Showing papers on "Osimertinib published in 2019"

Resistance mechanisms to osimertinib in EGFR-mutated non-small cell lung cancer.

Abstract: Osimertinib is an irreversible, third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor that is highly selective for EGFR-activating mutations as well as the EGFR T790M mutation in patients with advanced non-small cell lung cancer (NSCLC) with EGFR oncogene addiction. Despite the documented efficacy of osimertinib in first- and second-line settings, patients inevitably develop resistance, with no further clear-cut therapeutic options to date other than chemotherapy and locally ablative therapy for selected individuals. On account of the high degree of tumour heterogeneity and adaptive cellular signalling pathways in NSCLC, the acquired osimertinib resistance is highly heterogeneous, encompassing EGFR-dependent as well as EGFR-independent mechanisms. Furthermore, data from repeat plasma genotyping analyses have highlighted differences in the frequency and preponderance of resistance mechanisms when osimertinib is administered in a front-line versus second-line setting, underlying the discrepancies in selection pressure and clonal evolution. This review summarises the molecular mechanisms of resistance to osimertinib in patients with advanced EGFR-mutated NSCLC, including MET/HER2 amplification, activation of the RAS–mitogen-activated protein kinase (MAPK) or RAS–phosphatidylinositol 3-kinase (PI3K) pathways, novel fusion events and histological/phenotypic transformation, as well as discussing the current evidence regarding potential new approaches to counteract osimertinib resistance.

AXL confers intrinsic resistance to osimertinib and advances the emergence of tolerant cells.

Abstract: A novel EGFR-tyrosine kinase inhibitor (TKI), osimertinib, has marked efficacy in patients with EGFR-mutated lung cancer. However, some patients show intrinsic resistance and an insufficient response to osimertinib. This study showed that osimertinib stimulated AXL by inhibiting a negative feedback loop. Activated AXL was associated with EGFR and HER3 in maintaining cell survival and inducing the emergence of cells tolerant to osimertinib. AXL inhibition reduced the viability of EGFR-mutated lung cancer cells overexpressing AXL that were exposed to osimertinib. The addition of an AXL inhibitor during either the initial or tolerant phases reduced tumor size and delayed tumor re-growth compared to osimertinib alone. AXL was highly expressed in clinical specimens of EGFR-mutated lung cancers and its high expression was associated with a low response rate to EGFR-TKI. These results indicated pivotal roles for AXL and its inhibition in the intrinsic resistance to osimertinib and the emergence of osimertinib-tolerant cells.

Single and Dual Targeting of Mutant EGFR with an Allosteric Inhibitor.

Abstract: Allosteric kinase inhibitors offer a potentially complementary therapeutic strategy to ATP-competitive kinase inhibitors due to their distinct sites of target binding. In this study, we identify and study a mutant-selective EGFR allosteric inhibitor, JBJ-04-125-02, which as a single agent can inhibit cell proliferation and EGFRL858R/T790M/C797S signaling in vitro and in vivo. However, increased EGFR dimer formation limits treatment efficacy and leads to drug resistance. Remarkably, osimertinib, an ATP-competitive covalent EGFR inhibitor, uniquely and significantly enhances the binding of JBJ-04-125-02 for mutant EGFR. The combination of osimertinib and JBJ-04-125-02 results in an increase in apoptosis, a more effective inhibition of cellular growth, and an increased efficacy in vitro and in vivo compared with either single agent alone. Collectively, our findings suggest that the combination of a covalent mutant-selective ATP-competitive inhibitor and an allosteric EGFR inhibitor may be an effective therapeutic approach for patients with EGFR-mutant lung cancer. SIGNIFICANCE: The clinical efficacy of EGFR tyrosine kinase inhibitors (TKI) in EGFR-mutant lung cancer is limited by acquired drug resistance, thus highlighting the need for alternative strategies to inhibit EGFR. Here, we identify a mutant EGFR allosteric inhibitor that is effective as a single agent and in combination with the EGFR TKI osimertinib.This article is highlighted in the In This Issue feature, p. 813.

MET inhibitors for targeted therapy of EGFR TKI-resistant lung cancer

Abstract: Treatment of non-small cell lung cancer (NSCLC) harboring epidermal growth factor receptor (EGFR) activating mutation with EGFR-TKIs has achieved great success, yet faces the development of acquired resistance as the major obstacle to long-term disease remission in the clinic. MET (or c-MET) gene amplification has long been known as an important resistance mechanism to first- or second-generation EGFR-TKIs in addition to the appearance of T790 M mutation. Recent preclinical and clinical studies have suggested that MET amplification and/or protein hyperactivation is likely to be a key mechanism underlying acquired resistance to third-generation EGFR-TKIs such as osimertinib as well, particularly when used as a first-line therapy. EGFR-mutant NSCLCs that have relapsed from first-generation EGFR-TKI treatment and have MET amplification and/or protein hyperactivation should be insensitive to osimertinib monotherapy. Therefore, combinatorial therapy with osimertinib and a MET or even a MEK inhibitor should be considered for these patients with resistant NSCLC carrying MET amplification and/or protein hyperactivation.

