TWIST1 is a critical downstream target of the HGF/MET pathway and is required for MET driven acquired resistance in oncogene driven lung cancer

MET amplification/mutations are important targetable oncogenic drivers in NSCLC, however, acquired resistance is inevitable and the majority of patients with targetable MET alterations fail to respond to MET tyrosine kinase inhibitors (TKIs). Furthermore, MET amplification is among the most common mediators of TKI resistance. As such, novel therapies to target MET pathway and overcome MET TKI resistance are clearly needed. Here we show that the epithelial-mesenchymal transition (EMT) transcription factor, TWIST1 is a key downstream mediator of HGF/MET induced resistance through suppression of p27 and targeting TWIST1 can overcome resistance. We found that TWIST1 is overexpressed at the time of TKI resistance in multiple MET-dependent TKI acquired resistance PDX models. We have shown for the first time that MET directly stabilized the TWIST protein leading to TKI resistance and that TWIST1 was required for MET-driven lung tumorigenesis as well as could induce MET TKI resistance when overexpressed. TWIST1 mediated MET TKI resistance through suppression of p27 expression and genetic or pharmacologic inhibition of TWIST1 overcame TKI resistance in vitro and in vivo. Our findings suggest that targeting TWIST1 may be an effective therapeutic strategy to overcome resistance in MET-driven NSCLC as well as in other oncogene driven subtypes in which MET amplification is the resistance mechanism.

A Path to Persistence after EGFR Inhibition

Residual cancer cells persist even after targeted therapies, serving as a reservoir for the subsequent acquisition of genetic alterations that lead to acquired drug resistance and tumor relapse. These initial drug-tolerant persisters (DTP) are phenotypically heterogenous with transient phenotypes attributed to epigenetic, metabolic, and cell-cycle changes. DTPs are responsible for the inevitable relapse seen in EGFR-mutant non-small cell lung cancer (NSCLC) despite high initial response to tyrosine kinase inhibitor (TKI) treatment. While past in vitro studies identified diverse drivers of drug-tolerant persistence to EGFR TKIs in NSCLC, the resultant phenotypic plasticity is not well understood and in vivo models of persistence are lacking. In this issue of Cancer Research, Hu and colleagues used patient-derived xenograft models of EGFR-mutant lung cancer treated with the third-generation TKI osimertinib to investigate mechanisms of persistence at the time of maximal response. Using bulk and single-cell RNA sequencing, the authors identified a DTP transcriptional cluster mediated by the key neuroendocrine lineage transcription factor ASCL1, which triggers an epithelial-to-mesenchymal transition transcriptional program. ASCL1 overexpression increased osimertinib tolerance in vitro as well, apparently independent of its role in neuroendocrine differentiation. Interestingly, the ability of ASCL1 to induce persistence was context dependent as this occurred only in epigenetically permissive cells. Overall, these findings contribute to our understanding of DTP heterogeneity seen after osimertinib treatment and provide insights into potential therapeutic targets. See related article by Hu et al., p. 1303.

p90RSK pathway inhibition synergizes with cisplatin in TMEM16A overexpressing head and neck cancer

Head and neck squamous cell carcinoma (HNSCC) constitutes one of the most common types of human cancers and often metastasizes to lymph nodes. Platinum-based chemotherapeutic drugs are commonly used for treatment of a wide range of cancers, including HNSCC. Its mode of action relies on its ability to impede DNA repair mechanisms, inducing apoptosis in cancer cells. However, due to acquired resistance and toxic side-effects, researchers have been focusing on developing novel combinational therapeutic strategies to overcome cisplatin resistance. In the current study, we identified p90RSK, an ERK1/2 downstream target, as a key mediator and a targetable signaling node against cisplatin resistance. Our results strongly support the role of p90RSK in cisplatin resistance and identify the combination of p90RSK inhibitor, BI-D1870, with cisplatin as a novel therapeutic strategy to overcome cisplatin resistance. In addition, we have identified TMEM16A expression as a potential upstream regulator of p90RSK through the ERK pathway and a biomarker of response to p90RSK targeted therapy in the context of cisplatin resistance.

Lorlatinib and capmatinib in a ROS1-rearranged NSCLC with MET-driven resistance: tumor response and evolution

Acquired drug resistance remains a major problem across oncogene-addicted cancers. Elucidation of mechanisms of resistance can inform rational treatment strategies for patients relapsing on targeted therapies while offering insights into tumor evolution. Here, we report acquired MET amplification as a resistance driver in a ROS1-rearranged lung adenocarcinoma after sequential treatment with ROS1 inhibitors. Subsequent combination therapy with lorlatinib plus capmatinib, a MET-selective inhibitor, induced intracranial and extracranial tumor response. At relapse, sequencing of the resistant tumor revealed a MET D1246N mutation and loss of MET amplification. We performed integrated molecular analyses of serial tumor and plasma samples, unveiling dynamic alterations in the ROS1 fusion driver and MET bypass axis at genomic and protein levels and the emergence of polyclonal resistance. This case illustrates the complexity of longitudinal tumor evolution with sequential targeted therapies, highlighting challenges embedded in the current precision oncology paradigm and the importance of developing approaches that prevent resistance.

Male sex and pretreatment weight loss are associated with poor outcome in patients with advanced non-small cell lung cancer treated with immunotherapy: a retrospective study

The influence of sex and body mass index (BMI) on the efficacy of immune checkpoint inhibitors (ICIs) in advanced non-small cell lung cancer (NSCLC) patients remains unclear. We conducted a retrospective study to evaluate the relationship between sex, BMI, pretreatment weight loss (PWL), and clinical outcomes in 399 stage IV NSCLC patients treated with ICIs using data abstracted from medical records. Multivariable Cox proportional hazards models were used to assess the impact on overall survival and progression-free survival. Females were significantly more likely to experience immune-related adverse events and had a significantly lower risk of death compared to males in our patient cohort. In stratified analyses, the latter was limited to those receiving first-line monotherapy. BMI was overall not significantly associated with outcome. However, underweight patients had a significantly higher risk of both progression and death compared to normal weight patients in the first-line monotherapy group. When stratified by sex, underweight males had a significantly higher risk of progression and death compared to normal weight males. This was not observed among females. Those with PWL had overall significantly worse outcomes compared to those without. In stratified analyses, PWL was associated with significantly worse OS in both females and males. Stratified by treatment, the worse outcome was limited to those receiving ICI monotherapy. In summary, utilizing real-world data, this study suggests that male sex, being underweight, and PWL negatively impact ICI efficacy in NSCLC patients. Therapeutic approaches to improve ICI outcomes in underweight patients and those with PWL should be investigated.

Phase II Study of Docetaxel and Trametinib in Patients with KRAS Mutation Positive Recurrent Non-Small Cell Lung Cancer (NSCLC; SWOG S1507, NCT-02642042)

PURPOSE

Efficacy of MEK inhibitors in KRAS+ NSCLC may differ based on specific KRAS mutations and comutations. Our hypothesis was that docetaxel and trametinib would improve activity in KRAS+ NSCLC and specifically in KRAS G12C NSCLC.

PATIENTS AND METHODS

S1507 is a single-arm phase II study assessing the response rate (RR) with docetaxel plus trametinib in recurrent KRAS+ NSCLC and secondarily in the G12C subset. The accrual goal was 45 eligible patients, with at least 25 with G12C mutation. The design was two-stage design to rule out a 17% RR, within the overall population at the one-sided 3% level and within the G12C subset at the 5% level.

RESULTS

Between July 18, 2016, and March 15, 2018, 60 patients were enrolled with 53 eligible and 18 eligible in the G12C cohort. The RR was 34% [95% confidence interval (CI), 22-48] overall and 28% (95% CI, 10-53) in G12C. Median PFS and OS were 4.1 and 3.3 months and 10.9 and 8.8 months, overall and in the subset, respectively. Common toxicities were fatigue, diarrhea, nausea, rash, anemia, mucositis, and neutropenia. Among 26 patients with known status for TP53 (10+ve) and STK11 (5+ve), OS (HR, 2.85; 95% CI, 1.16-7.01), and RR (0% vs. 56%, P = 0.004) were worse in patients with TP53 mutated versus wild-type cancers.

CONCLUSIONS

RRs were significantly improved in the overall population. Contrary to preclinical studies, the combination showed no improvement in efficacy in G12C patients. Comutations may influence therapeutic efficacy of KRAS directed therapies and are worthy of further evaluation. See related commentary by Cantor and Aggarwal, p. 3563.

Targeting the epidermal growth factor receptor following complete surgical resection in patients with early-stage non-small cell lung cancer

INTRODUCTION

Activating mutations in the epidermal growth factor receptor (EGFR) gene are one of the most common targetable oncogenic drivers of non-small cell lung cancer (NSCLC). Osimertinib is a third-generation EGFR tyrosine kinase inhibitor (EGFR-TKI) that selectively inhibits EGFR-TKI sensitizing (ex19del or L858R) and T790M mutations and has superior CNS penetration. Osimertinib is approved in EGFR mutant stage IB-IIIA NSCLC following complete tumor resection.

AREAS COVERED

This review opinion article summarizes the pivotal studies that led to the approval of current adjuvant therapies in NSCLC with the primary focus on EGFR-TKI osimertinib and outlines the future strategies in the era of neoadjuvant immunotherapy and emerging novel roles of EGFR targeting therapies. The literature search has been performed using PubMed, Food and Drug Administration website, and Google search.

EXPERT OPINION

Osimertinib showed significant and clinically meaningful disease-free survival benefit compared to placebo in EGFR mutant stage IB-IIIA NSCLC following complete tumor resection. Whether this will lead to improvement in overall survival and the optimal length of treatment remain open questions and are much-debated topic in the lung cancer field.

A single-arm, multicenter, phase II trial of osimertinib in patients with epidermal growth factor receptor exon 18 G719X, exon 20 S768I, or exon 21 L861Q mutations

BACKGROUND

For patients with stage IV non-small-cell lung cancer with epidermal growth factor receptor (EGFR) exon 19 deletions and exon 21 L858R mutations, osimertinib is the standard of care. Investigating the activity and safety of osimertinib in patients with EGFR exon 18 G719X, exon 20 S768I, or exon 21 L861Q mutations is of clinical interest.

PATIENTS AND METHODS

Patients with stage IV non-small-cell lung cancer with confirmed EGFR exon 18 G719X, exon 20 S768I, or exon 21 L861Q mutations were eligible. Patients were required to have measurable disease, an Eastern Cooperative Oncology Group performance status of 0 or 1, and adequate organ function. Patients were required to be EGFR tyrosine kinase inhibitor-naive. The primary objective was objective response rate, and secondary objectives were progression-free survival, safety, and overall survival. The study used a two-stage design with a plan to enroll 17 patients in the first stage, and the study was terminated after the first stage due to slow accrual.

