Translational insights and overall survival in the U31402-A-U102 study of patritumab deruxtecan (HER3-DXd) in EGFR-mutated NSCLC

BACKGROUND

Human epidermal growth factor receptor 3 (HER3) is broadly expressed in non-small-cell lung cancer (NSCLC) and is the target of patritumab deruxtecan (HER3-DXd), an antibody-drug conjugate consisting of a HER3 antibody attached to a topoisomerase I inhibitor payload via a tetrapeptide-based cleavable linker. U31402-A-U102 is an ongoing phase I study of HER3-DXd in patients with advanced NSCLC. Patients with epidermal growth factor receptor (EGFR)-mutated NSCLC that progressed after EGFR tyrosine kinase inhibitor (TKI) and platinum-based chemotherapy (PBC) who received HER3-DXd 5.6 mg/kg intravenously once every 3 weeks had a confirmed objective response rate (cORR) of 39%. We present median overall survival (OS) with extended follow-up in a larger population of patients with EGFR-mutated NSCLC and an exploratory analysis in those with acquired genomic alterations potentially associated with resistance to HER3-DXd.

PATIENTS AND METHODS

Safety was assessed in patients with EGFR-mutated NSCLC previously treated with EGFR TKI who received HER3-DXd 5.6 mg/kg; efficacy was assessed in those who also had prior PBC.

RESULTS

In the safety population (N = 102), median treatment duration was 5.5 (range 0.7-27.5) months. Grade ≥3 adverse events occurred in 76.5% of patients; the overall safety profile was consistent with previous reports. In 78/102 patients who had prior third-generation EGFR TKI and PBC, cORR by blinded independent central review (as per RECIST v1.1) was 41.0% [95% confidence interval (CI) 30.0% to 52.7%], median progression-free survival was 6.4 (95% CI 4.4-10.8) months, and median OS was 16.2 (95% CI 11.2-21.9) months. Patients had diverse mechanisms of EGFR TKI resistance at baseline. At tumor progression, acquired mutations in ERBB3 and TOP1 that might confer resistance to HER3-DXd were identified.

CONCLUSIONS

In patients with EGFR-mutated NSCLC after EGFR TKI and PBC, HER3-DXd treatment was associated with a clinically meaningful OS. The tumor biomarker characterization comprised the first description of potential mechanisms of resistance to HER3-DXd therapy.

Safety, Tolerability, and Antitumor Activity of Zipalertinib Among Patients With Non-Small-Cell Lung Cancer Harboring Epidermal Growth Factor Receptor Exon 20 Insertions

PURPOSE

Although several agents targeting epidermal growth factor receptor (EGFR) exon 20 insertions (ex20ins) have recently been approved by the US Food and Drug Administration, toxicities related to the inhibition of wild-type (WT) EGFR are common with these agents and affect overall tolerability. Zipalertinib (CLN-081, TAS6417) is an oral EGFR tyrosine kinase inhibitor (TKI) with a novel pyrrolopyrimidine scaffold leading to enhanced selectivity for EGFR ex20ins-mutant versus WT EGFR with potent inhibition of cell growth in EGFR ex20ins-positive cell lines.

METHODS

This phase 1/2a study of zipalertinib enrolled patients with recurrent or metastatic EGFR ex20ins-mutant non-small-cell lung cancer (NSCLC) previously treated with platinum-based chemotherapy.

RESULTS

Seventy-three patients were treated with zipalertinib at dose levels including 30, 45, 65, 100, and 150 mg orally twice a day. Patients were predominantly female (56%), had a median age of 64 years, and were heavily pretreated (median previous systemic therapies 2, range 1-9). Thirty six percent of patients had received previous non-ex20ins EGFR TKIs and 3/73 (4.1%) patients received previous EGFR ex20ins TKIs. The most frequently reported treatment-related adverse events of any grade included rash (80%), paronychia (32%), diarrhea (30%), and fatigue (21%). No cases of grade 3 or higher drug-related rash or diarrhea were observed at 100 mg twice a day or below. Objective responses occurred across all zipalertinib dose levels tested, with confirmed partial response (PR) observed in 28/73 (38.4%) response-evaluable patients. Confirmed PRs were seen in 16/39 (41%) response-evaluable patients at the dose of 100 mg twice a day.

CONCLUSION

Zipalertinib has encouraging preliminary antitumor activity in heavily pretreated patients with EGFR ex20ins-mutant NSCLC, with an acceptable safety profile, including low frequency of high-grade diarrhea and rash.

APOBEC mutagenesis, kataegis, chromothripsis in EGFR-mutant osimertinib-resistant lung adenocarcinomas

BACKGROUND

Studies of targeted therapy resistance in lung cancer have primarily focused on single-gene alterations. Based on prior work implicating apolipoprotein b mRNA-editing enzyme, catalytic polypeptide-like (APOBEC) mutagenesis in histological transformation of epidermal growth factor receptor (EGFR)-mutant lung cancers, we hypothesized that mutational signature analysis may help elucidate acquired resistance to targeted therapies.

PATIENTS AND METHODS

APOBEC mutational signatures derived from an Food and Drug Administration-cleared multigene panel [Memorial Sloan Kettering Cancer Center Integrated Mutation Profiling of Actionable Cancer Targets (MSK-IMPACT)] using the Signature Multivariate Analysis (SigMA) algorithm were validated against the gold standard of mutational signatures derived from whole-exome sequencing. Mutational signatures were decomposed in 3276 unique lung adenocarcinomas (LUADs), including 93 paired osimertinib-naïve and -resistant EGFR-mutant tumors. Associations between APOBEC and mechanisms of resistance to osimertinib were investigated. Whole-genome sequencing was carried out on available EGFR-mutant lung cancer samples (10 paired, 17 unpaired) to investigate large-scale genomic alterations potentially contributing to osimertinib resistance.

RESULTS

APOBEC mutational signatures were more frequent in receptor tyrosine kinase (RTK)-driven lung cancers (EGFR, ALK, RET, and ROS1; 25%) compared to LUADs at large (20%, P < 0.001); across all subtypes, APOBEC mutational signatures were enriched in subclonal mutations (P < 0.001). In EGFR-mutant lung cancers, osimertinib-resistant samples more frequently displayed an APOBEC-dominant mutational signature compared to osimertinib-naïve samples (28% versus 14%, P = 0.03). Specifically, mutations detected in osimertinib-resistant tumors but not in pre-treatment samples significantly more frequently displayed an APOBEC-dominant mutational signature (44% versus 23%, P < 0.001). EGFR-mutant samples with APOBEC-dominant signatures had enrichment of large-scale genomic rearrangements (P = 0.01) and kataegis (P = 0.03) in areas of APOBEC mutagenesis.

CONCLUSIONS

APOBEC mutational signatures are frequent in RTK-driven LUADs and increase under the selective pressure of osimertinib in EGFR-mutant lung cancer. APOBEC mutational signature enrichment in subclonal mutations, private mutations acquired after osimertinib treatment, and areas of large-scale genomic rearrangements highlights a potentially fundamental role for APOBEC mutagenesis in the development of resistance to targeted therapies, which may be potentially exploited to overcome such resistance.

Phase 1/2 study of BLU-451, a central nervous system (CNS) penetrant, small molecule inhibitor of EGFR, in incurable advanced cancers with EGFR exon 20 insertion (ex20ins) mutations

TPS9155

Background: Oncogenic EGFR ex20ins mutations, found in ̃2% of non-small cell lung cancers (NSCLC) and a small percentage of other cancers, are generally not responsive to EGFR-targeted agents that have been approved for treatment of NSCLC with a common EGFR mutation, including L858R and exon 19 deletion. Similar to these more common types of EGFR-mutated NSCLC, CNS metastases are a challenge with EGFR ex20ins NSCLC and are associated with poor outcomes. While two EGFR ex20ins-targeting drugs were recently approved by the FDA (amivantamab and mobocertinib), neither have established CNS activity. BLU-451 is a CNS penetrant, wild type-sparing, covalent small molecule inhibitor of EGFR ex20ins as well as atypical (G719C, G719S, L861Q) and common EGFR mutants. Preclinical data have shown BLU-451 to have potent antitumor activity, including in an intracranial xenograft model, which has led to its clinical development in EGFR-mutant NSCLC. Methods: BLU-451-1101 (NCT05241873) is a phase 1/2, global, open-label study designed to evaluate single-agent BLU-451 in patients with NSCLC harboring EGFR ex20ins that has progressed following prior treatment for incurable recurrent or metastatic disease. Patients with Eastern Cooperative Oncology Group performance status 0–1 and EGFR ex20ins, exon 18 G719X or exon 21 L861Q mutant NSCLC (phases 1 and 2) or other cancers except primary CNS tumors (phase 1 only) are eligible. Patients with known ROS, RAF, ALK, or EGFR C797S mutations will be excluded. Stable, asymptomatic brain metastases are permitted, and active asymptomatic brain metastases are permitted in specific cohorts. Primary endpoints are determination of maximum tolerated dose (MTD), recommended phase 2 dose (RP2D), safety and tolerability (phase 1), in addition to evaluation of antitumor activity at the RP2D by RECIST v1.1 (phase 2). Secondary endpoints are evaluation of pharmacokinetics (PK) and antitumor activity by RECIST v1.1.(phase 1) and PK, safety, tolerability, and CNS antitumor activity (phase 2). Dose escalation will utilize a 3+3 design with up to 6 patients per cohort in phase 1 dose escalation and up to 12 per cohort in phase 1 dose expansion. Phase 2 will enroll patients in 3 cohorts (n = 18 each): patients with prior platinum-based chemotherapy and an EGFR ex20ins-targeted agent; patients with prior platinum but no EGFR ex20ins-targeted agent; and patients with active asymptomatic brain metastases with prior platinum with or without an EGFR ex20ins-targeted agent. The study is planned for approximately 40 centers in North America, the Asia-Pacific region, and/or Europe. Clinical trial information: NCT05241873.