Epithelial-mesenchymal transition (EMT) beyond EGFR mutations per se is a common mechanism for acquired resistance to EGFR TKI.

Abstract: Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) is a major advance in treating NSCLC with EGFR-activating mutations. However, acquired resistance, due partially to secondary mutations limits their use. Here we report that NSCLC cells with acquired resistance to gefitinib or osimertinib (AZD9291) exhibit EMT features, with a decrease in E-cadherin, and increases in vimentin and stemness, without possessing any EGFR secondary mutations. Knockdown of E-cadherin in parental cells increased gefitinib resistance and stemness, while knockdown of vimentin in resistant cells resulted in opposite effects. Src activation and Hakai upregulation were found in gefitinib-resistant cells. Knockdown of Hakai elevated E-cadherin expression, attenuated stemness, and resensitized the cells to gefitinib. Clinical cancer specimens with acquired gefitinib resistance also showed a decrease in E-cadherin and an increase in Hakai expression. The dual HDAC and HMGR inhibitor JMF3086 inhibited the Src/Hakai and Hakai/E-cadherin interaction to reverse E-cadherin expression, and attenuated vimentin and stemness to restore gefitinib sensitivity. The EMT features of AZD9291-resistant H1975 cells were related to the upregulation of Zeb1. Both gefitinib and AZD9291 sensitivity was restored by JMF3086 through reversing EMT. Our study not only revealed a common mechanism of EMT in both gefitinib and AZD9291 resistance beyond EGFR mutations per se, but also provides a new strategy to overcome it.

Novel Third-Generation EGFR Tyrosine Kinase Inhibitors and Strategies to Overcome Therapeutic Resistance in Lung Cancer

Abstract: EGFR-activating mutations are observed in approximately 15% to 20% of patients with non–small cell lung cancer. Tyrosine kinase inhibitors have provided an illustrative example of the successes in targeting oncogene addiction in cancer and the role of tumor-specific adaptations conferring therapeutic resistance. The compound osimertinib is a third-generation tyrosine kinase inhibitor, which was granted full FDA approval in March 2017 based on targeting EGFR T790M resistance. The compound has received additional FDA approval as first-line therapy with improvement in progression-free survival by suppressing the activating mutation and preventing the rise of the dominant resistance clone. Drug development has been breathtaking in this space with other third-generation compounds at various stages of development: rociletinib (CO-1686), olmutinib (HM61713), nazartinib (EGF816), naquotinib (ASP8273), mavelertinib (PF-0647775), and AC0010. However, therapeutic resistance after the administration of third-generation inhibitors is complex and not fully understood, with significant intertumoral and intratumoral heterogeneity. Repeat tissue and plasma analyses on therapy have revealed insights into multiple mechanisms of resistance, including novel second site EGFR mutations, activated bypass pathways such as MET amplification, HER2 amplification, RAS mutations, BRAF mutations, PIK3CA mutations, and novel fusion events. Strategies to understand and predict patterns of mutagenesis are still in their infancy; however, technologies to understand synthetically lethal dependencies and track cancer evolution through therapy are being explored. The expansion of combinatorial therapies is a direction forward targeting minimal residual disease and bypass pathways early based on projected resistance.

Targeting the EMT transcription factor TWIST1 overcomes resistance to EGFR inhibitors in EGFR-mutant non-small-cell lung cancer.

Abstract: Patients with EGFR-mutant non-small-cell lung cancer (NSCLC) have significantly benefited from the use of EGFR tyrosine kinase inhibitors (TKIs) However, long-term efficacy of these therapies is limited due to de novo resistance (~30%) as well as acquired resistance Epithelial–mesenchymal transition transcription factors (EMT-TFs), have been identified as drivers of EMT-mediated resistance to EGFR TKIs, however, strategies to target EMT-TFs are lacking As the third generation EGFR TKI, osimertinib, has now been adopted in the first-line setting, the frequency of T790M mutations will significantly decrease in the acquired resistance setting Previously less common mechanisms of acquired resistance to first generation EGFR TKIs including EMT are now being observed at an increased frequency after osimertinib Importantly, there are no other FDA approved targeted therapies after progression on osimertinib Here, we investigated a novel strategy to overcome EGFR TKI resistance through targeting the EMT-TF, TWIST1, in EGFR-mutant NSCLC We demonstrated that genetic silencing of TWIST1 or treatment with the TWIST1 inhibitor, harmine, resulted in growth inhibition and apoptosis in EGFR-mutant NSCLC TWIST1 overexpression resulted in erlotinib and osimertinib resistance in EGFR-mutant NSCLC cells Conversely, genetic and pharmacological inhibition of TWIST1 in EGFR TKI-resistant EGFR-mutant cells increased sensitivity to EGFR TKIs TWIST1-mediated EGFR TKI resistance was due in part to TWIST1 suppression of transcription of the pro-apoptotic BH3-only gene, BCL2L11 (BIM), by directly binding to BCL2L11 intronic regions and promoter As such, pan-BCL2 inhibitor treatment overcame TWIST1-mediated EGFR TKI resistance and were more effective in the setting of TWIST1 overexpression Finally, in a mouse model of autochthonous EGFR-mutant lung cancer, Twist1 overexpression resulted in erlotinib resistance and suppression of erlotinib-induced apoptosis These studies establish TWIST1 as a driver of resistance to EGFR TKIs and provide rationale for use of TWIST1 inhibitors or BCL2 inhibitors as means to overcome EMT-mediated resistance to EGFR TKIs

