1st Generation EGFR-TKI Research Articles

Abstract 4651: A macrocyclic kinase inhibitor overcomes the compound mutations that cause the resistance to all approved EGFR inhibitors in EGFR-positive lung cancer

Abstract EGFR mutant cancers account for 20-30 % of non-small cell lung cancers and show marked sensitivity to EGFR tyrosine kinase inhibitors (TKIs). However, the tumor almost inevitably relapses due to acquired resistance. To date, several EGFR-TKIs have been approved, and the third-generation EGFR-TKI, osimertinib, has been widely used both as first-line therapy and for patients with the EGFR-T790M mutation after 1st or 2nd generation EGFR-TKI therapy. However, the EGFR-T790M+C797S compound mutation confers resistance to all approved EGFR-TKIs. In our previous study, we experimentally demonstrated that brigatinib with anti-EGFR antibody was effective against osimertinib-resistant EGFR-C797S and EGFR-T790M+C797S mutants, and is currently undergoing clinical studies. However, the tumor would relapse because of the acquisition of additional resistance mutations. Here, we first demonstrated the binding mode of brigatinib to the EGFR-T790M/C797S mutant by crystal structure analysis and predicted brigatinib-resistant mutations through a cell-based assay, including N-ethyl-N-nitrosourea (ENU) mutagenesis. We found that clinically reported L718 and G796 compound mutations appeared, consistent with their proximity to the binding site of brigatinib, and brigatinib-resistant quadruple mutants, such as EGFR-activating mutation/T790M/C797S/L718M, were resistant to all clinically available EGFR-TKIs. BI-4020, a fourth-generation macrocyclic EGFR inhibitor plus anti-EGFR antibody, overcomes the quadruple and major EGFR-activating mutants in vitro and in vivo, but not the minor mutants such as L747P. Microsecond molecular dynamics simulations revealed the binding mode and affinity between BI-4020 and the EGFR mutants. This study identified potential therapeutic strategies using new-generation macrocyclic EGFR inhibitor to overcome the emerging resistance mutants. Citation Format: Ryohei Katayama, Ken Uchibori, Makoto Nishio, Naoya Fujita. A macrocyclic kinase inhibitor overcomes the compound mutations that cause the resistance to all approved EGFR inhibitors in EGFR-positive 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 4651.

24P Efficacy and safety of 1st generation EGFR TKI retreatment in EGFR mutation-positive, T790M-negative patients previously treated with 1st or 2nd generation EGFR TKI and cytotoxic chemotherapy

24P Efficacy and safety of 1st generation EGFR TKI retreatment in EGFR mutation-positive, T790M-negative patients previously treated with 1st or 2nd generation EGFR TKI and cytotoxic chemotherapy

EP08.02-027 T790M Detection Rate After First-Line Treatment with Bevacizumab Plus 1st or 2nd Generation EGFR-TKI in Advanced NSCLC

EP08.02-027 T790M Detection Rate After First-Line Treatment with Bevacizumab Plus 1st or 2nd Generation EGFR-TKI in Advanced NSCLC

O6-3 The significance of ultra-low EGFR T790M mutations on EGFR-TKI efficacy in patients with NSCLC -the WJOG13119L study

The significance of ultra-low pretreatment EGFR T790M mutations on EGFR-tyrosine kinase inhibitor (TKI) efficacy in patients with non-small cell lung cancer (NSCLC) remains uncertain. Therefore, we retrospectively investigated the association between ultra-low EGFR T790M mutations and time to treatment failure (TTF) in patients treated with 1st, 2nd or 3rd generation (1G, 2G, 3G) EGFR-TKI.

MO45-1 Osimertinib vs. erlotinib + bevacizumab or ramucirumab for EGFR mutated NSCLC; a retrospective study from LC-SCRUM-Asia

Both osimertinib and erlotinib plus bevacizumab or ramucirumab (ERL+BEV/RAM) showed prolonged progression free survival (PFS) compared with 1st generation EGFR-TKIs for patients with EGFR-mutated non-small cell lung cancer (NSCLC). However, it remains unclear which is the optimal regimen as frontline therapy especially for patients with L858R in which osimertinib failed to show prolonged overall survival (OS) in FLAURA.