Efficacy of osimertinib in patients with EGFR mutant lung cancer harboring the uncommon exon 19 deletion, L747_A750>P

e21112

Background: EGFR exon 19 deletions (del19) are largely considered to have uniform sensitivity to EGFR tyrosine kinase inhibitors (TKIs). Approximately 70% of del19 tumors harbor the most common deletion, E756_A750del; however, many “uncommon” variants comprise the remainder of this group. In preclinical studies, the uncommon del19, L747_A750 > P, demonstrates diminished sensitivity to the third generation TKI, osimertinib [. Identifying differences in clinical outcomes with osimertinib treatment could have therapeutic implications for patients (pts) with EGFR del19 non-small cell lung cancer (NSCLC). Methods: We conducted a multi-center retrospective cohort study of pts with metastatic EGFR del19 NSCLC treated with osimertinib. We compared progression free survival (PFS, time from TKI initiation to clinically significant growth of existing lesions or new lesions on imaging or death) and overall survival (OS) of pts with tumors harboring E746_A750del and L747_A750 > P who received osimertinib in the first line (1L) or in second or later lines of therapy and were T790M+ (≥2L). The Kaplan Meier method and Cox model were used to estimate PFS and OS, and multivariable logistic regression was used to estimate the odds of achieving PFS > 12 months. Multivariable analyses adjusted for baseline covariates- age, sex, race, and smoking. Results: From March 2013 to December 2021, 86 pts with EGFR E746_A750del and 36 with L747_A750 > P were treated with osimertinib. For 1L osimertinib, E746_A750del was associated with significantly prolonged PFS vs. L747_A750 > P (median 21.3 months (95% CI 17.0-31.7) vs. 11.7 months (10.8-29.4)) in the adjusted analysis (hazard ratio [HR] 0.52 [95% CI, 0.28-0.98, p = 0.043]). Pts with the common del19 mutation were more likely to achieve PFS > 12 months with 1L osimertinib than those with the L747_A750 > P mutation (Odds Ratio 4.14 (1.41-12.15), p 0.0097). OS exhibited a similar trend with a median OS that that was not reached (NR) at 40 months of follow-up among those with E746_A750del vs 26 months for L747_A750 > P (adjusted HR 0.52 [95% CI, 0.23-1.19], p = 0.120). For pts treated with ≥2L osimertinib, there was also a trend towards favorable PFS and OS for pts with tumors harboring E746_A750del. Conclusions: The del19 mutation L747_A750 > P is associated with inferior PFS compared to the common E746_A750del mutation in pts treated with 1L osimertinib. Understanding differences in osimertinib efficacy among EGFR del19 subtypes could alter management of these pts in the future.[Table: see text]

A phase 1/2 study of the highly selective EGFR inhibitor, BLU-701, in patients with EGFR-mutant non–small cell lung cancer (NSCLC)

TPS9142

Background: Although 3rd-generation tyrosine kinase inhibitors (TKIs), such as osimertinib, are highly effective in front-line metastatic EGFR-mutated ( EGFRm) NSCLC, treatment resistance ultimately occurs, including the emergence of the on-target C797X mutation for which there are no approved TKIs. BLU-701 is an investigational, reversible, brain-penetrant, wildtype-sparing oral TKI with nanomolar potency on common activating (exon 19 deletion and L858R) and C797X resistance mutations (Tavera L et al. AACR 2022). BLU-701 has shown promising preclinical data, including antitumor central nervous system (CNS) activity that may improve patient outcomes. Additionally, combining BLU-701 with standard of care therapies may provide enhanced disease control across multiple lines of treatment, including against heterogenous tumors, in patients with EGFRm NSCLC. Methods: HARMONY (NCT05153408) is an ongoing, global phase 1/2, open-label, first-in-human study designed to evaluate the safety, tolerability, pharmacokinetics (PK), pharmacodynamics (PD), and antitumor activity of BLU-701 as a monotherapy or in combination with osimertinib or platinum-based chemotherapy in patients with EGFRm NSCLC. Key inclusion criteria include patients ≥18 years of age with metastatic EGFRm NSCLC; Eastern Cooperative Oncology Group performance status 0–1; and previous treatment with ≥1 EGFR-targeted TKI. Patients in the phase 2 monotherapy part must harbor an EGFR C797X resistance mutation (locally assessed). Key exclusion criteria are tumors harboring EGFR T790M mutations, EGFR exon 20 insertions, or other known driver alterations, including KRAS, BRAF V600E, NTRK1/2/3, HER2, ALK, ROS1, MET, or RET. Phase 1 primary endpoints are maximum tolerated dose, recommended phase 2 dose (RP2D), and safety. The phase 2 primary endpoint is overall response rate (ORR) by RECIST 1.1. Secondary endpoints include ORR (phase 1), duration of response, and PK/PD (phase 1 and phase 2); disease control rate, progression-free survival, overall survival, antitumor CNS activity, and safety (phase 2). The phase 1 dose escalation will adopt a Bayesian optimal interval design. Patients will be enrolled into 3 treatment cohorts: part 1A (n≈40–80; BLU-701), part 1B (n≈35; BLU-701 + osimertinib), and part 1C (n≈18; BLU-701 + carboplatin and pemetrexed). Patients in the phase 2 dose expansion (n≈24) will be treated at the RP2D of BLU-701 as monotherapy. Patients may receive treatment until disease progression, unacceptable toxicity, or other discontinuation criteria are met. Enrollment in this study has started, and sites will be open across North America, Europe, and Asia. Clinical trial information: NCT05153408.

Phase II randomized study comparing proton craniospinal irradiation with photon involved-field radiotherapy for patients with solid tumor leptomeningeal metastasis

2000

Background: Leptomeningeal metastasis (LM) is associated with limited survival and treatments. Photon involved-field radiotherapy (IFRT) is the standard of care radiotherapy (RT) but benefits are limited. We hypothesized that proton craniospinal irradiation (pCSI) encompassing the central nervous system (CNS) compartment would result in superior CNS disease control compared to IFRT. Methods: We conducted a randomized phase 2 study comparing pCSI vs. IFRT in patients with non-small cell lung cancer (NSCLC) or breast cancer LM. Eligibility criteria included radiographic and/or cytologic LM and Karnofsky performance status (KPS) ≥ 60. Patients were stratified by histology (breast vs. NSCLC) and systemic disease (active vs. stable) and were randomized in a 2:1 ratio of pCSI:IFRT. Patients with all other solid tumor histologies were enrolled to an exploratory pCSI arm. RT was 3Gy x 10 fractions for all patients. The primary endpoint is CNS progression-free survival (CNS PFS), defined as time from randomization to CNS progression (POD); secondary endpoints include overall survival (OS) and treatment-related adverse events (TAEs). A target of 81 patients to compare pCSI and IFRT was designed with a one-sided alpha of 0.025 and a power of 0.8 based on stratified log-rank test. Analysis is based on intent-to-treat. Results: From 4/2020-10/2021, 42 and 21 patients were randomized to pCSI and IFRT, respectively. Baseline factors were not different: median age was 56 vs. 61 years (p = 0.5); both cohorts included 57% NSCLC and 52% with active systemic disease. At median follow up of 7.1 months, 25 patients had CNS POD (pCSI = 9 [21%], IFRT = 16 [76%]) and 28 died (pCSI = 15 [36%], IFRT = 13 [62%]). At planned interim analysis, significant benefit in CNS PFS was observed with pCSI (median = 7.5 months, 95% CI: 6.6-NA) vs. IFRT (median = 2.0, 95% CI: 1.0-5.1, p < 0.001). As a result, the Data and Safety Monitoring Committee recommended early discontinuation of the trial. In addition, OS benefit with pCSI (median = 8.2 months, 95% CI: 7.4-NA) vs. IFRT (median = 4.9 months, 95% CI: 3.1-NA, p = 0.04) was observed. In a multivariable analysis including age, KPS and stratification factors, CNS PFS and OS benefit for pCSI remained significant. Grade 3 non-heme TAEs occurred in 3 patients with pCSI and 5 with IFRT. For the exploratory pCSI cohort, 35 patients enrolled, the median age was 61, 20 (57%) had active systemic disease and ovarian (7 [20%]) was the most common histology. At median follow up of 9.6 months, 7 (20%) had CNS POD and 20 (57%) died. Median CNS PFS was 5.4 months (95% CI: 4.8-9.1), OS was 6.6 months (95% CI: 5.4-12.1) and 4 patients had Grade 3 TAEs. Conclusions: In this trial, the first randomized study of RT for LM, we demonstrated improved CNS PFS of pCSI compared to IFRT, meeting the primary endpoint. pCSI also had a significant OS benefit. Grade 3 toxicities were comparable. Clinical trial information: NCT04343573.

A phase Ia/Ib study of intrathecal deferoxamine in patients with leptomeningeal metastases

TPS2074

Background: Leptomeningeal metastases (LM) represent an aggressive form of advanced cancer with few durable therapeutic options. One of the principal barriers in treating LM is the paucity of knowledge on cancer cell survival and proliferation within the nutrient-sparse cerebrospinal fluid (CSF). Single-cell RNA sequencing of patient-derived CSF has identified that cancer cells in the spinal fluid employ the single iron-binding transporter and receptor system, lipocalin-2/SLC22A17, to gather sparse iron to sustain their metabolic needs. This phenotype is recapitulated in preclinical mouse models of LM. Depletion of CSF iron via intracisternal administration of deferoxamine, a parenteral iron chelator, dramatically reduced LM growth and significantly prolonged survival in preclinical models. Exploiting LM iron dependency using intrathecal deferoxamine (IT-DFO) represents a novel therapeutic approach for patients with LM. Methods: This is a prospective, open-label, single center phase Ia dose escalation study of IT-DFO in patients with LM from any solid tumor malignancy to determine the maximum tolerated dose (MTD) and recommended phase II dose (RP2D), followed by a phase Ib dose expansion of IT-DFO at the RP2D in patients with LM from non-small-cell lung cancer (NSCLC). Eligibility criteria include newly diagnosed or recurrent LM identified by magnetic resonance imaging (MRI), positive CSF cytology, and/or elevated CSF circulating tumor cells (CTCs), age ≥ 18 years, Karnofsky Performance Status ≥ 60, and life expectancy ≥ 8 weeks. All patients will receive IT-DFO in 28-day cycles at a frequency of twice weekly (cycle 1), once weekly (cycle 2), and once every two weeks (cycle 3+). Patients will be monitored for LM progression by neurological examination, neuraxial MRI, and CSF cytology as per modified Response Assessment in Neuro-Oncology LM criteria. Phase Ia will involve a modified accelerated titration over 9 dosing cohorts (IT-DFO dose range 10mg to 495mg) with monitoring for dose-limiting toxicities until the MTD is reached. Phase Ib will further explore the safety of IT-DFO at the RP2D in 20 patients with NSCLC LM. Secondary objectives include the determination of pharmacokinetic and pharmacodynamic properties of IT-DFO and its metabolite, ferrioxamine, in the CSF and serum (phase Ia/Ib), and efficacy outcomes (phase Ib) including LM-objective response rate, LM-clinical benefit rate, LM-duration of response, LM-progression-free survival, and overall survival. Exploratory analyses will prospectively correlate CSF CTC enumeration with treatment response and characterize the impact of IT-DFO on cancer cell metabolism, resistance pathways, and the CSF immune microenvironment. Clinical trial information: NCT05184816.