Osimertinib in patients with T790M mutation‐positive, advanced non–small cell lung cancer: Long‐term follow‐up from a pooled analysis of 2 phase 2 studies

Abstract: Background Osimertinib is a third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) that is selective for both EGFR-TKI-sensitizing and T790M (threonine-to-methionine substitution at codon 790)-resistance mutations. The authors present long-term follow-up data from a preplanned, pooled analysis of phase 2 studies, the AZD9291 First Time in Patients Ascending Dose Study (AURA) extension trial (clincialtrials.gov identifier NCT01802632) and the AURA2 trial (NCT02094261). Methods Patients with centrally confirmed, T790M mutation-positive, advanced non-small cell lung cancer received osimertinib 80 mg once daily until disease progression or study discontinuation. Response was assessed by a blinded, independent, central review using Response Evaluation Criteria in Solid Tumors, version 1.1. The primary endpoint was the objective response rate. Results In total, 411 patients received osimertinib (second line, 129 patients; third line or later, 282 patients). At the data cutoff date of November 1, 2016, the median treatment exposure was 16.4 months (range, 0-29.7 months), the objective response rate was 66% (95% confidence interval [CI], 61%-70%), the median response duration was 12.3 months (95% CI, 11.1-13.8 months), and the median progression-free survival was 9.9 months (95% CI, 9.5-12.3 months). At the data cutoff date of May 1, 2018, 271 patients (66%) had died, and 140 patients (34%) had discontinued before death. The median overall survival was 26.8 months (95% CI, 24.0-29.1 months); and the 12-month, 24-month, and 36-month survival rates were 80%, 55%, and 37%, respectively. Grade ≥3 possibly causally related (investigator assessed) adverse events were reported in 65 patients (16%), and the most common were rash (grouped terms; 42%; grade ≥3, 1%) and diarrhea (39%; Conclusions This pooled analysis represents the most mature clinical trial data for osimertinib in patients with pretreated, T790M-positive, advanced non-small cell lung cancer, further establishing osimertinib as a standard of care for this patient population.

First- and Second-Generation EGFR-TKIs Are All Replaced to Osimertinib in Chemo-Naive EGFR Mutation-Positive Non-Small Cell Lung Cancer?

Abstract: Activating mutations of the epidermal growth factor receptor gene (EGFR) are a driving force for some lung adenocarcinomas. Several randomized phase III studies have revealed that treatment with first- or second-generation EGFR tyrosine kinase inhibitors (TKIs) results in an improved progression-free survival (PFS) compared to standard chemotherapy in chemonaive patients with advanced non–small cell lung cancer (NSCLC), selected based on the presence of EGFR mutations. Patients treated with second-generation EGFR-TKIs have also shown an improved PFS relative to those treated with first-generation EGRF-TKIs. Osimertinib is a third-generation EGFR-TKI that still irreversibly inhibits the activity of EGFR after it has acquired the secondary T790M mutation that confers resistance to first- and second-generation drugs. Its efficacy has been validated for patients whose tumors have developed T790M-mediated resistance, as well as for first-line treatment of those patients with EGFR mutation–positive NSCLC. Although there are five EGFR-TKIs (gefitinib, erlotinib, afatinib, dacomitinib, and osimertinib) currently available for the treatment of EGFR-mutated lung cancer, the optimal sequence for administration of these drugs remains to be determined. In this review, we addressed this issue with regard to maximizing the duration of the EGFR-TKI treatment.

Efficacy and safety of first line treatments for patients with advanced epidermal growth factor receptor mutated, non-small cell lung cancer: systematic review and network meta-analysis