Abstract 5158: Detection of EGFR mutations in plasma cfDNA and paired CTCs of NSCLC patients before and after osimertinib therapy using crystal digital PCR

Abstract Background: Circulating tumor DNA (ctDNA) analysis has clinical utility in EGFR mutantNSCLC. Circulating tumor cells (CTCs) constitute a unique source of information at thecellular level. Digital PCR (dPCR) is a valuable tool for accurate and valid mutation analysisin liquid biopsy. The aim of the current study was to detect EGFR mutations in plasma cfDNA and paired CTC-fractions of NSCLC patients before the initiation of osimertinib therapy and at progression of disease using crystal digital PCR (cdPCR). Patients and Methods: Forty-eight patients with EGFR mutated lung adenocarcinomas resistant to 1st or 2nd generation EGFR TKIs were treated with osimertinib in the context of a multicenter Phase II clinical study (NCT02771314). 2 mL of plasma were used for cfDNA extraction using the IDXtract kit (ID-Solutions, France). Crystal dPCR (naica® system, StillaTechnologies, France) was used to quantify mutation allele frequencies (MAF) of EGFRmutations in 91 cfDNA samples before and after osimertinib. 80 identical plasma samples were also analyzed with the FDA-approved cobas® technology. In parallel, EGFR mutations were detected with cdPCR in 64 matched CTC-fractions enriched by Parsortix™ (ANGLE plc, UK).Quality control steps were followed both at the preanalytical and analytical level. Results: Direct comparison between cdPCR and cobas® revealed high concordance rates forall EGFR mutations; however, in case of T790M, cdPCR proved to be more sensitive. Patients with higher %MAFs at PD presented significantly lower PFS compared to those with lower levels or without EGFR mutations. Direct comparison of EGFR genotyping between primary tissue and baseline plasma cfDNA samples revealed high concordance rates, too. During EGFR mutation analysis in paired CTC-derived gDNA, 11 samples were found positive for EGFR mutations with %MAF ranging from 0.2 to 2.25%. Conclusions: Crystal dPCR combines the unique benefits of sensitivity and accuracy with the multiplexing capacity for the detection of multiple EGFR mutations in plasma cfDNA samples and CTCs. High concordance rates were observed between cdPCR and cobas® assay. For the first time, cdPCR was applied to detect EGFR mutations in CTC-derived gDNA of NSCLC patients under osimertinib. Discordance between plasma and CTC-fractions might be indicative of tumor heterogeneity and predictive for acquired resistance. Acknowledgements-The research presented was carried out within the framework of a Stavros NiarchosFoundation grant to the National and Kapodistrian University of Athens-The authors would like to thank Larry Ba (Stilla Technologies, France) and Daniel Henaff(ID-solutions, France) for kindly providing the naica® digital PCR system and the ID-solutionskits, respectively. Citation Format: Aliki Ntzifa, Athanasios Kotsakis, Vassilis Georgoulias, Evi Lianidou. Detection of EGFR mutations in plasma cfDNA and paired CTCs of NSCLC patients before and after osimertinib therapy using crystal digital PCR [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5158.

The significance of micro-EGFR T790M mutation on EGFR-TKI efficacy in patients with NSCLC: The WJOG13119L study.

e21177 Background: The significance of micro-pretreatment EGFR T790M mutation on EGFR-tyrosine kinase inhibitor (TKI) efficacy in patients with non-small cell lung cancer (NSCLC) remains uncertain. In addition, there has been no method to examine the micro-T790M mutation after excluding formalin-fixed and paraffin-embedded (FFPE)-derived artificial mutations. Therefore, we used a novel method to examine the variant allele frequency (VAF) of T790M mutation in the FFPE samples after excluding the artificial mutations. Subsequently, we retrospectively investigated the association between micro-T790M mutations and time to treatment failure (TTF) in patients treated with 1st, 2nd, or 3rd generation (1G, 2G, 3G) EGFR-TKIs. Methods: We enrolled patients with NSCLC who harbored EGFR exon 19 deletion (Del19) or L858R without T790M mutation using conventional methods. Patients who received 1G or 2G EGFR-TKIs until June 2018 or 3G EGFR-TKI until June 2019 from 31 institutions were included. Droplet digital PCR was performed using pretreatment FFPE tumor samples. We defined cases as micro-T790M positive when the VAF of T790M was higher than that of F795F, owing to the FFPE-derived artificial mutations. The ratio of micro-T790M mutation was calculated as follows: {(VAF of T790M) – (VAF of F795F)} /VAF of (Del19 or L858R). The lowest value was set as 0. Results: A total of 110, 102, and 103 patients received 1G, 2G, and 3G EGFR-TKIs, respectively. Of these patients, 48.1%, 47.0%, and 47.6% were classified as micro-T790M positive, respectively. The ratios of micro-T790M mutation, represented as median (%) (interquartile range), in 1G, 2G, and 3G EGFR-TKI groups were 0.27 (0.12-0.87), 0.28 (0.13-0.47), and 0.42 (0.20-0.68), respectively. The VAF of T790M or F795F in all patients, represented as median (%) (interquartile range), was 0.26 (0.19-0.35) or 0.25 (0.19-0.33), respectively. The TTF was not significantly different between the T790M-positive and negative groups in analysis based on each generation TKIs. In the Del19 group, the TTF of the 1G EGFR-TKI was significantly shorter, while that of the 3G EGFR-TKI was significantly longer in the T790M-positive group than in the negative group ( p= 0.02, 0.04, respectively). In the T790M-positive group, the TTF of the 2G or 3G EGFR-TKI group was significantly longer than that of the 1G EGFR-TKI group ( p= 0.04, 0.01, respectively). This result was observed in the Del19 group but not in the L858 group. Furthermore, TTF did not significantly differ between the 1G, 2G, and 3G EGFR-TKIs in the T790M-negative group. Conclusions: This study showed that micro- EGFR T790M mutations influence the EGFR-TKI efficacy. Detection of micro-T790M mutations will facilitate selection of the optimal EGFR-TKI for patients with EGFR mutated NSCLC.

