharmacology options are currently available. BLU-945 is a novel, reversible, and orally available next-generation EGFR-TKI that selectively targets EGFR-activating (EGFRm) and resistance mutations (including EGFR_C797S) with nanomolar potency while sparing wild-type EGFR in vitro. In vitro activity of BLU-945 as a single agent and in combination with osimertinib was tested in engineered EGFR-mutant cell lines as well as patient-derived cells and patient-derived organoids. In vivo activity was evaluated in osimertinib-resistant patient-derived xenograft mouse models. Three patient cases from the global, first-in-human, phase I/II SYMPHONY trial (NCT04862780) demonstrating the clinical efficacy of BLU-945 were reported. In vitro BLU-945 demonstrated inhibited cell viability and growth of EGFR-mutant/osimertinib-resistant cell lines. BLU-945 demonstrated in vivo tumor shrinkage in osimertinib-resistant models of NSCLC (osimertinib second line: EGFR_L858R/C797S and third line: EGFR_ex19del/T790M/C797S and L858R/T790M/C797S) both as monotherapy and in combination with osimertinib. BLU-945 also demonstrated tumor shrinkage in patients from the SYMPHONY trial. Our findings demonstrate the preclinical and early clinical activity of BLU-945 in EGFRm NSCLC progressing on previous EGFR-TKIs.

Nanoenabled intracellular zinc bursting for efficacious reversal of gefitinib resistance in lung cancer.

Following the identification of specific epidermal growth factor receptor (EGFR)-activating mutations, gefitinib, one of the first-generation tyrosine kinase inhibitors (TKIs), has proven efficacious in targeting NSCLC that is driven by specific EGFR-activating mutations. However, most patients who initially respond to gefitinib, develop acquired resistance. In the current study, we devised a novel strategy to enhance the efficacy of gefitinib. We developed a simple and effective, nano-interrupter termed zeolitic imidazolate framework-8@Gefitinib@hyaluraonic nanoparticle (ZIF-8@G@HA NP). This nanoparticle was prepared by loading gefitinib onto a ZIF-8 nanoplatform followed by coating with hyaluronic acid (HA). The burst of Zn2+ release triggered by pH-sensitive degradation of ZIF-8@G@HA NPs was shown to enhance the efficacy of gefitinib in parental lung carcinoma HCC827 cells and overcame acquired gefitinib resistance in gefitinib drug resistant (GDR) HCC827 cells. We found that when treated with ZIF-8@G@HA NPs, Zn2+ acts synergistically with gefitinib via increased apoptosis in both parental and GDR HCC827 cells. Consistently, this in vitro activity was correlated with in vivo tumor growth inhibition. Interestingly, GDR cells were more sensitive to Zn2+ when compared with parental cells. We further found that ZIF-8 NPs overcame gefitinib resistance by triggering reactive oxygen species (ROS) generation and consequent cell cycle arrest at the G2/M phase, resulting in cancer cell apoptosis. Zn2+ was also found to block P-gp activity, facilitating the accumulation of gefitinib in GDR cells, thus enhancing the anti-tumor efficacy of gefitinib resulting in reversal of gefitinib resistance. Thus, this study offers a novel and promising strategy to surmount acquired gefitinib resistance via cell cycle arrest at the G2/M phase by facilitating gefitinib accumulation in GDR cells.

RELAY, Erlotinib Plus Ramucirumab in Untreated, EGFR-Mutated, Metastatic NSCLC: Outcomes by EGFR Exon 19 Deletion Variants

IntroductionEGFR gene mutations are drivers of NSCLC. The RELAY double-blind, placebo (PBO)-controlled phase 3 study revealed superior progression-free survival (PFS) for ramucirumab plus erlotinib (RAM + ERL) versus PBO (PBO + ERL) in patients with untreated advanced NSCLC and an EGFR-activating mutation. This exploratory analysis evaluated potential associations between EGFR exon 19 deletion (ex19del) variants and clinical outcomes. MethodsPatients (N = 449) were randomized (1:1) to RAM plus ERL or PBO plus ERL. Plasma samples were collected at baseline, on treatment, and at 30-day post-study treatment discontinuation follow-up. Baseline and treatment-emergent gene alterations were investigated by Guardant360 next-generation sequencing. Patients with a valid baseline plasma sample and ex19del were included (RAM + ERL, n = 62; PBO + ERL, n = 72). ResultsThe most common ex19del variant was E746_A750del (67.2%); EGFR E746 deletions (E746del) occurred more frequently than L747 deletions (74.6% versus 25.4%, respectively). TP53 mutations were the most frequently co-occurring baseline gene alterations. With treatment arms combined, median PFS was 18.0 months versus 12.5 months for patients with uncommon (non-E746_A750del, n = 44) versus common (E746_A750del, n = 90) ex19del variants (hazard ratio [HR] = 1.657 [95% confidence interval or CI:1.044–2.630]). Median PFS was longer with RAM plus ERL versus PBO plus ERL for patients with the common (15.2 versus 9.9 mo; HR = 0.564 [95% CI: 0.344–0.926]) and E746del (15.4 versus 9.9 mo; HR = 0.587 [95% CI: 0.363–0.951]) variants. Treatment-emergent post-progression EGFR T790M rates were higher in the common versus uncommon and E746del versus L747 deletion subgroups. ConclusionsRAM plus ERL provides benefit and improves treatment outcomes for patients with metastatic NSCLC with EGFR ex19del variants.

