Comprehensive analysis of transcription factor-based molecular subtypes and their correlation to clinical outcomes in small-cell lung cancer

BACKGROUND

Recent studies have reported the predictive and prognostic value of novel transcriptional factor-based molecular subtypes in small-cell lung cancer (SCLC). We conducted an in-depth analysis pairing multi-omics data with immunohistochemistry (IHC) to elucidate the underlying characteristics associated with differences in clinical outcomes between subtypes.

METHODS

IHC (n = 252), target exome sequencing (n = 422), and whole transcriptome sequencing (WTS, n = 189) data generated from 427 patients (86.4% males, 13.6% females) with SCLC were comprehensively analysed. The differences in the mutation profile, gene expression profile, and inflammed signatures were analysed according to the IHC-based molecular subtype.

FINDINGS

IHC-based molecular subtyping, comprised of 90 limited-disease (35.7%) and 162 extensive-disease (64.3%), revealed a high incidence of ASCL1 subtype (IHC-A, 56.3%) followed by ASCL1/NEUROD1 co-expressed (IHC-AN, 17.9%), NEUROD1 (IHC-N, 12.3%), POU2F3 (IHC-P, 9.1%), triple-negative (IHC-TN, 4.4%) subtypes. IHC-based subtype showing high concordance with WTS-based subtyping and non-negative matrix factorization (NMF) clusterization method. IHC-AN subtype resembled IHC-A (rather than IHC-N) in terms of both gene expression profiles and clinical outcomes. Favourable median overall survival was observed in IHC-A (15.2 months) compared to IHC-N (8.0 months, adjusted HR 2.3, 95% CI 1.4-3.9, p = 0.002) and IHC-P (8.3 months, adjusted HR 1.7, 95% CI 0.9-3.2, p = 0.076). Inflamed tumours made up 25% of cases (including 53% of IHC-P, 26% of IHC-A, 17% of IHC-AN, but only 11% of IHC-N). Consistent with recent findings, inflamed tumours were more likely to benefit from first-line immunotherapy treatment than non-inflamed phenotype (p = 0.002).

INTERPRETATION

This study provides fundamental data, including the incidence and basic demographics of molecular subtypes of SCLC using both IHC and WTS from a comparably large, real-world Asian/non-Western patient cohort, showing high concordance with the previous NMF-based SCLC model. In addition, we revealed underlying biological pathway activities, immunogenicity, and treatment outcomes based on molecular subtype, possibly related to the difference in clinical outcomes, including immunotherapy response.

FUNDING

This work was supported by AstraZeneca, Future Medicine 2030 Project of the Samsung Medical Center [grant number SMX1240011], the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT) [grant number 2020R1C1C1010626] and the 7th AstraZeneca-KHIDI (Korea Health Industry Development Institute) oncology research program.

Neoadjuvant chemotherapy plus nivolumab with or without ipilimumab in operable non-small cell lung cancer: the phase 2 platform NEOSTAR trial

Neoadjuvant ipilimumab + nivolumab (Ipi+Nivo) and nivolumab + chemotherapy (Nivo+CT) induce greater pathologic response rates than CT alone in patients with operable non-small cell lung cancer (NSCLC). The impact of adding ipilimumab to neoadjuvant Nivo+CT is unknown. Here we report the results and correlates of two arms of the phase 2 platform NEOSTAR trial testing neoadjuvant Nivo+CT and Ipi+Nivo+CT with major pathologic response (MPR) as the primary endpoint. MPR rates were 32.1% (7/22, 80% confidence interval (CI) 18.7-43.1%) in the Nivo+CT arm and 50% (11/22, 80% CI 34.6-61.1%) in the Ipi+Nivo+CT arm; the primary endpoint was met in both arms. In patients without known tumor EGFR/ALK alterations, MPR rates were 41.2% (7/17) and 62.5% (10/16) in the Nivo+CT and Ipi+Nivo+CT groups, respectively. No new safety signals were observed in either arm. Single-cell sequencing and multi-platform immune profiling (exploratory endpoints) underscored immune cell populations and phenotypes, including effector memory CD8+ T, B and myeloid cells and markers of tertiary lymphoid structures, that were preferentially increased in the Ipi+Nivo+CT cohort. Baseline fecal microbiota in patients with MPR were enriched with beneficial taxa, such as Akkermansia, and displayed reduced abundance of pro-inflammatory and pathogenic microbes. Neoadjuvant Ipi+Nivo+CT enhances pathologic responses and warrants further study in operable NSCLC. (ClinicalTrials.gov registration: NCT03158129 .).

BRAF v600E-mutant cancers treated with vemurafenib alone or in combination with everolimus, sorafenib, or crizotinib or with paclitaxel and carboplatin (VEM-PLUS) study

Combined BRAF + MEK inhibition is FDA approved for BRAF V600E-mutant solid tumors except for colorectal cancer. However, beyond MAPK mediated resistance several other mechanisms of resistance such as activation of CRAF, ARAF, MET, P13K/AKT/mTOR pathway exist among other complex pathways. In the VEM-PLUS study, we performed a pooled analysis of four phase one studies evaluating the safety and efficacy of vemurafenib monotherapy and vemurafenib combined with targeted therapies (sorafenib, crizotinib, or everolimus) or carboplatin plus paclitaxel in advanced solid tumors harboring BRAF V600 mutations. When vemurafenib monotherapy was compared with the combination regimens, no significant differences in OS or PFS durations were noted, except for inferior OS in the vemurafenib and paclitaxel and carboplatin trial (P = 0.011; HR, 2.4; 95% CI, 1.22-4.7) and in crossover patients (P = 0.0025; HR, 2.089; 95% CI, 1.2-3.4). Patients naïve to prior BRAF inhibitors had statistically significantly improved OS at 12.6 months compared to 10.4 months in the BRAF therapy refractory group (P = 0.024; HR, 1.69; 95% CI 1.07-2.68). The median PFS was statistically significant between both groups, with 7 months in the BRAF therapy naïve group compared to 4.7 months in the BRAF therapy refractory group (P = 0.016; HR, 1.80; 95% CI 1.11-2.91). The confirmed ORR in the vemurafenib monotherapy trial (28%) was higher than that in the combination trials. Our findings suggest that, compared with vemurafenib monotherapy, combinations of vemurafenib with cytotoxic chemotherapy or with RAF- or mTOR-targeting agents do not significantly extend the OS or PFS of patients who have solid tumors with BRAF V600E mutations. Gaining a better understanding of the molecular mechanisms of BRAF inhibitor resistance, balancing toxicity and efficacy with novel trial designs are warranted.