MA02.07 T-DM1 and Osimertinib (TRAEMOS) To Target HER2 Bypass Track Resistance in EGFRm+ NSCLC: Interim Analysis of a Phase II Trial

Despite high response rates to osimertinib in patients with EGFR mutation positive (EGFRm+) NSCLC, resistance inevitably develops. HER2 overexpression and amplification is detected in 13% of NSCLC-patients with acquired TKI-resistance. Previously, we showed that trastuzumab and paclitaxel in this setting is associated with a 41% ORR. Here, we evaluated the efficacy and toxicity of trastuzumab-emtansine (T-DM1) and osimertinib in patients with HER2 overexpression and/or amplification after progression on osimertinib as last line of treatment. We report a pre-planned interim analysis. In this multicenter single arm phase II study with a safety run-in (NCT03784599), eligible patients (≥18 years, WHO PS ≤2) with EGFRm+ NSCLC, progressing on EGFR TKI treatment and with HER2 overexpression (IHC ≥2+ in ≥10% of the cells) and/or HER2 amplification (ISH and/or NGS) were included. Patients were treated with T-DM1 3.6 mg/kg (IV infusion) every 3 weeks and osimertinib 80 mg QD. For patients with progression on 1st or 2nd generation EGFR TKIs, osimertinib monotherapy was initiated and T-DM1 was added at time of progression on osimertinib. Primary endpoints were to assess the ORR after 12 weeks and to evaluate safety of the combination treatment. In the safety run in, assessed in a classical 3+3 design, the first 3 patients received T-DM1 3.0 mg/kg. If none of these 3 patients developed a dose limiting toxicity (DLT), the T-DM1 dose was escalated to the standard dose of 3.6 mg/kg. Responses were assessed every 6 weeks according to RECIST 1.1. Treatment was continued until progression or unacceptable toxicity. Sample size was calculated using Simon’s two stage minimax design (H0=41%, H1>55%, 80% power, one-sided type I error rate of 10%, sample size: 58 patients, cohort A ORR 16/36 in order to proceed to cohort B). From January 15 2019 until April 6 2021, 27 patients were included and started with T-DM1. In the safety run in, none of the patients developed a DLT. Therefore, the study continued with osimertinib 80 mg QD and T-DM1 3.6 mg/kg IV infusion q 3 weeks. ORR and DCR after 6 weeks of treatment, evaluable in 24 patients, was 0% and 63% (16/24) respectively. One patient is not yet evaluable for the primary endpoint. ORR and DCR after 12 weeks of treatment were 13% (3/23) and 43% (10/23). DCR in HER2 IHC2+ and 3+ cohort was 36% (5/14) and 55% (5/9). Median PFS was 2.8 months (95% CI, 2.3-3.3 months), median duration of disease control was 20 weeks (range 4-47 weeks). Grade 2/3 adverse events occurred in 29%/21% of patients, including pneumonitis, LVEF decrease, fatigue, erythema and CK elevation. There were no grade 4 and 5 therapy-related adverse events. TRAEMOS is the first trial combining T-DM1 and osimertinib in patients with EGFRm+ NSCLC and progression on osimertinib to target HER2 bypass track resistance. Safety profile is favorable compared to cytotoxic chemotherapy, however this treatment strategy showed very limited efficacy. Further clinical evaluation of this regimen is not warranted.