Abstract: Objective To compare the efficacy and safety of first line treatments for patients with advanced epidermal growth factor receptor (EGFR) mutated non-small cell lung cancer (NSCLC). Design Systematic review and network meta-analysis. Data sources PubMed, Embase, Cochrane Central Register of Controlled Trials, ClinicalTrials.gov, and several international conference databases, from inception to 20 May 2019. Eligibility criteria for selecting studies Published and unpublished randomised controlled trials comparing two or more treatments in the first line setting for patients with advanced EGFR mutated NSCLC were included in a bayesian network meta-analysis. Eligible studies reported at least one of the following clinical outcome measures: progression free survival, overall survival, objective response rate, and adverse events of grade 3 or higher. Results 18 eligible trials involved 4628 patients and 12 treatments: EGFR tyrosine kinase inhibitors (TKIs; osimertinib, dacomitinib, afatinib, erlotinib, gefitinib, and icotinib), pemetrexed based chemotherapy, pemetrexed free chemotherapy, and combination treatments (afatinib plus cetuximab, erlotinib plus bevacizumab, gefitinib plus pemetrexed based chemotherapy, and gefitinib plus pemetrexed). Consistent with gefitinib plus pemetrexed based chemotherapy (hazard ratio 0.95, 95% credible interval 0.72 to 1.24), osimertinib showed the most favourable progression free survival, with significant differences versus dacomitinib (0.74, 0.55 to 1.00), afatinib (0.52, 0.40 to 0.68), erlotinib (0.48, 0.40 to 0.57), gefitinib (0.44, 0.37 to 0.52), icotinib (0.39, 0.24 to 0.62), pemetrexed based chemotherapy (0.24, 0.17 to 0.33), pemetrexed free chemotherapy (0.16, 0.13 to 0.20), afatinib plus cetuximab (0.44, 0.28 to 0.71), and gefitinib plus pemetrexed (0.65, 0.46 to 0.92). Osimertinib and gefitinib plus pemetrexed based chemotherapy were also consistent (0.94, 0.66 to 1.35) in providing the best overall survival benefit. Combination treatments caused more toxicity in general, especially erlotinib plus bevacizumab, which caused the most adverse events of grade 3 or higher. Different toxicity spectrums were revealed for individual EGFR-TKIs. Subgroup analyses by the two most common EGFR mutation types indicated that osimertinib was associated with the best progression free survival in patients with the exon 19 deletion, and gefitinib plus pemetrexed based chemotherapy was associated with the best progression free survival in patients with the Leu858Arg mutation. Conclusions These results indicate that osimertinib and gefitinib plus pemetrexed based chemotherapy were associated with the best progression free survival and overall survival benefits for patients with advanced EGFR mutated NSCLC, compared with other first line treatments. The treatments resulting in the best progression free survival for patients with the exon 19 deletion and Leu858Arg mutations were osimertinib and gefitinib plus pemetrexed based chemotherapy, respectively. Systematic review registration PROSPERO CRD42018111954.

Liquid-Biopsy-Based Identification of EGFR T790M Mutation-Mediated Resistance to Afatinib Treatment in Patients with Advanced EGFR Mutation-Positive NSCLC, and Subsequent Response to Osimertinib

Abstract: Acquired epidermal growth factor receptor (EGFR) T790M mutation is the primary resistance mechanism to first-generation EGFR tyrosine kinase inhibitors (TKIs) used in advanced, EGFR mutation-positive non-small-cell lung cancer (NSCLC). Available data, predominantly in Asian patients, suggest that this mutation is also the major cause of resistance to the irreversible ErbB family blocker, afatinib. For EGFR T790M-positive patients who progress on EGFR TKI therapy, osimertinib is an effective treatment option. However, data on osimertinib use after afatinib are, to date, scarce. To identify the prevalence of EGFR T790M mutations in predominantly Caucasian patients with stage IV EGFR mutation-positive NSCLC who progressed on afatinib, and to investigate the subsequent response to osimertinib. In this single-center, retrospective analysis, EGFR T790M mutation status after afatinib failure was assessed using liquid biopsy and tissue rebiopsy. EGFR T790M-positive patients subsequently received osimertinib. Sixty-seven patients received afatinib in the first-, second-, or third-line (80.6%, 14.9%, and 4.5%, respectively). After afatinib failure, the T790M mutation was identified in 49 patients (73.1%). Liquid biopsy and tissue rebiopsy were concordant in 79.4% of cases. All patients with T790M-positive tumors received osimertinib (73.5% after first-line afatinib); 37 (75.5%) of these had an objective response (complete response: 22.4%; partial response: 53.1%). Response rate was independent of T790M copy number. EGFR T790M mutation is a major mechanism of acquired resistance to afatinib. Osimertinib confers high response rates after afatinib failure in EGFR T790M-positive patients and its use in sequence potentially allows extended chemotherapy-free treatment.

