EGFR-TKI Osimertinib Research Articles

ECOG-ACRIN 5162: A phase II study of osimertinib 160 mg in NSCLC with EGFR exon 20 insertions.

9513 Background: EGFR exon 20 insertions (ins20), which comprise 4-10% of EGFR-mutant NSCLC, are generally refractory to first- and second-generation EGFR TKIs. While the clinical activity of the third-generation EGFR TKI osimertinib against EGFR ins20 is unknown, preclinical studies suggest its favorable therapeutic window may allow for inhibition of EGFR isn20 at clinically-achievable doses (Hirano, Oncotarget 2015). We report the results of EA5162, a single-arm, phase II study of osimertinib 160 mg in NSCLC pts with EGFR ins20 (NCT03191149). Methods: Pts with advanced NSCLC with an EGFR ins20 mutation identified by any local, CLIA-certified tissue assay were treated with osimertinib 160 mg daily until progression, intolerable toxicity or withdrawal. At least one prior line of therapy was required; stable, asymptomatic brain metastases were allowed. The primary endpoint was objective response rate (ORR). Secondary endpoints included safety, progression-free survival (PFS) and overall survival. The estimated sample size was 19 patients. Results: 21 pts were enrolled between 4/2018 and 7/2019 (median age 65; 15 female, 6 male; median 2 prior therapies); 1 patient did not meet eligibility criteria due to laboratory studies obtained 1 day out of window. As of 1/21/20, 6 pts remain on treatment. Among the 20 eligible pts, the best response was PR in 4 pts and CR in one pt, for a confirmed ORR of 25%; 12 (60%) pts had SD. The median PFS was 9.7 months (95% CI, 4.07, NA), median duration of response (DOR) was 5.7 months (95% CI, 4.73, NA.) Grade > 3 treatment-related adverse events (TRAE) observed in > 1 pt included anemia (n=2), fatigue (n=2), prolonged QT interval (n=2.) One pt had grade 4 respiratory failure, there were no grade 5 TRAEs. One pt discontinued study treatment due to grade 3 anemia. Conclusions: Osimertinib 160mg daily is well-tolerated and showed clinical activity in EGFR ins20-mutant NSCLC with a response rate of 25%, disease control rate of 85%, and mPFS of 9.7 months. The adverse events with osimertinib 160 mg QD in this cohort were consistent with other reports of this regimen; grade 3 rash and diarrhea were not observed. Clinical trial information: NCT03191149 .

Serum CRIPTO does not confer drug resistance against osimertinib but is an indicator of tumor burden in non-small cell lung cancer

BackgroundAdenocarcinoma is the most common subtype of non-small cell lung cancer (NSCLC) and often harbors oncogenic driver mutations in the epidermal growth factor receptor (EGFR). Osimertinib (AZD9291), a third generation EGFR TKI, has replaced earlier generation EGFR TKIs for first line treatment of EGFR mutant lung cancer due to its improved overall survival, longer progression free survival, and better tolerability compared to earlier generation inhibitors. However, like earlier generation EGFR TKIs, only about two thirds of patients respond, indicating an unknown mechanism of intrinsic resistance for the non-responders. We previously identified overexpression of CRIPTO as a potential mechanism of intrinsic resistance to EGFR TKIs of first and second generation. ObjectiveTo determine if CRIPTO could promote drug resistance against the third generation EGFR-TKIs osimertinib. We also wanted to investigate whether this resistance was conferred by both membrane bound and secreted CRIPTO. Finally, we wanted to explore the potential of secreted CRIPTO as a non-invasive biomarker for EGFR-TKI resistance. Materials and methodsHCC827 and H1975, EGFR mutant non-small cell lung carcinoma (NSCLC) cell lines, were transfected with wildtype CRIPTO, two secreted variants of CRIPTO, a membrane only version of CRIPTO, and the mock backbone vector as the control. Western blotting, immunoprecipitation, and in vitro viability experiments were performed.In vivo work was carried out in athymic nude mice; 2 × 106 CRIPTO overexpressing HCC827 cells were implanted per mouse.EGFR mutant NSCLC patient blood samples were collected before treatment with and EGFR-TKI, during response while on treatment, and at progression while on treatment. ResultsAlthough both membrane bound and secreted CRIPTO forms were able to activate downstream pathways such as SRC, CRIPTO was unable to elicit resistance towards osimertinib in vitro or in vivo. CRIPTO serum levels in mice were higher in larger xenograft tumors. Furthermore, CRIPTO serum levels were higher in patients with progressing lung cancer when compared to their CRIPTO serum levels during EGFR-TKI response. ConclusionsCRIPTO does not cause resistance against third generation EGFR-TKI osimertinib. CRIPTO levels in serum might be a potentially useful biomarker for tumor burden in NSCLC patients.