RESULTS

Between May 2018 and March 2020, 17 patients were enrolled and received study therapy. The median age of patients was 70 years (interquartile range 62-76), the majority were female (n = 11), had a performance status of 1 (n = 10), and five patients had brain metastases at baseline. The objective response rate was 47% [95% confidence interval (CI) 23% to 72%], and the radiographic responses observed were partial response (n = 8), stable disease (n = 8), and progressive disease (n = 1). The median progression-free survival was 10.5 months (95% CI 5.0-15.2 months), and the median OS was 13.8 months (95% CI 7.3-29.2 months). The median duration on treatment was 6.1 months (range 3.6-11.9 months), and the most common adverse events (regardless of attribution) were diarrhea, fatigue, anorexia, weight loss, and dyspnea.

CONCLUSIONS

This trial suggests osimertinib has activity in patients with these uncommon EGFR mutations.

Sotorasib in KRAS p.G12C-Mutated Advanced Pancreatic Cancer

BACKGROUND

KRAS p.G12C mutation occurs in approximately 1 to 2% of pancreatic cancers. The safety and efficacy of sotorasib, a KRAS G12C inhibitor, in previously treated patients with KRAS p.G12C-mutated pancreatic cancer are unknown.

METHODS

We conducted a single-group, phase 1-2 trial to assess the safety and efficacy of sotorasib treatment in patients with KRAS p.G12C-mutated pancreatic cancer who had received at least one previous systemic therapy. The primary objective of phase 1 was to assess safety and to identify the recommended dose for phase 2. In phase 2, patients received sotorasib at a dose of 960 mg orally once daily. The primary end point for phase 2 was a centrally confirmed objective response (defined as a complete or partial response). Efficacy end points were assessed in the pooled population from both phases and included objective response, duration of response, time to objective response, disease control (defined as an objective response or stable disease), progression-free survival, and overall survival. Safety was also assessed.

RESULTS

The pooled population from phases 1 and 2 consisted of 38 patients, all of whom had metastatic disease at enrollment and had previously received chemotherapy. At baseline, patients had received a median of 2 lines (range, 1 to 8) of therapy previously. All 38 patients received sotorasib in the trial. A total of 8 patients had a centrally confirmed objective response (21%; 95% confidence interval [CI], 10 to 37). The median progression-free survival was 4.0 months (95% CI, 2.8 to 5.6), and the median overall survival was 6.9 months (95% CI, 5.0 to 9.1). Treatment-related adverse events of any grade were reported in 16 patients (42%); 6 patients (16%) had grade 3 adverse events. No treatment-related adverse events were fatal or led to treatment discontinuation.

CONCLUSIONS

Sotorasib showed anticancer activity and had an acceptable safety profile in patients with KRAS p.G12C-mutated advanced pancreatic cancer who had received previous treatment. (Funded by Amgen and others; CodeBreaK 100 ClinicalTrials.gov number, NCT03600883.).

Abstract 1091: TWIST1 inhibition overcomes resistance to tyrosine kinase inhibitors in MET driven non-small cell lung cancer

Background: The mesenchymal-epidermal transition (cMET/MET) tyrosine kinase receptor and its ligand, the hepatocyte growth factor (HGF) are overexpressed in a large percentage of non-small cell lung cancers (NSCLCs) and MET mutation and/or amplification leads to oncogene addiction in small subset of NSCLC. In addition, MET amplification is an established mechanism of resistance to EGFR and other oncogenic targeted TKIs. Several MET-inhibitors have been developed and two MET TKIs have been approved for MET exon 14 skipping mutant NSCLC and have shown activity against MET amplified NSCLC. However, long-term efficacy of MET TKIs is limited as acquired resistance is inevitable. HGF overexpression has been identified as one of the mechanisms of resistance to MET TKIs in MET-altered NSCLC, but the mechanism(s) by which the HGF-MET pathway causes resistance are poorly understood. Here, we investigated the requirement of the EMT-transcription factor, TWIST1 in HGF-mediated resistance to MET TKIs and the role of TWIST1 in de-novo and acquired resistance to MET TKIs.

Methods: TWIST1 expression was measured in wild type and TWIST1 over expressing cell lines in presence and absence of HGF. TWIST1 was inhibited with shRNA and harmine. Apoptosis was assessed via immunoblotting and cleaved caspase 3 staining. We utilized MET altered (mutant/amplified) NSCLC cell lines, patient derived xenografts and a novel transgenic mouse model of Hgf, Twist1 overexpressing lung cancer to evaluate TWIST1 as a driver of MET TKI resistance.

Results: We found that HGF induced TWIST1 expression and MET TKI treatment decreased TWIST1 expression through a post-translational mechanism. Re-expression of TWIST1 led to MET TKI resistance in MET amplified or MET mutant cell lines. Conversely, genetic and pharmacological inhibition of TWIST1 sensitizes to MET inhibition and overcame HGF-mediated MET TKI resistance and MET amplification mediated EGFR TKI resistance in vitro and in vivo. Furthermore, the role of TWIST1 in HGF/MET lung tumorigenesis was evaluated both in human NSCLC xenografts and an Hgf-driven NSCLC mouse model. Genetic inhibition of TWIST1 in MET mutant or amplified cell lines prevented tumor growth in vivo. Furthermore, TWIST cooperated with Hgf in a CCSP-Hgf (CH) mice model that constitutively overexpresses Hgf in the lung and develops NSCLC after treatment with the tobacco carcinogen, 4-(methylnitrosoamino)-1-(3-pyridyl)-1-butanone (NNK) was utilized. We demonstrated that the Twist1 overexpressing CHT (CCSP-rtTA/CCSP-Hgf/Twist1-tetO-luc) mice developed significantly larger and more aggressive tumors as compared to CH and CCSP-rtTA/Twist1-tetO-luc (CT) mice and that continued TWIST1 expression was required for these tumors.

Conclusions: Our findings suggest that targeting TWIST1 may be an effective therapeutic strategy to overcome HGF-MET-driven resistance in MET-driven NSCLC.

Citation Format: Vinod Kumar, Zachary A. Yochum, Princey Devadassan, Eric Huang, Ethan Miller, Vasavi Ayyala, Laura P. Stabile, Timothy F. Burns, Purva H. Rumde. TWIST1 inhibition overcomes resistance to tyrosine kinase inhibitors in MET driven non-small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1091.

A phase 1b/2 study of PF-06747775 as monotherapy or in combination with Palbociclib in patients with epidermal growth factor receptor mutant advanced non-small cell lung cancer

INTRODUCTION

This Phase 1/2 study (NCT02349633) explored the safety and antitumor activity of PF-06747775 (oral, third-generation epidermal growth factor receptor [EGFR] tyrosine kinase inhibitor) in patients with advanced non-small cell lung cancer after progression on an EGFR inhibitor.

METHODS

Phase 1 was a dose-escalation study of PF-06747775 monotherapy (starting dose: 25 mg once daily [QD]). Phase 1b/2 evaluated PF-06747775 monotherapy at recommended Phase 2 dose (RP2D; Cohort 1); PF-06747775 200 mg QD plus palbociclib (starting dose: 100 mg QD orally; Cohort 2A); and PF-06747775 monotherapy at RP2D in a Japanese lead-in cohort.

RESULTS

Sixty-five patients were treated. Median treatment duration was 40.1 weeks. Monotherapy maximum tolerated dose was not determined. Two patients in Cohort 2A had dose-limiting toxicities. The monotherapy RP2D was estimated to be 200 mg QD. Most frequently reported adverse events (AEs) were diarrhea (69.2%), paronychia (69.2%), and rash (60.0%). Most AEs were grades 1-3. Overall, objective response rate (90% confidence interval [CI]) was 41.5% (31.2-52.5%). Median (range) duration of response was 11.09 (2.70-34.57) months. Median progression-free survival (90% CI) was 8.1 (5.4-23.3) months.

CONCLUSIONS

PF-06747775 had a manageable safety profile and the study design highlights important considerations for future anti-EGFR agent development.

First data for sotorasib in patients with pancreatic cancer with KRAS p.G12C mutation: A phase I/II study evaluating efficacy and safety

360490

Background: KRAS mutation is present in 90% of pancreatic ductal adenocarcinomas with p.G12C accounting for 1% to 2% of these mutations. Sotorasib, a small molecule that specifically and irreversibly inhibits KRASG12C, has been investigated in the CodeBreaK100 trial in patients with KRASG12C-mutated advanced solid tumors. Herein, we report on the largest dataset evaluating efficacy and safety of a KRASG12C inhibitor in patients with pretreated KRASG12C-mutated pancreatic cancer. Methods: CodeBreaK100 (NCT03600883) is an international, single arm, phase I/II study evaluating the efficacy and safety of sotorasib in patients with KRASG12C-mutated advanced solid tumors with ≥ 1 prior systemic therapy unless intolerant or ineligible for available therapies. The primary efficacy endpoint is confirmed objective response rate (ORR), assessed by blinded independent central review (BICR) per RECIST 1.1. Secondary endpoints include duration of response (DoR), disease control rate (DCR), progression-free survival (PFS), and overall survival (OS). Results: As of November 1, 2021, 38 patients with pancreatic cancer (mean age: 65 years, 76.3% male) from the combined phase I/II study received sotorasib 960 mg once daily. Stage IV disease was present in 55.3% of patients at diagnosis, and in all patients at enrollment. Baseline ECOG scores were 0, 1, or 2 in 31.6%, 57.9%, and 10.5% of patients, respectively. Most patients (79%) had ≥ 2 prior lines of therapy (median: 2 [range: 1-8]). Median treatment duration was 4.1 months with a median follow-up of 16.8 months. Eight patients had confirmed partial response by BICR with a resulting ORR of 21.1% (95% CI: 9.55%-37.32%). DCR was 84.2% (Table 1). Treatment-related adverse events (TRAEs) of any grade occurred in 16 (42.1%) patients. Grade ≥ 3 TRAEs occurred in 6 patients: diarrhea (2); fatigue (2); abdominal pain, ALT increase, AST increase, pleural effusion, and pulmonary embolism (1 each). No TRAEs were fatal or resulted in sotorasib discontinuation. Conclusions: Sotorasib demonstrated clinically meaningful anticancer activity and tolerability in patients with heavily pretreated KRASG12C-mutated advanced pancreatic cancer, who have limited treatment options and poor prognosis. Clinical trial information: NCT03600883. [Table: see text]

A phase 1b study of sotorasib, a specific and irreversible KRASG12C inhibitor, in combination with other anticancer therapies in advanced colorectal cancer (CRC) and other solid tumors (CodeBreaK 101)