Abstract B167: Preclinical characterization of THE-349, a mutant-selective, CNS-active, fourth-generation EGFR inhibitor to overcome T790M- and C797S-mediated resistance in NSCLC

Abstract Background: EGFR activating mutations are observed in 10-50% of NSCLC patients. Although the common mutations (L858R [L] and exon 19 deletions [D]) are initially sensitive to first-, second-, and third-generation EGFR inhibitors (e.g., erlotinib [1G], afatinib [2G], and osimertinib [3G], respectively), on-target resistance is observed in a substantial percentage of patients, with T790M (T) and C797S (C) observed most frequently (post-1G/2G and post-3G, respectively). Furthermore, EGFR mutational heterogeneity can increase during treatment with existing inhibitors, inhibition of wild type (WT) EGFR leads to dose-limiting toxicities, and tumors commonly metastasize to the brain. We have designed THE-349 to be a fourth-generation EGFR inhibitor with potent activity against all 8 major single- (L, D), double- (LT, DT, LC, DC), and triple- (LTC, DTC) mutant variants, selectivity over WT EGFR, and activity in the CNS. Methods: Kinome selectivity was evaluated biochemically against a panel of 412 kinases. In vitro potency was determined by assessing effects (IC50s) on human and BaF3 cell lines expressing WT or mutant forms of EGFR. Efficacy studies were conducted using engineered BaF3 cell lines, a luciferase-tagged human NSCLC cell line, and a patient-derived xenograft (PDX) model dosed orally, once-daily at levels that did not exceed the maximum tolerated dose (40 mg/kg THE-349 and 25 mg/kg osimertinib). Results:THE-349 potently inhibited the biochemical activity of all major EGFR mutant variants (IC50s &amp;lt;2 nM) with a high degree of kinome selectivity. In engineered BaF3 cells in vitro, THE-349 potently inhibited viability of all 8 major EGFR mutant variants (L, LT, LC, LTC, D, DT, DC, and DTC), with IC50s &amp;lt;6 nM and with ≥10-fold selectivity over WT EGFR. Similarly, THE-349 demonstrated robust anti-tumor activity against the same 8 EGFR variants in vivo, in all cases inducing deep tumor regressions (&amp;gt;80% TR) in mice implanted with engineered BaF3 cells. In a PDX model from an osimertinib-resistant tumor containing D and DTC variants, THE-349 induced deep and sustained regressions (99% TR) through 56 days of dosing, and tumor regrowth that occurred during a subsequent 5-week dosing holiday was reversed (88% TR) upon redosing with THE-349. In an intracranial tumor model using a triple-mutant (LTC) NSCLC cell line, THE-349 significantly prolonged median survival (from 42.5 to 71.5 days), while osimertinib had no effect. THE-349 has a favorable ADME profile and promising safety profile in IND-enabling toxicology studies. Conclusion: THE-349 is a fourth-generation, CNS-active, mutant-selective EGFR inhibitor that has potent, single-agent activity against all major classes of EGFR activating and resistance mutations. A phase 1 clinical trial of THE-349 is planned. Citation Format: Sen Zhang, Sara Nadworny, Wei-Sheng Huang, Adam Talbot, Emily Ye, Narayana Narasimhan, William C Shakespeare, Victor M Rivera. Preclinical characterization of THE-349, a mutant-selective, CNS-active, fourth-generation EGFR inhibitor to overcome T790M- and C797S-mediated resistance in NSCLC [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 B167.