Protein tyrosine kinase 2: a novel therapeutic target to overcome acquired EGFR-TKI resistance in non-small cell lung cancer

BackgroundProtein tyrosine kinase 2 (PTK2) expression has been reported in various types of human epithelial cancers including lung cancer; however, the role of PTK2 in epidermal growth factor receptor (EGFR)-mutant non-small cell lung cancer (NSCLC) has not been elucidated. We previously reported that pemetrexed-resistant NSCLC cell line PC-9/PEM also acquired EGFR-TKI resistance with constitutive Akt activation, but we could not find a therapeutic target.MethodsCell viability in EGFR-mutant NSCLC cell lines was measured by the WST-8 assay. Phosphorylation antibody array assay for receptor tyrosine kinases was performed in PC-9 and PC-9/PEM cell lines. We evaluated the efficacy of EGFR and PTK2 co-inhibition in EGFR-TKI-resistant NSCLC in vitro. Oral defactinib and osimertinib were administered in mice bearing subcutaneous xenografts to evaluate the efficacy of the treatment combination in vivo. Both the PTK2 phosphorylation and the treatment combination efficacy were evaluated in erlotinib-resistant EGFR-mutant NSCLC cell lines.ResultsPTK2 was hyperphosphorylated in PC-9/PEM. Defactinib (PTK2 inhibitor) and PD173074 (FGFR inhibitor) inhibited PTK2 phosphorylation. Combination of PTK2 inhibitor and EGFR-TKI inhibited Akt and induced apoptosis in PC-9/PEM. The combination treatment showed improved in vivo therapeutic efficacy compared to the single-agent treatments. Furthermore, erlotinib-resistant NSCLC cell lines showed PTK2 hyperphosphorylation. PTK2 inhibition in the PTK2 hyperphosphorylated erlotinib-resistant cell lines also recovered EGFR-TKI sensitivity.ConclusionPTK2 hyperphosphorylation occurs in various EGFR-TKI-resistant NSCLCs. Combination of PTK2 inhibitor and EGFR-TKI (defactinib and osimertinib) recovered EGFR-TKI sensitivity in the EGFR-TKI-resistant NSCLC. Our study result suggests that this combination therapy may be a viable option to overcome EGFR-TKI resistance in NSCLC.

LBA17 - Longitudinal circulating tumour DNA (ctDNA) monitoring for early detection of disease progression and resistance in advanced NSCLC in FLAURA

LBA17 - Longitudinal circulating tumour DNA (ctDNA) monitoring for early detection of disease progression and resistance in advanced NSCLC in FLAURA

LBA85 - Longitudinal circulating tumour DNA (ctDNA) monitoring for early detection of disease progression and resistance in advanced NSCLC in FLAURA

LBA85 - Longitudinal circulating tumour DNA (ctDNA) monitoring for early detection of disease progression and resistance in advanced NSCLC in FLAURA

Comparative review of drug-drug interactions with epidermal growth factor receptor tyrosine kinase inhibitors for the treatment of non-small-cell lung cancer.

The development of small-molecule tyrosine kinase inhibitors (TKIs) that target the epidermal growth factor receptor (EGFR) has revolutionized the management of non-small-cell lung cancer (NSCLC). Because these drugs are commonly used in combination with other types of medication, the risk of clinically significant drug–drug interactions (DDIs) is an important consideration, especially for patients using multiple drugs for coexisting medical conditions. Clinicians need to be aware of the potential for clinically important DDIs when considering therapeutic options for individual patients. In this article, we describe the main mechanisms underlying DDIs with the EGFR-TKIs that are currently approved for the treatment of NSCLC, and, specifically, the potential for interactions mediated via effects on gastrointestinal pH, cytochrome P450-dependent metabolism, uridine diphosphate-glucuronosyltransferase, and transporter proteins. We review evidence of such DDIs with the currently approved EGFR-TKIs (gefitinib, erlotinib, afatinib, osimertinib, and icotinib) and discuss several information sources that are available online to aid clinical decision-making. We conclude by summarizing the most clinically relevant DDIs with these EFGR-TKIs and provide recommendations for managing, minimizing, or avoiding DDIs with the different agents.