Phase (Ph) 1/2a study of CLN-081 in patients (pts) with NSCLC with EGFR exon 20 insertion mutations (Ins20)

9007

Background: EGFR ins20-mutant NSCLC has historically been challenging to treat. While new agents targeting EGFR ins20 have recently been approved, adverse events (AEs), particularly wild type (WT) EGFR-related AEs are common. CLN-081 is a novel EGFR tyrosine kinase inhibitor (TKI) with broad activity against EGFR mutations, including ins20, and increased selectivity for ins20 versus WT EGFR. CLN-081 has been granted FDA Breakthrough Therapy Designation for the treatment of pts with EGFR ins20 NSCLC. We present updated results of the initial multicenter Ph1/2a study of CLN-081 in pts with advanced, EGFR ins20-mutant NSCLC, including 39 pts treated in an expanded cohort at the dose of 100 mg twice daily (BID). Methods: Ph1 dose escalation utilized an accelerated titration (AT) and rolling six design. Individual cohorts were expanded in Phase 1 and 2a based on prespecified protocol criteria. Pts were required to have received prior platinum-based chemotherapy. Stable, treated brain metastasis (mets) were allowed. CLN-081 is dosed in 21-day cycles. Results: As of 13 December 2021, 73 pts [median age: 65 (36-82), median lines of prior therapy: 2 (1-9), 28 (39%) with a history of brain mets] received CLN-081 at 30 mg (8), 45 mg (1), 65 mg (14), 100 mg (39), and 150 mg (11), all BID. Treatment-related AEs in ≥ 15% of pts were rash (74%), diarrhea (27%), paronychia (25%), fatigue (19%), anemia (18%), dry skin (18%), nausea (16%). Treatment-related Gr ≥ 3 AEs in ≥ 4 % of pts included anemia (10%), increased ALT (4%), and increased AST (4%). Gr 3 rash and Gr 3 diarrhea were observed in 1 and 2 pts, respectively, at 150 mg BID, while no pts treated at ≤ 100 mg BID experienced Gr 3 rash or diarrhea. Treatment-related dose reductions and discontinuations across all dose levels occurred in 10 pts (14%) and 5 pts (7%) respectively. Among 70 response-evaluable pts across all dose levels, 25 (36%) had a confirmed partial response (PR), 34 (49%) had stable disease (SD), and 3 (4%) had progressive disease as a best response. Seven pts (10%) had a PR that remained unconfirmed; 1 (1%) pt was pending a confirmatory scan. Of 36 response-evaluable pts at 100 mg BID, 14 (39%) had a confirmed PR, 17 (47%) had SD, and 1 (3%) had PD. Three pts had a PR that remained unconfirmed (8%); 1 (3%) pt was pending a confirmatory scan. Notably, among Ph1 pts treated at 100 mg BID (N = 13) in whom longer follow-up is available, the mDOR and mPFS (estimated by Kaplan-Meier) was > 15 months and 12 months, respectively. Disease control (SD ≥ 6 months or any PR) was observed in 12/13 pts (92%). Updated data with additional follow-up will be presented. Conclusions: In pts with heavily-pretreated advanced EGFR ins20 NSCLC, CLN-081 has a manageable safety profile, with anti-tumor activity across the range of doses tested. Further, CLN-081 has demonstrated a favorable clinical profile at the dose of 100 mg BID, with an encouraging objective response rate, response durability, and no Gr 3 rash or diarrhea. Clinical trial information: NCT04036682.

Identification of pretreatment genomic biomarkers and mechanisms of acquired resistance to first-line osimertinib in advanced EGFR-mutant lung cancers

9100

Background: Despite its widespread use, few series explore genomic biomarkers that impact progression-free survival (PFS) for first line osimertinib use and how mechanisms of acquired resistance impact post-osimertinib progression survival. Methods: All pts treated with first line osimertinib at Memorial Sloan Kettering Cancer Center were identified; available pre-osimertinib and post-progression tumor samples underwent next-generation sequencing (NGS) using MSK-IMPACT. Real-world (rw)PFS was estimated with Kaplan-Meier methods from start of osimertinib to progression, defined using interpretation of imaging reports. Post-baseline factors were evaluated using time-dependent covariate Cox model. Results: We identified 331 pts, of which 67 had paired tumor samples and 28 had post-progression tumor samples that underwent MSK-IMPACT. Most pts with biopsies were women (68%), never smokers (83%) and did not have baseline brain metastases (56%). With median follow-up of 24 months (mo), median rwPFS was 14 mo (95% confidence interval (CI) 13 -17 mo, n = 331). EGFR driver alterations (n = 40 atypical, n = 108 L858R, n = 182 exon 19 deletion) were associated with distinct rwPFS (median 8 (95% CI 6-12), 14 (12-18) and 16 mo (13-21), respectively, p < 0.001 logrank test). Pts with concurrent pre-treatment TP53 (14 mo,12-17) or TP53/RB1 (12 mo, 9-15) alterations had shorter median rwPFS compared to pts without these alterations (20 mo,16-24, p < 0.001, logrank test). Fifty patients (53%) had an identified mechanism of resistance. Off target mechanisms (n = 9 MET amplification (amp), n = 3 HER2 amp, n = 3 PIK3CA mutations, n = 3 acquired fusions, n = 2 RB1 loss and n = 1 CCND1 amp, MYC amp, CDK4 amp, KRAS G12A, respectively) and histological transformation (n = 7 small cell, n = 5 squamous and n = 2 large cell neuroendocrine) were detected. On target acquired mechanisms were EGFR amplification (n = 7), and G724S (n = 2) and C797S (n = 3) mutations. Pts with an identified mechanism of resistance did not have improved post-progression survival (12 mo HR 1.6, p = 0.09), but receiving next line of therapy based on post-progression tumor biopsy results (including platinum-etoposide for transformation) did improve post-progression survival (12 mo HR 0.4, p = 0.01). Conclusions: Pts with atypical EGFR drivers or concurrent TP53+/- RB1 alterations have significantly shorter rwPFS on first line osimertinib, highlighting need for additional interventions for these patients. Given the high frequency of transformation and improvement in post-progression survival by tailoring next line of therapy to the identified mechanism, pts with EGFR-mutant lung cancer on first line osimertinib may benefit from tissue biopsies at progression. For pts without an identified resistance mechanism by NGS, additional methods of interrogating tumors at progression are needed.

Clinical outcomes of immune checkpoint inhibitors in HER2-amplified non-small cell lung cancers

e21098

Background: HER2 (ERBB2) amplification is a distinct actionable oncogenic driver in 2-3% of non-small cell lung cancer (NSCLC). While HER2-targeted agents are now in development for lung cancers harboring HER2 mutations, the therapeutic landscape for patients with HER2 amplification is not well elucidated. Although immune checkpoint inhibitors (ICIs) alone or in combination with chemotherapy are widely used as treatment for NSCLC, little is known about the impact of ICIs in patients with HER2-amplified NSCLC. This study aimed to assess the efficacy of ICIs in this patient population. Methods: Patients with HER2-amplified NSCLC were identified from January 2014 to October 2021. HER2 amplification was detected by next generation sequencing (NGS) on the MSK-IMPACT platform. Clinicopathologic and molecular features, as well as response to therapy with ICIs were assessed. Patients were excluded if they harbored concurrent HER2 mutations, had localized disease, or received concurrent chemotherapy. Patient records were reviewed to evaluate overall survival (OS), progression free survival (PFS) and overall response rate (ORR). Results: Eighteen patients with metastatic HER2-amplified NSCLC who received ICI alone as first line treatment or subsequent therapy after progression met inclusion criteria. Histologic subtypes included adenocarcinoma (78%) and squamous cell carcinoma (22%). PD-L1 expression was available for 16 patients, with 69% having no expression of PD-L1. The median tumor mutation burden (TMB) was 9.2 mutations/Mb (range 3.0-35.4). The median OS was 11 months (95% CI: 4 to 37), with 6-month and 12-month survival being 67% (95% CI: 40% to 83%) and 49% (95% CI: 25% to 70%), respectively. Median PFS was 2 months (95% CI: 1 to 7). In the 15 patients that were assessed for response, the ORR was 0% (95% CI 0% to 19%), including 3 cases with PD-L1 expression of ≥ 50% and 9 cases with TMB ≥ 10 mutation/Mb. Conclusions: Patients with HER2-amplified NSCLC showed minimal response to immunotherapy, regardless of PD-L1 status and TMB. These findings underscore the importance of developing novel HER2-targeted agents for these patients with unmet medical need.

Chemo-immunotherapy outcomes of KRAS-G12C mutant lung cancer compared to other molecular subtypes of KRAS-mutant lung cancer

9088

Background: KRAS mutations are identified in approximately 30% of NSCLC, with G12C mutations being the most common subtype and representing 12% of all non-small cell lung cancer cases. Novel direct inhibitors are in clinical development and have shown promising activity, although the efficacy of these agents compared to other standard therapies for lung cancer is not yet known. We hypothesized that patients with KRAS-G12C mutations may have distinct responses to chemo-immunotherapy regimens both with respect to STK11 and KEAP1 co-mutation status and compared to patients with non-G12C subtypes. Methods: Patients with KRAS-mutant lung cancers at Memorial Sloan Kettering Cancer Center and Dana Farber Cancer Institute treated with chemo-immunotherapy regimens as first line therapy for advanced/metastatic disease were identified. Subset with KRAS G12C mutations non-G12C subtypes were compared and response to therapy was assessed by investigator. Baseline characteristics were compared with the Chi-square and Fisher’s exact test for categorical data and Wilcoxon rank-rum test for continuous data. Response evaluations where performed by investigators and compared between groups with the Fisher’s exact test. Progression free survival and overall survival was calculated from start of therapy to date of progression or death/last follow up, respectively and compared between groups using the Cox proportional-hazards model. Results: We identified 137 patients with KRAS -mutant NSCLC treated with chemo-immunotherapy: 45% (62/137) had mutations in KRAS-G12C and 55% harbored non-G12C mutations (17% G12V, 15% G12D, 4% G12A, 4% G12S, 3% G13D). The median OS was 21 and 14 months for G12C and non-G12C patients, respectively (p = 0.24). ORR to chemo-immunotherapy for patients harboring a KRAS-G12C mutation was 40% (25/62) compared to 31% (23/75) in non-G12C subtypes (p = 0.3). Median PFS was similar for both G12C and non-G12C subtypes (7.3 vs 6.1 months, respectively, p = 0.12). Concurrent STK11 mutation was identified in 40% of patients with KRAS-G12C and KEAP1 alterations were observed in 32% of patients. In patients with KRAS-G12C, co-mutation in STK11 and/or KEAP1 was associated with shorter PFS (15.8 vs 5.1 months, p = 0.01). Conclusions: KRAS-G12C mutations are present in 12% of patients with NSCLC and represent a relevant subtype of NSCLC given KRAS G12C inhibitors now in clinical development. Treatment outcomes to chemo-immunotherapy are similar in patients with G12C and non-G12C subtypes. Outcomes are poor for patients with concurrent STK11 and/or KEAP1 mutations representing a significant unmet need.