TPS214

Background: Approximately 3% of patients (pts) with CRC have the oncogenic Kirsten rat sarcoma viral oncogene homolog (KRAS) p.G12C mutation. Sotorasib, a small molecule that specifically and irreversibly inhibits the KRAS G12C mutant protein, has demonstrated modest clinical activity and no dose-limiting toxicities as a single agent in heavily pretreated pts with KRAS p.G12C-mutated CRC. The combination of sotorasib with other anticancer therapies, such as EGFR or MEK inhibitors, may enhance antitumor efficacy and counteract potential escape mechanisms. Other attractive partners for sotorasib in CRC include biologics and chemotherapy combinations. The CodeBreaK 101 master protocol is designed to evaluate safety, tolerability, pharmacokinetics (PK), and efficacy of multiple sotorasib-based combinations in pts with KRAS p.G12C mutated solid tumors. Key subprotocols with CRC combination treatment arms are highlighted here. Methods: This is a phase 1b, open-label study evaluating sotorasib alone and in combination regimens in pts with advanced KRAS p.G12C mutated CRC, NSCLC, and other solid tumors. Key regimens being explored in CRC include (1) Subprotocol A: Sotorasib + trametinib (MEK inhibitor) +/- panitumumab (EGFR inhibitor), (2) Subprotocol H: Sotorasib + panitumumab and sotorasib + panitumumab + FOLFIRI, and (3) Subprotocol M: Sotorasib + bevacizumab-awwb + FOLFIRI or FOLFOX. Key eligibility criteria include advanced or metastatic solid tumor with KRAS p.G12C mutation identified through molecular testing in treatment-naïve and pretreated patients depending on cohort. Primary endpoints include dose-limiting toxicities and treatment-emergent or treatment-related adverse events. Secondary endpoints include PK profile of combination regimens and efficacy (objective response, disease control, duration of response, time to response, and progression-free survival assessed per RECIST 1.1, and overall survival). Enrollment is ongoing. Contact Amgen Medical Information for more information: medinfo@amgen.com (NCT04185883). Abbreviations: EGFR = epidermal growth factor receptor; FOLFIRI = 5-fluorouracil + leucovorin + irinotecan; FOLFOX = 5-fluorouracil + leucovorin + oxaliplatin; MEK = mitogen-activated protein kinase. Clinical trial information: NCT04185883.

Abstract 2218: MET alterations are enriched in lung adenocarcinoma brain metastases and define a distinct molecular and transcriptomic subtype

Lung cancer has the highest incidence of metastases to the brain, with up to 40% of non-small cell lung cancer (NSCLC) patients developing brain metastases (BM). There is a critical need to develop novel treatments to effectively prevent and treat NSCLC BM. MET is a receptor tyrosine kinase that upon binding hepatocyte growth factor (HGF), mediates proliferation, epithelial-mesenchymal transition (EMT), invasion, angiogenesis and metastasis. Recent studies have suggested that the MET pathway may be a significant determinant of metastatic potential to the brain. We evaluated 125 lung adenocarcinoma (LUAD) BM and 477 primary LUAD for MET amplification (amp) by FISH (MET/CEP > 2) as well as other molecular alterations using targeted next-generation sequencing in a subset of LUAD BM (N=74) and primary LUAD (N=171) samples, including 13 paired primary and brain sets. We identified a significant enrichment of MET amp in LUAD BM (19%) compared to primary LUAD (3%; p<0.00001) or liver metastases (4%, N=80; p=0.002). High MET amp (MET/CEP7 ratio >5) was present in 6.5% of BM compared to 1.3% of primary LUAD cases (p=0.0006). In matched samples, BM-specific MET amp was observed. Non-exon 14 skipping MET activating mutations were also significantly more frequent in LUAD BM (22%) compared to primary LUAD (12%; p=0.05), as well as TP53, KRAS, SMAD4, APC, RB1, RET, ABL1, ALK, and VHL variants (adj. p values <0.02). VHL and IDH1 mutations were significantly increased in MET altered compared to non-MET altered BM. In addition, KRAS Q61X variants were more common in LUAD BM compared to LUAD and specifically more common in MET amp BM. We also examined MET activation in paired tumors using an HGF-MET proximity binding, dual-antibody assay. MET expression was increased in the majority of BM compared to the paired LUAD, and there were brain-specific MET activation was observed. RNASeq analysis identified distinct gene signatures in MET amplified (N=11) versus non-MET amplified (N=24) LUAD BM, including upregulation of the EMT and glycolytic pathways. We validated the importance of the EMT transcription factor, TWIST1 in MET-driven NSCLC tumorigenesis preclinically and confirmed activation of the glycolytic pathway in MET amplified NSCLC. Finally, non-invasive strategies to detect brain-specific MET alterations will be needed to identify BM patients who can benefit from MET inhibitors. Therefore, we examined 277 metastatic NSCLC patients that underwent standard of care circulating tumor DNA testing with the Guardant360 platform, and found that both MET mutation and/or amp were more frequently detected in LUAD patients with BM (p=0.04). Together, we show that over a third of LUAD BM patients have MET alterations compared to primary LUAD and may be responsive to MET inhibitors. Further, our liquid biopsy approach may allow us to identify BM-specific alterations for patient selection in clinical trials.

Citation Format: Timothy F. Burns, Sanja Dacic, Maria A. Velez, Ashwin Somasundaram, Saveri Bhattacharya, Anish Chakka, Zachary A. Yochum, Jingxiao Jin, Ethan Miller, Brenda F. Kurland, Riyue Bao, Danielle P. Normolle, Sameer Agnihotri, Uma R. Chandran, Laura P. Stabile. MET alterations are enriched in lung adenocarcinoma brain metastases and define a distinct molecular and transcriptomic subtype [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2218.

The effect of sex and BMI on outcomes in patients with metastatic non-small cell lung cancer treated with immunotherapy

e21085

Background: Recent studies suggest that among non-small cell lung cancer (NSCLC) patients treated with immunotherapy (IT), those who are male and/or have higher body mass index (BMI) benefit most; however, the role of other factors such as pretreatment weight loss is not clear. We conducted a retrospective study to further characterize the relationship between sex, BMI and response to IT in NSCLC. Methods: Patients with stage IV NSCLC treated with IT between 2017 and 2019 at UPMC Hillman Cancer Center were included. Demographic and clinical data were obtained from medical records. Chi-square test was used to compare baseline patient characteristics, best response (CR, PR and SD vs. PD), and presence of immune-related adverse events (iRAEs) between BMI and sex categories. Cox proportional hazards models were used to assess the effect of BMI and sex on progression free survival (PFS) and overall survival (OS). Analyses were conducted overall as well as stratified by treatment regime (1st line monotherapy, non-1st line monotherapy, and concurrent chemotherapy). Results: The study population consisted of 297 patients; 50.2% female (N=149), 87.8% white (N=261), and mean age at IT initiation 68 yrs (range: 36-91 yrs). Median follow-up time: 21 months. At IT initiation, 27 patients were underweight (BMI <18.5), 107 normal weight (BMI 18.5-24.9), 96 overweight (BMI 25-29.9), and 67 obese (BMI ≥30). Among underweight patients, weight loss pretreatment (≥10 lbs) was significantly more common ( P=0.02), and response to IT significantly worse (33% vs 61% good response; P=0.005) compared to those with BMI ≥18.5. No significant difference in response was observed between normal, overweight and obese patients, nor between men and women. The presence of iRAEs did not differ by BMI or sex. Females had better OS than males [HR (95%CI): 0.65 (0.47-0.90)] but PFS was similar. In stratified analyses, better OS among females was limited to the concurrent chemotherapy group [0.52 (0.30-0.92)]. Overall, underweight patients had worse OS than those with BMI ≥18.5 [1.71 (1.01-2.92)]; this was not significant after adjusting for pretreatment weight loss [1.48 (0.87-2.53)]. No difference was observed in OS and PFS between normal, overweight and obese patients. In stratified analyses, underweight individuals had worse OS [4.12 (1.55-10.94)] and PFS [3.87 (1.44-10.38)] than those with BMI ≥18.5 when treated with 1st line monotherapy. Weight loss pretreatment was independently associated with worse OS [2.20 (1.51-3.20)] and PFS [1.47 (1.05-2.05)]. Conclusions: In contrast to prior reports, NSCLC patients receiving IT did not benefit from higher BMI or male sex. Females treated with concurrent chemotherapy had improved OS, and pretreatment weight loss was an indicator of poor prognosis. Further study is required to understand the pathobiology behind these predictors.

Trial in progress: A phase 1b study of sotorasib, a specific and irreversible KRASG12C inhibitor, as monotherapy in non-small cell lung cancer (NSCLC) with brain metastasis and in combination with other anticancer therapies in advanced solid tumors (CodeBreaK 101)

TPS2669

Background: Kirsten rat sarcoma viral oncogene homolog ( KRAS) p.G12C mutation is an oncogenic driver mutation in several solid tumors. Sotorasib is a specific, irreversible, small molecule inhibitor of KRASG12C that has demonstrated durable clinical benefit in NSCLC, with mild and manageable toxicities. The combination of sotorasib with other anticancer therapies may enhance antitumor efficacy. This master protocol is designed to evaluate safety, tolerability, pharmacokinetics (PK), and efficacy of multiple sotorasib combinations in patients (pts) with KRASp.G12C mutated solid tumors. Herein, we overview 1 monotherapy and 11 combination cohorts. Methods: This is a phase 1b, open-label study evaluating sotorasib alone and in combination regimens (Table) in pts with advanced KRAS p.G12C mutated solid tumors. Dose exploration will evaluate the safety and tolerability of sotorasib alone and in combination regimens; dose expansion will then verify the safety and tolerability profile of sotorasib regimens and assess antitumor efficacy. Key eligibility criteria include locally-advanced or metastatic solid tumor with KRAS p.G12C mutation identified through molecular testing in pts who have received ≥1 lines of prior systemic therapy. Primary endpoints include dose-limiting toxicities and treatment-emergent or treatment-related adverse events. Secondary endpoints include PK profile of combination regimens and efficacy (eg, objective response, disease control, duration of response, progression-free survival, and duration of stable disease assessed per RECIST 1.1). Enrollment began in December 2019 and is ongoing. Clinical trial information: NCT04185883. [Table: see text]

Syngeneic tobacco carcinogen-induced mouse lung adenocarcinoma model exhibits PD-L1 expression and high tumor mutational burden

Human lung adenocarcinoma (LUAD) in current or former smokers exhibits a high tumor mutational burden (TMB) and distinct mutational signatures. Syngeneic mouse models of clinically relevant smoking-related LUAD are lacking. We established and characterized a tobacco-associated, transplantable murine LUAD cell line, designated FVBW-17, from a LUAD induced by the tobacco carcinogen 4-(methylnitrosoamino)-1-(3-pyridyl)-1-butanone in the FVB/N mouse strain. Whole-exome sequencing of FVBW-17 cells identified tobacco-associated KrasG12D and Trp53 mutations and a similar mutation profile to that of classic alkylating agents with a TMB greater than 500. FVBW-17 cells transplanted subcutaneously, via tail vein, and orthotopically generated tumors that were histologically similar to human LUAD in FVB/N mice. FVBW-17 tumors expressed programmed death ligand 1 (PD-L1), were infiltrated with CD8+ T cells, and were responsive to anti-PD-L1 therapy. FVBW-17 cells were also engineered to express green fluorescent protein and luciferase to facilitate detection and quantification of tumor growth. Distant metastases to lung, spleen, liver, and kidney were observed from subcutaneously transplanted tumors. This potentially novel cell line is a robust representation of human smoking-related LUAD biology and provides a much needed preclinical model in which to test promising new agents and combinations, including immune-based therapies.