Abstract 3999: Advanced lung adenocarcinoma cell bank (ALACB) : A comprehensive preclinical platform

Abstract Purpose: Patients with advanced lung adenocarcinoma often lack large clinical specimens required for molecular testing which limits next therapeutic options. Patient-derived cells (PDC) from malignant effusions can predict patient drug responses and provide a valuable tool for studying drug resistance mechanisms. In this study, we created an Advanced Lung Adenocarcinoma Cell Bank (ALACB) consisting of 28 unique PDCs established from patients who progressed on various tyrosine kinase inhibitor TKIs including 3rd generation EGFR TKI osimertinib. Experimental design: Patient malignant effusion samples were tested for malignancy, processed, observed by light microscopy, and cultured with appropriate media and supplements. The criteria for established PDCs include the following: sharing the same driver mutation as the patient; free of stromal fibroblasts confirmed by FACS staining; recapitulating patient’s drug response; and can be cryopreserved and re-grown. Established PDCs were further authenticated by STR profiling and microplasma testing to maintain cell quality. We were able to perform various in vitro assays and next generation sequencing for detailed analysis of individual PDC. Results: We were able to successfully establish 28 PDCs incorporating unique patient characteristics. Among the total 146 samples, we observed a success rate of 30% only accounting 95 malignancy positive samples. Established PDCs consists of 20 EGFR mutation positive cell lines, 3 with ALK rearrangements, 6 with ROS1 rearrangements, 1 with BRAF K601E mutation and 1 with KRAS G12D mutation. Seven PDCs were established from patients who progressed on osimertinib, two from olmutinib (HM61713), and others from 1st and 2nd generation EGFR TKI such as gefitininb and erlotinib. We were able to newly generate 3 PDCs harboring a T790M mutation with an activating EGFR mutation. Moreover, we are one of the few labs to successfully establish an EGFR del19/T790M/C797S triple mutant PDC showing resistance to osimertinib treatment in vitro. Other established PDCs harbored rare EGFR mutations including exon 20 insertion, L861Q and G719X/S768I. PDC with EGFR G719X/S768I compound mutation showed high sensitivity to afatinib but was resistant to gefitininb and osimertinib treatment. Three ALK-positive PDCs were derived from crizotinib-resistant, alectinib-resistant and ceritinib-resistant tumors. Furthermore, of 6 ROS1 fusion positive PDCs, 3 were derived from TKI-naïve tumors, and 3 from crizotinib-resistant tumors. Conclusions: Successfully established PDCs reflecting patient genomic profiles and drug response is a valuable resource for biological assays, generating in vitro drug-resistant models, and evaluating novel drugs and therapeutic targets. Further advances in drug development combined with a library of cell bank will facilitate lung cancer translational research. Citation Format: Hyeong-Seok Joo, Dong Hwi Kim, Seok-Young Kim, Ji-Yeon Lee, Mi-Ran Yun, Han-Na Kang, Byoung Chul Cho, Hye Ryun Kim. Advanced lung adenocarcinoma cell bank (ALACB) : A comprehensive preclinical platform [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3999.

Abstract 4899: The impact of the EGFR-T790M mutation detection by re-biopsy in EGFR mutant NSCLC patients in the retrospective analysis