Safety and activity of CLN-081 (TAS6417) in NSCLC with EGFR Exon 20 insertion mutations (Ins20)

9077

Background: NSCLC with EGFR ins20 represents a significant area of unmet need, with no approved targeted therapies. While several agents targeting EGFR ins20 are in development, wild-type (WT) EGFR-related adverse events (AEs) have been common and challenging to manage. CLN-081 is a novel oral EGFR TKI with broad activity against clinically relevant EGFR mutations, including ins20, and has attenuated activity against WT EGFR relative to EGFR ins20 in vitro, suggesting that CLN-081 may have a more favorable clinical therapeutic window. We present interim results of a multicenter, Phase (Ph) 1/2a trial evaluating CLN-081 in advanced, EGFR ins20 NSCLC (NCT04036682). Methods: Patients (pts) with EGFR ins20 previously treated with platinum-based therapy (tx) were eligible to enroll. Ph 1 dose escalation in this adaptive trial began with an accelerated titration (AT) design, and converted to a rolling six design based upon pre-specified safety criteria or at clinically active doses. Cohort expansion in Ph 1 occurred at any dose where responses were seen. Transition from Ph 1 to 2a was based on a Simon-Two Stage design. Prior tx with EGFR ins20-specific inhibitors was allowed in AT cohorts only. CLN-081 was dosed twice daily (BID) in 21-day cycles. Results: As of 10 November 2020, 37 pts [median age 64 years (44-82); median 2 (1-9) prior lines of tx] received CLN-081 at doses of 30 mg (n = 8), 45 mg (1), 65 mg (12), 100 mg (13), and 150 mg (3) BID. The most common all-grade (gr) treatment-related AEs (TRAEs) were rash (49%), diarrhea (24%), paronychia (16%), nausea (14%), stomatitis (14%), and dry skin (11%). Gr 3 TRAEs included anemia (5%), diarrhea (3%), and increased alkaline phosphatase (ALP) (3%). There was 1 DLT, gr 3 diarrhea at 150 mg BID. No gr ≥ 3 rash or gr 4/5 TRAEs were reported. Four pts (11%) required dose reductions for rash (2), diarrhea (1), and increased ALP (1). Two pts (5%) discontinued tx due to TRAEs of gr 2 hypersensitivity reaction (1) and gr 2 pneumonitis (1); the latter also experienced pneumonitis while receiving prior osimertinib. Among the 25 response evaluable pts (RECIST 1.1), 10 (40 %) had a partial response (PR) (6 confirmed, 2 pending confirmation, 2 unconfirmed), 14 (56%) had stable disease (SD), and 1 (4%) had progressive disease as best response. Of the 4 pts that received prior EGFR ins20 inhibitors, 2 had PR and 2 SD. Of pts with SD or PR as best response, 20/24 (83 %) experienced tumor regression [median regression: -18 % (-100 to +3)]. Enrollment is ongoing and updated data will be presented. Conclusions: CLN-081 has an acceptable safety profile, including diarrhea in < 25% of pts treated to date. CLN-081 has demonstrated encouraging preliminary anti-tumor activity across the full dose range tested, in multiple distinct EGFR ins20 variants, and in heavily pre-treated pts that are either naïve or refractory to other EGFR ins20 inhibitors. Since the time of the data cut, a Ph 2a expansion has been initiated at 100 mg BID. Clinical trial information: NCT04036682.

Efficacy and safety of patritumab deruxtecan (HER3-DXd) in EGFR inhibitor-resistant, EGFR-mutated (EGFRm) non-small cell lung cancer (NSCLC)

9007

Background: Patients (pts) with advanced EGFRm NSCLC have limited treatment options after failure of EGFR TKI and platinum-based chemotherapy (PBC). HER3-DXd is an antibody drug conjugate consisting of a fully human monoclonal antibody to HER3 attached to a topoisomerase I inhibitor payload via a tetrapeptide-based cleavable linker. We previously presented efficacy/safety data (median follow-up, 5.4 mo) from an ongoing study of HER3-DXd in EGFRm NSCLC after failure of EGFR TKI therapy. We now present extended follow-up of pts receiving the recommended dose for expansion (5.6 mg/kg IV Q3W). Methods: This Ph 1 dose-escalation/expansion study included pts with locally advanced or metastatic EGFRm NSCLC with prior EGFR TKI therapy (NCT03260491). Pts with stable brain metastases (BM) were allowed. The primary endpoint was confirmed ORR by blinded independent central review (BICR) per RECIST v1.1; secondary endpoints included DOR, PFS and safety. Results: At data cutoff (Sept 24, 2020), 57 pts were treated with HER3-DXd 5.6 mg/kg IV Q3W; median follow-up, 10.2 mo (range, 5.2-19.9 mo). Median number of prior anticancer regimens was 4 (range, 1-10). 100% had prior EGFR TKI (86% prior osimertinib [OSI]) and 91% had prior PBC. 47% had a history of BM. Median treatment duration was 5.5 mo (range, 0.7-18.6 mo); treatment was ongoing in 18 pts (32%). Confirmed ORR by BICR was 39% (22/57; 95% CI, 26.0%-52.4%; 1 CR, 21 PR, 19 SD) with 14/22 responses occurring within 3 mo of starting HER3-DXd. DCR was 72% (95% CI, 58.5%-83.0%). Median DOR was 6.9 mo (95% CI, 3.1 mo-NE), and median PFS was 8.2 mo (95% CI, 4.4-8.3 mo). Antitumor activity was observed across diverse mechanisms of EGFR TKI resistance, including those not directly related to HER3 ( EGFR C797S, MET or HER2 amp, and BRAF fusion). Among pts with prior PBC, ORR was 37% (19/52; 95% CI, 23.6%-51.0%); in pts with prior OSI and PBC, ORR was 39% (17/44; 95% CI, 24.4%-54.5%). Among 43 pts evaluable for HER3 expression, nearly all expressed HER3; median membrane H-score by IHC was 180 (range, 2-280). Median H-score (range; N) was 195 (92-268; 15) in pts with CR/PR, 180 (4-280; 15) with SD, 126.5 (2-251; 6) with PD, and 180 (36-180; 7) in pts unevaluable for best overall response. The most common grade ≥3 adverse events (AEs) were thrombocytopenia (30%), neutropenia (19%), and fatigue (14%). Drug-related interstitial lung disease by central adjudication occurred in 4 pts (7%; 1 grade ≥3 [2%]; no grade 5). 6/57 pts (11%) had AEs associated with treatment discontinuation (none were due to thrombocytopenia). Conclusions: HER3-DXd 5.6 mg/kg IV Q3W demonstrated antitumor activity across various EGFR TKI resistance mechanisms in heavily pretreated metastatic/locally advanced EGFRm NSCLC. The safety profile was consistent with previous reports. A Ph 2 study of HER3-DXd in pts with EGFRm NSCLC after failure of EGFR TKI and PBC has been initiated (NCT04619004). Clinical trial information: NCT03260491.

HERTHENA-Lung01: A randomized phase 2 study of patritumab deruxtecan (HER3-DXd) in previously treated metastatic EGFR-mutated NSCLC

TPS9139

Background: Few treatment options have demonstrated therapeutic benefit in epidermal growth factor receptor–mutated ( EGFRm) non–small cell lung cancer (NSCLC) that has progressed after treatment with EGFR tyrosine kinase inhibitors (TKIs) and platinum-based chemotherapy. HER3, a member of the human epidermal growth factor family, is detectable in most EGFRm NSCLC, and its expression has been linked to worse clinical outcomes. There are no approved HER3 directed therapies for the treatment of NSCLC. HER3-DXd is a novel, potentially first-in-class HER3 directed antibody drug conjugate that has demonstrated preliminary evidence of safety and antitumor activity in patients (pts) with EGFRm TKI–resistant NSCLC in an ongoing Phase 1 study, providing proof of concept of HER3-DXd. The Phase 2 study (HERTHENA-Lung01) is further evaluating HER3-DXd in pts with previously treated metastatic or locally advanced EGFRm NSCLC. Methods: This randomized, open-label Phase 2 study will enroll up to 420 pts at approximately 135 study sites in North America, Europe and the Asia-Pacific region. Eligible pts will have metastatic or locally advanced NSCLC with an activating EGFR mutation (exon 19 deletion or L858R), progression during or after systemic treatment with ≥1 EGFR TKI and ≥1 platinum-based chemotherapy regimen, and ≥1 measurable lesion confirmed by blinded independent central review (BICR) per RECIST v1.1. Pts with an EGFR T790M mutation must have received and progressed on prior osimertinib. Pts with stable brain metastases are eligible. Exclusion criteria include evidence of previous small cell or combined small cell/non–small cell histology or any history of interstitial lung disease. Tumor tissue will be assessed retrospectively for HER3 expression and molecular mechanisms of TKI resistance. HER3 expression will not be used to select pts for enrollment. Pts will be randomized 1:1 to receive 1 of 2 HER3-DXd Q3W dose regimens that will be independently evaluated: a 5.6 mg/kg fixed-dose regimen (Arm 1) or an up-titration dose regimen (Arm 2: Cycle 1, 3.2 mg/kg; Cycle 2, 4.8 mg/kg; Cycle 3 and beyond, 6.4 mg/kg). After review of data from an ongoing Phase 1 study with similar patients treated with either of these dose regimens, a decision could be made to continue enrollment into 1 or both arms. The primary objective is to evaluate the efficacy of HER3-DXd as measured by objective response rate (ORR) by BICR. Secondary objectives are to evaluate the efficacy and safety/tolerability of HER3-DXd and to assess the relationship between efficacy and HER3 expression. Secondary endpoints include duration of response, progression-free survival, ORR by investigator, disease control rate, time to response, best percentage change in the sum of diameters of measurable tumors, and overall survival. The study is enrolling and is planned to finish in 2023. Clinical trial information: NCT04619004.