KRASG12C Inhibition with Sotorasib in Advanced Solid Tumors

BACKGROUND

No therapies for targeting KRAS mutations in cancer have been approved. The KRAS p.G12C mutation occurs in 13% of non-small-cell lung cancers (NSCLCs) and in 1 to 3% of colorectal cancers and other cancers. Sotorasib is a small molecule that selectively and irreversibly targets KRAS^G12C.

METHODS

We conducted a phase 1 trial of sotorasib in patients with advanced solid tumors harboring the KRAS p.G12C mutation. Patients received sotorasib orally once daily. The primary end point was safety. Key secondary end points were pharmacokinetics and objective response, as assessed according to Response Evaluation Criteria in Solid Tumors (RECIST), version 1.1.

RESULTS

A total of 129 patients (59 with NSCLC, 42 with colorectal cancer, and 28 with other tumors) were included in dose escalation and expansion cohorts. Patients had received a median of 3 (range, 0 to 11) previous lines of anticancer therapies for metastatic disease. No dose-limiting toxic effects or treatment-related deaths were observed. A total of 73 patients (56.6%) had treatment-related adverse events; 15 patients (11.6%) had grade 3 or 4 events. In the subgroup with NSCLC, 32.2% (19 patients) had a confirmed objective response (complete or partial response) and 88.1% (52 patients) had disease control (objective response or stable disease); the median progression-free survival was 6.3 months (range, 0.0+ to 14.9 [with + indicating that the value includes patient data that were censored at data cutoff]). In the subgroup with colorectal cancer, 7.1% (3 patients) had a confirmed response, and 73.8% (31 patients) had disease control; the median progression-free survival was 4.0 months (range, 0.0+ to 11.1+). Responses were also observed in patients with pancreatic, endometrial, and appendiceal cancers and melanoma.

CONCLUSIONS

Sotorasib showed encouraging anticancer activity in patients with heavily pretreated advanced solid tumors harboring the KRAS p.G12C mutation. Grade 3 or 4 treatment-related toxic effects occurred in 11.6% of the patients. (Funded by Amgen and others; CodeBreaK100 ClinicalTrials.gov number, NCT03600883.).

Phase I expansion study of XMT-1536, a novel NaPi2b-targeting antibody-drug conjugate (ADC): Preliminary efficacy, safety, and biomarker results in patients with previously treated metastatic ovarian cancer (OC) or non-small cell lung cancer (NSCLC)

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Background: XMT-1536 is a first-in-class ADC targeting the sodium-dependent phosphate transport protein NaPi2b, broadly expressed in NSCLC and ovarian cancer. XMT-1536 utilizes the Dolaflexin platform to deliver 10-12 DolaLock auristatin payload molecules per antibody. In the dose-escalation portion of the Phase I study (NCT03319628), XMT-1536 showed clinical activity at doses >20mg/m2 with confirmed responses and prolonged stable disease in heavily pretreated OC and NSCLC patients, without preselection for NaPi2b expression. XMT-1536 was generally well-tolerated without the severe toxicities observed with other ADC platforms such as neutropenia, peripheral neuropathy, or ocular toxicity (Tolcher et al., ASCO 2019; Richardson et al., SGO 2020). Here, we report on the expansion (EXP) cohort, which included patients with fewer prior lines of therapy, in the ongoing Phase I study. Methods: Doses administered intravenously every 4 weeks (q4w) of 36 and 43 mg/m2 were evaluated in two cohorts (1) high grade serous ovarian, fallopian tube, or primary peritoneal cancer (OC) with up to 4 prior lines of therapy and (2) NSCLC adenocarcinoma; prior treatment with a platinum-based therapy, immune checkpoint inhibitor, and TKI, if indicated. Archival tumor tissue and tissue from a new tumor biopsy were required for retrospective evaluation of NaPi2b expression. Results: As of 10 February 2020, 23 patients (19 OC and 4 NSCLC) were enrolled in the EXP cohort: 16 dosed at 36 mg/m2 and 7 dosed at 43 mg/m2. Adverse events were generally similar to those previously reported, including transient AST elevation, fatigue, nausea, and pyrexia. Clinical responses and stable diseases have been observed. Efficacy data (objective response rate) and initial correlation of NaPi2b score with clinical response will be reported. Available data from all patients with data cutoff in May 2020 will be included. Conclusions: Overall, XMT-1536 treatment demonstrated clinical activity in high grade serous ovarian cancer and NSCLC adenocarcinoma and was generally well-tolerated with no new safety signal trends identified in the EXP. Clinical efficacy and the relevance of NaPi2b expression for treatment with XMT-1536 will be presented. Clinical trial information: NCT03319628 .

CodeBreak 100: Phase I study of AMG 510, a novel KRASG12C inhibitor, in patients (pts) with advanced solid tumors other than non-small cell lung cancer (NSCLC) and colorectal cancer (CRC)

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Background: Kirsten rat sarcoma viral oncogene homolog ( KRAS) p.G12C mutation occurs in approximately 13% of NSCLC and 1%–3% of CRC and other solid tumors. AMG 510 is a first-in-class small molecule that specifically and irreversibly inhibits KRASG12C. Previously, AMG 510 showed preliminary antitumor activity and favorable tolerability in pts with KRAS p.G12C mutant NSCLC or CRC in the phase 1, first-in-human trial. Here, we report results in pts with other tumor types from the same trial. Methods: This study evaluates AMG 510 in pts with locally-advanced or metastatic KRAS p.G12C mutant solid tumors. Key inclusion criteria: KRAS p.G12C mutation via local testing and prior systemic anticancer treatment (tx). Oral daily doses of 180, 360, 720, and 960 mg were tested in the dose escalation, and 960 mg was selected for expansion. Primary endpoint is safety; key secondary endpoints include pharmacokinetics and objective response rate as assessed per RECIST 1.1. Response is assessed every 6 weeks (wks) for 24 wks then every 12 wks thereafter. Results: As of January 8, 2020, 25 pts (9 female, median age 60 years [range: 40–75]) with tumor types categorized by investigators as histology other than NSCLC and CRC were enrolled and dosed (10 pancreatic cancer, 4 appendiceal cancer, 2 endometrial cancer, 2 unknown primary cancer, 1 bile duct cancer, 1 sinonasal cancer, 1 ampullary cancer, 1 small bowel cancer, 1 melanoma, 1 small cell lung cancer, and 1 esophageal cancer). 23 pts received 960 mg dose. 20 pts (80.0%) had ≥2 prior lines of tx. At data cutoff, 13 pts (52.0%) remained on tx; 9 (36.0%) and 3 (12.0%) pts remained on tx for ≥3 and ≥6 months, respectively. Median follow up was 4.3 months (range: 0.1–12.6). Tx-related adverse events (TRAEs) occurred in 9 pts (36.0%). 2 pts (8.0%) had grade 3 TRAEs, including diarrhea (1/25) and pneumonia (1/25, serious AE). No dose-limiting toxicities, grade ≥4, or fatal TRAEs were reported. No TRAEs led to tx discontinuation. 3 pts had not been followed up for ≥7 wks by the data cutoff. 22 pts were followed up for ≥7 wks, and their best overall responses were: 3 confirmed partial response (1 appendiceal, 1 melanoma, and 1 endometrial), 13 stable disease (6 pancreatic, 2 appendiceal, 1 ampullary, 1 bile duct, 1 endometrial, 1 sinonasal, and 1 unknown primary), and 6 progressive disease. Conclusions: AMG 510 was well tolerated and demonstrated clinical activity in pts with advanced KRAS p.G12C mutant solid tumors other than NSCLC and CRC. Clinical trial information: NCT03600883 .

Phase 2 study of the focal adhesion kinase inhibitor defactinib (VS-6063) in previously treated advanced KRAS mutant non-small cell lung cancer

OBJECTIVES

KRAS mutations, which occur in approximately 25% of lung adenocarcinoma cases, represent a major unmet clinical need in thoracic oncology. Preclinical studies have demonstrated that KRAS mutant NSCLC cell lines and xenografts with additional alterations in either TP53 or CDKN2A (INK4A/ARF) loci are sensitive to focal adhesion kinase (FAK) inhibition. Defactinib (VS-6063) is a selective oral inhibitor of FAK.

MATERIALS AND METHODS

Patients with previously treated advanced KRAS mutant NSCLC were prospectively assigned to one of four molecularly defined cohorts based on the presence or absence of TP53 or CDKN2A alterations and received treatment with defactinib 400 mg orally BID until disease progression or intolerable toxicity. The primary endpoint was progression-free survival (PFS) at 12 weeks.

RESULTS

Fifty-five patients were enrolled. Mean age was 62 years; 51% were female. The median number of prior lines of therapy was 4 (range 1-8). Fifteen (28%) patients met the 12-week PFS endpoint, with one patient achieving a partial response. Median PFS was 45 days. Clinical efficacy did not correlate with TP53 or CDKN2A status. The most common adverse events were fatigue, gastrointestinal, and increased bilirubin, and were generally grade 1 or 2 in severity.

CONCLUSION

In heavily pretreated patients with KRAS mutant NSCLC, defactinib monotherapy demonstrated modest clinical activity. Efficacy was not associated with TP53 and CDKN2A status. Defactinib was generally well tolerated.

Combined Modality Treatment With Brentuximab Vedotin and Radiation Therapy for Primary Cutaneous Anaplastic Large Cell Lymphoma: A Case Report

Primary cutaneous anaplastic large cell lymphoma (pcALCL) is a rare form of non-Hodgkins lymphoma. Current frontline treatments for pcALCL include surgical resection, anthracycline-based chemotherapy, and/or radiation therapy (RT) depending on disease severity. While brentuximab vedotin (BV) has been used for refractory/relapsed cases, it recently received Food and Drug Administration (FDA) approval for use in combination with chemotherapy for peripheral T-cell lymphomas. In this case report, we utilized a combined modality therapy of RT and BV for a limited stage aggressive pcALCL presentation for which routine management is contraindicated. A 59-year-old man with a history of peripheral vascular disease (PVD) presented with an aggressive pcALCL involving the left inferior eyelid and small ipsilateral level II hypermetabolic lymph nodes at stage IIE. Due to the patient’s history of PVD, the tumor’s rapid growth, possible lymph node involvement, and eye proximity, BV was chosen as the initial chemotherapy treatment followed by RT. Complete metabolic resolution of the primary cutaneous lesion and lymphadenopathy was reached after BV treatment alone; complete clinical response of the primary tumor was reached following radiation therapy. Relapse occurred within 7 months. Salvage cyclophosphamide, vincristine, etoposide, and prednisone were not effective. Retreatment with BV + RT is currently being used to treat the new lesions. Our case illustrates that a combination of BV and RT can be a safe and effective initial treatment in patients with limited stage pcALCL who cannot tolerate anthracycline-based chemotherapy. Our patient had a complete response but ultimately relapsed; thus larger clinical trials are needed to better understand early-stage disease.