Abstract Background: EGFR-TKIs show a good anticancer effect in to most of patients with advanced non-small cell lung cancer (NSCLC) harboring EGFR activating mutations. However, it ultimately acquires resistance to EGFR-TKIs. We currently attempt to detect EGFR-T790M mutation by re-biopsy after disease progression, because the third generation EGFR-TKI osimertinib was effective against the refractory tumors with EGFR-T790M mutation. However, the re-biopsy from tumors is relatively invasive and some cases are impossible to biopsy. Therefore, it is a beneficial if we predict the EGFR-T790M mutation before re-biopsy. In this study, we analyzed the patients with disease progression after initial EGFR-TKIs to address the issues. Methods: 78 advanced NSCLC patients with EGFR mutations were enrolled from five institutions in Japan. In all patients, re-biopsy samples were obtained successfully after the resistance to initial EGFR-TKI treatment We analyzed the relationship between the emergence of EGFR-T790M mutation and clinical parameters including clinical outcomes with EGFR-TKI treatment and EGFR activating mutation status. Results: Of 78 advanced NSCLC patients with EGFR mutations, 39 patients were EGFR-T790M positive and 39 were negative based on the re-biopsy samples. Of 39 EGFR-T790M positive patients, 2 patients achieved complete response (CR), 33 partial response (PR), and 4 stable disease (SD) by initial EGFR-TKI treatment. In contrast, 1 patient experienced a CR, 19 a PR, 18 SD, and 1 progressive disease (PD) in 39 T790M negative patients. The objective response rate was higher in patients with T790M positive mutations than those with T790M negative mutations (89.7% versus 51.2%, p< 0.01). There was no statistically significant difference in progression free survival and time to failure treated with initial EGFR-TKIs between both groups. Conclusion: The response to initial EGFR-TKIs treatment might be one of good predictors for emerging of refractory tumors with EGFR-T790M mutation. Citation Format: Akihiro Yoshimura, Tadaaki Yamada, Naoko Okura, Junji Uchino, Koichi Takayama. The impact of the EGFR-T790M mutation detection by re-biopsy in EGFR mutant NSCLC patients in the retrospective analysis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4899.

Zebrafish Xenograft Model of Human Lung Cancer for Evaluating Osimertinib Resistance.

About half of NSCLC patients with EGFR mutation had secondary mutation T790M after treatment with a first-generation tyrosine kinase inhibitor (TKI), Gefitinib. The third-generation of EGFR-TKI Osimertinib is suitable for patients with EGFR mutation and T790M mutation. However, drug screening for NSCLC patients after the emergence of acquired resistance has become a difficult problem for clinicians. In this study, we established drug-resistant cell lines of Gefitinib and Osimertinib to evaluate cell proliferation in vitro. And we investigated the inhibitory effect of different drug concentration gradients on cancer cells. Zebrafish with high homology to human genes were selected as xenotransplantation models to compare the effects of different concentrations of Osimertinib on the proliferation and angiogenesis of zebrafish tumors after transplantation of different lung cancer cell lines. It was confirmed that Osimertinib could inhibit the proliferation of tumor cells with EGFR mutation and T790M resistance mutation in zebrafish, which was consistent with the clinical research conclusion.

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

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.

Integrating Osimertinib in Clinical Practice for Non-Small Cell Lung Cancer Treatment.

Treatment of non-small cell lung cancer (NSCLC) is evolving with the use of precision medicine for patients with sensitizing epidermal growth factor receptor (EGFR) mutation. First- and second-generation EGFR tyrosine kinase inhibitors (TKIs) remained the standard of care for patients with EGFR-mutated advanced NSCLC for about a decade. However, treatment resistance eventually develops for most patients who experience initial response to these agents. The most commonly acquired resistance mechanism is the T790M gatekeeper mutation. Poor drug penetration leading to central nervous system (CNS) relapse and dose-limiting toxicities are other concerns. The third-generation EGFR-TKI osimertinib, initially approved as the second-line treatment for patients with T790-mutant NSCLC, demonstrated survival benefits in TKI-naïve EGFR-mutated patients, especially in patients with CNS metastasis. The FLAURA study has shown statistically significant progression-free survival benefit and prolongation of all post-progression outcome endpoints, time to first subsequent therapy, second subsequent therapy, and second progression on subsequent treatment, along with acceptable toxicity and better quality of life outcomes. These data favor osimertinib in the first-line setting for EGFR-mutated NSCLC. This is an important milestone since sequencing the TKI therapy based on accurate prediction of T790M is clinically challenging. In countries like India, T790M testing is not routinely conducted and two-thirds of patients with NSCLC do not receive any second-line therapy. Osimertinib can be administered pragmatically as a first-line therapy. Mature overall survival data from the FLAURA study will be important and could help define the optimal personalized treatment for patients with advanced NSCLC.Funding: AstraZeneca Pharma India Ltd.

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

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.

KRAS and EGFR Amplifications Mediate Resistance to Rociletinib and Osimertinib in Acquired Afatinib-Resistant NSCLC Harboring Exon 19 Deletion/T790M in EGFR.