Triple blockade of Ido-1, PD-L1 and MEK as a potential therapeutic strategy in NSCLC

BACKGROUND

Despite the recent progress in the treatment and outcome of Non Small Cell Lung Cancer (NSCLC), immunotherapy has still significant limitations reporting a significant proportion of patients not benefiting from therapy, even in patients with high PD-L1 expression. We have previously demonstrated that the combined inhibition of MEK and PD-L1 in NSCLC patients derived three dimensional cultures exerted significant synergistic effect in terms of immune-dependent cancer cell death. However, subsequent experiments analyzing the expression of Indoleamine 2,3-dioxygenase-1 (Ido-1) gene expression demonstrated that Ido-1 resulted unaffected by the MEK inhibition and even increased after the combined inhibition of MEK and PD-L1 thus representing a potential escape mechanism to this combination.

METHODS

We analyzed transcriptomic profile of NSCLC lung adenocarcinoma cohort of TCGA (The Cancer Genome Atlas), stratifying tumors based on EMT (Epithelial mesenchymal Transition) score; in parallel, we investigated the activation of Ido-1 pathway and modulation of immune cytokines productions both in NSCLC cells lines, in peripheral blood mononuclear cells (PBMCs) and in ex-vivo NSCLC spheroids induced by triple inhibition with an anti-PD-L1 monoclonal antibody, the MEK inhibitor and the Ido-1 inhibitor.

RESULTS

In NSCLC lung adenocarcinoma patient cohort (from TCGA) Ido-1 gene expression was significantly higher in samples classified as mesenchymal according EMT score. Similarly, on a selected panel of NSCLC cell lines higher expression of MEK and Ido-1 related genes was detected in cells with mesenchymal phenotype according EMT score, thus suggesting a potential correlation of co-activation of these two pathways in the context of EMT, with cancer cells sustaining an immune-suppressive microenvironment. While exerting an antitumor activity, the dual blockade of MEK and PD-L1 enhances the secretion of pro-inflammatory cytokines (IFNγ, TNFα, IL-12 and IL-6) and, consequently, the expression of new immune checkpoints such as Ido-1. The triple inhibition with an anti-PD-L1 monoclonal antibody, the MEK inhibitor and the Ido-1 inhibitor demonstrated significant antiproliferative and proapoptotic activity on ex-vivo NSCLC samples; at the same time the triple combination kept increased the levels of pro-inflammatory cytokines produced by both PBMCs and tumor spheroids in order to sustain the immune response and simultaneously decreased the expression of other checkpoint (such as CTLA-4, Ido-1 and TIM-3) thus promoting an immune-reactive and inflamed micro-environment.

CONCLUSIONS

We show that Ido-1 activation is a possible escape mechanism to immune-mediated cell death induced by combination of PD-L1 and MEK inhibitors: also, we show that triple combination of anti-PD-L1, anti-MEK and anti-Ido-1 drugs may overcome this negative feedback and restore anti-tumor immune response in NSCLC patients' derived three dimensional cultures.

SWOG S2012: Randomized phase II/III trial of first line platinum/etoposide (P/E) with or without atezolizumab (NSC#783608) in patients (pts) with poorly differentiated extrapulmonary small cell neuroendocrine carcinomas (NEC)

TPS4179

Background: Poorly differentiated, extrapulmonary small cell NEC are rare cancers with median overall survival (OS) < 1 year. Treatment is extrapolated from small cell lung cancer (SCLC) with use of P (cisplatin or carboplatin) + E. More effective treatment regimens and predictive biomarkers are needed to improve outcomes. In SCLC, induction therapy with combination of P/E + PD-L1 checkpoint inhibitor atezolizumab and maintenance atezolizumab improved OS (12.3 months vs 10.3 months; HR 0.70, 95% CI 0.54 – 0.91, P = 0.007) vs P/E alone (Horn L, et al. N Engl J Med 2018). No study to date has compared PD-1/PD-L1 inhibition during induction only vs during induction and maintenance therapy. In SCLC, distinct molecular subtypes can be identified by the presence of specific transcription factors (e.g., ASCL1, NEUROD1, POU2F3) or an Inflamed gene signature (SCLC-I), with SCLC-I pts more likely to benefit clinically from the addition of immunotherapy (Gay CM, et al. Cancer Cell 2021). In this study we plan to test the benefit of adding atezolizumab to induction P/E plus maintenance vs P/E alone, as well as the role of adding maintenance atezolizumab vs observation after induction chemo-immunotherapy. We also plan to correlate tumor- and blood-based subtype biomarkers with response to therapy. Methods: Eligible pts ≥18 years old have evaluable, histologically confirmed extrapulmonary small cell NEC, Zubrod PS ≤2, and are allowed to have up to 1 cycle of P/E prior to enrollment. P (cisplatin 75 mg/m2 or carboplatin AUC 5, iv) on day 1, E 100 mg/m2 iv on days 1-3, and atezolizumab 1200 mg iv on day 1 of q21 day cycles. Treatment consists of an induction phase x 4 cycles, and if no disease progression, a maintenance/observation phase given until disease progression for up to 1 year. Pts are randomized to 1 of 3 arms: A) Induction P/E + atezolizumab → maintenance atezolizumab B) Induction P/E + atezolizumab → observation C) Induction P/E → observation. The primary endpoint is to compare the OS (from randomization) between arms in a fixed sequence: A vs C → B vs C → A vs B. Secondary endpoints include comparing OS (from start of maintenance/observation), progression free survival, response rate, duration of response, and safety/tolerability across arms. Tumor and blood samples will be banked for future biomarker analyses, including immunohistochemistry of transcription factors on tissue and whole exome sequencing on tumor and circulating tumor DNA. With 189 pts, the study is powered to detect an improvement in 12-months OS from 35% to 57.5% (HR 0.53). Both phase 2 and phase 3 portions include interim analyses. Accrual will not pause for phase 2 analysis, expected early 2024. This study was activated December, 2021 and is open to accrual across the NCI National Clinical Trials Network (NCTN). Clinical trial information: NCT05058651.