P47.08 A Phase II, Single-arm, Multicenter, Efficacy of 80 mg Osimertinib in Patients With Leptomeningeal Metastases Associated With EGFR Mutated NSCLC

Leptomeningeal metastases (LM) are severe, an aggressive complication of cancer, characterized by tumor cell spread to the cerebrospinal fluid (CSF) and leptomeninges. The higher incidence of LM in EGFR mutated non-small cell lung cancer (NSCLC) has been observed, especially after treated with 1st or 2nd generation EGFR TKI. The Osimertinib, the third generation irreversible EGFR TKI, has been developed to target T790M mutation. Unlike other EGFR TKIs, Osimertinib showed homogenous distribution to the brain suggesting high penetration of blood-brain barrier, and clinical efficacy in intracranial lesions has been demonstrated from the retrospective analyses.

1214P High dose osimertinib in patients with advanced stage EGFR exon 20 mutation-positive NSCLC: Results from a phase II multicenter study, POSITION20

Clinical benefit to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR TKI’s) is lacking for non-small cell lung cancer (NSCLC) patients with an EGFR exon 20 mutation (EGFRex20+), with known response rate (RR) from 0-28%, and median progression free survival (PFS) of ∼3 months to 1st and 2nd generation EGFR TKI’s (Remon, Cancer Treatment Reviews 2020). A high dose of the 3rd generation TKI osimertinib shows promising antitumor activity to EGFRex20+ in vitro. The safety and efficacy results from a multicenter single arm phase II study investigating osimertinib in EGFRex20+ NSCLC patients are reported here.

The efficacy and clinical survival outcome of different first-line treatments in EGFR-mutant non-small cell lung cancer with brain metastases.

2028 Background: Brain metastasis is one of the most important factors for poor prognosis of lung cancer, and the incidence of brain metastasis in EGFR-mutant(m+) advanced NSCLC is more common. The first-generation EGFR TKI is a standard first-line treatment. The purpose of this study is to explore the best method for EGFRm+ NSCLC with brain lesions, and to find out correlative factors influencing survival outcome. Methods: The clinical data of NSCLC with brain metastases was retrospectively analyzed. All patients had received 1st generation EGFR TKI, and patients were divided into 4 group, group A : EGFR TKI monotherapy, group B: EGFR TKI plus chemotheapy(CT),Group C:EGFR TKI plus bevacizumab, group D :EGFR TKI plus CT plus bevacizumab.The efficacy of intracranial and extracranial lesions and survival outcome were analyzed. Results: A total of 584 EGFRm+ advanced NSCLC patients from December 2017 to May 2020 were screened,and 228(39%) had brain metastasis at baseline in the treatment-naive. Among them, 194pts had complete medical record and follow-up data. At the follow-up date (January 1, 2021), 147pts had disease progressed and 78pts had died. Intracranial PFS of group A,B,C,D were 11.1m(n = 97), 11.3m(n = 59)，21.2m(n = 19), and 18.9m(n = 19), respectively. No difference was found between A and B group (P = 0.745), so as C and D group (P = 0.684).But, the intracranial PFS of group C+D(with bevacizumab) was significantly longer than group A+B(11.3m (95%CI 12.2-14.8) vs 21.0m (95%CI 15.2-22.7), P = 0.007).The extracranial PFS of groups A, B, C, and D were 11.0m, 14.3m, 21.7m, and 18.9m, respectively,and the P value were 0.006, 0.002, and 0.011, respectively when compared with group A. The mOS of groups A,B were 27.8m and 24.2m,respectively, but group C and D had not yet reached. The intracranial ORR of group A, B, C, and D were 17.9% (14/78), 37.3% (19/51), 60.0% (9/15), and 66.7% (10/15), respectively. The extracranial ORR were 48.5% (47/97), 81.1% (43/53), 73.7% (14/19), and 73.7% (14/19),respectively. Conclusions: For EGFR-mutant NSCLC with brain metastases, the first-generation EGFR-TKI plus bevacizumab can significantly improve the efficacy of intracranial lesions, delay the progression of intracranial lesions, and prolong suvival time, Although the first-generation EGFR-TKI plus CT could improve extracranial ORR when compared with ERGF-TKI monotherapy, it has limited efficacy on intracranial lesions and could not increase survival time.

P76.93 The Efficacy of Second-Line Osimertinib Plus Bevacizumab in Chinese Patients with Advanced Non-Small Cell Lung Cancer (NSCLC)

Osimertinib has become the standard treatment for advanced non-small cell lung cancer patients with T790M mutation, who are resistant to EGFR tyrosine kinase inhibitors (EGFR TKIs). Moreover, Osimertinib has proven superior efficacy and safety over 1st-generation EGFR-TKIs in front-line setting, However, there is still insufficient evidence for the effect of Osimertinib combined with antiangiogenic therapy. Here, we reported the efficacy of Osimertinib plus Bevacizumab as second line treatment in advanced NSCLC patients in the real world setting.