The estrogen pathway as a modulator of response to immunotherapy

Lung cancer is the leading cause of cancer deaths worldwide, with a 5-year survival rate of about 18%. Thus, there is a great need for novel therapeutic approaches to treat non-small-cell lung cancer (NSCLC). Immune checkpoint inhibitors (ICIs) have improved outcomes for a subset of patients, especially those with high programmed death-ligand 1 expression and/or high tumor mutational burden, but have failed in the majority of patients. Increasing evidence suggests that the estrogen signaling pathway may be a therapeutic target in metastatic NSCLC and that the estrogen pathway may play a role in sex-based responses to ICIs. This report will review the epidemiologic, preclinical and clinical data on the estrogen pathway in NSCLC, its implications in sex-based responses to ICIs and the potential use of antiestrogen therapy in combination with ICIs.

The HGF-MET signaling pathway is enriched in LUAC brain metastases

e20597

Background: Brain metastases occur in over 40% of non-small cell lung cancer (NSCLC) patients leading to a poor prognosis. c-Met (MET) is a receptor tyrosine kinase that upon binding hepatocyte growth factor (HGF), mediates proliferation, epithelial-mesenchymal transition (EMT), invasion, angiogenesis and metastasis. We have previously shown that the EMT transcription factor, TWIST1 is required for proliferation in MET driven NSCLC. Therefore, the HGF/MET/TWIST1 pathway may be a significant determinant of metastatic potential to the brain. Methods: We evaluated 125 lung adenocarcinoma (LUAC) brain metastases for MET amplification by FISH as well as other molecular alterations using targeted next generation sequencing in a subset of brain metastases (N = 74) and primary LUAC (N = 171) samples including 13 paired primary and brain sets. MET activation was examined in paired tumors using a HGF-MET proximity binding, dual-antibody assay (VeraTag; Monogram Biosciences). TWIST1 and EMT markers in the paired sets were measured by immunohistochemistry. Results: Compared to primary LUAC, we found that 17 pathogenic variants including TP53, SMAD4, RB1, RET, APC, ALK, FGFR3, EGFR, STK11 and MET alterations were significantly more common in LUAC brain metastases (adj. p values ≤ 0.02). Specifically, MET amplification was significantly enriched in LUAC brain metastases (23/125, 19%) compared to 2-4% in non-brain metastatic and primary sites. Among paired samples, 2/13 brain metastases had MET amplification that was not found in the primary tumor. MET mutations were also present in 16/74 brain cases (22%) compared to 9% (16/171) observed in the lung. VHL mutations were associated with MET altered cases compared to non- MET altered cases. MET expression was increased in the majority of brain metastases compared to the paired LUAC and there were 3 cases with brain specific MET activation. We found that TWIST1 was induced by HGF and determined response to MET TKIs in vitro. Among paired samples, TWIST1 was increased in brain metastases compared to primary LUAC in a subset of cases. Further analyses of TWIST1 and EMT markers is ongoing. Conclusions: Over a third of brain metastases have MET alterations compared to primary LUAC and may be responsive to MET inhibitors.

Phase 1 dose escalation study of XMT-1536, a novel NaPi2b-targeting antibody-drug conjugate (ADC), in patients (pts) with solid tumors likely to express NaPi2b

3010

Background: XMT-1536 is a Dolaflexin ADC targeting the sodium-phosphate cotransporter NaPi2b, expressed in ovarian, non-squamous lung, papillary thyroid, endometrial, papillary renal and salivary duct cancers. Methods: In this ongoing Phase 1 study, pts with solid tumors likely to express NaPi2b, who progressed on standard therapy, are treated with intravenous XMT-1536 using a 3+3 design with a modified Fibonacci escalation. NaPi2b expression by IHC is being examined retrospectively in archived tumors. Primary objectives in dose escalation are safety and tolerability and determination of maximum tolerated dose (MTD) and recommended Phase 2 dose (RP2D). (ClinicalTrials.gov NCT03319628). Results: As of Jan. 28, 2019, 36 pts (22 ovarian, 7 endometrial, 4 NSCLC, 3 other) have received treatment with XMT-1536. Treatment was initially given every 3 weeks (q3w); 20 pts were treated in dose cohorts from 3 to 40 mg/m2. There was one DLT of reversible AST elevation at 40 mg/m2. The dosing interval was then changed to every 4 weeks (q4w), and dose escalation was restarted at 20 mg/m2. There was one DLT of reversible AST elevation at 30 mg/m2 on the q4w schedule. Further followup and dose escalation are ongoing. The most common (≥10% of patients) treatment-related adverse events (TRAEs) have been nausea, fatigue, headache, increased AST, anorexia, increased alkaline phosphatase, fever, increased GGT, myalgia, and vomiting. Grade 3 TRAEs were reversible AST increases in 3 patients and increased GGT, decreased lymphocytes, and systolic congestive heart failure in 1 patient each. Treatment-related serious AEs of fever and systolic congestive heart failure occurred in 1 patient each. Among patients dosed at 20 mg/m2 or higher who had restaging scans (n=20), there were 2 PR, in ovarian cancer pts at 30 mg/m2 q3w and 20 mg/m2 q4w, and 11 SD, with disease control maintained for up to 24 weeks. Patient-level results for NaPi2b expression will be presented. The systemic exposure of total payload showed approximately dose-proportional increase. Plasma concentration of free drug payload and its active metabolite were low. Conclusions: XMT-1536 has been well-tolerated up to the 30 mg/m2 dose level with early signs of anti-tumor activity. Dose escalation continues in pts with advanced solid tumors likely to express NaPi2b. Clinical trial information: NCT03319628.

S1507: Phase II study of docetaxel and trametinib in patients with G12C or non-G12C KRAS mutation positive (+) recurrent non-small cell lung cancer (NSCLC)

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Background: KRAS+ NSCLC remains the most common genetically defined subset of NSCLC. Despite promising pre-clinical data, MEK inhibitors have failed to provide meaningful clinical benefit both as single agents and in combination with chemotherapy in KRAS+ NSCLC patients. Pre-clinical data suggest that efficacy of MEK inhibitors in KRAS+ NSCLC differs based on specific KRAS mutations such as G12C and by status of p53 or LKB1 mutations. We conducted a phase II study to assess the efficacy of docetaxel plus trametinib in KRAS+ NSCLC patients and in specific genetic subsets. Methods: KRAS+ NSCLC patients who had progressive cancer following 1 or 2 prior regimens were eligible. Docetaxel was given at 75 mg/m2 every 3 weeks and trametinib orally at 2 mg daily. The study was 2-stage design to rule out a response rate (RR) of 17% at the 3% level with 90% power if the true rate were 37%. The study required 45 pts with a futility analysis at 30 pts; 13/45 responses would indicate a success. RR was also assessed in G12C and non-G12C cohorts and will be assessed according to presence of co-mutations in p53 and LKB1. Progression free survival (PFS) and overall survival (OS) were secondary endpoints. Multivariate analysis including age, sex, number of prior treatments, prior immunotherapy (IO) and G12C status was conducted. Results: The study enrolled 54 evaluable pts (19 G12C, 9 G12D, 9 G12A); median age 65 years; female 57%; never smokers 7%; adenocarcinoma 89%; liver metastases 31%; 2 prior regimens 70%; prior IO 57%. Outcomes are summarized in Table. Median duration of therapy was 2.2 months and most common toxicities were fatigue (78%), diarrhea (68%), nausea (57%) and vomiting (28%). One patient died of treatment related respiratory failure. There was a trend for worse PFS (HR- 1.86, p = 0.06) and survival (HR- 1.80, p = 0.14) in G12C patients. Analysis of efficacy data according to co-mutations in p53 or LKB1 is ongoing. Conclusions: Docetaxel plus trametinib met the primary endpoint of the study, with a RR of 33% and median survival of 11.1 months in patients with KRAS+ NSCLC, 70% of whom had received 2 prior regimens. Although, there was no statistical difference between KRAS+ subtypes, these data suggest that outcomes may differ between G12C and non-G12C patients. Clinical trial information: NCT02642042. [Table: see text]

Survival Outcomes of Younger Patients With Mantle Cell Lymphoma Treated in the Rituximab Era

PURPOSE

Mantle cell lymphoma (MCL) is a B-cell lymphoma characterized by cyclin D1 expression. Autologous hematopoietic cell transplantation (AHCT) consolidation after induction chemotherapy is often used for eligible patients; however, the benefit remains uncertain in the rituximab era. Herein we retrospectively assessed the impact of AHCT consolidation on survival in a large cohort of transplantation-eligible patients age 65 years or younger.

PATIENTS AND METHODS

We retrospectively studied transplantation-eligible adults age 65 years or younger with newly diagnosed MCL treated between 2000 and 2015. The primary objective was to assess for improved progression-free survival (PFS) with AHCT consolidation and secondarily to assess for improved overall survival (OS). Cox multivariable regression analysis and propensity score-weighted (PSW) analysis were performed.

RESULTS

Data were collected from 25 medical centers for 1,254 patients; 1,029 met inclusion criteria. Median follow-up for the cohort was 76 months. Median PFS and OS were 62 and 139 months, respectively. On unadjusted analysis, AHCT was associated with improved PFS (75 v 44 months with v without AHCT, respectively; P < .01) and OS (147 v 115 months with v without AHCT, respectively; P < .05). On multivariable regression analysis, AHCT was associated with improved PFS (hazard ratio [HR], 0.54; 95% CI, 0.44 to 0.66; P < .01) and a trend toward improved OS (HR, 0.77; 95% CI, 0.59 to 1.01; P = .06). After PSW analysis, AHCT remained associated with improved PFS (HR, 0.70; 95% CI, 0.59 to 0.84; P < .05) but not improved OS (HR, 0.87; 95% CI, 0.69 to 1.1; P = .2).

CONCLUSION

In this large cohort of younger, transplantation-eligible patients with MCL, AHCT consolidation after induction was associated with significantly improved PFS but not OS after PSW analysis. Within the limitations of a retrospective analysis, our findings suggest that in younger, fit patients, AHCT consolidation may improve PFS.