Results of a phase 1b study of osimertinib plus sapanisertib or alisertib for osimertinib-resistant, EGFR-mutant non–small cell lung cancer (NSCLC)

9105

Background: The aurora kinase and mTOR pathways are implicated in resistance to EGFR inhibitor osimertinib. Here, we investigated the safety and efficacy of the aurora kinase inhibitor alisertib and the mTOR inhibitor sapanisertib in combination with osimertinib. Methods: This is a phase 1b study with dose finding and expansion portions (NCT04479306). The dose finding portion used a Bayesian optimal interval (BOIN) design to assess two arms: osimertinib 80 mg daily in combination with alisertib 20 mg, 30 mg, and 40 mg daily day 1-21 of 28-day cycle (osi-ali arm) and osimertinib 80 mg daily in combination with sapanisertib 2 mg and 3 mg daily (osi-sapa arm). Dose limiting toxicities (DLTs) were predefined in the protocol. Patients with EGFR (L858R/exon 19 deletion) mutant NSCLC whose disease have progressed on osi and up to one additional line of systemic therapy were assigned, at investigator discretion, to either study arm. Tumor biopsy was mandatory at study entry and optional upon progression. Results: As of February 1, 2022, 40 patients are enrolled (20 in each arm). One DLT was observed in each arm: grade 3 nausea in ali-osi arm and grade 3 AST elevation in osi-sapa arm. Grade 3 treatment emergent adverse events (TEAEs) occurred in 10% of each arm, and no grade 4 TEAEs were observed. The most common TEAEs in osi-ali arm was leucopenia (45%) and anemia (35%) while in osi-sapa arm, hyperglycemia (45%) and stomatitis (40%). In osi-ali arm (n = 20), median progression free survival (mPFS) was 1.9 months while objective response rate (ORR) and disease control rate (DCR) were 5% (95% CI: 0.1 ̃ 24.9%) and 40% (95% CI: 19.1 ̃ 63.9%), respectively. In osi-sapa arm (n = 16, evaluated for response to date), mPFS was 4.6 months while ORR and DCR were 12.5% (95% CI: 1.6 ̃ 38.3%) and 68.7% (95% CI: 35.7 ̃ 82.7%), respectively. Conclusions: Osimertinib with alisertib or sapanisertib is well tolerated in osimertinib-resistant, EGFR mutant NSCLC. The sapanisertib combination, but not the alisertib combination, demonstrates antitumor activity suggesting that mTOR inhibition warrants further exploration in this population. Biomarker analysis is ongoing to identify the molecular determinants of response and resistance to sapasertib. Clinical trial information: NCT04479306.

Distinct tumor-infiltrating lymphocyte landscapes are associated with clinical outcomes in localized non-small-cell lung cancer

BACKGROUND

Despite the importance of tumor-infiltrating T lymphocytes (TILs) in cancer biology, the relationship between TIL phenotypes and their prognostic relevance for localized non-small-cell lung cancer (NSCLC) has not been well established.

PATIENTS AND METHODS

Fresh tumor and normal adjacent tissue was prospectively collected from 150 patients with localized NSCLC. Tissue was comprehensively characterized by high-dimensional flow cytometry of TILs integrated with immunogenomic data from multiplex immunofluorescence, T-cell receptor sequencing, exome sequencing, RNA sequencing, targeted proteomics, and clinicopathologic features.

RESULTS

While neither the magnitude of TIL infiltration nor specific TIL subsets were significantly prognostic alone, the integration of high-dimensional flow cytometry data identified two major immunotypes (IM1 and IM2) that were predictive of recurrence-free survival independent of clinical characteristics. IM2 was associated with poor prognosis and characterized by the presence of proliferating TILs expressing cluster of differentiation 103, programmed cell death protein 1, T-cell immunoglobulin and mucin-domain containing protein 3, and inducible T-cell costimulator. Conversely, IM1 was associated with good prognosis and differentiated by an abundance of CD8⁺ T cells expressing cytolytic enzymes, CD4⁺ T cells lacking the expression of inhibitory receptors, and increased levels of B-cell infiltrates and tertiary lymphoid structures. While increased B-cell infiltration was associated with good prognosis, the best prognosis was observed in patients with tumors exhibiting high levels of both B cells and T cells. These findings were validated in patient tumors from The Cancer Genome Atlas.

CONCLUSIONS

Our study suggests that although the number of infiltrating T cells is not associated with patient survival, the nature of the infiltrating T cells, resolved in distinct TIL immunotypes, is prognostically relevant in NSCLC and may inform therapeutic approaches to clinical care.

Abstract P079: The impact of BCL2 expression on sensitivity to the novel Aurora kinase B inhibitor AZD2811 in small cell lung cancer

Purpose: Small cell lung cancer (SCLC) is a highly lethal malignancy, with rapidly-acquired therapeutic resistance. In contrast to non-SCLC, treatment strategies based on molecular subtypes have not been well established. Aurora kinase family proteins (AURKA and AURKB) are essential for cell division, regulating chromosomal segregation during mitosis, and are upregulated in cancer. Our group has demonstrated that cMYC-driven SCLC tumors were susceptible to an AURKA inhibitor, alisertib, making AURK proteins an attractive targeted therapeutic approach. A novel AURKB inhibitor, AZD2811NP (nanoparticle), is now being investigated in relapsed SCLC patients (NCT02579226), but molecular mechanisms of resistance have not yet been identified. Here, we hypothesize that targeting predictive markers related to the effect of AZD2811 may reinforce susceptibility to AURKB inhibition. Experimental Design: We evaluated susceptibility to AZD2811 in 63 human-derived SCLC cell lines using 96-hour proliferation assays. To identify translatable biomarkers of response, we correlated AZD2811 IC50 values with genomic (whole exome sequencing, WES), transcriptomic (RNASeq), and proteomic profiling (Reverse Phase Protein Array, RPPA) data. We validated changes in apoptosis and DNA damage markers induced by AZD2811 in SCLC cells infected with the lentivirus vectors expressing BCL-2 and shRNA against BCL-2 using western blot. We used SCLC patient-derived xenograft (PDX) models with distinct BCL-2 profiles to evaluate in vivo antitumor effect. Results: In the SCLC cells treated with AZD2811, 15/63 (24%) and 10/63 (16%) cell lines showed high sensitivity (IC50&lt;30 nM, Cmax) and intermediate sensitivity (IC50=30-100nM). Comparing protein expression, we found that cMYC (Fold change, FC:2.5; P = 0.015) were a positive biomarker of sensitivity, while high BCL-2 (FC:1.86; P = 0.032) associated with resistance. cMYC-high SCLC cell lines that were susceptible to AZD2811 became resistant when BCL-2 was overexpressed. Conversely, BCL-2 knock-down enhanced response to AZD2811, inducing apoptosis and DNA damage, in BCL-2-high cells that were originally resistant to single-agent AZD2811. Similar to Bcl-2 knock-down, treatment with venetoclax (a BCL-2 inhibitor routinely used in other cancers) enhanced apoptosis and DNA damage induction in combination with AZD2811 in cells overexpressing BCL-2. In PDX models with high BCL-2, combination of AZD2811 and venetoclax prominently induced tumor regression and apoptosis compared with each monotherapy, while there was no significant difference in PDX models with low BCL-2 between the combination and the monotherapy. Conclusions: Our preclinical results indicate that high BCL-2 expression reduced the efficacy of AZD2811 in SCLC models, but that Bcl2-driven resistance could be overcome with the combined use of BCL-2 and AURKB inhibitors. Findings support a promising rational combination therapy for BCL-2-high SCLC to enhance response to aurora kinase B inhibition.