Initial results from a dose finding study of TNO155, a SHP2 inhibitor, in adults with advanced solid tumors

3005

Background: SHP2 transduces signals from activated receptor tyrosine kinases to downstream pathways including MAPK. TNO155 is a selective, allosteric, oral inhibitor of SHP2. Methods: CTNO155X2101 (NCT03114319) is an ongoing first-in-human, open-label dose escalation/expansion trial of TNO155 in adults with advanced solid tumors. The primary objective is to characterize the safety and tolerability of TNO155 and identify regimen(s) for future study. Secondary assessments included pharmacokinetics, pharmacodynamics, and preliminary clinical efficacy. Here we present data from TNO155 single agent escalation. Results: As of 10/26/2020, 118 patients received TNO155 in variable schedules: once (QD; 1.5–70 mg; n = 55) or twice daily (BID; 30–50 mg; n = 25) in a 2 weeks on/1 week off (2w/1w) cycle; or QD in a 3w/1w cycle (30–60 mg; n = 32), or continuously (40 or 50 mg QD; n = 6). The most common cancer diagnoses treated were colorectal (54%), gastrointestinal stromal tumor (16%), non-small cell lung (12%), and head & neck (8%). The median number of prior antineoplastic therapies was 4 (range 1–10). Overall 109 patients (92%) have discontinued study treatment, 94 (80%) for progressive disease and 6 (5%) for adverse events (AEs). TNO155 showed rapid absorption (median day 1 Tmax ̃1.1 hours), an effective median T½ of ̃34 hours, and near dose-proportional exposure at day 14 (power model: AUCτ beta = 1.09 [90% CI 1.02–1.16]). AEs were mostly Grade 1/2 and generally consistent with on-target effects of SHP2 inhibition. The most common treatment-related AEs (all grades) were increased blood creatine phosphokinase (n = 33, 28%), peripheral edema (n = 31, 26%), diarrhea (n = 31, 26%), and acneiform dermatitis (n = 27, 23%). The most common treatment-related Grade ≥3 AEs were decreased platelets (n = 5, 4%), increased aspartate aminotransferase, diarrhea, and decreased neutrophils (each n = 4, 3%). The best observed response was stable disease (SD) per RECIST 1.1, reported in 24 (20%) patients, with a median duration of SD of 4.9 months (range 1.7–29.3). Evidence of SHP2 inhibition, as measured by change in DUSP6 expression by qPCR in paired pre- vs. on-treatment tumor samples, was seen in the majority of patients treated with TNO155 doses ≥20 mg/day (≥25% reduction, 38/42 [90%]; ≥50% reduction, 25/42 [60%]). Analysis of tumor whole-transcriptome RNA sequencing data is ongoing. Conclusions: TNO155 shows favorable pharmacokinetic properties and promising early safety and tolerability data at doses with evidence of target inhibition. The optimal dose using several schedules is still under evaluation. Studies of TNO155 in combination with other agents, including nazartinib (mutant-selective EGFR inhibitor[i]), adagrasib (KRAS G12Ci), spartalizumab (anti-PD-1 antibody), ribociclib (CDK4/6i), and dabrafenib (BRAFi) with LTT462 (ERKi), are ongoing (NCT03114319, NCT04330664, NCT04000529, NCT04294160). Clinical trial information: NCT03114319.

Overall survival with circulating tumor DNA-guided therapy in advanced non-small cell lung cancer

9009

Background: The effectiveness of circulating tumor DNA (ctDNA) at matching patients to life prolonging therapy has been studied mostly in small cohorts with limited follow up. The prognostic value of ctDNA alterations, particularly those absent on tissue, is also unclear. To address these questions, we studied survival outcomes in a prospective cohort of patients (N = 1002) with non-small cell lung cancer (NSCLC). Methods: Adults with metastatic or recurrent NSCLC were eligible if they had no known driver mutation or a known driver with progression following targeted therapy. Patients were enrolled at Memorial Sloan Kettering Cancer Center (New York, NY) starting October 21, 2016; analysis here is from a snapshot November 1, 2020. All patients had ctDNA sequenced via the Resolution ctDx Lung platform. To reduce inclusion of incidental germline mutations, we excluded non-functionally significant mutations with an allele frequency 35-65% that were present in gnomAD. Patients could also receive, at their provider’s discretion, tissue sequencing with MSK-IMPACT, which filters germline and clonal hematopoietic (CH) mutations with matched white blood cell sequencing. We performed survival analyses using Cox proportional hazards models from time of diagnosis of advanced disease to death, left truncating at time of study entry. Results: Of 1002 patients, 348 (35%) were treated with targeted therapy; in 181 of these (52%) the targetable alteration was detected in ctDNA. Patients treated with targeted therapy had prolonged survival whether matched by tissue-based methods (HR 0.39, 95%CI 0.30-0.51) or ctDNA (HR 0.47, 95%CI 0.37-0.61). These benefits persisted across multiple subgroups. ctDNA alterations themselves were associated with worse survival (HR 2.2, 95%CI 1.8-2.8), in a manner that scaled with allele fraction and burden. Of 401 patients with time-matched tissue sampling, 62 (15%) had ctDNA alterations that were absent on IMPACT (“unique” ctDNA alterations). Three such patients had unique ctDNA EGFR T790M mutations leading to changes in therapy. However, unique ctDNA alterations were generally associated with worse survival than no ctDNA alterations (HR 2.5, 95%CI 1.7-3.7) and even tissue-matched ctDNA alterations (HR 1.7, 95%CI 1.1-2.4). Of 98 unique ctDNA mutations, 48 (49%) were detectable in tissue at subthreshold levels, 12 (12%) were filtered by IMPACT as CH or germline, and 38 mutations (39%) were absent even at subthreshold levels. ctDNA alteration burden correlated with radiographic disease extent. In multivariate models with radiographic disease extent and other clinical variables, ctDNA alterations were the strongest independent predictor of worse survival. Conclusions: Our results show that ctDNA may match patients to life-prolonging targeted therapy and have prognostic importance. ctDNA may provide data about a patient’s cancer missed by spatially restricted tissue sequencing. Clinical trial information: NCT01775072.

COVID-19 in patients with lung cancer

BACKGROUND

Patients with lung cancers may have disproportionately severe coronavirus disease 2019 (COVID-19) outcomes. Understanding the patient-specific and cancer-specific features that impact the severity of COVID-19 may inform optimal cancer care during this pandemic.

PATIENTS AND METHODS

We examined consecutive patients with lung cancer and confirmed diagnosis of COVID-19 (n = 102) at a single center from 12 March 2020 to 6 May 2020. Thresholds of severity were defined a priori as hospitalization, intensive care unit/intubation/do not intubate ([ICU/intubation/DNI] a composite metric of severe disease), or death. Recovery was defined as >14 days from COVID-19 test and >3 days since symptom resolution. Human leukocyte antigen (HLA) alleles were inferred from MSK-IMPACT (n = 46) and compared with controls with lung cancer and no known non-COVID-19 (n = 5166).

RESULTS

COVID-19 was severe in patients with lung cancer (62% hospitalized, 25% died). Although severe, COVID-19 accounted for a minority of overall lung cancer deaths during the pandemic (11% overall). Determinants of COVID-19 severity were largely patient-specific features, including smoking status and chronic obstructive pulmonary disease [odds ratio for severe COVID-19 2.9, 95% confidence interval 1.07-9.44 comparing the median (23.5 pack-years) to never-smoker and 3.87, 95% confidence interval 1.35-9.68, respectively]. Cancer-specific features, including prior thoracic surgery/radiation and recent systemic therapies did not impact severity. Human leukocyte antigen supertypes were generally similar in mild or severe cases of COVID-19 compared with non-COVID-19 controls. Most patients recovered from COVID-19, including 25% patients initially requiring intubation. Among hospitalized patients, hydroxychloroquine did not improve COVID-19 outcomes.

CONCLUSION

COVID-19 is associated with high burden of severity in patients with lung cancer. Patient-specific features, rather than cancer-specific features or treatments, are the greatest determinants of severity.

YES1 amplification as a primary driver of lung tumorigenesis and YES1/YAP1 amplifications as mediators of acquired resistance (AR) to ALK and EGFR tyrosine kinase inhibitors (TKIs)

e21591

Background: Our previous work identified YES1 amplification as a mechanism of AR to EGFR TKIs. The current study investigates the potential role of YES1 amplification as a primary driver of tumorigenesis and of YES1/YAP1 amplifications as mediators of AR to ALK and EGFR TKIs. Methods: Models of ectopic expression were established and characterized for YES1 and YAP1 in human bronchial epithelial cells (HBECs) and ALK fusion-positive ( ALK+) and EGFR-mutant ( EGFRm) lung adenocarcinoma (LUAD) cell lines. MSK-IMPACT data for all LUAD cases and for ALK and EGFR TKI AR cases were surveyed for YES1 and YAP1 amplification. Results: YES1 was found to be amplified in 0.5% of all LUAD cases currently in the MSK-IMPACT database. To demonstrate its potential as a primary driver of tumorigenesis, YES1 was inducibly expressed in HBECs and shown to promote EGF-independent growth, focus formation, and increases in proliferation rate and sensitivity to Src family kinase (SFK) TKIs. Consistent with these findings, a partial response by RECIST criteria to third-line dasatinib was observed for a patient with stage IV LUAD in which MSK-IMPACT detected YES1 amplification and no established primary driver alteration. In models of AR, overexpression of either YES1 or YAP1 in multiple ALK+ and EGFRm cell lines conferred resistance to ALK and EGFR TKIs. Sensitivity to ALK or EGFR TKIs was partially recovered in YES1-overexpressing cells lines by siRNA-mediated gene knockdown of YAP1, and was restored in YAP1-overexpressing cells lines by knockdown of YES1 or mutation of the YES1-phosphorylation site on YAP1. ALK + or EGFR m cells overexpressing either YES1 or YAP1 were sensitive to dual inhibition of the primary driver and SFKs with single-agent repotrectinib or dasatinib, respectively. In contrast, treatment of YAP1-overexpressing ALK+ H3122 cells with alectinib induced changes in morphology and gene expression consistent with epithelial-to-mesenchymal transition (EMT) and rendered the cells insensitive to repotrectinib. Similar resistance to dual inhibition was seen in other YAP1-overexpressing cell lines after treatment with only ALK or EGFR blockade. To date, one LUAD case each of EGFR and ALK TKI AR has been found through MSK-IMPACT™ to be associated with YAP1 amplification. Conclusions: SFK inhibition can potentially be exploited to therapeutically target YES1 amplification as a primary driver in tumorigenesis and YES1/YAP1 amplifications as mediators of AR to ALK and EGFR TKIs.