The critical T790M mutation in EGFR, which mediates resistance to first- and second-generation EGFR tyrosine kinase inhibitors (TKI; gefitinib, erlotinib, and afatinib), has facilitated the development of third-generation mutation-selective EGFR TKIs (rociletinib and osimertinib). We previously reported heterogeneous afatinib-resistant mechanisms, including emergence of T790M-EGFR, and responses to third-generation EGFR TKIs. Here, we used afatinib-resistant lung adenocarcinoma cells [AfaR (formerly AFR3) cells], carrying exon 19 deletion/T790M in EGFR To identify the novel resistance mechanisms in post-afatinib treatment, RocR1/RocR2 and OsiR1/OsiR2 cells were established using increasing concentrations of rociletinib and osimertinib, respectively. Attenuation of exon 19 deletion and T790M was confirmed in both rociletinib-resistant cells; in addition, EGFR and KRAS amplification was observed in RocR1 and RocR2, respectively. Significant KRAS amplification was observed in the osimertinib-resistant cell lines, indicating a linear and reversible increase with increased osimertinib concentrations in OsiR1 and OsiR2 cells. OsiR1 cells maintained osimertinib resistance with KRAS amplification after osimertinib withdrawal for 2 months. OsiR2 cells exhibited KRAS attenuation, and osimertinib sensitivity was entirely recovered. Phospho-EGFR (Y1068) and growth factor receptor-bound protein 2 (GRB2)/son of sevenless homolog 1 (SOS1) complex was found to mediate osimertinib resistance in OsiR1 cells with sustained KRAS activation. After 2 months of osimertinib withdrawal, this complex was dissociated, and the EGFR signal, but not the GRB2/SOS1 signal, was activated. Concomitant inhibition of MAPK kinase and EGFR could overcome osimertinib resistance. Thus, we identified a heterogeneous acquired resistance mechanism for third-generation EGFR TKIs, providing insights into the development of novel treatment strategies.

Frequency and clinical significance of NF1 mutation in lung adenocarcinomas from East Asian patients.

NF1 is a tumor suppressor gene that negatively regulates Ras signaling. NF1 deficiency plays an important role in carcinogenesis. To investigate the frequency and clinical significance of NF1 mutation, we examined mutation status of NF1, TP53, LKB1 and RB1 in 704 surgically resected lung adenocarcinomas from East Asian patients using semiconductor-based Ion Torrent sequencing platform. Common driver events, including mutations in EGFR, KRAS, HER2, BRAF, MET, and fusions affecting ALK, RET and ROS1, were also concurrently detected. The correlation between NF1 mutations and clinicomolecular features of patients was further evaluated. Among 704 patients, 42 NF1 mutations were found in 33 patients (33/704, 4.7%), including 14 patients harboring EGFR/NF1 comutations (14/33, 42.4%). Comparing with EGFR-mutant patients, patients harboring NF1 mutations were closely associated with solid component subtype (p = 0.028). Comparing with KRAS mutations, NF1 mutations were found more common in female and never smokers (p = 0.003 and p = 0.004, respectively). Kaplan-Meier survival analysis revealed that patients harboring NF1 mutation had similar disease-free survival (DFS) and overall survival (OS) with patients with KRAS mutation. Although frequently overlapped with EGFR mutation, patients harboring NF1 mutation had significantly shorter DFS (p = 0.019) and OS (p = 0.004) than patients with EGFR mutation. During follow-up, one female patient with EGFR exon 19 deletion and NF1 Q1815X comutation showed poor response to EGFR TKIs (Gefitinib and Osimertinib) after disease relapse. In conclusion, NF1 mutations define a unique molecular and clinicopathologic subtype of lung adenocarcinoma. Examination of NF1 mutation may contribute to molecular subtyping and therapeutic intervention of lung adenocarcinoma.