Citation Format: Azusa Tanimoto, Carminia M. Della Corte, Kavya Ramkumar, Robert J. Cardnell, Allison C. Stewart, Carl M. Gay, Lauren Averett Byers, Qi Wang, Li Shen, Jing Wang, Jon Travers. The impact of BCL2 expression on sensitivity to the novel Aurora kinase B inhibitor AZD2811 in small cell lung cancer [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P079.

Veliparib in Combination With Platinum-Based Chemotherapy for First-Line Treatment of Advanced Squamous Cell Lung Cancer: A Randomized, Multicenter Phase III Study

PURPOSE

Squamous non-small-cell lung cancer (sqNSCLC) is genetically complex with evidence of DNA damage. This phase III study investigated the efficacy and safety of poly (ADP-ribose) polymerase inhibitor veliparib in combination with conventional chemotherapy for advanced sqNSCLC (NCT02106546).

PATIENTS AND METHODS

Patients age ≥ 18 years with untreated, advanced sqNSCLC were randomly assigned 1:1 to carboplatin and paclitaxel with veliparib 120 mg twice daily (twice a day) or placebo twice a day for up to six cycles. The primary end point was overall survival (OS) in the veliparib arm versus the control arm in current smokers, based on phase II findings. Archival tumor samples were provided for biomarker analysis using a 52-gene expression histology classifier (LP52).

RESULTS

Overall, 970 patients were randomly assigned to carboplatin and paclitaxel plus either veliparib (n = 486) or placebo (n = 484); 57% were current smokers. There was no significant OS benefit with veliparib in current smokers, with median OS 11.9 versus 11.1 months (hazard ratio [HR], 0.905; 95% CI, 0.744 to 1.101; P = .266). In the overall population, OS favored veliparib; median OS was 12.2 versus 11.2 months (HR, 0.853; 95% CI, 0.747 to 0.974), with no difference in progression-free survival (median 5.6 months per arm). In patients with biomarker-evaluable tumor samples (n = 360), OS favored veliparib in the LP52-positive population (median 14.0 v 9.6 months; HR, 0.66; 95% CI, 0.49 to 0.89), but favored placebo in the LP52-negative population (median 11.0 v 14.4 months; HR, 1.33; 95% CI, 0.95 to 1.86). No new safety signals were observed in the experimental arm.

CONCLUSION

In current smokers with advanced sqNSCLC, there was no therapeutic benefit of adding veliparib to first-line chemotherapy. The LP52 signature may identify a subgroup of patients likely to derive benefit from veliparib with chemotherapy.

Lung Cancer Models Reveal Severe Acute Respiratory Syndrome Coronavirus 2-Induced Epithelial-to-Mesenchymal Transition Contributes to Coronavirus Disease 2019 Pathophysiology

INTRODUCTION

Coronavirus disease 2019 is an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which enters host cells through the cell surface proteins ACE2 and TMPRSS2.

METHODS

Using a variety of normal and malignant models and tissues from the aerodigestive and respiratory tracts, we investigated the expression and regulation of ACE2 and TMPRSS2.

RESULTS

We find that ACE2 expression is restricted to a select population of epithelial cells. Notably, infection with SARS-CoV-2 in cancer cell lines, bronchial organoids, and patient nasal epithelium induces metabolic and transcriptional changes consistent with epithelial-to-mesenchymal transition (EMT), including up-regulation of ZEB1 and AXL, resulting in an increased EMT score. In addition, a transcriptional loss of genes associated with tight junction function occurs with SARS-CoV-2 infection. The SARS-CoV-2 receptor, ACE2, is repressed by EMT through the transforming growth factor-β, ZEB1 overexpression, and onset of EGFR tyrosine kinase inhibitor resistance. This suggests a novel model of SARS-CoV-2 pathogenesis in which infected cells shift toward an increasingly mesenchymal state, associated with a loss of tight junction components with acute respiratory distress syndrome-protective effects. AXL inhibition and ZEB1 reduction, as with bemcentinib, offer a potential strategy to reverse this effect.

CONCLUSIONS

These observations highlight the use of aerodigestive and, especially, lung cancer model systems in exploring the pathogenesis of SARS-CoV-2 and other respiratory viruses and offer important insights into the potential mechanisms underlying the morbidity and mortality of coronavirus disease 2019 in healthy patients and patients with cancer alike.

Resolving the Spatial and Cellular Architecture of Lung Adenocarcinoma by Multiregion Single-Cell Sequencing

Little is known of the geospatial architecture of individual cell populations in lung adenocarcinoma (LUAD) evolution. Here, we perform single-cell RNA sequencing of 186,916 cells from five early-stage LUADs and 14 multiregion normal lung tissues of defined spatial proximities from the tumors. We show that cellular lineages, states, and transcriptomic features geospatially evolve across normal regions to LUADs. LUADs also exhibit pronounced intratumor cell heterogeneity within single sites and transcriptional lineage-plasticity programs. T regulatory cell phenotypes are increased in normal tissues with proximity to LUAD, in contrast to diminished signatures and fractions of cytotoxic CD8+ T cells, antigen-presenting macrophages, and inflammatory dendritic cells. We further find that the LUAD ligand-receptor interactome harbors increased expression of epithelial CD24, which mediates protumor phenotypes. These data provide a spatial atlas of LUAD evolution, and a resource for identification of targets for its treatment. SIGNIFICANCE: The geospatial ecosystem of the peripheral lung and early-stage LUAD is not known. Our multiregion single-cell sequencing analyses unravel cell populations, states, and phenotypes in the spatial and ecologic evolution of LUAD from the lung that comprise high-potential targets for early interception.This article is highlighted in the In This Issue feature, p. 2355.