FP14.07 Combination Osimertinib plus Selpercatinib for EGFR-mutant Non-Small Cell Lung Cancer (NSCLC) with Acquired RET fusions

Selpercatinib is a highly selective and potent FDA-approved RET inhibitor that has demonstrated marked and durable efficacy in RET fusion-positive NSCLC. While RET fusions are the primary oncogenic driver in ∼2% of NSCLC, RET fusions have also been identified as acquired resistance alterations following treatment with EGFR inhibitors, including osimertinib, in EGFR-mutant NSCLC. We sought to evaluate the safety and preliminary efficacy of the combination of osimertinib and selpercatinib in patients progressing on osimertinib. Patients received selpercatinib in combination with osimertinib across three selpercatinib compassionate access programs: single patient protocols (SPP), named patient programs (NPPs), and an expanded access program (EAP). All patients had advanced EGFR-mutated NSCLC with a RET fusion detected from tissue or plasma following osimertinib therapy. Clinicopathologic and outcomes data were collected retrospectively. Across 12 patients identified, 11 had an EGFR exon 19 deletion (92%) and one had an EGFR L858R mutation (8%). The most common emergent RET fusion was CCDC6-RET (five patients, 42%), followed by NCOA4-RET (four patients, 33%), KIF5B-RET (two patients, 17%), and RUFY2-RET (one patient, 8%). All patients had received prior osimertinib and seven (58%) had also received a 1st or 2nd generation EGFR TKI. Most patients received selpercatinib at 80 mg BID (92%, range 100 mg QD - 120 mg BID) and osimertinib at 80 mg daily (75%, range 40 mg QD - 80 mg BID). Of twelve identified patients, 10 were evaluable for response per RECIST 1.1. Among RECIST evaluable patients five had a response (50%, four confirmed partial responses, one unconfirmed partial response). One patient, unevaluable per RECIST for non-measurable disease at baseline, demonstrated sustained clinical radiographic improvement ongoing at 8.2 months. The second unevaluable patient discontinued treatment prior to reassessment for unrelated clinical events preventing oral medication administration. The median duration of combination treatment across all 12 identified patients was 7.4 months (range 0.6 – 16.7+ months). For patients who achieved a RECIST response, the median treatment duration was 11 months (range 7.4 – 16.7+ months). Treatment was discontinued due to disease progression in seven patients, one patient discontinued for toxicity (grade 2 pneumonitis), one patient for intolerance to oral medication administration, and three patients remained on therapy at data cut-off. In one patient with a response lasting 10 months, plasma sequencing at resistance revealed persistence of EGFR 19del (22% AF) and RET fusion (0.4% AF) plus newly detected second-site resistance mutations in both EGFR (C797S, 0.1%) and RET (G810S, 0.8%), providing additional confirmation of the biologic relevance of the acquired RET fusion. For patients with EGFR-mutant NSCLC with an acquired RET fusion as a mechanism of EGFR inhibitor resistance, the addition of selpercatinib to osimertinib was feasible, with evidence of radiographic responses and durable benefit. These findings support future investigation of this combination, which will be evaluated prospectively as an arm of the phase 2 ORCHARD platform study (NCT03944772). The availability of active combination targeted therapy strategies highlights the need for assessment for genomic mechanisms of resistance following initial EGFR targeted therapy in NSCLC.

Efficacy and safety of treatment modalities across EGFR selected/unselected populations with non-small cell lung cancer and brain metastases: A systematic review and Bayesian network meta-analysis