P1.13-10 Aurora Kinase A Drives the Evolution of Resistance to Third Generation EGFR Inhibitors in Lung Cancer

Paradigm defining for precision medicine, EGFR inhibitors are a major breakthrough in the treatment of EGFR-mutant non-small cell lung cancer (NSCLC). Although these EGFR-TKI therapies often elicit profound initial therapeutic responses, their effects are transient due to residual disease. This residual disease and subsequent disease progression occurs through tumor evolution and molecular drivers behind the formation, maintenance and evolution of residual disease and acquired resistance have remained elusive. Although in many cases pre-existing clones with bona-fide genetic resistance have been identified, majority of patients have undetectable resistance causing genetic alterations suggesting that non-genetic alterations may drive altered cell state and signaling associated with EGFR inhibitor resistance. Furthermore, in the case of osimertinib now used in first line setting, mechanisms of acquired resistance have been ill defined and no effective second line therapies exist. Using EGFR mutant lung cancer cells we developed eight distinct in vitro models of acquired resistance to 3rd generation EGFR-TKI inhibitors, osimertinib and rociletinib. We examined the efficacy of drug combinations in vivo using both cell line xenografts and PDX models of EGFR TKI resistance. We measured the level of staining of the candidate biomarker, TPX2, in patients progressing on first and third-generation EGFR TKIs. Chemical screens in acquired resistant cell lines revealed that Aurora kinase inhibitors are highly synergistic when combined with third-generation EGFR inhibitors. Resistant cells harbored heightened activation of AURKA caused by upregulation of its co-activator protein TPX2. In in-vitro and in-vivo models of acquired resistance the combination induced potent cell death by reactivating BIM-mediated apoptosis. We found that tumors from the majority of patients progressing on first and third-generation EGFR TKIs harbored high levels of TPX2, indicating that AURKA is likely activated and driving resistance in a significant fraction of EGFR-mutant lung cancers. Tracking the kinetics of AURKA activation, we found that AURKA activity is required for the formation and maintenance of residual drug tolerant cells, precursors of acquired resistance. Either single agent EGFR-TKI, the AURKA inhibitor MLN8237 or the combination enhanced the magnitude of response and forestalled the emergence of resistance in vitro as compared to monotherapies. The combination robustly induced tumor regressions in an EGFR L858R PDX tumor model generated from a residual disease surgical specimen. This synthetic lethal interaction between EGFR TKIs and Aurora kinase inhibitors has important clinical implications for the development of better treatment strategies using EGFR-TKIs and suggest a new paradigm for preventing the emergence of resistance.

P3.13-08 Assessment of EGFR Gene Mutations In cf-DNA in Monitoring of Response to EGFR TKIs in Patients with Lung Adenocarcinoma

Molecular analysis of cf-DNA in NSCLC patients enables detection and monitoring of EGFR mutations. It allows for detection of the acquired resistance for 1st and 2nd generation of EGFR-TKIs caused Thr790Met substitution. The third generation of EGFR-TKIs (osimertinib) could overcome the resistance in patients with Thr790Met mutation. The studied group included 23 Caucasian patients (8 male and 15 female, median age 71±9) with diagnosed lung adenocarcinoma and with EGFR mutations detected in tumor samples. Blood samples were collected before administration of EGFR-TKIs in all patients, and re-collected repeatedly from 10 patients during therapy. EGFR mutations and content of mutated cf-DNA were analyzed using ctEGFR Mutation Analysis Kit (Entrogen, USA) in Rotor-Gene Real-Time PCR device (Qiagen, Germany). Analysis of EGFR activating mutations in cf-DNA showed 82.61% concordance/sensitivity (19/23) with tumor samples. The mean content of mutated cf-DNA was 7.44% and it was significantly lower (p<0.000035) than in tumor samples (34.54%). Concentration of mutated cf-DNA positively correlated with advanced stage of the disease. Monitoring of EGFR status in cf-DNA showed reduction and stabilization of mutant DNA content with the emergence of response to EGFR-TKIs treatment. Primary Thr790Met substitution was undetectable in cf-DNA and in tumor samples. Acquired resistance in Thr790Met mechanism during EGFR-TKIs treatment was detected only in one patient (1/10). This patient responded to osimertinib therapy. Analysis of EGFR mutations in cf-DNA shows lower sensitivity than in DNA isolated from tumor samples. Multiple evaluations of EGFR status may be useful in monitoring of therapy and allows for early detection of acquired resistance.

P3.01-80 Retrospective Analysis of the Impact of EGFR T790M Mutation Detection by Re-Biopsy in Patients with NSCLC Harboring EGFR Mutations.