Prognostic factors in RET dependent cancers treateded with RET inhibitors in early phase clinical trials

3117

Background: Activation of the RET proto-oncogene has been identified in multiple cancer types, for example, gene rearrangements in non-small cell lung cancer (NSCLC) and papillary thyroid cancer (PTC) and activating mutations in medullary thyroid cancer (MTC), amongst others. The recent FDA approval of two highly selective RET inhibitors, selpercatinib and pralsetinib has changed the treatment paradigm of RET-driven cancers, but the significance of historical prognostic factors is unknown. Herein, we analyzed the outcomes of patients with RET-altered cancers enrolled in phase I trials and assess the utility of prognostic scores. Methods: A retrospective analysis was performed of patients treated with selective RET inhibitors at the MD Anderson Cancer Center (MDACC). Baseline clinical factors and survival data were assessed. Overall and progression free survival (OS and PFS) were estimated using the Kaplan-Meier method and multivariable Cox models were constructed. For all a p-value of < 0.05 was consider significant. Results: Among 126 patients, median age was 58 years (range, 15-82), most with ECOG 0-1 (n = 124). RET-mutant MTC was most frequent (n = 81), followed by RET fusion-positive NSCLC (n = 30) and RET fusion positive thyroid cancer (n = 9). RET fusion partners were KIF5B (n = 17), CCD6 (n = 12) and NCOA4 (n = 7). RET M918T mutation was the most frequent (n = 50, 63%). Most patients were treated in the relapsed/refractory (R/R) setting (n = 85) and received a median of 1 prior line of therapy (range, 0-11). Median follow up was 20 months (range, 1-43). The estimated median PFS and OS were 24 and 35 months, respectively. Overall objective response rate was 64% (81/126), 2 complete response, 79 partial response, 32 had stable disease (25%) and 13 had progressive disease (PD). The following were associated with shorter PFS and OS: age ≥50 years (p < 0.05), albumin < 4 g/dL (p < 0.01), brain metastases (p < 0.0001), hemoglobin < 12 g/dL ( < 0.05), LDH > normal (p < 0.05), WBC ≥8 (p < 0.01), PD (p < 0.0001) and NSCLC (p < 0.01). The M918T mutation and ECOG > 0 were associated with shorter OS but not PFS (p < 0.05). > 3 metastatic sites and R/R disease were associated with inferior PFS (p = 0.04 and p = 0.01, respectively) but not OS. The Royal Marsden Hospital (RMH) and MDACC prognostic scores were significantly associated with PFS and OS (p < 0.01). In multivariable models including all variables significantly associated with PFS and OS (excluding LDH as this was only tested in 58 patients) albumin < 4 (HR 6.10, p = 0.013), brain metastases (HR 4.90, p = 0.027) and WBC ≥8 (HR 4.67, p = 0.031) were associated with inferior OS. NSCLC was significantly associated with inferior PFS (HR 5.45, p = 0.02). Conclusions: The RMH and MDACC prognostic scores predict OS in RET-aberrant cancers treated on early phase trials. Low albumin, WBC > 8 and brain metastases are significantly associated with inferior survival.

KEYLYNK-013: A phase 3 study of pembrolizumab in combination with concurrent chemoradiation therapy followed by pembrolizumab with or without olaparib versus concurrent chemoradiation therapy in patients with newly diagnosed limited-stage SCLC

TPS8587

Background: Concurrent chemoradiotherapy with etoposide and platinum (carboplatin/cisplatin) plus the anti‒PD-1 antibody pembrolizumab (pembro) has shown antitumor activity and acceptable safety in patients with limited-stage small-cell lung cancer (LS-SCLC). The poly (ADP-ribose) polymerase (PARP) inhibitor, olaparib, has shown clinical activity in combination with checkpoint inhibitors in patients with SCLC. KEYLYNK-013 (NCT04624204) is a randomized, placebo-controlled, double-blind phase 3 trial of pembro plus concurrent chemoradiation therapy followed by pembro with or without olaparib in patients with newly diagnosed LS-SCLC. Methods: Eligible patients are those aged ≥18 years with previously untreated LS-SCLC, ECOG PS 0/1, and adequate pulmonary function. Patients are randomized 1:1:1 to receive pembro 200 mg Q3W (groups A and B) or pembro placebo (saline) Q3W (group C) during the chemoradiation phase. All patients also receive 4 cycles of chemotherapy (etoposide 100 mg/m2 on days 1, 2, and 3 of each cycle and investigator’s choice of carboplatin AUC 5 mg/mL/min or cisplatin 75 mg/m2 on day 1 of each cycle) with definitive thoracic radiotherapy (total dose of 45 Gy in 30 fractions twice daily over 3 weeks or 66 Gy in 33 fractions once daily over 6.5 weeks starting on day 1 of cycle 2). After chemoradiation, prophylactic cranial irradiation is strongly recommended for patients with CR/PR or at investigator’s discretion for patients with SD. Postchemoradiation patients receive pembro 400 mg Q6W plus olaparib placebo (group A), or pembro 400 mg Q6W plus olaparib 300 mg BID (group B), or pembro placebo plus olaparib placebo (group C) for 9 cycles/12 months. Randomization is stratified by ECOG PS (0 vs 1), SCLC stage (I/II vs III), radiation fractionation (twice vs once daily), and region (east Asia vs North America/western Europe/UK/Australia vs rest of world). Tumor imaging occurs at baseline, within 12 weeks of cycle 1 day 1, followed by Q9W to the end of year 2, Q12W in year 3, Q16W in year 4, every 6 months in year 5, and annually thereafter. Imaging is assessed per RECIST v1.1 by blinded independent central review. AEs are monitored from randomization to 30 days after cessation of study treatment (90 days for serious AEs) and graded per NCI-CTCAE v5.0. Health-related quality of life is assessed using EORTC-QLQ-C30 and QLQ-LC13. Primary endpoints are OS and PFS per RECIST v1.1 by blinded independent central review. OS and PFS are estimated by the Kaplan-Meier method. Between-group differences will be evaluated with stratified log-rank tests and Cox proportional hazard models with Efron’s method of tie handling. Secondary endpoints include ORR, duration of response, safety, and patient-reported outcomes. The study began enrollment in December 2020. Clinical trial information: NCT04624204.

Ph I/II study of oral selective AXL inhibitor bemcentinib (BGB324) in combination with erlotinib in patients with advanced EGFRm NSCLC: End of trial update