ObjectiveTo compare the efficacy and safety of treatment modalities across different populations with non-small cell lung cancer and brain metastases. MethodsA comprehensive search for randomized controlled trials was conducted in databases including PubMed, Embase, the Cochrane library, the ClinicalTrials.gov, and major international conferences. The main outcomes of interest were progression-free survival, overall survival, and severe adverse events. Bayesian network meta-analytical techniques were implemented, to compare treatment modalities based on efficacy and safety profiles. The protocol for this study has been registered in the Prospective Register of Systematic Reviews (PROSPERO, CRD42020155330). Results15 randomized controlled trials with a total of 1216 patients were analyzed. Network meta-analysis generated six comparisons both in EGFR positive and EGFR unselected populations. For patients harboring EGFR positive mutations, osimertinib appears to significantly increase progression-free survival, compared to 1st generation EGFR-TKI (HR 0.46, 95 %CI 0.38–0.55), 2nd generation EGFR-TKI (HR: 0.59, 95 %CI 0.34–0.99), conventional chemotherapy (HR 0.30, 95 %CI 0.14–0.66), radiotherapy (HR 0.20, 95 %CI 0.14–0.29), and radiotherapy plus 1st generation TKI (HR 0.21, 95 %CI 0.14–0.32). Osimertinib also appears to increase the likelihood of survival and prolong overall survival. For EGFR unselected patients, combined anti-PD1 monoclonal antibody with conventional chemotherapy appears superior to radiotherapy (HR: 0.20, 95 % CI 0.14–0.29), conventional chemotherapy (HR: 0.42, 95 %CI 0.28–0.68), radiotherapy plus conventional chemotherapy (HR: 0.59, 95 %CI 0.32–0.98), radiotherapy plus 1st generation TKI (HR:0.49, 95 %CI 0.25–0.96), and immune checkpoint inhibitors monotherapy (HR:0.44, 95 %CI 0.28–0.69). However, combination therapies are generally more toxic causing an increased number of severe adverse events, particularly when anti-PD1 monoclonal antibody is combined with conventional chemotherapy. ConclusionsOsimertinib appears to be the most effective and safest treatment in NSCLC patients with brain metastases, harboring EGFR positive mutations. The anti-PD1 monoclonal antibody and conventional chemotherapy combination increases survival for NSCLC patients with brain metastases who were not selected according to EGFR mutation, although this increased benefit positively correlates with an increased number of severe adverse events.

Low T790M relative allele frequency indicates concurrent resistance mechanisms and poor responsiveness to osimertinib.

BackgroundT790M relative allele frequency (RAF) in plasma, calculated by the ratio of T790M to epidermal growth factor receptor (EGFR)-sensitizing mutation allele frequencies (AF), is associated with osimertinib response in patients with progressive non-small cell lung cancer (NSCLC) post 1st generation EGFR-tyrosine kinase inhibitor (TKI) treatment. However, which subgroup of patients carry concurrent resistance mechanisms and have poor responsiveness to osimertinib remains unknown.MethodsMatched re-biopsy tissue and plasma samples obtained from 32 patients who had progression following 1st generation EGFR-TKI treatment were genotyped using next-generation sequencing (NGS) to investigate which subgroup of patients, classified by plasma position 790 (T790M) RAF, were more likely to carry concurrent resistance mechanisms. In another independent cohort, consisting of 21 T790M-positive patients, we validated whether these patients had a poor response to osimertinib treatment.ResultsIn the discovery cohort, patients with T790M RAF less than 20% were more likely to harbor concurrent resistance mechanisms (P=0.018), such as MET or ERBB2 amplification, and small cell lung cancer transformation. In the validation cohort, we found that patients with low T790M RAF (<20%) had significantly lower objective response rates (ORRs) (0 vs. 68.8%, P=0.03) and disease control rates (DCRs) (60% vs. 100%, P=0.048) in response to osimertinib compared to patients with high T790M RAF.ConclusionsIn patients with progressive NSCLC post 1st generation EGFR-TKI treatment, plasma T790M RAFs of less than 20% can be used to identify patients who carry concurrent resistance mechanisms, and can predict a poorer response to osimertinib.Trial registrationThis study was registered on http://www.chictr.org.cn (registration number: ChiCTR-DDD-16007900).

1195P The value of detecting resistance through liquid biopsy

Liquid biopsy has been established as an important diagnostic step in identifying EGFR T790M resistance to 1st and 2nd generation EGFR TKIs. This has led to significant interest in exploring the value of liquid biopsy in patients with other oncogene-addicted cancers and acquired resistance to targeted therapy.

Abstract 5198: JNJ-61186372, a novel EGFR/c-Met bispecific antibody, exhibits potent antitumor activity in broad-spectrum of acquired resistance to EGFR-TKIs