High-dose osimertinib for CNS progression in EGFR+ non-small cell lung cancer (NSCLC): A multi-institutional experience

9586

Background: High-dose osimertinib 160 mg QD (osi160) has activity in osi-naïve, EGFR+ NSCLC pts with CNS or leptomeningeal disease (LMD) per the BLOOM trial, but the role of dose-escalation for CNS progression (PD) and/or LMD that develops while on 80 mg QD (osi80) is unclear. We describe here our multi-institutional experience with osi160. Methods: 105 pts from 8 institutions with advanced EGFR+ NSCLC treated with osi160 were retrospectively reviewed. To assess the CNS efficacy of dose escalation for CNS PD, we focused on pts who escalated from osi80 to osi160 for CNS PD without the addition of chemo and/or RT during dose escalation (cohort A, 24 pts). We also examined osi escalation for CNS PD while receiving chemo and/or RT (cohort B, 34 pts) and those who started on osi160 for CNS PD as the initial osi dose without overlapping therapies (cohort C, 11 pts). Radiographic responses were clinically assessed via chart review of scan reports. Kaplan-Meier analysis was used for time-to-event endpoints. We defined median duration of CNS disease control (MedDurCNSCon) on osi160 as time from the start of osi160 to CNS PD or discontinuation of osi160. Results: Among the 105 pts, 69 (26M, 43F; median age 57) EGFR+ NSCLC pts (29 del19, 31 L858R, 9 other) received osi160 for CNS PD between 10/2013 and 1/2020. Median lines of therapy pre-osi was 1 (range 0-8). While all 69 pts had CNS PD at the start of osi160, 61 (90%) had isolated CNS/LMD PD, without systemic PD. In cohort A, osi160 monotherapy had a MedDurCNSCon of 3.8 mos (95% CI, 1.7 – 5.8). Cohort A pts with isolated LMD (11) had MedDurCNSCon 5.8 mos (95% CI, 1.7 – 9) while those with parenchymal mets only (11) had MedDurCNSCon of 2 mos (95% CI, 1 - 4.9). In cohort B, osi160 in combination with RT (22) and/or chemo (14), had a MedDurCNSCon of 5.1 mos (95% CI, 3.1 – 6.5). In cohort C, osi160 monotherapy had a MedDurCNSCon of 4.2 mos (95% CI, 1.6 – NA). Pts on osi160 had no severe or life-threatening side effects. Conclusions: In this real-world cohort of EGFR+ NSCLC pts with CNS and/or LMD PD on osi80, dose escalation to 160 provided modest benefit with median 3.8 mos added CNS disease control. Dose escalation appeared more effective in pts with LMD versus parenchymal disease (MedDurCNSCon of 5.8 vs 2 mos). Treatment intensification with osi escalation plus RT and/or chemo appeared to confer about 1 month additional CNS disease control (power for comparison limited). Osi naïve pts started at 160 for CNS PD derived similar benefit. While limited by small numbers and retrospective design, this study suggests we need improved strategies to optimally manage CNS PD arising on osi80.

Clinical characteristics and anti-PD-(L)1 treatment outcomes of KRAS-G12C mutant lung cancer compared to other molecular subtypes of KRAS-mutant lung cancer

9596

Background: KRAS mutations are identified in approximately 30% of NSCLC. There are no FDA approved targeted therapies for patients with KRAS-mutant non-small cell lung cancer (NSCLC) but novel direct inhibitors of KRAS G12C have shown some activity in early phase clinical trials. We hypothesized that patients with KRAS-G12C mutations may have distinct clinical characteristics and responses to systemic therapies compared to patients with non-G12C subtypes. Methods: We identified patients with KRAS-mutant lung cancers who underwent next-generation sequencing with MSK-IMPACT, between January 2014 and December 2018. Baseline characteristics were compared with the Chi-square and Fisher’s exact test for categorical data and Wilcoxon rank-rum test for continuous data. Overall survival was calculated from time of diagnosis of metastatic/recurrent disease to date of death or last follow up, with left truncation to account for time of MSK-IMPACT. Overall survival was compared between groups using the Cox proportional-hazards model. Response evaluations where performed by independent thoracic radiologists according to RECIST 1. and compared between group with the Fisher’s exact test. Results: We identified 1194 patients with KRAS -mutant NSCLC, 772 with recurrent or metastatic disease. Of patients with advanced disease, 46% (352/772) had mutations in KRAS-G12C and 54% harbored non-G12C mutations (15% G12D, 16% G12V, 8% G12A, 4% G13D). Co-mutation patterns were similar with respect to KEAP1 (p=0.9) and STK11 (p=1.0). Patients with non-G12C mutations had a higher proportion of never smokers (10% vs 1.4% p<0.001). The median OS from diagnosis was 13 months for G12C and non-G12C patients (p=0.99). 45% (347/772) received 1L or 2L line treatment with PD-(L)1 inhibitor. RECIST measurements were available for 290/347 cases (84%). ORR with anti-PD-(L)1 treatment was 24% vs 28% in G12C vs non-G12C patients (p=0.5). In patients with PD-L1 50% (n=103), ORR was 39% for G12C vs 58% non-G12C patients (p=0.06). Conclusions: KRAS G12C mutations are present in 12% of patients with NSCLC and represent a relevant subtype of NSCLC given KRAS G12C inhibitors now in clinical development. Baseline characteristics including co-mutation patterns are similar between patients with G12C and non-G12C, except for smoking history. The efficacy of KRAS G12C direct inhibitors will need to be compared to other available therapies for KRAS mutant NSCLC (chemotherapy and PD-(L)1 inhibitors) to identify most effective therapeutic strategy.

EGFR mutation subtypes and response to immune checkpoint blockade treatment in non-small-cell lung cancer

BACKGROUND

Although EGFR mutant tumors exhibit low response rates to immune checkpoint blockade overall, some EGFR mutant tumors do respond to these therapies; however, there is a lack of understanding of the characteristics of EGFR mutant lung tumors responsive to immune checkpoint blockade.

PATIENTS AND METHODS

We retrospectively analyzed de-identified clinical and molecular data on 171 cases of EGFR mutant lung tumors treated with immune checkpoint inhibitors from the Yale Cancer Center, Memorial Sloan Kettering Cancer Center, University of California Los Angeles, and Dana Farber Cancer Institute. A separate cohort of 383 EGFR mutant lung cancer cases with sequencing data available from the Yale Cancer Center, Memorial Sloan Kettering Cancer Center, and The Cancer Genome Atlas was compiled to assess the relationship between tumor mutation burden and specific EGFR alterations.

RESULTS

Compared with 212 EGFR wild-type lung cancers, outcomes with programmed cell death 1 or programmed death-ligand 1 (PD-(L)1) blockade were worse in patients with lung tumors harboring alterations in exon 19 of EGFR (EGFRΔ19) but similar for EGFRL858R lung tumors. EGFRT790M status and PD-L1 expression did not impact response or survival outcomes to immune checkpoint blockade. PD-L1 expression was similar across EGFR alleles. Lung tumors with EGFRΔ19 alterations harbored a lower tumor mutation burden compared with EGFRL858R lung tumors despite similar smoking history.

CONCLUSIONS

EGFR mutant tumors have generally low response to immune checkpoint inhibitors, but outcomes vary by allele. Understanding the heterogeneity of EGFR mutant tumors may be informative for establishing the benefits and uses of PD-(L)1 therapies for patients with this disease.

A phase 1/2 study of osimertinib and bevacizumab as initial treatment for patients with metastatic EGFR-mutant lung cancers

9086

Background: Osimertinib (osi) demonstrated improved progression-free survival (PFS) over erlotinib as initial treatment (trmt) for EGFR-mutant (EGFR+) lung cancers. The addition of bevacizumab (bev) to erlotinib as initial trmt resulted in improved PFS compared to erlotinib alone (16 vs 10 months, HR 0.41). The phase 1 study of osi and bev confirmed the ability to combine osi and bev at full doses. Methods: The phase 2 study is assessing safety and efficacy of the combination. The primary endpoint is PFS at 12 months; secondary endpoints include overall response (ORR), overall survival (OS), and CNS PFS. All pts had interval CNS as well as systemic imaging. Pre-treatment and post-progression (PD) tumor tissue and interval plasma samples are being collected to identify mechanisms of resistance (MOR) and for biomarker assessment. Results: From Nov 2016 to May 2018, 49 pts were enrolled, including 6 pts from the phase 1. Median age: 60; Women 69%; Never-smokers 65%. 13 pts had CNS metastases (9 untreated, 5 measurable) prior to study initiation. 49 pts are eligible for response; 34/49 pts had a confirmed partial response (PR)(ORR 69%). PFS at 12 months is 0.70 (95% CI: 0.57-0.84), with 8/49 pts on study without PD for less than 12 months. All pts with measurable CNS disease had a PR in the CNS; PD in the CNS was uncommon (17%). 24 pts remain on study without PD; 2 are being treated beyond PD. Reasons for study discontinuation include PD (n = 16), resection of all sites of disease (n = 3), withdrawal of consent (n = 3), unrelated death (n = 2), toxicity (n = 1). The most frequent trtmt-related adverse events (any grade) were thrombocytopenia (61%), diarrhea (57%), hypertension (55%), and rash (47%). 24% required a dose reduction of osi, 18% discontinued bev and median doses of bev was 17. 9 pts have paired pre-trtmt and post-progression tissue biopsies; MOR identified include squamous cell (n = 2) and small cell (n = 1) transformation, PTEN loss, and CCNE amplification. Conclusions: Combination osi and bev was well-tolerated and efficacy to date supports further evaluation. Results of secondary endpoints including PFS, mechanisms of resistance, cfDNA data are forthcoming. A randomized study of osi compared to osi and bev is planned (EA5182). Supported by AstraZeneca Clinical trial information: NCT02803203.