Osimertinib versus standard-of-care EGFR-TKI as first-line treatment for EGFRm advanced NSCLC: FLAURA Japanese subset

Abstract: Background The FLAURA study was a multicenter, double-blind, Phase 3 study in which patients with previously untreated epidermal growth factor receptor mutation-positive advanced non-small-cell lung carcinoma were randomized 1:1 to oral osimertinib 80 mg once daily or standard-of-care (gefitinib 250 mg or erlotinib 150 mg, once daily) to compare safety and efficacy. In the overall FLAURA study, significantly better progression-free survival was shown with osimertinib versus standard-of-care. Methods Selected endpoints, including progression-free survival (primary endpoint), overall survival, objective response rate, duration of response and safety were evaluated for the Japanese subset of the FLAURA study. Results In Japan, 120 eligible Japanese patients were randomized to osimertinib (65 patients) or gefitinib (55 patients) treatment from December 2014 to June 2017. Median progression-free survival was 19.1 (95% confidence interval, 12.6, 23.5) and 13.8 (95% confidence interval, 8.3, 16.6) months with osimertinib and gefitinib, respectively (hazard ratio, 0.61; 95% confidence interval, 0.38, 0.99). Median overall survival was not reached in either treatment arm (data were immature). In the osimertinib and gefitinib arms, objective response rate was 75.4% (49/65) and 76.4% (42/55), and median duration of response from onset was 18.4 (95% confidence interval, not calculated) and 9.5 (95% confidence interval, 6.2, 13.9) months, respectively. The incidence of adverse events was similar in the two groups. The frequency of Grade ≥3 interstitial lung disease and pneumonitis in the two groups were the same (one patient). Conclusions As the first-line therapy, osimertinib showed significantly improved efficacy versus gefitinib in the Japanese population of the FLAURA study. No new safety concerns were raised. Clinical trial registration NCT02296125 (ClinicalTrials.gov).

EGFR exon 20 insertion mutations and response to osimertinib in non-small-cell lung cancer

Abstract: Epidermal growth factor receptor exon 20 insertion (EGFRex20ins) mutations represent approximately 4–12% of EGFR mutations and are generally refractory to the 1st and 2nd generation EGFR tyrosine kinase inhibitors (TKIs). Development of effective therapies for patients with EGFRex20ins mutant non-small-cell lung carcinoma (NSCLC) represents a great unmet need. Preclinical models have shown that osimertinib is active in NSCLC harboring EGFRex20ins, while the antitumor activity of osimertinib remains to be evaluated in patients with EGFRex20ins mutations. Tumor genotyping was performed in 2316 Chinese NSCLC cases with targeted next generation sequencing (NGS) covering the whole exons of EGFR gene. The frequency and genetic characteristics of EGFRexon20ins mutations were analyzed. Furthermore, six patients with specific EGFRexon20ins mutations and receiving osimertinib 80 mg once daily were retrospectively included to assess the antitumor activity and safety of monotherapy osimertinib. EGFRex20ins mutations were identified in 4.8% (53/1095) of EGFR mutant NSCLC and 2.3% (53/2316) of all NSCLC cases. The most frequently identified EGFRexon20ins is A767_V769dup (17/53,32.1%). We found that the genetic characteristics of EGFRex20ins mutations in Chinese patients with NSCLC were comparable to those reported in Caucasian patients. Four patients with osimertinib therapy achieved partial response and the rest stable disease. Median progression free survival (PFS) was 6.2 months (95% confidence interval 5.0–12.9 months; range 4.9–14.6 months). The most common adverse events (AEs) were diarrhea (2/6), pruritis (2/6), stomatitis (1/6) and nausea (1/6). No grade 3 or more AEs were documented. This study revealed that the genetic characteristics of EGFRex20ins mutations in Chinese patients with NSCLC were comparable to those reported in Caucasian patients. Furthermore, our study firstly demonstrated promising antitumor activity of osimertinib in certain EGFRex20ins mutant advanced NSCLC patients, indicating that osimertinib treatment for EGFRex20ins positive patients deserves further study.

Tissue and Plasma EGFR Mutation Analysis in the FLAURA Trial: Osimertinib versus Comparator EGFR Tyrosine Kinase Inhibitor as First-Line Treatment in Patients with EGFR-Mutated Advanced Non-Small Cell Lung Cancer.

Abstract: Purpose: To assess the utility of the cobas EGFR Mutation Test, with tissue and plasma, for first-line osimertinib therapy for patients with EGFR-mutated (EGFRm; Ex19del and/or L858R) advanced or metastatic non–small cell lung cancer (NSCLC) from the FLAURA study (NCT02296125). Experimental Design: Tumor tissue EGFRm status was determined at screening using the central cobas tissue test or a local tissue test. Baseline circulating tumor (ct)DNA EGFRm status was retrospectively determined with the central cobas plasma test. Results: Of 994 patients screened, 556 were randomized (289 and 267 with central and local EGFR test results, respectively) and 438 failed screening. Of those randomized from local EGFR test results, 217 patients had available central test results; 211/217 (97%) were retrospectively confirmed EGFRm positive by central cobas tissue test. Using reference central cobas tissue test results, positive percent agreements with cobas plasma test results for Ex19del and L858R detection were 79% [95% confidence interval (CI), 74–84] and 68% (95% CI, 61–75), respectively. Progression-free survival (PFS) superiority with osimertinib over comparator EGFR-TKI remained consistent irrespective of randomization route (central/local EGFRm-positive tissue test). In both treatment arms, PFS was prolonged in plasma ctDNA EGFRm-negative (23.5 and 15.0 months) versus -positive patients (15.2 and 9.7 months). Conclusions: Our results support utility of cobas tissue and plasma testing to aid selection of patients with EGFRm advanced NSCLC for first-line osimertinib treatment. Lack of EGFRm detection in plasma was associated with prolonged PFS versus patients plasma EGFRm positive, potentially due to patients having lower tumor burden.