Abstract C052: Circumventing EGFR inhibitor resistance in NSCLC using transomics

Abstract Drug discovery continues to be refined to enhance efficiency, yet &amp;gt;80% of new drugs fail in the clinical trial stage. It is apparent that a novel approach is needed. COMPASS is a transomic analysis platform that integrates data across multiple omics layers; genomics, transcriptomics, proteomics, and phosphoproteomics. This analysis allows us to interpret complex biological relationships and provide a functional map of the biochemical drivers of disease. We have used EGFR inhibitor (EGFRi) resistance as a case study. EGFRi have been successful in treating non-small cell lung cancer (NSCLC) patients with activating EGFR mutations (EGFRm), however, this success is temporary. The emergence of resistance is a problem and limits long-term treatment for many patients, even with osimertinib, a third-generation inhibitor and current standard of care. As resistance to EGFRi occurs through mutations in EGFR we adopted a novel strategy using COMPASS to identify and validate alternative, non-EGFR targets that could potentially recapitulate the pharmacological effects of EGFRi in EGFRm NSCLC. The transomic signatures of EGFRi were generated using a NSCLC cell line containing the activating mutation ex19del. The drug concentration required to inhibit cell growth (IC50) was first determined. For transomic analyses, cells were incubated for 24 h with the drug IC50 concentration and harvested for genomic, transcriptomic, proteomic, and phosphoproteomic analyses. We have previously shown transomics analysis can differentiate between EGFRi that have been designed to treat EGFRm NSCLC with the transomics signature for osimertinib being significantly different from comparator drugs that failed during drug development. We employed our proprietary target prioritization algorithm to further analyze the omics data to identify and rank novel targets. Targets were then filtered to select those with an available pharmacological tool compound (PTC). The PTCs were used to evaluate the targets in a xenograft model of osimertinib resistant NSCLC, PC9-Del19/T790M/C797S; which contains the activating EGFR mutation (ex19del), and two mutations conferring EGFRi resistance, T790M gatekeeper mutation, and C797S which confers resistance to osimertinib. Of the targets tested 82% (9/11) were associated with &amp;gt;25% inhibition of tumor growth. Furthermore, 36% (4/11) targets were associated with &amp;gt;50% inhibition by the PTCs, with inhibition of one target giving &amp;gt;85% inhibition resulting in stasis of tumor growth. Future work will investigate targets using gene silencing, as PTCs were not available for many of the novel high-ranked targets. These data show that using COMPASS transomic analysis, it is possible to identify novel drug targets to treat difficult-to-treat cancers such as EGFRi-resistant NSCLC and provides validation of this discovery platform by disease-relevant in vivo pharmacology. Further validation studies are ongoing against other difficult-to-treat cancers to identify novel clinical targets and drug candidates. Citation Format: Christopher J Nicholson, Samuel J Roth, Arudhir Singh, Caitlin Brown, Simon P Fricker, Jon Hu, Samantha Dale Strasse. Circumventing EGFR inhibitor resistance in NSCLC using transomics [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 C052.

Abstract C025: Trial in progress: First-in-human study of BBT-207 in advanced non-small cell lung cancer harboring EGFR mutation after treatment with EGFR TKI

Abstract Background: There is a high unmet need for an effective therapy for the treatment of non-small cell lung cancer (NSCLC) following osimertinib or other 3rd generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) failure, especially when resistance is driven by the occurrence of the C797S mutation. BBT-207 is a fourth-generation EGFR inhibitor. Preclinically BBT-207 has shown activity against treatment-emergent complex EGFR mutations containing T790M and/or C797S as well as drug-naïve mutants providing a possibility to overcome resistance to prior TKIs. Activity to intracranial lesions is also anticipated from animal models. Methods: Study BBT207-ONC-001 is an open-label, phase 1/2 study evaluating safety, tolerability, pharmacokinetic profile, pharmacodynamic characterization, and preliminary antitumor activity of BBT-207 monotherapy in approximately 92 patients with EGFR-mutant NSCLC. It consists of 3 phases: Phase 1a (dose escalation), phase 1b (recommended phase 2 dose selection), and phase 2 (dose expansion). Key eligibility criteria include patients ≥18 years of age with advanced stage and refractory NSCLC with an activating EGFR mutation, documented partial response, complete response, or durable stable disease after treatment of an EGFR TKI, and previous treatment with all standard therapeutic options and at least one third-generation EGFR TKI. There is no limit on the number of previous treatments received. Phase 1a requires confirmation that the tumor harbors a classical EGFR mutation (19Del or L858R), and phase 1b and phase 2 require confirmation that the tumor or the blood harbors complex EGFR mutations containing C797S. Patients with asymptomatic brain metastases who are on stable dose of corticosteroid are eligible. Primary endpoints are to determine recommended dose range (RDR) which is defined between the minimal reproducibly active dose, and the maximum tolerated dose or maximum administered dose and to characterize the overall safety and tolerability of BBT-207 (phase 1a); to determine the recommended phase 2 dose (phase 1b); to evaluate preliminary antitumor activity with objective response rate (phase 2). Phase 1a dose escalation will be guided by Bayesian logistic regression model. The safety monitoring committee will determine RDR and two recommended dose levels (RDs) within the RDR to be explored in phase 1b. In phase 1b, up to 20 patients will be randomized to each of the two RDs. At the end of phase 1b, a futility test will be performed in the dose level to be treated with the RP2D using Bayesian analysis. Phase 2 will be a non-randomized, open-label phase with up to 20 patients. Patients may receive treatment until disease progression or unacceptable toxicity. Treatment continuation beyond progression will be allowed if potential benefits are justified. Investigational new drug application was cleared by the U.S. FDA. Patient enrollment will begin in approximately August 2023 in the U.S. and Republic of Korea. Clinical trial information: NCT05920135. Citation Format: NaEun Jeon, Alexander Spira, Douglas Orr, Lyudmila Bazhenova, Misako Nagasaka, Jin Seok Ahn, Dong-Wan Kim, Yu Jung Kim, Jimin Cho, Agnes Jung, Eunsoo Jung, Chul-Won Kim, Taiguang Jin, Yong-Hee Lee, Sang-Yoon Lee. Trial in progress: First-in-human study of BBT-207 in advanced non-small cell lung cancer harboring EGFR mutation after treatment with EGFR TKI [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 C025.