Abstract 5889: TWIST1 is a key mediator of HGF-MET-driven resistance to targeted therapies in EGFR mutant and MET-driven lung cancer

The c-Met (MET) receptor and its ligand, hepatocyte growth factor (HGF), have been shown to mediate epithelial-mesenchymal transition (EMT), proliferation, invasion, motility, and angiogenesis. The HGF/MET pathway is frequently altered in non-small cell lung cancer (NSCLC) and has emerged as a targetable oncogenic driver, as patients with MET amplification and/or mutations have demonstrated marked responses to the MET tyrosine kinase inhibitor (TKI), crizotinib. However, long-term efficacy of MET TKIs is limited as acquired resistance is inevitable and almost half of patients with MET alterations fail to respond to MET TKIs. HGF overexpression has been identified as a mechanism of resistance to both MET and EGFR TKIs in MET altered and EGFR mutant NSCLC. Furthermore, MET amplification has been implicated in EGFR TKI resistance. However, the mechanism(s) by which the HGF-MET pathway causes resistance are poorly understood. We have previously shown that the EMT-transcription factor, TWIST1, is required for MET-driven NSCLC. Here, we investigated the requirement of TWIST1 in HGF-mediated resistance to MET and EGFR TKIs and the role of TWIST1 in de novo and acquired resistance to MET and EGFR TKIs. We found that HGF treatment induced EMT in NSCLC cell lines and increased TWIST1 protein expression through a post-translational mechanism. We demonstrated that targeting TWIST1 pharmacologically with the TWIST1 inhibitor, harmine, overcame HGF-mediated resistance to both MET and EGFR TKIs in MET and EGFR-driven NSCLC. This suggests that TWIST1 is specifically required for HGF-mediated resistance to targeted therapies. We also found that TWIST1 is overexpressed in a subset of MET and EGFR altered cell lines and TWIST1 overexpression was sufficient to cause resistance to MET and EGFR TKIs. In MET-driven and EGFR mutant cell lines that express TWIST1 and are resistant to targeted therapies, we demonstrated that harmine treatment resensitized resistant cells to MET and EGFR TKIs, respectively. To investigate the role of TWIST1 overexpression in Hgf-driven lung cancer, we utilized a CCSP-Hgf (CH) mouse model that constitutively overexpresses Hgf in the lung and develops crizotinib-sensitive tumors following treatment with the tobacco carcinogen, nicotine-derived nitrosamine ketone (NNK). We demonstrated that the Twist1 overexpressing CTH (CCSP-rtTA/Twist1-tetO-luc/CCSP-Hgf) mice developed significantly larger tumors in response to NNK as compared to CH and CCSP-rtTA/Twist1-tetO-luc (CT) mice. In summary, we established that HGF-regulated TWIST1 expression and that TWIST1 expression is required for resistance to MET and EGFR TKIs in the presence and absence of HGF overexpression. These studies suggest that targeting TWIST1 may be an effective therapeutic strategy to overcome HGF-MET-driven resistance in EGFR mutant NSCLC as well as MET TKI resistance in MET-driven NSCLC.

Citation Format: Zachary A. Yochum, Suman Chatterjee, Eric H. Huang, Deena M. Maurer, Myriam A. Attar, Sanja Dacic, Laura P. Stabile, Timothy F. Burns. TWIST1 is a key mediator of HGF-MET-driven resistance to targeted therapies in EGFR mutant and MET-driven 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 5889.

Real-world outcomes and management strategies for venetoclax-treated chronic lymphocytic leukemia patients in the United States

Venetoclax is a BCL2 inhibitor approved for 17p-deleted relapsed/refractory chronic lymphocytic leukemia with activity following kinase inhibitors. We conducted a multicenter retrospective cohort analysis of patients with chronic lymphocytic leukemia treated with venetoclax to describe outcomes, toxicities, and treatment selection following venetoclax discontinuation. A total of 141 chronic lymphocytic leukemia patients were included (98% relapsed/refractory). Median age at venetoclax initiation was 67 years (range 37-91), median prior therapies was 3 (0-11), 81% unmutated IGHV, 45% del(17p), and 26.8% complex karyotype (≥ 3 abnormalities). Prior to venetoclax initiation, 89% received a B-cell receptor antagonist. For tumor lysis syndrome prophylaxis, 93% received allopurinol, 92% normal saline, and 45% rasburicase. Dose escalation to the maximum recommended dose of 400 mg daily was achieved in 85% of patients. Adverse events of interest included neutropenia in 47.4%, thrombocytopenia in 36%, tumor lysis syndrome in 13.4%, neutropenic fever in 11.6%, and diarrhea in 7.3%. The overall response rate to venetoclax was 72% (19.4% complete remission). With a median follow up of 7 months, median progression free survival and overall survival for the entire cohort have not been reached. To date, 41 venetoclax treated patients have discontinued therapy and 24 have received a subsequent therapy, most commonly ibrutinib. In the largest clinical experience of venetoclax-treated chronic lymphocytic leukemia patients, the majority successfully completed and maintained a maximum recommended dose. Response rates and duration of response appear comparable to clinical trial data. Venetoclax was active in patients with mutations known to confer ibrutinib resistance. Optimal sequencing of newer chronic lymphocytic leukemia therapies requires further study.

HSP90 inhibition targets autophagy and induces a CASP9-dependent resistance mechanism in NSCLC

Macroautophagy/autophagy has emerged as a resistance mechanism to anticancer drug treatments that induce metabolic stress. Certain tumors, including a subset of KRAS-mutant NSCLCs have been shown to be addicted to autophagy, and potentially vulnerable to autophagy inhibition. Currently, autophagy inhibition is being tested in the clinic as a therapeutic component for tumors that utilize this degradation process as a drug resistance mechanism. The current study provides evidence that HSP90 (heat shock protein 90) inhibition diminishes the expression of ATG7, thereby impeding the cellular capability of mounting an effective autophagic response in NSCLC cells. Additionally, an elevation in the expression level of CASP9 (caspase 9) prodomain in KRAS-mutant NSCLC cells surviving HSP90 inhibition appears to serve as a cell survival mechanism. Initial characterization of this survival mechanism suggests that the altered expression of CASP9 is mainly ATG7 independent; it does not involve the apoptotic activity of CASP9; and it localizes to a late endosomal and pre-lysosomal phase of the degradation cascade. HSP90 inhibitors are identified here as a pharmacological approach for targeting autophagy via destabilization of ATG7, while an induced expression of CASP9, but not its apoptotic activity, is identified as a resistance mechanism to the cellular stress brought about by HSP90 inhibition.

Caveolin-1 promotes the tumor suppressor properties of oncogene-induced cellular senescence

Oncogene-induced senescence (OIS) is considered a powerful tumor suppressor mechanism. Caveolin-1 acts as a scaffolding protein to functionally regulate signaling molecules. We demonstrate that a lack of caveolin-1 expression inhibits oncogenic K-Ras (K-Ras^G12V)-induced premature senescence in mouse embryonic fibroblasts and normal human bronchial epithelial cells. Oncogenic K-Ras induces senescence by limiting the detoxification function of MTH1. We found that K-Ras^G12V promotes the interaction of caveolin-1 with MTH1, which results in inhibition of MTH1 activity. Lung cancer cells expressing oncogenic K-Ras have bypassed the senescence barrier. Interestingly, overexpression of caveolin-1 restores cellular senescence in both A549 and H460 lung cancer cells and inhibits their transformed phenotype. In support of these findings, our in vivo data demonstrate that overexpression of oncogenic K-Ras (K-Ras^G12D) induces cellular senescence in the lung of wildtype but not caveolin-1-null mice. A lack of K-Ras^G12D-induced premature senescence in caveolin-1-null mice results in the formation of more abundant lung tumors. Consistent with these data, caveolin-1-null mice overexpressing K-Ras^G12D display accelerated mortality. Finally, our animal data were supported by human sample analysis in which we show that caveolin-1 expression is dramatically down-regulated in lung adenocarcinomas from lung cancer patients, both at the mRNA and protein levels, and that low caveolin-1 expression is associated with poor survival. Together, our data suggest that lung cancer cells escape oncogene-induced premature senescence through down-regulation of caveolin-1 expression to progress from premalignant lesions to cancer.

Wnt/β-Catenin Pathway Activation Mediates Adaptive Resistance to BRAF Inhibition in Colorectal Cancer

One of the most encouraging developments in oncology has been the success of BRAF inhibitors in BRAF-mutant melanoma. However, in contrast to its striking efficacy in BRAF-mutant melanomas, BRAF inhibitor monotherapy is ineffective in BRAF-mutant colorectal cancer. Although many studies on BRAF inhibitor resistance in colorectal cancer have focused on mechanisms underlying the reactivation of the EGFR/RAS/RAF/MEK/ERK pathway, the current study focuses on identifying novel adaptive signaling mechanisms, a fresh angle on colorectal cancer resistance to BRAF inhibition. We found that treatment with BRAF inhibitors (both current and next-generation BRAF inhibitors) upregulated the Wnt/β-catenin pathway in BRAF^V600E-mutant colorectal cancer cell lines through activating the cytoplasmic tyrosine kinase focal adhesion kinase (FAK). The results showed that FAK activation upon BRAF inhibitor treatment did not require EGFR or ERK1/2 activation, implying that BRAF inhibitor treatment-induced hyperactivation of Wnt signaling is "pathway reactivation"-independent. BRAF inhibition-induced Wnt pathway activation was further validated in preclinical models of BRAF^V600E-mutant colorectal cancer, including cell line xenograft model and a patient-derived xenograft model. Combined inhibition of BRAF/Wnt pathways or BRAF/FAK pathways exerted strong synergistic antitumor effects in cell culture model and mouse xenograft model. Overall, the current study has identified activation of the Wnt/β-catenin pathway as a novel fundamental cause of colon cancer resistance to BRAF inhibition. Our results suggest that although complete vertical pathway blockade is pivotal for effective and durable control of BRAF-mutant colorectal cancer, cotargeting parallel adaptive signaling-the Wnt/β-catenin pathway-is also essential. Mol Cancer Ther; 17(4); 806-13. ©2017 AACR.

TMEM16A/ANO1 Inhibits Apoptosis Via Downregulation of Bim Expression

Purpose: TMEM16A is a calcium-activated chloride channel that is amplified in a variety of cancers, including 30% of head and neck squamous cell carcinomas (HNSCCs), raising the possibility of an anti-apoptotic role in malignant cells. This study investigated this using a multimodal, translational investigation.Experimental Design: Combination of (i) in vitro HNSCC cell culture experiments assessing cell viability, apoptotic activation, and protein expression (ii) in vivo studies assessing similar outcomes, and (iii) molecular and staining analysis of human HNSCC samples.Results: TMEM16A expression was found to correlate with greater tumor size, increased Erk 1/2 activity, less Bim expression, and less apoptotic activity overall in human HNSCC. These findings were corroborated in subsequent in vitro and in vivo studies and expanded to include a cisplatin-resistant phenotype with TMEM16A overexpression. A cohort of 41 patients with laryngeal cancer demonstrated that cases that recurred after chemoradiation failure were associated with a greater TMEM16A overexpression rate than HNSCC that did not recur.Conclusions: Ultimately, this study implicates TMEM16A as a contributor to tumor progression by limiting apoptosis and as a potential biomarker of more aggressive disease. Clin Cancer Res; 23(23); 7324-32. ©2017 AACR.