Tumor clonality and resistance mechanisms in EGFR mutation-positive non-small-cell lung cancer: implications for therapeutic sequencing.

Abstract: While the development of EGFR-targeted tyrosine kinase inhibitors (TKIs) has revolutionized treatment of EGFR mutation-positive non-small-cell lung cancer, acquired resistance to therapy is inevitable, reflecting tumor evolution. Recent studies show that EGFR mutation-positive non-small-cell lung cancer is highly heterogeneous at the cellular level, facilitating clonal expansion of resistant tumors via multiple molecular mechanisms. Here, we review the mechanistic differences between first-, second- and third-generation EGFR-targeted TKIs and speculate how these features could explain differences in clinical activity between these agents from a clonal evolution perspective. We hypothesize that the molecular dissection of tumor resistance mechanisms will facilitate optimal sequential use of EGFR TKIs in individual patients, thus maximizing the duration of chemotherapy-free treatment and survival benefit.

On-target Resistance to the Mutant-Selective EGFR Inhibitor Osimertinib Can Develop in an Allele-Specific Manner Dependent on the Original EGFR-Activating Mutation.

Abstract: Purpose: The third-generation EGFR inhibitor, osimertinib, is the first mutant-selective inhibitor that has received regulatory approval for the treatment of patients with EGFR-mutant lung cancer. Despite the development of highly selective third-generation inhibitors, acquired resistance remains a significant clinical challenge. Recently, we and others have identified a novel osimertinib resistance mutation, G724S, which was not predicted in in vitro screens. Here, we investigate how G724S confers resistance to osimertinib. Experimental Design: We combine structure-based predictive modeling of G724S in combination with the 2 most common EGFR-activating mutations, exon 19 deletion (Ex19Del) and L858R, with in vitro drug-response models and patient genomic profiling. Results: Our simulations suggest that the G724S mutation selectively reduces osimertinib-binding affinity in the context of Ex19Del. Consistent with our simulations, cell lines transduced with Ex19Del/G724S demonstrate resistance to osimertinib, whereas cells transduced with L858R/G724S are sensitive to osimertinib. Subsequent clinical genomic profiling data further suggest G724S occurs with Ex19Del but not L858R. Furthermore, we demonstrate that Ex19Del/G724S retains sensitivity to afatinib, but not to erlotinib, suggesting a possible therapy for patients at the time of disease relapse. Conclusions: Altogether, these data suggest that G724S is an allele-specific resistance mutation emerging in the context of Ex19Del but not L858R. Our results fundamentally reframe the problem of targeted therapy resistance from one focused on the “drug–resistance mutation” pair to one focused on the “activating mutation–drug–resistance mutation” trio. This has broad implications across clinical oncology.

FDA- and EMA-Approved Tyrosine Kinase Inhibitors in Advanced EGFR-Mutated Non-Small Cell Lung Cancer: Safety, Tolerability, Plasma Concentration Monitoring, and Management.

Abstract: Non-small-cell lung cancer (NSCLC) is the most common form of primary lung cancer. The discovery of several oncogenic driver mutations in patients with NSCLC has allowed the development of personalized treatments based on these specific molecular alterations, in particular in the tyrosine kinase (TK) domain of the epidermal growth factor receptor (EGFR) gene. Gefitinib, erlotinib, afatinib, and osimertinib are TK inhibitors (TKIs) that specifically target EGFR and are currently approved by the Food and Drug Administration (FDA) and the European Medicines Agency (EMA) as first line treatment for sensitive EGFR-mutant patients. However, these four drugs are associated with severe adverse events (AEs) that can significantly impact patient health-related quality of life and patient monitoring. EGFR-TKIs are commonly used together with other types of medication that can substantially interact. Here, we review approaches used for the management of TKI-AEs in patients with advanced NSCLC to promote the benefits of treatments and minimize the risk of TKI treatment discontinuation. We also consider potential TKI–drug interactions and discuss the usefulness of plasma concentration monitoring TKIs based on chromatographic and mass spectrometry approaches to guide clinical decision-making. Adjusting the most appropriate therapeutic strategies and drug doses may improve the performance therapy and prognosis of patients with advanced EGFR-mutated NSCLC.

Heterogeneous Responses to Epidermal Growth Factor Receptor (EGFR) Tyrosine Kinase Inhibitors (TKIs) in Patients with Uncommon EGFR Mutations: New Insights and Future Perspectives in this Complex Clinical Scenario.