Droplet Digital PCR as a Molecular Tool for the Detection of the EGFR T790M Mutation in NSCLC Patients with the EGFR Activating Mutations.

Almost 50% of NSCLC patients who initially show a successful response to tyrosine kinase inhibitors targeted therapy (TKI therapy) eventually develop acquired EGFR T790M mutation. The T790M secondary mutation can cause resistance to the targeted therapy and disease relapse. Since this mutation can be present at very low frequencies in liquid biopsy samples, droplet digital PCR (ddPCR), due to its high sensitivity, has opened the possibility for minimally invasive monitoring of the disease during TKI targeted therapy. For this study, a total of 45 plasma samples from NSCLC patients with previously detected EGFR-activating mutations were analyzed. Extracted circulating free DNA was amplified and examined for the presence of T790M mutation using ddPCR technology. For the data analysis, QuantaSoft Software was used. Of 45 tested plasma samples, a total of 14 samples were identified as positive for the T790M mutation. The same samples eventually showed the presence of T790M mutation in FFPE. Droplet digital PCR showed its great advantage in high sensitivity detection of rare allele variants. Our ddPCR assay detected T790M mutant allele in frequencies from 0.1%. The average number of droplets generated by ddPCR was 9571. Monitoring of the T790M mutation has an important role in the examination of the effects of the prescribed TKI therapy. Since monitoring of potential changes during TKI therapy requires repeated sampling, our results showed that ddPCR technology has made it possible to use liquid biopsy as an adequate minimally invasive alternative for single nucleotide polymorphisms (SNP) detection.

Dacomitinib in EGFR-mutant non-small-cell lung cancer with brain metastasis: a single-arm, phase II study

Dacomitinib showed superior progression-free survival (PFS) and overall survival compared to gefitinib in patients with advanced non-small-cell lung cancer (NSCLC) harboring epidermal growth factor receptor (EGFR) mutations in the ARCHER1050 study. However, because that study did not include patients with brain metastases, the efficacy of dacomitinib in patients with brain metastases has not been clarified. This single-arm phase II study enrolled 30 patients with treatment-naïve advanced NSCLC harboring activating EGFR mutations from January 2021 to June 2021 and started them on dacomitinib (45 mg/day). All patients had non-irradiated brain metastases with a diameter of ≥5 mm. The primary endpoint was confirmed intracranial objective response rate (iORR). Patients had exon 19 deletions (46.7%) and L858R mutations in exon 21 (55.3%). The confirmed iORR was 96.7% (29/30), with an intracranial complete response of 63.3%. Median intracranial PFS (iPFS) was not reached, with 12- and 18-month iPFS rates of 78.6% [95% confidence interval (CI) 64.8% to 95.4%] and 70.4% (95% CI 54.9% to 90.1%), respectively. In the competing risk analysis, the 12-month cumulative incidence of intracranial progression was 16.7%. Regarding the overall efficacy for intracranial and extracranial lesions, the overall ORR was 96.7%, and the median PFS was 17.5 months (95% CI 15.2 months-not reached). Grade 3 or higher treatment-related adverse events were reported in 16.7% of patients, and 83.3% required a reduced dacomitinib dose to manage adverse events. However, none permanently discontinued dacomitinib treatment due to treatment-related adverse events. Dacomitinib has outstanding intracranial efficacy in patients with EGFR-mutant NSCLC with brain metastases.