EGFR-TKIs show a good response to most of patients with advanced non-small cell lung cancer (NSCLC) harboring EGFR activating mutations. However, it ultimately becomes the acquired resistance to EGFR-TKIs after various periods. We currently attempt to detect EGFR-T790M mutation by re-biopsy that induced a half of acquired resistances to them, because the third generation EGFR-TKI osimertinib had an effective response against the refractory tumors with EGFR-T790M mutations. However, the re-biopsy from tumors is relatively invasive and some cases are impossible to perform them. Therefore, it is a critical issue to select the population with EGFR-T790M mutations. In this study, we analyzed the refractory cases to initial EGFR-TKIs with successful re-biopsy samples to disclose these clinical questions. 78 advanced NSCLC patients with EGFR mutations who had successful re-biopsy samples after the resistance to initial EGFR-TKI treatment are enrolled at five institutions in Japan. We validated for the association between the emergence of EGFR-T790M mutation and their profiles, such as clinical outcomes with EGFR-TKI treatment and EGFR activating mutation status. s Of 78 advanced NSCLC patients with EGFR mutations, 39 cases were EGFR-T790M positive and 39 were negative in the re-biopsy samples. Of EGFR-T790M positive patients, 2 cases achieved a complete response (CR), 33 a partial response (PR), and 4 stable disease (SD). In contrast, 1 patient experienced a CR, 19 a PR, 18 SD, and 1 progressive disease (PD) in T790M negative patients. The objective response rate was higher in patients with T790M positive mutations than in those with T790M negative mutations (89.7% versus 51.2%, p< 0.01). There were no differences between each patients in progression free survival and time to failure treated with initial EGFR-TKIs. The response to initial EGFR TKI treatment might be one of good predictors for emerging of refractory tumors with EGFR-T790M mutations. Further experiments are needed to identify them.

Abstract B27: Osimertinib (AZD9291) is sensitive and bound with affinity to EGFR exon 20 insertion mutant models

Abstract Background: Although EGFR exon 20 insertion mutation is the third most common among EGFR-mutant NSCLC, this mutation has not been well studied and the first-generation EGFR TKIs are ineffective. In addition, the efficacy of the third-generation EGFR TKIs is controversial. Methods: Various EGFR exon 20 insertion mutation models were developed using Ba/F3 system as follows: C-helix (n=1, A763_Y764insFQEA) and loop following C-helix (n=7). In addition, SNU-3173 cell line was derived from NSCLC patient with EGFR exon 20 insertion mutation. Cell viability assays were performed using EGFR TKIs (gefitinib, erlotinib, dacomitinib, afatinib, rociletinib, olmutinib, nazartinib, and osimertinib). Immunoblotting was performed to evaluate the downstream signals of EGFR pathway. Additionally, the docking homology models of EGFR exon 20 insertion mutations with osimertinib were developed with SWISS-Model and SwissDock for estimation of the structural appropriateness. Results: Cell viability assay showed that EGFR exon 20 insertion mutants are resistant to the first-generation EGFR TKIs, except for A763_Y764insFQEA mutant Ba/F3 cells. IC50 values of second-generation EGFR TKIs are five- to hundreds-folds lower than gefitinib and erlotinib. Dacomitinib and afatinib have good efficacy for the most of them, and regulated down signaling pathways. The third-generation TKIs showed moderate efficacy against EGFR exon 20 insertion mutants. Overall, osimertinib has the most successful inhibition of EGFR exon 20 insertion mutants (IC50 values for C-helix and loop following C-helix mutants for afatinib, &amp;lt;0.1nM and 16.7-352.5nM; rociletinib 1022.1nM and 288.0-3034.6nM; olmutinib, 351.8nM and 30.4-626.7nM; osimertinib 131.6nM and 14.7-65.7nM; and nazartinib, 351.8nM and 36.3-509.9nM, respectively). Ribbon diagram with in silico homology docking simulations showed how exon 20 insertion mutations change the structures of kinase domain and the suitable binding values with various EGFR exon 20 insertion mutant subtypes with osimertinib. Conclusions: Osimertinib showed an outstanding effectiveness against various EGFR exon 20 insertion mutations. In addition, docking simulation of in silico homology models corresponded with the in vitro results. Consequently, osimertinib is effective against EGFR exon 20 insertion mutant models. Citation Format: Yusoo Lee, Tae Min Kim, Dong-Wan Kim, Yong-Oon Ahn, Soyeon Kim, Bhumsuk Keam, Miso Kim, Dae Seog Heo. Osimertinib (AZD9291) is sensitive and bound with affinity to EGFR exon 20 insertion mutant models [abstract]. In: Proceedings of the Fifth AACR-IASLC International Joint Conference: Lung Cancer Translational Science from the Bench to the Clinic; Jan 8-11, 2018; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(17_Suppl):Abstract nr B27.