Abstract Background: 1st generation (erlotinib &amp; gefitinib), 2nd generation (afatinib), and 3rd generation (osimertinib) EGFR TKIs have marked efficacy in patient with EGFR-mutant NSCLC. Unfortunately, patients who show T790M (-) mutation after treated with 1st and 2nd generation EGFR TKI or have C797S (+) mutation or other mechanisms of acquired resistance to 3rd generation EGFR TKI have no therapeutic options for curing cancer in clinic. We introduce a potent therapeutics for overcoming acquired resistance to EGFR-TKIs in several EGFR mutant NSCLC models using JNJ-61186372 (JNJ-372), a bispecific antibody that targets the EGFR and c-Met receptors. Methods: We classified PDC and PDX models into two groups: i) 1st and 2nd generation EGFR TKI acquired resistance models with T790M (-) mutation (YU-1093, YU-1152), ii) 3rd generation EGFR TKI acquired resistance models with C797S (+) mutation (YU-1097), and C797S (-) mutation with unknown resistance mechanisms (YU-1095, YU-1089, YU-1096, YUX-1024_YH1R, YHIM-1035, YHIM-1045, and YHIM-1053). We established 7 patient-derived cells (PDC) and 3 patient-derived xenografts (PDX) model from patients with broad-spectrum acquired resistance to EGFR-TKIs. We performed cell viability test and western blot to investigate antitumor activity of JNJ-372. We evaluated then in vivo antitumor activity of JNJ-372 in PDX and PDC-xenograft models. JNJ-372 was administrated i.p. twice a week at 30 mg/kg. Results: We assessed the ability of JNJ-372 to overcome broad-spectrum of EGFR-TKI acquired resistances. JNJ-372 significantly inhibited cancer cell growth in vitro and in vivo in PDC model harboring T790M (-) mutation. JNJ-372 significantly decreased cell proliferation rate and EGFR downstream signaling in BaF3 cell harboring Del19 (L858R)/T790M/C797S mutant and PDC model harboring Del19/T790M/C797S mutant with amplified KRAS and loss of Rb. C797S (-) cases of four PDCs and three PDX models had i) loss of T790M with c-Met amplification or other acquired resistance mutation and ii) T790M (+) with amplified c-Met. In these models we identified dramatic tumor regression and reduction of EGFR and c-Met expression in vitro and in vivo PDX and PDC-xenograft models. Interestingly, we observed combination treatment of JNJ-372 and c-Met inhibitor showed synergistic immune cell mediated cellular cytotoxicity in EGFR-TKI acquired resistance models harboring c-Met amplification. JNJ-372 exhibited potent inhibition of tumor growth in preclinical models through targeting EGFR and c-Met receptor, decreasing EGFR and c-Met receptor level, inhibiting EGFR downstream signaling cascade and activating ADCC effect in vivo. Conclusion: Our results suggest that JNJ-372 will provide potential and effective therapeutic options for patients with no therapeutic option to overcome broad-spectrum of acquired resistance to EGFR-TKIs. Citation Format: SooHwan Lee, Jiyeon Yun, Seo-Yoon Jeong, Chae Won Park, Seok-Young Kim, Min Hee Hong, Hye Ryun Kim, Byoung Chul Cho. JNJ-61186372, a novel EGFR/c-Met bispecific antibody, exhibits potent antitumor activity in broad-spectrum of acquired resistance to EGFR-TKIs [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5198.

Identification and in silico structural insights of rare recurrent EGFR mutations as resistance mechanisms to osimertinib in EGFR-mutated lung cancer.

9531 Background: Inevitable progression on 3rd-generation EGFR-tyrosine kinase inhibitor (TKI) osimertinib of EGFR-mutated lung cancer patients represents a great challenge in clinic. Previous studies have revealed that one-third of the resistant mechanisms are due to acquired EGFR secondary mutations, mainly on C797, L718 and L792 residues. Our study aims to gain insights into novel mechanisms of acquired resistance to osimertinib. Methods: We performed genomic profiling on a total of 1,058 EGFR-mutated lung cancer patients with progressed disease on osimertinib, and a cohort of 1,803 patients who received only 1st-generation EGFR TKIs upon progression. Recurrent EGFR mutations with a significant enrichment in the osimertinib group were identified. We further established and applied molecular dynamic simulation-based computational model of the mutant EGFR protein to predict its sensitivity to osimertinib. Results: As expected, compared with 1st-TKIs alone group, EGFR mutations, including C797S/G (22.1% vs. 0.5%), L718Q/V (6.2% vs. 0.3%), L792F/H (4.4% vs. 0.3%), were significantly more enriched in the osimertinib cohort. Our computational model has also successfully predicted their sensitivities to osimertinib: WT (-35.19 kcal/mol) &gt; L792F (-34.10 kcal/mol) &gt; L718Q (-30.33kcal/mol) &gt; C797S (-28.02 kcal/mol), which are consistent with our previous in vitro validations. Importantly, a total of 14 low-frequency EGFR mutations were exclusively observed in the osimertinib group, seven of which, including EGFR G796S(n = 6), V802F(n = 3), T725M(n = 2), Q791L/H(n = 2), P794S/R(n = 2), were predicted to dramatically reduce the binding affinity of osimertinib to EGFR. Of note, analysis of the pretreatment samples of two patients supported that EGFR V802F and Q791L/H were acquired during osimertinib treatment. Interestingly, EGFR G796S was predicted to be sensitive to gefitinib, suggesting the possibility of administration of gefitinib in patients with acquired EGFR G796S to first-line osimertinib treatment. Further in vitro functional validations are currently ongoing. Conclusions: Our study represents the largest EGFR-mutated lung cancer cohort so far to investigate osimertinib resistance in a real-world setting, and has uncovered a list of recurrent low-frequency EGFR mutations that may confer acquired resistance to osimertinib. Our in silico structural model was proved to be powerful and robust in the prediction of osimertinib sensitivity of EGFR mutants.