9110

Background: AXL, a receptor tyrosine kinase, is over-expressed in many cancers, and has been identified as a marker of poor prognosis in NSCLC. AXL overexpression is implicated in development of resistance to EGFR inhibitors including erlotinib (Erl) and osimertinib. AXL inhibition by bemcentinib (Bem), a first-in-class, oral, selective and potent AXL kinase inhibitor, abrogates resistance to EGFR inhibitors in vivo. Bem is currently under evaluation as a monotherapy and in combination with EGFRi, CPIs and chemotherapy across several PhII trials. Methods: Phase I of this study was designed to confirm safety/tolerability of Bem in NSCLC pts as monotherapy and in combination with Erl in pts previously progressing on Erl (arm A). In Phase II, pts who had progressed on an approved EGFRi (arm B) or who were responding/stable on Erl in the 1L setting (arm C) were treated with Bem 200mg and Erl 150mg od to evaluate the safety and activity of the combination, assessing reversal or prevention of resistance to EGFR inhibition in these 2 groups, respectively. Plasma protein biomarker levels were sequentially measured using the DiscoveryMap v3.3 panel (Myriad RBM). Results: As of 7 Oct 2020, all arms have completed recruitment. Median exposure to Bem was 63d (mean: 200d, range: 2d-1175d). Treatment was generally well-tolerated. Common TRAEs (>20% pts) were diarrhea (70%; G3 20%), nausea (50%; G3 0%), QTc prolongation (35%; G3 3%), vomiting (35%; G3 0%), and fatigue (25%; G3 5%). 1 unrelated G4, 0 G5 reported. In the run-in arm (5 female, median age 61 yrs [57-76]), 2/8 pts achieved SD for ̃1 yr, including 19% tumor shrinkage in 1 pt. In arm A (5 female, median age 58 yrs [38-67]), 1/8 pts (68 F) achieved tumor shrinkage of 38%, with treatment duration of 2 yrs until progression. A further 5 pts reported SD. In arm B, 11 pts (7 female, median age 63 yrs [49-78]) had received a median of 1 (0 - 4) prior lines of chemotherapy and a median of 2 prior lines of EGFRi. One achieved a PR (51M) and one a SD (62F) on the combination (CBR of 18%); durations on treatment were 1 yr, and 6 mos, respectively. Neither had EGFR T790M. mPFS was 1.4 mos. In arm C, 13 pts (10 female, median age 66 yrs [32-80]) were enrolled. 11/13 pts were evaluable for efficacy. 1 PR (58M) was reported with 47% tumor shrinkage, duration of treatment was 315d. 9 other pts achieved SD (CBR of 91%), including 4 (3 F/1 M, age range 64-71yrs) who continued on trial for 772+ to 1008+ d. mPFS is currently 12.2 mos. Protein biomarkers predictive of pt benefit upon Bem treatment are being explored. Conclusions: Bem with Erl combination is feasible and tolerable in NSCLC pts, with benefit was seen in a subset of pts who either progressed on an EGFRi or were receiving Erl concurrently in remission in the first line. Further studies of Bem + EGFRi are warranted to explore the potential benefits of this combination. Clinical trial information: NCT02424617.

Veliparib in Combination with Carboplatin and Etoposide in Patients with Treatment-Naïve Extensive-Stage Small Cell Lung Cancer: A Phase 2 Randomized Study

PURPOSE

This study investigated the efficacy and safety of oral PARP inhibitor veliparib, plus carboplatin and etoposide in patients with treatment-naïve, extensive-stage small cell lung cancer (ED-SCLC).

PATIENTS AND METHODS

Patients were randomized 1:1:1 to veliparib [240 mg twice daily (BID) for 14 days] plus chemotherapy followed by veliparib maintenance (400 mg BID; veliparib throughout), veliparib plus chemotherapy followed by placebo (veliparib combination only), or placebo plus chemotherapy followed by placebo (control). Patients received 4-6 cycles of combination therapy, then maintenance until unacceptable toxicity/progression. The primary endpoint was progression-free survival (PFS) with veliparib throughout versus control.

RESULTS

Overall (N = 181), PFS was improved with veliparib throughout versus control [hazard ratio (HR), 0.67; 80% confidence interval (CI), 0.50-0.88; P = 0.059]; median PFS was 5.8 and 5.6 months, respectively. There was a trend toward improved PFS with veliparib throughout versus control in SLFN11-positive patients (HR, 0.6; 80% CI, 0.36-0.97). Median overall survival (OS) was 10.1 versus 12.4 months in the veliparib throughout and control arms, respectively (HR, 1.43; 80% CI, 1.09-1.88). Grade 3/4 adverse events were experienced by 82%, 88%, and 68% of patients in the veliparib throughout, veliparib combination-only and control arms, most commonly hematologic.

CONCLUSIONS

Veliparib plus platinum chemotherapy followed by veliparib maintenance demonstrated improved PFS as first-line treatment for ED-SCLC with an acceptable safety profile, but there was no corresponding benefit in OS. Further investigation is warranted to define the role of biomarkers in this setting.

A Phase II Trial of Prexasertib (LY2606368) in Patients With Extensive-Stage Small-Cell Lung Cancer

BACKGROUND

This study assessed the checkpoint kinase 1 inhibitor prexasertib in patients with extensive-stage small-cell lung cancer (ED-SCLC).

PATIENTS AND METHODS

This was a parallel-cohort phase II study of 105 mg/m² prexasertib once every 14 days for patients who progressed after no more than two prior therapies and had platinum-sensitive (Cohort 1) or platinum-resistant/platinum-refractory (Cohort 2) disease. The primary endpoint was objective response rate (ORR). Secondary endpoints included disease control rate (DCR), progression-free survival (PFS), overall survival (OS), safety, and pharmacokinetics. Exploratory endpoints included biomarker identification and assessment of an alternative regimen (Cohort 3: 40 mg/m² days 1-3, 14-day cycle).

RESULTS

In Cohort 1 (n = 58), ORR was 5.2%; DCR, 31%; median PFS, 1.41 months (95% confidence interval [CI], 1.31-1.64); and median OS, 5.42 months (95% CI, 3.75-8.51). In Cohort 2 (n = 60), ORR was 0%; DCR, 20%; median PFS, 1.36 months (95% CI, 1.25-1.45); and median OS, 3.15 months (95% CI, 2.27-5.52). The most frequent all-grade, related, treatment-emergent adverse events were decreased neutrophil count (Cohort 1, 69.6%; Cohort 2, 73.3%), decreased platelet count (Cohort 1, 51.8%; Cohort 2, 50.0%), decreased white blood cell count (Cohort 1, 28.6%; Cohort 2, 40.0%), and anemia (Cohort 1, 39.3%; Cohort 2, 28.3%). Eleven patients (19.6%) in Cohort 1 and one patient (1.7%) in Cohort 2 experienced grade ≥3 febrile neutropenia. Prexasertib pharmacokinetics were consistent with prior studies. Cohort 3 outcomes were similar to those of Cohorts 1 and 2. No actionable biomarkers were identified.

CONCLUSION

Prexasertib did not demonstrate activity to warrant future development as monotherapy in ED-SCLC.

A Reversible Shift of Driver Dependence from EGFR to Notch1 in Non-Small Cell Lung Cancer as a Cause of Resistance to Tyrosine Kinase Inhibitors

Notch1 plays a key role in epithelial-mesenchymal transition (EMT) and in the maintenance of cancer stem cells. In the present study we tested whether high levels of activated Notch1 in oncogene-driven NSCLC can induce a reversible shift of driver dependence from EGFR to Notch1, and thus causing resistance to EGFR inhibitors. Adherent cells (parental) and tumor spheres (TS) from NSCLC H1975 cells and patient-derived CD133-positive cells were tested for EGFR and Notch1 signaling cascade. The Notch1-dependent modulation of EGFR, NCID, Hes1, p53, and Sp1 were then analyzed in parental cells by binding assays with a Notch1 agonist, DLL4. TS were more resistant than parental cells to EGFR inhibitors. A strong upregulation of Notch1 and a concomitant downregulation of EGFR were observed in TS compared to parental cells. Parental cell exposure to DLL4 showed a dose-dependent decrease of EGFR and a simultaneous increase of NCID, Hes1, p53, and Sp1, along with the dislocation of Sp1 from the EGFR promoter. Furthermore, an enhanced interaction between p53 and Sp1 was observed in TS. In NSCLC cells, high levels of active Notch1 can promote a reversible shift of driver dependence from EGFR to Notch1, leading to resistance to EGFR inhibitors.