Abstract: Uncommon Epidermal Growth Factor Receptor (EGFR) mutations represent a distinct and highly heterogeneous subgroup of Non-Small Cell Lung Cancers (NSCLCs), that accounts for approximately 10% of all EGFR-mutated patients. The incidence of uncommon EGFR mutations is growing, due to the wider adoption of next-generation sequencing (NGS) for diagnostic purposes, which enables the identification of rare variants, usually missed with available commercial kits that only detect a limited number of EGFR mutations. However, the sensitivity of uncommon mutations to first- and second-generation EGFR Tyrosine Kinase Inhibitors (TKIs) is widely heterogeneous and less well known, compared with classic mutations (i.e., exon 19 deletions and exon 21 L858R point mutation), since most of the pivotal studies with EGFR TKIs in the first line, with few exceptions, excluded patients with rare and/or complex variants. Recently, the third generation EGFR TKI osimertinib further revolutionized the therapeutic algorithm of EGFR-mutated NSCLC, but its role in patients harboring EGFR mutations besides exon 19 deletions and/or L858R is largely unknown. Therefore, a better knowledge of the sensitivity of uncommon mutations to currently available EGFR TKIs is critical to guiding treatment decisions in clinical practice. The aim of this paper is to provide a comprehensive overview of the treatment of NSCLC patients harboring uncommon EGFR mutations with currently approved therapies and to discuss the emerging therapeutic opportunities in this peculiar subgroup of patients, including chemo-immunotherapy combinations, next-generation EGFR TKIs, and novel targeted agents.

Sequential afatinib and osimertinib in patients with EGFR mutation-positive non-small-cell lung cancer: updated analysis of the observational GioTag study.

Abstract: Aims: Overall survival (OS) and updated time to treatment failure (TTF) analysis of patients with EGFR mutation-positive (Del19, L858R) non-small-cell lung cancer who received sequential afatinib/osimertinib in the real-world GioTag study. Patients & methods: Patients had T790M-positive disease following first-line afatinib and received osimertinib treatment (n = 203). Primary outcome was TTF. The OS analysis was exploratory. Results: Median OS was 41.3 months (90% CI: 36.8-46.3) overall and 45.7 months (90% CI: 45.3-51.5) in patients with Del19-positive tumors (n = 149); 2-year survival was 80 and 82%, respectively. Updated median TTF with afatinib and osimertinib was 28.1 months (90% CI: 26.8-30.3). Conclusion: Sequential afatinib/osimertinib was associated with encouraging OS/TTF in patients with EGFR T790M-positive non-small-cell lung cancer, especially in patients with Del19-positive tumors. Trial registration number: NCT03370770.

AXL degradation in combination with EGFR-TKI can delay and overcome acquired resistance in human non-small cell lung cancer cells

Abstract: Acquired resistance to epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) has been a major obstacle in the treatment of non-small cell lung cancer (NSCLC) patients. AXL has been reported to mediate EGFR-TKIs. Recently, third generation EGFR-TKI osimertinib has been approved and yet its acquired resistance mechanism is not clearly understood. We found that AXL is involved in both gefitinib and osimertinib resistance using in vitro and in vivo model. In addition, AXL overexpression was correlated with extended protein degradation rate. We demonstrate targeting AXL degradation is an alternative route to restore EGFR-TKIs sensitivity. We confirmed that the combination effect of YD, an AXL degrader, and EGFR-TKIs can delay or overcome EGFR-TKIs-driven resistance in EGFR-mutant NSCLC cells, xenograft tumors, and patient-derived xenograft (PDX) models. Therefore, combination of EGFR-TKI and AXL degrader is a potentially effective treatment strategy for overcoming and delaying acquired resistance in NSCLC.

YH25448, an Irreversible EGFR-TKI with Potent Intracranial Activity in EGFR Mutant Non–Small Cell Lung Cancer

Abstract: Purpose: Given that osimertinib is the only approved third-generation EGFR-TKI against EGFR activating and resistant T790M mutated non–small cell lung cancer (NSCLC), additional mutant-selective inhibitors with a higher efficacy, especially for brain metastases, with favorable toxicity profile are still needed. In this study, we investigated the antitumor efficacy of YH25448, an oral, mutant-selective, irreversible third-generation EGFR-TKI in preclinical models. Experimental Design: Antitumor activity of YH25448 was investigated in vitro using mutant EGFR-expressing Ba/F3 cells and various lung cancer cell lines. In vivo antitumor efficacy, ability to penetrate the blood–brain barrier (BBB), and skin toxicity of YH25448 were examined and compared with those of osimertinib using cell lines and PDX model. Results: Compared with osimertinib, YH25448 showed a higher selectivity and potency in kinase assay and mutant EGFR-expressing Ba/F3 cells. In various cell line models harboring EGFR activating and T790M mutation, YH25448 effectively inhibited EGFR downstream signaling pathways, leading to cellular apoptosis. When compared in vivo at equimolar concentrations, YH25448 produced significantly better tumor regression than osimertinib. Importantly, YH25448 induced profound tumor regression in brain metastasis model with excellent brain/plasma and tumor/brain area under the concentration–time curve value. YH25448 rarely suppressed the levels of p-EGFR in hair follicles, leading to less keratosis than osimertinib in animal model. The potent systemic and intracranial activity of YH25448 has been shown in an ongoing phase I/II clinical trial for advanced EGFR T790M mutated NSCLC (NCT03046992). Conclusions: Our findings suggest that YH25448 is a promising third-generation EGFR inhibitor, which may be more effective and better tolerated than the currently approved osimertinib.