Tissue-based molecular and histological landscape of acquired resistance to osimertinib given initially or at relapse in patients with EGFR-mutant lung cancers

9028

Background: Even though osimertinib (osi) is now the initial treatment for patients with EGFR-mutant lung cancers, our knowledge about mechanisms of resistance (MOR) is largely derived from patients who received osi after developing acquired resistance to initial EGFR inhibitor. Further, studies of osi resistance to date have mainly reported genotyping of plasma which suboptimally detects lineage plasticity, copy number changes, and chromosomal rearrangements. Methods: To identify MOR to osi and characterize clinical, molecular and histologic factors associated with duration of response, we identified patients with EGFR-mutant lung cancers who had next-generation sequencing performed on tumor tissue after developing acquired resistance to osi. Results: From January 2016 to December 2018, post-osi tumor tissue was collected from 71 patients (42 with paired pre-treatment specimens). See mechanisms of resistance below. Histologic transformation was identified in 19% of initial cases and 14% of all cases. When osi is given as initial treatment, with median follow up of 17 months, early emerging MOR rarely included on-target resistance mechanisms (1/16 cases of acquired EGFR G724S). Acquired alterations representing potential resistance mechanisms included CCNE1 and MYC amplifications, and mutations in MTOR and MET H1094Y. We confirmed in preclinical studies that an amino acid substitution at MET H1094 can reduce sensitivity to osi. Conclusions: In this analysis of MOR identified on NGS from tumor tissue, we found a different spectrum of resistance mechanisms to initial and later-line osi, with histologic transformation (including squamous cell transformation) a dominant MOR, particularly in the first-line setting, that cannot be identified on plasma testing. Subsequent studies are needed to assess patients with a longer time on initial osi as there may be a temporal bias to MOR, with off-target MOR emerging earlier and on-target resistance mutations later. [Table: see text]

Safety and preliminary antitumor activity of U3-1402: A HER3-targeted antibody drug conjugate in EGFR TKI-resistant, EGFRm NSCLC

9010

Background: Treatment options are limited for EGFRm NSCLC resistant to EGFR TKIs. HER3 is expressed in a majority of NSCLC tumors. U3-1402 is a HER3-targeted antibody drug conjugate with a fully human HER3-targeted antibody, novel cleavable peptide-based linker, and topoisomerase I inhibitor payload. Methods: An ongoing multicenter phase 1 dose escalation and expansion study is assessing U3-1402 safety/tolerability and preliminary activity in metastatic or unresectable EGFRm NSCLC patients (pts) who are T790M negative after disease progression while on erlotinib, gefitinib or afatinib; or develop disease progression while on osimertinib regardless of T790M status. Dose escalation is based on dose-limiting toxicities (DLTs) and guided by the modified Continuous Reassessment Method. U3-1402 is administered via intravenous infusion in 21-day cycles. Pretreatment tumor tissue is required. Results: As of 11 Nov 2018, 15 pts (6 M; 9 F) were enrolled across 3 dose levels (3.2, 4.8, 6.4 mg/kg). Median age was 63 y; 10 pts had EGFR exon 19 deletion and 5 EGFR L858R mutation. Median sum of longest diameters (SLD) at baseline was 69 (range 22–143) mm. All pts had prior EGFR TKIs; 14 had 2nd line or later osimertinib. Six had prior chemotherapy. All 11 evaluable tumors demonstrated HER3 expression (median HER3 membrane H-score 188, range 150–290). Five pts discontinued treatment: 4 due to progressive disease, 1 due to adverse event (AE). All Grade (Gr) treatment-emergent AEs (TEAEs) in ≥20% of pts were nausea (60%), vomiting (40%), fatigue (33%), decreased appetite (27%), and alopecia (20%). Gr≥3 TEAEs were nausea (1/15; Gr3; related), hypoxia (1/15; Gr3; unrelated), and platelet count decreased (2/15; both Gr4 at 6.4 mg/kg and considered DLTs). In 13 evaluable pts, all but 1 had a decrease in SLD (median best change −29%, range +10% to −67%), 2 had confirmed partial response per RECIST v1.1 (best changes −44%, −67%). Conclusions: U3-1402 showed a manageable safety profile and preliminary antitumor activity in EGFR TKI-resistant EGFRm NSCLC. Evaluation of candidate biomarkers, including HER3 expression, which correlate with U3-1402 response is ongoing. Clinical trial information: NCT03260491.

Severe immune-related adverse events are common with sequential PD-(L)1 blockade and osimertinib

BACKGROUND

Concurrent programmed death-ligand-1 (PD-(L)1) plus osimertinib is associated with severe immune related adverse events (irAE) in epidermal growth factor receptor (EGFR)-mutant non-small-cell lung cancer (NSCLC). Now that PD-(L)1 inhibitors are routinely used as adjuvant and first-line treatments, sequential PD-(L)1 inhibition followed by osimertinib use may become more frequent and have unforeseen serious toxicity.

METHODS

We identified patients with EGFR-mutant NSCLC who were treated with PD-(L)1 blockade and EGFR- tyrosine kinase inhibitors (TKIs), irrespective of drug or sequence of administration (total n = 126). Patient records were reviewed to identify severe (NCI-CTCAE v5.0 grades 3-4) toxicity.

RESULTS

Fifteen percent [6 of 41, 95% confidence interval (CI) 7% to 29%] of all patients treated with sequential PD-(L)1 blockade followed later by osimertinib developed a severe irAE. Severe irAEs were most common among those who began osimertinib within 3 months of prior PD-(L)1 blockade (5 of 21, 24%, 95% CI 10% to 45%), as compared with >3-12 months (1 of 8, 13%, 95% CI 0% to 50%), >12 months (0 of 12, 0%, 95% CI 0% to 28%). By contrast, no severe irAEs were identified among patients treated with osimertinib followed by PD-(L)1 (0 of 29, 95% CI 0% to 14%) or PD-(L)1 followed by other EGFR-TKIs (afatinib or erlotinib, 0 of 27, 95% CI 0% to 15%). IrAEs occurred at a median onset of 20 days after osimertinib (range 14-167 days). All patients with irAEs required steroids and most required hospitalization.

CONCLUSION

PD-(L)1 blockade followed by osimertinib is associated with severe irAE and is most frequent among patients who recently received PD-(L)1 blockade. No irAEs were observed when osimertinib preceded PD-(L)1 blockade or when PD-(L)1 was followed by other EGFR-TKIs. This association appears to be specific to osimertinib, as no severe irAEs occurred with administration of other EGFR-TKIs.

Pulse-continuous dose erlotinib as initial targeted therapy for patients with EGFR-mutant lung cancers with untreated brain metastases

9039

Background: Clarke (Neurooncol 2010) reported responses with intermittent high pulse doses of erlotinib (leading to higher concentrations in CSF) given to patients with EGFR-mutant central nervous system metastases developing on standard erlotinib doses. In a phase 1 study of pulse-continuous dose erlotinib, no patient developed progression in existing or new brain or leptomeningeal metastases (Yu Ann Oncol 2016). This phase 2 trial tested pulse-continuous dose erlotinib in patients with lung cancers with EGFRmutations with brain metastases. Methods: Patients had no prior EGFR TKI or radiation to the brain and at least 1 target brain metastasis. All received initial daily "pulse" doses of erlotinib 1200 mg days 1&2 and "continuous" 50 mg doses days 3-7 (doses and schedule from the Yu Phase 1 study), weekly until progression. The co-primary endpoints were overall and brain metastasis response by RECIST 1.1. Results: We enrolled 19 patients with EGFR-mutant lung cancers: median age 61yrs (range 45-80), 74% women, 95% Karnofsky PS ≥80%, 1 leptomeningeal disease, 33% prior pemetrexed-based chemotherapy. The median size of target brain metastases was 13 mm (range 10-19 mm). 32% were on dexamethasone for cerebral edema. The partial response rate overall was 74% (95% CI 51-89%) and also 74% in brain metastases. Of 10 patients with progression, 9/10 occurred in non-brain sites (4 EGFRT790M, 1 with progression in brain as well), 1 with leptomeningeal. The median progression free survival was 10 mo (range 7-NR mo). Pulse doses were reduced in 68% (median delivered pulse dose 1050 mg days 1&2, range 600-1200 mg). Incidences of any gradeof rash and diarrhea were 84% and 63% respectively. There were no grade 4 or 5 toxicities. Conclusions: Pulse-continuous dose erlotinib alone controlled brain and leptomeningeal metastases in 89% (95% CI 67-98%) of patients with EGFR-mutant lung cancers with central nervous system spread pretreatment, with an overall response rate of 74% and progression free survival and rates of rash and diarrhea comparable to series with erlotinib 150 mg daily. Supported by Astellas, CA 129243, CA 008748. NCT01967095 Clinical trial information: NCT01967095.

Response to osimertinib following treatment with EGF816 in patients with T790M EGFR mutant NSLCLC

e20673

Background: Third generation (3rd gen) epidermal growth factor (EGFR) tyrosine kinase inhibitors (TKIs) have been developed to treat EGFR T790M-mediated resistance to EGFR TKIs by inhibiting EGFR T790M, as well as EGFR L858R and EGFR exon 19 deletions. The mechanisms of resistance to third-generation EGFR TKIs are largely unknown and clinical cross-resistance among 3rd gen EGFR TKIs has not been routinely evaluated. Osimertinib is an FDA-approved irreversible 3rd gen EGFR TKI. In patients with EGFR T790M mutant NSCLC, the response rate (ORR) to osimertinib is 61%. EGF816 is a covalent, irreversible, 3rd gen EGFR TKI in clinical development. In early phase data of EGF816, the ORR was 47% and disease control rate was 87% in patients with EGFR T790M mutant NSCLC. To assess clinical cross-resistance between EGF816 and osimertinib, we evaluated the clinical outcomes of patients treated with osimertinib in patients previously treated with EGF816 during the phase I/II trial. Methods: Patients with metastatic EGFR mutant lung adenocarcinoma were identified who were previously treated with EGF816 and received osimertinib after progression of disease on EGF816 (NCT02108964). All patients had documented T790M mutation prior to treatment with EGF816. The best overall response to osimertinib was determined by RECIST 1.1 criteria. Duration of clinical benefit was defined as duration of osimertinib therapy. Results: Fourteen (3 men, 11 women, median age 58 [range 33-77]) patients met eligibility criteria at our centers. The ORR to subsequent osimertinib therapy was 14% (1 CR, 1 PR, 8 SD, 4 POD). Patients continued treatment with osimertinib for a median of 9 months (95% CI 3.8-10.1, [median follow up 11 months, range 1-13 months]). 5 patients are still on osimertinib to date (one patient each 3+, 6+, 8+, 11+, and 12+ months). Conclusions: This series suggests a potentially meaningful clinical benefit for patients with sequential therapy with two different third-generation EGFR inhibitors, emphasizing the importance of understanding resistance mechanisms (genetic alteration of target, bypass signaling, pharmacology, etc.) and raising the possibility of the need for multiple third generation EGFR TKIs in clinical practice.