Patterns of transcription factor programs and immune pathway activation define four major subtypes of SCLC with distinct therapeutic vulnerabilities

Despite molecular and clinical heterogeneity, small cell lung cancer (SCLC) is treated as a single entity with predictably poor results. Using tumor expression data and non-negative matrix factorization, we identify four SCLC subtypes defined largely by differential expression of transcription factors ASCL1, NEUROD1, and POU2F3 or low expression of all three transcription factor signatures accompanied by an Inflamed gene signature (SCLC-A, N, P, and I, respectively). SCLC-I experiences the greatest benefit from the addition of immunotherapy to chemotherapy, while the other subtypes each have distinct vulnerabilities, including to inhibitors of PARP, Aurora kinases, or BCL-2. Cisplatin treatment of SCLC-A patient-derived xenografts induces intratumoral shifts toward SCLC-I, supporting subtype switching as a mechanism of acquired platinum resistance. We propose that matching baseline tumor subtype to therapy, as well as manipulating subtype switching on therapy, may enhance depth and duration of response for SCLC patients.

Lung cancer models reveal SARS-CoV-2-induced EMT contributes to COVID-19 pathophysiology

COVID-19 is an infectious disease caused by SARS-CoV-2, which enters host cells via the cell surface proteins ACE2 and TMPRSS2. Using a variety of normal and malignant models and tissues from the aerodigestive and respiratory tracts, we investigated the expression and regulation of ACE2 and TMPRSS2. We find that ACE2 expression is restricted to a select population of highly epithelial cells. Notably, infection with SARS-CoV-2 in cancer cell lines, bronchial organoids, and patient nasal epithelium, induces metabolic and transcriptional changes consistent with epithelial to mesenchymal transition (EMT), including upregulation of ZEB1 and AXL, resulting in an increased EMT score. Additionally, a transcriptional loss of genes associated with tight junction function occurs with SARS-CoV-2 infection. The SARS-CoV-2 receptor, ACE2, is repressed by EMT via TGFbeta, ZEB1 overexpression and onset of EGFR TKI inhibitor resistance. This suggests a novel model of SARS-CoV-2 pathogenesis in which infected cells shift toward an increasingly mesenchymal state, associated with a loss of tight junction components with acute respiratory distress syndrome-protective effects. AXL-inhibition and ZEB1-reduction, as with bemcentinib, offers a potential strategy to reverse this effect. These observations highlight the utility of aerodigestive and, especially, lung cancer model systems in exploring the pathogenesis of SARS-CoV-2 and other respiratory viruses, and offer important insights into the potential mechanisms underlying the morbidity and mortality of COVID-19 in healthy patients and cancer patients alike.

Single-cell analyses reveal increased intratumoral heterogeneity after the onset of therapy resistance in small-cell lung cancer

The natural history of small cell lung cancer (SCLC) includes rapid evolution from chemosensitivity to chemoresistance, although mechanisms underlying this evolution remain obscure due to scarcity of post-relapse tissue samples. We generated circulating tumor cell (CTC)-derived xenografts (CDXs) from SCLC patients to study intratumoral heterogeneity (ITH) via single-cell RNAseq of chemo-sensitive and -resistant CDXs and patient CTCs. We found globally increased ITH including heterogeneous expression of therapeutic targets and potential resistance pathways, such as EMT, between cellular subpopulations following treatment-resistance. Similarly, serial profiling of patient CTCs directly from blood confirmed increased ITH post-relapse. These data suggest that treatment-resistance in SCLC is characterized by coexisting subpopulations of cells with heterogeneous gene expression leading to multiple, concurrent resistance mechanisms. These findings emphasize the need for clinical efforts to focus on rational combination therapies for treatment-naïve SCLC tumors to maximize initial responses and counteract the emergence of ITH and diverse resistance mechanisms.

The MEK5-ERK5 Kinase Axis Controls Lipid Metabolism in Small-Cell Lung Cancer

Small-cell lung cancer (SCLC) is an aggressive form of lung cancer with dismal survival rates. While kinases often play key roles driving tumorigenesis, there are strikingly few kinases known to promote the development of SCLC. Here, we investigated the contribution of the MAPK module MEK5-ERK5 to SCLC growth. MEK5 and ERK5 were required for optimal survival and expansion of SCLC cell lines in vitro and in vivo. Transcriptomics analyses identified a role for the MEK5-ERK5 axis in the metabolism of SCLC cells, including lipid metabolism. In-depth lipidomics analyses showed that loss of MEK5/ERK5 perturbs several lipid metabolism pathways, including the mevalonate pathway that controls cholesterol synthesis. Notably, depletion of MEK5/ERK5 sensitized SCLC cells to pharmacologic inhibition of the mevalonate pathway by statins. These data identify a new MEK5-ERK5-lipid metabolism axis that promotes the growth of SCLC. SIGNIFICANCE: This study is the first to investigate MEK5 and ERK5 in SCLC, linking the activity of these two kinases to the control of cell survival and lipid metabolism.

This Is Our Cells Under Pressure: Decreased DNA Damage Repair in Response to Targeted Therapies Facilitates the Emergence of Drug-Resistant Clones

In a recent issue of Science, Russo et al. observe that colorectal cancer cells, when exposed to the pressure of EGFR- and BRAF-targeted therapies, transiently alter their transcriptional profiles to foster mutagenesis, thereby enhancing the stochastic development of acquired resistance mutations.

Evading the STING: LKB1 Loss Leads to STING Silencing and Immune Escape in KRAS-Mutant Lung Cancers

Mutations in STK11 (LKB1) are a major cause of primary resistance to immunotherapy in non-small cell lung cancer. Kitajima and colleagues dissect the underlying mechanism of this immune-resistant phenotype, demonstrating that LKB1 loss leads directly to suppression of stimulator of interferon genes (STING) and insensitivity to cytoplasmic double-strand DNA detection. Therapies that reactivate LKB1 or theSTING pathway may boost anticancer immune response in cancers with resistance to immune-checkpoint blockade.See related article by Kitajima et al., p. 34.

Temozolomide plus PARP Inhibition in Small-Cell Lung Cancer: Could Patient-Derived Xenografts Accelerate Discovery of Biomarker Candidates?