A First-in-Class TWIST1 Inhibitor with Activity in Oncogene-Driven Lung Cancer

TWIST1, an epithelial-mesenchymal transition (EMT) transcription factor, is critical for oncogene-driven non-small cell lung cancer (NSCLC) tumorigenesis. Given the potential of TWIST1 as a therapeutic target, a chemical-bioinformatic approach using connectivity mapping (CMAP) analysis was used to identify TWIST1 inhibitors. Characterization of the top ranked candidates from the unbiased screen revealed that harmine, a harmala alkaloid, inhibited multiple TWIST1 functions, including single-cell dissemination, suppression of normal branching in 3D epithelial culture, and proliferation of oncogene driver-defined NSCLC cells. Harmine treatment phenocopied genetic loss of TWIST1 by inducing oncogene-induced senescence or apoptosis. Mechanistic investigation revealed that harmine targeted the TWIST1 pathway through its promotion of TWIST1 protein degradation. As dimerization is critical for TWIST1 function and stability, the effect of harmine on specific TWIST1 dimers was examined. TWIST1 and its dimer partners, the E2A proteins, which were found to be required for TWIST1-mediated functions, regulated the stability of the other heterodimeric partner posttranslationally. Harmine preferentially promoted degradation of the TWIST1-E2A heterodimer compared with the TWIST-TWIST1 homodimer, and targeting the TWIST1-E2A heterodimer was required for harmine cytotoxicity. Finally, harmine had activity in both transgenic and patient-derived xenograft mouse models of KRAS-mutant NSCLC. These studies identified harmine as a first-in-class TWIST1 inhibitor with marked anti-tumor activity in oncogene-driven NSCLC including EGFR mutant, KRAS mutant and MET altered NSCLC.Implications: TWIST1 is required for oncogene-driven NSCLC tumorigenesis and EMT; thus, harmine and its analogues/derivatives represent a novel therapeutic strategy to treat oncogene-driven NSCLC as well as other solid tumor malignancies. Mol Cancer Res; 15(12); 1764-76. ©2017 AACR.

Abstract 4152: The p90RSK-CDC25C signaling pathway leads to bypass of the ganetespib induced G2/M arrest and mediates acquired resistance to ganetespib in KRAS mutant NSCLC

Lung cancer is the leading cause of cancer death in the United States and worldwide. A large fraction of non-small cell lung cancers (NSCLC) are dependent upon oncogenic driver mutations of which the most commonly observed driver is mutant KRAS. Unfortunately, NSCLC patients with oncogenic KRAS mutations have no effective therapies and prognosis is poor. As direct RAS targeting has been unsuccessful in the clinic to date, use of Heat shock protein 90 (Hsp90) inhibitors in KRAS mutant NSCLC appeared to be promising approach for targeting KRAS mutant NSCLC through its downstream effectors. However, limited clinical efficacy as monotherapy was observed due to rapid resistance. Furthermore, the combination of ganetespib and docetaxel was recently tested in a large phase III clinical trial (Galaxy-2) in advanced lung cancer and failed to demonstrate benefit. Here, we investigated the mechanism(s) of resistance to the Hsp90 inhibitor (Hsp90i), ganetespib by generating NSCLC cells with acquired resistance to Hsp90i’s including ganetespib (GR cells). We have not only identified the mechanism of acquired resistance to ganetespib but have also found that this mechanism induces cross resistance to docetaxel. Finally, we have identified novel Hsp90i combinations that can overcome and prevent this resistance. We report that hyperactivation of ERK and p90RSK and its downstream target, CDC25C leads to acquired resistance to ganetespib and docetaxel. Moreover, this resistance is mediated via bypass of a G2/M arrest. Overexpression of either p90RSK or CDC25C in naïve cells was sufficient to induce the bypass of this G2/M arrest as well induced resistance to both ganetespib and docetaxel. Remarkably, p90RSK or CDC25C overexpression also led to ganetespib resistance in vivo. The observed resistance was dependent on continued p90RSK/CDC25C signaling, as synthetic lethality to specific ERK, p90RSK or CDC25C inhibitors was observed. Importantly, we have found that the combination of ganetespib with inhibitors of ERK1/2, p90RSK, or CDC25C was highly efficacious. In summary, we propose that the hyperactivation of p90RSK induces CDC25C overexpression and activity which then induces G2/M progression via CyclinB1/cdc2 regulation resulting in ganetespib resistance. Despite two decades of testing in the clinic, either as monotherapy or in combination with chemotherapy, Hsp90 inhibitors have been ineffective due to acquired resistance. Our preclinical analyses provide a way forward for Hsp90 inhibitors through the development of novel rationally designed Hsp90 inhibitor combinations that may prevent or overcome resistance to Hsp90 inhibitors.

Citation Format: Suman Chatterjee, Eric H. Huang, Ian Christie, Timothy F. Burns. The p90RSK-CDC25C signaling pathway leads to bypass of the ganetespib induced G2/M arrest and mediates acquired resistance to ganetespib in KRAS mutant NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4152. doi:10.1158/1538-7445.AM2017-4152

Abstract 4118: The EMT transcription factor TWIST1 mediates resistance to EGFR inhibitors in EGFR-mutant non-small cell lung cancer

Recent advances in the treatment of non-small cell lung cancer (NSCLC) stem from the paradigm shift of classifying patients into subtypes based upon the presence of distinct molecular drivers. Subsets of patients, such as those with EGFR mutations and ALK translocations, have dramatic responses in their tumors to tyrosine kinase inhibitors (TKIs) that specifically inhibit these oncogenic drivers. While many patients initially response to TKIs, therapeutic resistance is inevitable. For EGFR-mutant NSCLC, there are multiple described mechanisms of resistance to EGFR TKIs, including epithelial-mesenchymal transition (EMT). Previous studies have implicated the AXL kinase and ZEB1, an EMT transcription factor (EMT-TF), in EMT-mediated EGFR TKI resistance. We have previously demonstrated that the EMT-TF, TWIST1, is required for oncogene-driven NSCLC tumorigenesis, including those tumors with EGFR mutations. In this study, we investigated the role of TWIST1 in EMT-mediated resistance to EGFR TKIs.

We have demonstrated that genetic or pharmacologic inhibition of TWIST1 resulted in growth inhibition in a panel of EGFR-mutant NSCLC cell lines and apoptosis in a subset of these lines. Interestingly, TWIST1 overexpression in EGFR-mutant NSCLC cell lines led to EGFR TKI resistance. Conversely, knockdown of TWIST1 in an erlotinib resistant EGFR-mutant NSCLC cell line restored erlotinib sensitivity. We found that TWIST1 mediates resistance to EGFR TKIs through suppression of apoptosis possibly through decreasing the expression of the pro-apoptotic Bcl-2 member, BCL2L11 (BIM). We observed that TWIST1 knockdown increased BIM levels, while TWIST1 overexpression decreased BIM expression. Furthermore, TWIST1-mediated resistance was overcome by treatment with the BCL-2/BCL-XL inhibitor, ABT-737. Knockdown of BIM recapitulated the resistance seen following TWIST1 overexpression, suggesting that TWIST1 suppression of BIM is a mechanism through which TWIST1 leads to EGFR TKI resistance. To explore the role of TWIST1 in modulating EGFR inhibitor sensitivity in vivo, we used an inducible EGFR-mutant transgenic mouse model, CCSP-rtTA/tetO-EGFRL858R (CE), which expresses EGFRL858R in the lung and a EGFR-mutant/Twist1 transgenic model, CCSP-rtTA/tetO-EGFRL858R/ Twist1- tetO7-luc (CET), which expresses both Twist1 and EGFRL858R in the lung. CET mice had a significantly increased tumor burden, decreased apoptosis and a decreased overall survival compared to CE mice following erlotinib treatment.

In summary, we found that TWIST1 overexpression leads to EGFR TKI resistance by suppressing EGFR TKI-induced apoptosis through suppressing BIM expression. Future studies aim to establish the mechanisms of TWIST1 suppression of BIM expression and determine if our TWIST1 inhibitor, harmine, is effective in overcoming EMT-mediated resistance.

Citation Format: Zachary A. Yochum, Hailun Wang, Jessica A. Cades, Susheel Khetarpal, Eric H. Huang, Phouc T. Tran, Timothy F. Burns. The EMT transcription factor TWIST1 mediates resistance to EGFR inhibitors in EGFR-mutant non-small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4118. doi:10.1158/1538-7445.AM2017-4118

Reactivation of the p90RSK-CDC25C Pathway Leads to Bypass of the Ganetespib-Induced G2-M Arrest and Mediates Acquired Resistance to Ganetespib in KRAS-Mutant NSCLC

A subset of non-small cell lung cancers (NSCLC) are dependent upon oncogenic driver mutations, including the most frequently observed driver mutant KRAS, which is associated with a poor prognosis. As direct RAS targeting in the clinic has been unsuccessful to date, use of Hsp90 inhibitors appeared to be a promising therapy for KRAS-mutant NSCLC; however, limited clinical efficacy was observed due to rapid resistance. Furthermore, the combination of the Hsp90 inhibitor (Hsp90i), ganetespib, and docetaxel was tested in a phase III clinical trial and failed to demonstrate benefit. Here, we investigated the mechanism(s) of resistance to ganetespib and explored why the combination with docetaxel failed in the clinic. We have not only identified a critical role for the bypass of the G₂-M cell-cycle checkpoint as a mechanism of ganetespib resistance (GR) but have also found that GR leads to cross-resistance to docetaxel. Reactivation of p90RSK and its downstream target, CDC25C, was critical for GR and mediated the bypass of a G₂-M arrest. Overexpression of either p90RSK or CDC25C lead to bypass of G₂-M arrest and induced ganetespib resistance in vitro and in vivo Moreover, resistance was dependent on p90RSK/CDC25C signaling, as synthetic lethality to ERK1/2, p90RSK, or CDC25C inhibitors was observed. Importantly, the combination of ganetespib and p90RSK or CDC25C inhibitors was highly efficacious in parental cells. These studies provide a way forward for Hsp90 inhibitors through the development of novel rationally designed Hsp90 inhibitor combinations that may prevent or overcome resistance to Hsp90i. Mol Cancer Ther; 16(8); 1658-68. ©2017 AACR.