Lung cancers with mutations in EGFR exon 18: Molecular characterization and clinical outcomes in response to tyrosine kinase inhibitors

9029

Background: Little data is available to guide clinical management of individuals with less common oncogenic drivers such as exon 18 mutations (ex18m) in EGFR. To better understand the impact of these rare mutations on treatment outcomes, we reviewed clinicopathologic data in patients (pts) with ex18m treated with tyrosine kinase inhibitors (TKI) in EGFR-mutant lung cancers. Methods: Pts with EGFR ex18m were detected via molecular diagnostics using Sequenom™, FoundationOne™ or MSK IMPACT™ NGS testing from 2003-2016. We reviewed their clinical data for molecular alterations in EGFR, treatment outcomes in response to TKI (time on treatment) and median overall survival (OS). Results: We identified mutations in EGFR ex18m in 63 pts. Median age at diagnosis was 68; 63% were women; 29% never smokers. Overall, 74 ex18m were found in 63 pts, including: G719A = 38, G719S = 11, G719C = 8, E709K = 6, E709_T710delinsD = 6, E709A = 3, G719D = 2. E709 and G719 co-mutations in ex18 were found in 9 pts, and 1 pt was found to have 3 separate tumors, each with a distinct ex18m. 29/63 (46%) patients with ex18m had a co-occurring EGFR mutation: 9 with another ex18m; 20 with ex19-21m. Using our IMPACT NGS, the median number of co-mutations was 8 (range 1-17). Two out of 63 pts had a pre-treatment T790M mutation. The 25 pts with non-metastatic disease presented in the following stages: IA = 19; IB = 3; IIB = 1; IIIA = 2; IIIB = 2. 34/38 pts with metastatic disease were treated with the following first-line EGFR-TKIs: erlotinib = 28, afatinib = 5, osimertinib = 1. Median duration on TKI treatment in months was: erlotinib = 10 mo, (range 1-25), afatinib = 3 mo (range 2-9), osimertinib = 4 mo. Median OS from the date of diagnosis of metastatic disease was 22 months (95% CI 18-29). In comparison, a similar cohort of pts with sensitizing EGFR exon19del/L858R mutations had a median OS of 31 months (95% CI 28-33) (Naidoo Cancer2015). Conclusions: Almost half of ex18m occur concurrently with another EGFR mutation. Overall, ex18m pts have a shorter median OS when compared to similar patient cohorts. EGFR-TKIs appear to be an effective treatment for pts with ex18m in EGFR-mutant lung cancers.

A phase 1 study of osimertinib and bevacizumab as initial treatment for patients with EGFR-mutant lung cancers

9033

Background: EGFR tyrosine kinase inhibitors (TKI) are the recommended first line treatment for EGFR-mutant lung cancers. Osimertinib, an EGFR TKI that inhibits both sensitizing EGFR mutations and EGFR T790M, is approved for use after progression on an EGFR TKI with evidence of EGFR T790M, and is currently being assessed as initial treatment for EGFR-mutant lung cancers. The addition of bevacizumab to erlotinib resulted in improved progression free survival (PFS) compared to erlotinib alone as initial treatment (16 vs 10 months, HR 0.41). This phase 1/2 study is assessing osimertinib and bevacizumab as initial treatment for patients with EGFR-mutant lung cancers. Methods: We evaluated toxicity and efficacy of osimertinib and bevacizumab as initial treatment for patients with advanced EGFR-mutant lung cancers. Using a 3+3 design, full doses of osimertinib (80mg PO daily) and bevacizumab (15mg/kg IV q3 weeks) were given, with a planned dose de-escalation (osimertinib 40mg PO daily) should grade 3 or greater toxicity be seen. Six patients must be treated without a dose-limiting toxicity (DLT) to determine the MTD. 43 additional patients will be treated at the MTD in the phase 2 study, with a primary endpoint of PFS at 12 months. Response was evaluated by RECIST 1.1. Results: From Sept 2016 to Jan 2017, 15 patients were enrolled. Median age: 63; Women 11; EGFR L858R = 8, Ex19del = 6, G709A/G719S = 1. After median duration of treatment of 2.7 months, no DLTs were seen in any patient. The MTD was determined to be osimertinib 80mg, bevacizumab 15mg/kg q3 weeks. In total, 15 patients are being treated at the MTD to date. Treatment-related adverse events (AE) were all grade 1-2, except for grade 3 hypertension. The most frequent treatment-related AEs (any grade) were rash (53%), diarrhea (40%), hypertension (33%), fatigue (20%), and itching (20%). All 15 patients continue on study. Conclusions: Combination osimertinib and bevacizumab is a tolerable first-line treatment for patients with EGFR-mutant lung cancers and the MTD is osimertinib 80mg and bevacizumab 15mg/kg q3 weeks. Assessment of efficacy with an endpoint of PFS at 12 months is ongoing. Supported by AstraZeneca (NCT02803203). Clinical trial information: NCT02803203.

YES1 amplification as a mechanism of acquired resistance (AR) to EGFR tyrosine kinase inhibitors (TKIs) identified by a transposon mutagenesis screen and clinical genomic testing

9043

Background: Overcoming AR to EGFR TKIs remains challenging, and in many cases the mechanisms are still unclear. To identify novel mechanisms of resistance to EGFR TKIs, we performed a forward genetic screen using transposon mutagenesis in EGFR-mutant lung adenocarcinoma cells. Methods: EGFR TKI-sensitive PC9 cells were co-transfected with plasmids encoding a mutagenic piggyBactransposon and hyperactive piggyBac transposase. Transposon-tagged, afatinib-resistant clones were generated by sequential selection of transfected cells with puromycin and 1µM afatinib. Transposon insertion sites were mapped using a modified TraDIS-type method and next-generation sequencing (NGS). Selected clones were characterized using Western blots, receptor tyrosine kinase (RTK) arrays, and viability assays following treatment with TKIs or siRNA-mediated gene knockdowns. We reviewed MSK-IMPACT™ NGS data on 100 patient tumors with EGFR TKI AR. Available tumor samples were analyzed by fluorescence in situ hybridization (FISH). Results: In 187/188 afatinib-resistant clones, transposon insertion sites consistent predominantly with gene upregulation were found in MET, the Src family kinase (SFK) member YES1, or both. Clones with activating YES1 insertions exhibited resistance to all three generations of EGFR TKIs; high levels of expression of tyrosine-phosphorylated YES1; sensitivity to the SFK TKI dasatinib and to siRNA-mediated knockdown of YES1; and tyrosine phosphorylation of YAP1 and ERBB3. A query of the MSK-IMPACT™ data on EGFR TKI AR patients revealed amplification of YES1 and no alteration of MET, ERBB2 or BRAF in 3/54 T790M-negative (95% CI 1 to 16%) and 1/46 (95% CI 1 to 12%) T790M-positive cases. Amplification of YES1was confirmed by FISH in 2/2 cases, and was absent in matched pre-TKI samples in 2/2 cases. Conclusions: YES1 amplification is found in 4% of patients with acquired resistance to EGFR TKIs and is potentially targetable by Src family kinase inhibitors. Forward genetic screens using transposon mutagenesis and routine clinical NGS of patient samples can identify novel mechanisms of resistance to targeted therapies.

Epidermal growth factor receptor exon 20 insertions in advanced lung adenocarcinomas: Clinical outcomes and response to erlotinib

BACKGROUND

Epidermal growth factor receptor (EGFR) exon 20 insertions (exon20ins) represent approximately 10% of EGFR-mutant lung adenocarcinomas, and are associated with resistance to EGFR tyrosine kinase inhibitors (TKIs). Clinical outcomes in comparison with patients with sensitizing EGFR mutations are not well established.

METHODS

Patients with stage IV lung adenocarcinomas with EGFR exon20ins were identified through routine molecular testing. Clinicopathologic data were collected. Overall survival (OS) was measured from the diagnosis of stage IV disease, and in patients treated with EGFR TKIs, the time to progression (TTP) on erlotinib was measured.

RESULTS

One thousand eight hundred and eighty-two patients with stage IV lung adenocarcinomas were identified: 46 patients had EGFR exon20ins (2%), and 258 patients had an EGFR exon 19 deletion (exon19del)/L858R point mutation (14%). Among 11 patients with lung adenocarcinomas with EGFR exon20ins who received erlotinib, 3 patients (27%) had a partial response (FQEA, 1; ASV, 1; and unknown variant, 1). TTP for patients with EGFR exon20ins and patients with EGFR exon19del/L858R on erlotinib were 3 and 12 months, respectively (P < .01). Responses to chemotherapy were similar for patients with lung adenocarcinomas with EGFR exon20ins and patients with lung adenocarcinomas with EGFR exon19del/L858R. Median OS from the diagnosis of stage IV disease for patients with EGFR exon20ins and patients with EGFR exon19del/L858R was 26 months (95% confidence interval, 19 months-not reached n = 46) and 31 months (95% confidence interval, 28-33 months; n = 258), respectively (P = .53).

CONCLUSIONS

The majority of patients with advanced lung adenocarcinomas harboring EGFR exon20ins do not respond to EGFR TKI therapy. Standard chemotherapy should be used as first-line therapy. These patients have an OS similar to that of patients with sensitizing EGFR mutations. Individuals with certain variants such as FQEA and ASV may respond to erlotinib.