Abstract 1957: Aurora kinase A drives the evolution of resistance to third-generation EGFR inhibitors in lung cancer

Abstract With the advent of precision medicine, EGFR inhibitors are a major breakthrough in the treatment of EGFR-mutant non-small cell lung cancer (NSCLC). Although these EGFR-TKI therapies often elicit profound initial therapeutic responses, their effects are transient due to residual disease. This residual disease and subsequent disease progression occurs through tumor evolution and molecular drivers behind the formation, maintenance and evolution of residual disease and acquired resistance have remained elusive. Although in many cases, pre-existing clones with bona fide genetic resistance have been identified, majority of patients have undetectable resistance causing genetic alterations, suggesting that nongenetic alterations may drive altered cell state and signaling associated with EGFR inhibitor resistance. Using EGFR mutant lung cancer cells, we developed several in vitro models of acquired resistance to third-generation EGFR-TKI inhibitors, osimertinib and rociletinib, and a chemical screen revealed that Aurora kinase inhibitors are highly synergistic when combined with third-generation EGFR inhibitors. Resistant cells harbored high activation of AURKA mediated by upregulation of its co-activator protein TPX2. In in vitro and in vivo models of acquired resistance, the combination induced potent cell death by reactivating BIM-mediated apoptosis. We found that tumors from patients progressing on first- and third-generation EGFR TKIs often harbored high levels of TPX2, indicating that AURKA is likely activated and driving resistance in a significant fraction of EGFR-mutant lung cancers. By tracking the kinetics of AURKA activation, we tested if AURKA activity is required for the formation and maintenance of residual cells leading to acquired resistance. In our sensitive in vitro models, either single-agent EGFR-TKI, MLN8237 or the combination enhanced the magnitude of response and forestalled the emergence of resistance as compared to monotherapies. We tested the combination in an EGFR L858R patient-derived xenograft (PDX) tumor model generated from a residual disease surgical specimen. In this PDX the combination robustly impaired tumor growth compared to both single agents alone and in most cases induced tumor regression This novel synthetic lethal interaction between EGFR TKIs and Aurora kinase inhibitors has important implications for the development of new treatment strategies for third-generation EGFR-TKI. These results invite a paradigm aimed at preventing the emergence of resistance. Citation Format: Khyati N. Shah, Roma Bhatt, Julia Rotow, Julia Rohrberg, Victor Olivas, Golzar Golzar Hemmati, Gregor Krings, Henry J. Haringsma, Andrew D. Simmons, Thomas C. Harding, Andrei Goga, Collin Blakely, Trever Bivona, Sourav Bandyopadhyay. Aurora kinase A drives the evolution of resistance to third-generation EGFR inhibitors in lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1957.

Treatment of EGFR mutation-positive non-small cell lung cancer complicated by Trousseau syndrome with gefitinib followed by osimertinib: a case report.

Malignant tumors can induce a hypercoagulable state known as Trousseau syndrome that increases the risk for venous thromboembolism including disabling cerebral infarction. Anticoagulant therapy without anticancer treatment is not effective for amelioration of this coagulation abnormality. Most patients with lung cancer positive for activating mutations of the epidermal growth factor receptor (EGFR) are sensitive to EGFR tyrosine kinase inhibitors (TKIs), but the efficacy and safety of EGFR-TKIs in such patients with a poor performance status (PS) due to Trousseau syndrome has been unclear. We here describe a patient with EGFR mutation–positive lung cancer who developed disabling cerebral infarction due to Trousseau syndrome. Administration of the EGFR-TKI gefitinib and anticoagulant therapy resulted in a partial tumor response and recovery from both the coagulation abnormality and the severe neurological symptoms. After the development of resistance to gefitinib, the EGFR-TKI osimertinib was safely administered until disease progression without recurrence of the coagulation abnormality. This case suggests that gefitinib followed by osimertinib may be a safe and effective treatment option for patients with EGFR mutation–positive lung cancer who experience disabling cerebral infarction due to Trousseau syndrome.