Phase 1/2 study of rilotumumab (AMG 102), a hepatocyte growth factor inhibitor, and erlotinib in patients with advanced non-small cell lung cancer

BACKGROUND

Activation of the mesenchymal-epidermal transition factor (MET) tyrosine kinase and its ligand, hepatocyte growth factor (HGF), is implicated in resistance to epidermal growth factor receptor (EGFR) inhibitors. In this phase 1/2 trial, rilotumumab (an anti-HGF antibody) combined with erlotinib was evaluated in patients with metastatic, previously treated non-small cell lung cancer.

METHODS

In phase 1, a dose de-escalation design was adopted with rilotumumab starting at 15 mg/kg intravenously every 3 weeks and oral erlotinib 150 mg daily. In phase 2, the disease control rate (DCR) (according to Response Evaluation Criteria in Solid Tumors) of the combination was evaluated using a Simon 2-stage design. The biomarkers examined included 10 plasma-circulating molecules associated with the EGFR and MET pathways.

RESULTS

Without indications for de-escalation, the recommended phase 2 dose was dose level 0. Overall, 45 response-evaluable patients were enrolled (13 with squamous carcinoma, 32 with adenocarcinoma; 2 had confirmed EGFR mutations, 33 had confirmed wild-type [WT] EGFR, and 7 had KRAS mutations). The DCR for all patients was 60% (90% confidence interval [CI], 47.1%-71.3%). Median progression-free survival was 2.6 months (90% CI, 1.4-2.7 months), and median overall survival was 6.6 months (90% CI, 5.6-8.9 months). Among patients with WT EGFR, the DCR was 60.6% (90% CI, 46.3%-73.3%), median progression-free survival was 2.6 months (90% CI, 1.4-2.7 months), and median overall survival was 7.0 months (90% CI, 5.6-13.4 months). Elevated baseline levels of neuregulin 1 were associated with longer progression-free survival (hazard ratio, 0.41; 95% CI, 0.19-0.87), whereas elevated amphiregulin levels were associated with more rapid progression (hazard ratio, 2.14; 95% CI, 1.48-3.08).

CONCLUSIONS

Combined rilotumumab and erlotinib had an acceptable safety profile, and the DCR met the prespecified criteria for success. In the EGFR WT group, the DCR exceeded published reports for erlotinib alone. High circulating levels of neuregulin 1 may indicate sensitivity to this combination. Cancer 2017;123:2936-44. © 2017 American Cancer Society.

The next generation of immunotherapy: keeping lung cancer in check

Lung cancer is the deadliest malignancy with more cancer deaths per year than the next three cancers combined. Despite remarkable advances in targeted therapy, advanced lung cancer patients have not experienced a significant improvement in mortality. Lung cancer has been shown to be immunogenic and responsive to checkpoint blockade therapy. Checkpoint signals such as CTLA-4 and PD-1/PD-L1 dampen T cell activation and allow tumors to escape the adaptive immune response. Response rates in patients with pretreated, advanced NSCLC were much higher and more durable with PD-1 blockade therapy compared to standard-of-care, cytotoxic chemotherapy. Therefore, PD-1 inhibitors such as nivolumab and pembrolizumab were rapidly approved for both squamous and nonsquamous lung cancer in the pretreated population. The advent of these new therapies have revolutionized the treatment of lung cancer; however, the majority of NSCLC patients still do not respond to PD-1/PD-L1 inhibition leaving an unmet need for a large and growing population.

Immunotherapy combinations with chemotherapy, radiation therapy, or novel immunomodulatory agents are currently being examined with the hope of achieving higher response rates and improving overall survival rate. Chemotherapy and radiation therapy has been theorized to increase the release of tumor antigen leading to increased responses with immunotherapy. However, cytotoxic chemotherapy and radiation therapy may also destroy actively proliferating T cells. The correct combination and order of therapy is under investigation. The majority of patients who do respond to immunotherapy have a durable response attributed to the effect of adaptive immune system’s memory. Unfortunately, some patients’ tumors do progress afterward and investigation of checkpoint blockade resistance is still nascent.

This review will summarize the latest efficacy and safety data for early and advanced NSCLC in both the treatment-naïve and pretreated settings. The emerging role of immunotherapy for the treatment of small cell lung cancer and malignant mesothelioma will also be discussed.

Acquired Resistance to the Hsp90 Inhibitor, Ganetespib, in KRAS-Mutant NSCLC Is Mediated via Reactivation of the ERK-p90RSK-mTOR Signaling Network

Approximately 25% of non-small cell lung cancer (NSCLC) patients have KRAS mutations, and no effective therapeutic strategy exists for these patients. The use of Hsp90 inhibitors in KRAS-mutant NSCLC appeared to be a promising approach, as these inhibitors target many KRAS downstream effectors; however, limited clinical efficacy has been observed due to resistance. Here, we examined the mechanism(s) of acquired resistance to the Hsp90 inhibitor, ganetespib, and identified novel and rationally devised Hsp90 inhibitor combinations, which may prevent and overcome resistance to Hsp90 inhibitors. We derived KRAS-mutant NSCLC ganetespib-resistant cell lines to identify the resistance mechanism(s) and identified hyperactivation of RAF/MEK/ERK/RSK and PI3K/AKT/mTOR pathways as key resistance mechanisms. Furthermore, we found that ganetespib-resistant cells are "addicted" to these pathways, as ganetespib resistance leads to synthetic lethality to a dual PI3K/mTOR, a PI3K, or an ERK inhibitor. Interestingly, the levels and activity of a key activator of the mTOR pathway and an ERK downstream target, p90 ribosomal S6 kinase (RSK), were also increased in the ganetespib-resistant cells. Genetic or pharmacologic inhibition of p90RSK in ganetespib-resistant cells restored sensitivity to ganetespib, whereas p90RSK overexpression induced ganetespib resistance in naïve cells, validating p90RSK as a mediator of resistance and a novel therapeutic target. Our studies offer a way forward for Hsp90 inhibitors through the rational design of Hsp90 inhibitor combinations that may prevent and/or overcome resistance to Hsp90 inhibitors, providing an effective therapeutic strategy for KRAS-mutant NSCLC. Mol Cancer Ther; 16(5); 793-804. ©2017 AACR.

Pembrolizumab in the treatment of metastatic non-small-cell lung cancer: patient selection and perspectives

Lung cancer is the leading killer of both men and women in the US, and the 5-year survival remains poor. However, the approval of checkpoint blockade immunotherapy has shifted the treatment paradigm and provides hope for improved survival. The ability of non-small-cell lung cancer (NSCLC) to evade the host immune system can be overcome by agents such as pembrolizumab (MK-3475/lambrolizumab), which is a monoclonal antibody targeting the programmed death 1 (PD-1) receptor. In early studies, treatment with pembrolizumab led to dramatic and durable responses in select patients (PD-L1+ tumors). This remarkable efficacy lead to approval of pembrolizumab in the second-line setting as response rates were almost doubled compared to standard of care (SOC) chemotherapy. Most recently, data in the first-line setting from the KEYNOTE-024 study have redefined the SOC therapy for a selected subset of patients. In patients with ≥50% PD-L1+ tumors, pembrolizumab had a clear progression-free survival and overall survival benefit. Toxicity was mostly immune related and similar to checkpoint blockade toxicities observed in previous studies. The initial approval and subsequent studies of pembrolizumab required and utilized a companion diagnostic test, Dako’s IHC 22C3, to assess PD-L1 status of patients. The evaluation and scoring system of this assay has been used by other companies as a reference to develop their own assays, which may complicate selection of patients. Finally, the impact of pembrolizumab in NSCLC is growing as evidenced by the numerous, ongoing trials open for combinations with chemotherapy, chemoradiation, other immunotherapeutics, immunomodulators, tyrosine kinase inhibitors, PI3K inhibitors, MEK inhibitors, hypomethylating agents, and histone deacetylase inhibitors. Further studies are also evaluating pembrolizumab in small-cell lung cancer and malignant pleural mesothelioma. This explosion of studies truly conveys the lack of therapeutic answers for lung cancer patients and the promise of pembrolizumab.

Abstract 3573: TWIST1/E2A signaling axis suppresses apoptosis in oncogene driven non-small cell lung cancer

Although a large fraction of non-small cell lung cancers (NSCLC) are dependent on defined oncogenic driver mutations, little progress has been made in the treatment of patients with the most common driver mutation, mutant KRAS. In addition, acquired resistance to currently available targeted therapies is inevitable. We previously demonstrated that inhibition of the basic helix-loop-helix transcription factor, TWIST1 in KRAS mutant, EGFR mutant, and MET amplified/mutant NSCLC can induce apoptosis, which suggests that a subset of oncogene dependent NSCLC are potentially “addicted” to TWIST1. Importantly, we have identified the harmala alkaloid, harmine, as a novel TWIST1 inhibitor which could inhibit growth in several oncogene driver defined NSCLC cell lines and decrease levels of TWIST1 and its dimerization partners, the E2A proteins, via degradation.

We examined the target genes and pathways required for suppression of apoptosis by TWIST1 and E2A. Genetic or pharmacological (harmine) inhibition of TWIST1 or E2A resulted in apoptosis in several oncogenic driver dependent cell lines. Additionally, treatment with a pan-caspase inhibitor resulted in rescue of growth inhibition following TWIST1 or E2A silencing or harmine treatment. This suggests that apoptosis is the mechanism of growth inhibition following TWIST1 inhibition. TWIST1 or E2A inhibition resulted in increased levels of Bid, Bim, and DR5, as well as, reduced c-FLIP and Bcl-2 levels. Conversely, we demonstrated that TWIST1 overexpression leads to increased levels of c-FLIP and anti-apoptotic Bcl-2 family members as well as decreased levels of Bim and Bid. c-FLIP appears to be a direct transcriptional target of TWIST1 as TWIST1 overexpression leads to transactivation of the c-FLIP promoter and is dependent on the ability of TWIST1 to bind DNA. Interestingly, the TWIST1-E2A heterodimer results in greater promoter transactivation when compared to the TWIST1 homodimer. Furthermore, knockdown of Bim, overexpression of Bcl-2, or overexpression of c-FLIPs resulted in partial rescue of growth inhibition and apoptosis following TWIST1 silencing. However, only knockdown of Bim or Bcl-2 overexpression was able to rescue apoptosis following harmine treatment. This suggests that apoptosis following harmine treatment only requires the intrinsic machinery, while specifically silencing TWIST1 also engages the extrinsic pathway.

In summary, we found that the apoptosis observed after TWIST1/E2A inhibition is dependent on the intrinsic and extrinsic pathways possibly mediated through its novel target genes, c-FLIP and Bim. Our studies will establish the target genes of TWIST1 that are required for suppression of apoptosis with the ultimate goal of identifying biomarkers of response to TWIST1 inhibitors. We also aim to determine if TWIST1, through its apoptotic target genes, modulates response to targeted therapies or standard chemotherapies.

Citation Format: Zachary A. Yochum, Susheel Khetarpal, Timothy F. Burns. TWIST1/E2A signaling axis suppresses apoptosis in oncogene driven non-small cell lung cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3573.