Comprehensive characterization and clinical impact of concomitant genomic alterations in EGFR-mutant NSCLCs treated with EGFR kinase inhibitors

ObjectivesAlthough the majority of epidermal growth factor receptor (EGFR)-mutant non-small cell lung cancer (NSCLC) patients respond to EGFR tyrosine kinase inhibitors (TKIs), significant heterogeneity in clinical response is observed which might be attributed to the distinct sub-molecular characteristics. The present study aims to identify genetic alterations correlated with clinical outcomes and treatment response to different EGFR-TKI inhibitors. Materials and methodsWe integrated the genomic data and clinical outcomes including progression-free survival (PFS) and overall survival (OS) in 179 patients with advanced EGFR-mutant NSCLC who were treated with EGFR-TKI as 1st line of treatment. ResultsWe found that EGFR-mutant patients harboring concomitant TP53 mutation (OS: 21 vs. 40 months, P = 0.05), ERBB2 amplification (PFS: 6.1 vs. 12.5 months, P = 0.01) or FGF19 amplification (OS: 11.2 vs. 27.1 months, P = 0.01) were significantly associated with a poorer clinical prognosis after treated with 1st generation EGFR-TKI. In contrast, the presence of TP53 mutation did not affect the PFS nor OS of patients treated with 2nd generation EGFR-TKI. Furthermore, EGFR-mutant and TP53-wild type (WT) patients benefited more from a combinatorial treatment consisting of EGFR-TKI and bevacizumab comparing to EGFR-TKI as a single agent (PFS: 21.7 vs. 9.3 months, P < 0.01). Copy number variation (CNV) (PFS: 4.6 vs.9.4 months, p = 0.018) was identified as an unfavorable predictive factor to 3rd-generation TKI. We also revealed distinct resistance mechanisms associated with different EGFR-TKIs. ConclusionOur study highlights the heterogeneity both in the primary molecular landscape and acquired alterations in EGFR-mutated NSCLCs, which might play a role in determining the clinical efficacy of EGFR-TKIs. We also revealed the differential prognostic role of TP53 mutation in patients treated with the 1st or 2nd generation of EGFR-TKI. Our study also suggests that EGFR-mutant and TP53-WT patients may benefit more from combinatorial treatment consisting of EGFR-TKI and bevacizumab, highlighting the importance of further stratifying EGFR-mutant patients.

Next-generation sequencing based mutation profiling reveals heterogeneity of clinical response and resistance to osimertinib

ObjectivesThe 3rd generation epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR TKI) osimertinib has shown promising efficacy both in EGFR-mutant, T790M positive non-small cell lung cancer (NSCLC) patients who have become resistant to 1st or 2nd generation EGFR TKIs and patients with sensitizing EGFR mutations as the first line therapy. However, the degree and duration of response to osimertinib are heterogeneous. We hypothesized that the concurrent genomic landscape of these tumors could play a role in clinical outcomes and/or mechanisms of resistance. Materials and methodsWe conducted a retrospective multicenter study of lung cancer patients who had developed resistance to osimertinib. Genomic profiling was done for all the patients by using targeted next-generation sequencing encompassing 59–1021 cancer-related genes. Results and conclusionKnown EGFR-dependent resistant mutations and activation of alternative pathways were identified in 44 % of all the patients with great heterogeneity. Gain-of-function mutations of CTNNB1 were highly enriched in our cohort. Some other putative resistance mechanisms to osimertinib, such as the recurrent EGFR V834 L mutation, were also identified. Moreover, pathogenic mutations of TP53 were negatively related to the efficacy of osimertinib. To sum up, heterogeneity of resistance to osimertinib was not only manifested by inter-individual differences, but also embodied in its intra-individual diversity.