Treatment of Non-small Cell Lung Cancer with EGFR-mutations.

Abstract: The discovery of activating mutations in the epidermal growth factor receptor (EGFR) gene and development of tyrosine kinase inhibitors (TKIs) of EGFR have achieved a paradigm shift in treatment strategy of non-small cell lung cancer (NSCLC). For advanced NSCLC harboring activating EGFR mutations, an EGFR-TKI is preferably prescribed as it provides a superior survival benefit over platinum-based chemotherapy. To further improve the therapeutic outcomes, more potent EGFR-TKIs through irreversible inhibition of tyrosine kinase have been developed. In a recent clinical trial, an irreversible EGFR-TKI (osimertinib) showed a superior survival benefit with lower toxicity profile. In addition, combination treatments such as an EGFR-TKI plus platinum-based chemotherapy may achieve a long-term survival. For earlier-stage resectable NSCLC with EGFR-mutations, several clinical trials to assess the efficacy of EGFR-TKIs in pre-operative induction setting and in postoperative adjuvant setting are now ongoing. Here we review and discuss the current status and future perspectives of treatment for EGFR-mutated NSCLC.

Understanding the Mechanisms of Resistance in EGFR-Positive NSCLC: From Tissue to Liquid Biopsy to Guide Treatment Strategy.

Abstract: Liquid biopsy has emerged as an alternative source of nucleic acids for the management of Epidermal Growth Factor Receptor (EGFR)-mutant non-Small Cell Lung Cancer (NSCLC). The use of circulating cell-free DNA (cfDNA) has been recently introduced in clinical practice, resulting in the improvement of the identification of druggable EGFR mutations for the diagnosis and monitoring of response to targeted therapy. EGFR-dependent (T790M and C797S mutations) and independent (Mesenchymal Epithelial Transition [MET] gene amplification, Kirsten Rat Sarcoma [KRAS], Phosphatidyl-Inositol 4,5-bisphosphate 3-Kinase Catalytic subunit Alpha isoform [PI3KCA], and RAF murine sarcoma viral oncogene homolog B1 [BRAF] gene mutations) mechanisms of resistance to EGFR tyrosine kinase inhibitors (TKIs) have been evaluated in plasma samples from NSCLC patients using highly sensitive methods (i.e., digital droplet PCR, Next Generation Sequencing), allowing for the switch to other therapies. Therefore, liquid biopsy is a non-invasive method able to detect the molecular dynamic changes that occur under the pressure of treatment, and to capture tumor heterogeneity more efficiently than is allowed by tissue biopsy. This review addresses how liquid biopsy may be used to guide the choice of treatment strategy in EGFR-mutant NSCLC.

Activation of AXL as a preclinical acquired resistance mechanism against osimertinib treatment in EGFR-mutant non-small cell lung cancer cells

Abstract: Osimertinib (AZD9291) has an efficacy superior to that of standard EGFR-tyrosine kinase inhibitors for the first-line treatment of patients with EGFR-mutant advanced non-small cell lung cancer (NSCLC). However, patients treated with osimertinib eventually acquire drug resistance, and novel therapeutic strategies to overcome acquired resistance are needed. In clinical or preclinical models, several mechanisms of acquired resistance to osimertinib have been elucidated. However, the acquired resistance mechanisms when osimertinib is initially used for EGFR-mutant NSCLC remain unclear. In this study, we experimentally established acquired osimertinib-resistant cell lines from EGFR-mutant NSCLC cell lines and investigated the molecular profiles of resistant cells to uncover the mechanisms of acquired resistance. Various resistance mechanisms were identified, including the acquisition of MET amplification, EMT induction, and the upregulation of AXL. Using targeted next-generation sequencing with a multigene panel, no secondary mutations were detected in our resistant cell lines. Among three MET-amplified cell lines, one cell line was sensitive to a combination of osimertinib and crizotinib. Acquired resistance cell lines derived from H1975 harboring the T790M mutation showed AXL upregulation, and the cell growth of these cell lines was suppressed by a combination of osimertinib and cabozantinib, an inhibitor of multiple tyrosine kinases including AXL, both in vitro and in vivo. Our results suggest that AXL might be a therapeutic target for overcoming acquired resistance to osimertinib. IMPLICATIONS: Upregulation of AXL is one of the mechanisms of acquired resistance to osimertinib, and combination of osimertinib and cabozantinib might be a key treatment for overcoming osimertinib resistance.