Effective options are limited for patients with small-cell lung cancer who develop progressive disease during or after etoposide plus platinum-based therapy. In this issue of Cancer Discovery, Farago and colleagues highlight the data for temozolomide plus olaparib in this patient population and demonstrate the potential to accelerate biomarker discovery through co-clinical trials utilizing patient-derived xenografts.See related article by Farago et al., p. 1372.

Genomic, Pathway Network, and Immunologic Features Distinguishing Squamous Carcinomas

This integrated, multiplatform PanCancer Atlas study co-mapped and identified distinguishing molecular features of squamous cell carcinomas (SCCs) from five sites associated with smoking and/or human papillomavirus (HPV). SCCs harbor 3q, 5p, and other recurrent chromosomal copy-number alterations (CNAs), DNA mutations, and/or aberrant methylation of genes and microRNAs, which are correlated with the expression of multi-gene programs linked to squamous cell stemness, epithelial-to-mesenchymal differentiation, growth, genomic integrity, oxidative damage, death, and inflammation. Low-CNA SCCs tended to be HPV(+) and display hypermethylation with repression of TET1 demethylase and FANCF, previously linked to predisposition to SCC, or harbor mutations affecting CASP8, RAS-MAPK pathways, chromatin modifiers, and immunoregulatory molecules. We uncovered hypomethylation of the alternative promoter that drives expression of the ΔNp63 oncogene and embedded miR944. Co-expression of immune checkpoint, T-regulatory, and Myeloid suppressor cells signatures may explain reduced efficacy of immune therapy. These findings support possibilities for molecular classification and therapeutic approaches.

Author Correction: Molecular subtypes of small cell lung cancer: a synthesis of human and mouse model data

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

A phase II study of talazoparib (BMN 673) in patients with homologous recombination repair deficiency (HRRD) positive stage IV squamous cell lung cancer (Lung-MAP Sub-Study, S1400G)

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Background: This signal finding study was designed to evaluate the clinical efficacy of a PARP inhibitor, talazoparib, in advanced stage squamous cell lung cancer harboring HRRD. Methods: Eligible patients (pts) identified through the parent S1400 screening platform were required to have a deleterious mutation in any of the study-defined HRR genes [ATM, ATR, BARD1, BRCA1, BRCA2, BRIP1, CHEK1, CHEK2, FANCA, FANCC, FANCD2, FANCF, FANCM, NBN (NBS1), PALB2, RAD51, RAD51B (RAD51L1), RAD54L, RPA1) defined as the full eligible population (FEP). The primary analysis population (PAP) is defined by a subset of genes [ATM, ATR, BRCA1, BRCA2, PALB2]. Pts have platinum sensitive disease (at least stable disease on platinum doublet) and progressed on most recent line of systemic therapy, a Zubrod performance status of 0-1, adequate organ function, and not have been previously exposed to a PARP inhibitor and not be on systemic therapy within 21 days of registration. A 2-stage design with exact 93% power and 1-sided 0.07 level type I error required enrollment of 40 patients in the PAP in order to rule out an ORR of 15% or less if the true ORR is 35% or greater. At least 3 or more responses were needed in the first 20 pts in order to proceed to full enrolment of 40 pts in the PAP. The total accrual goal was 60 FEP assuming 67% of patients would be in the PAP. Results: The study enrolled 51 patients of whom 47 are eligible and analyzable for response (FEP) with 24 in the PAP. In the FEP, median age 66.7 yrs; M/F 39/8 (83/17%); 85% White and 15% Black; 77% of the pts received at least 1 prior line of treatment for stage IV. The study was closed for futility with only one response in the PAP. In the PAP (n = 24, median age 68 yrs), ORR was 4% (95%CI: 0, 21) and DCR was 54% (95%CI: 33, 74); median PFS of 2.4 months (95%CI: 1.5-2.8) and median OS was 5.2 months (95%CI: 3.8-10, 7). There were five responders in the FEP with ORR of 11%; DCR of 53% and median DoR was 1.8 months (95% CI: 1.3, 4.2); median PFS was 2.5 months (95%CI: 1.6-3.0) and median OS was 5.7 months (95% CI: 4.5-8.7). The most frequent grade ≥3 adverse event in the FEP were: Anemia (14.9%), thrombocytopenia (12.8%); lymphopenia (8.5%) and nausea (6.4%). Conclusions: S1400G failed to show sufficient level of efficacy for talazoparib in a biomarker defined subset of squamous lung cancer with HRRD. There were no new safety signals and hematologic toxicities were the most frequent adverse events. Clinical trial information: NCT02154490.

S1206: A dose-finding study followed by a phase II randomized placebo-controlled trial of chemoradiotherapy (CRT) with or without veliparib in stage III non-small cell lung cancer (NSCLC)

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Background: Veliparib (V), a PARP inhibitor, may potentiate the antitumor effect of CRT in NSCLC. Methods: Eligibility included newly diagnosed unresectable stage III NSCLC. Patients were randomized to receive concurrent CRT with weekly carboplatin (AUC 2) and paclitaxel (45 mg/m2) with V at 120 mg or placebo (P) twice daily during CRT followed by 2 cycles (every 21 days) of consolidation carboplatin (AUC 6), paclitaxel (200 mg/m2) with V at 80 mg or P (per randomized arm) orally on days 1-7 of each cycle. Progression-free survival (PFS) was the primary endpoint. The accrual goal was 132 patients. Results: The dose-finding study results were previously presented (ASCO 2016;A8537). V 120 mg twice daily was the recommended phase II dose. A total of 31 eligible and evaluable patients were enrolled in the phase II randomized trial: 17 on V and 13 on P (1 patient in the V arm withdrew prior to starting any treatment, thus was not evaluable). The study was closed to accrual early due to the positive results from the PACIFIC trial that changed standard practice. Median follow-up among alive patients was 16 months. During CRT, the following grade (G) 3-4 adverse events (AE) were seen with V vs P: any G3 AE (6 vs 6), any G4 AE (2 vs 3), G3 pneumonitis (0 vs 1), G3 esophagitis (1 vs 1), G3 oral mucositis (1 vs 0), G3 anorexia (1 vs 1), G3 hyponatremia (0 vs 3), G3 anemia (1 vs 0), G3 neutropenia (3 vs 1), G3 thrombocytopenia (1 vs 0), G4 hypoglycemia (0 vs 1). Also, 2 patients per arm had G4 lymphopenia. During consolidation (11 evaluable patients with V; 10 with P), G3 anemia (1 vs 0), G3 anorexia (1 vs 0), G3 weight loss (0 vs 1), G3 dehydration (1 vs 0), G3 dysphagia (2 vs 0), G3 fatigue (1 vs 0), G3 hypomagnesemia (0 vs 1), G3 nausea (1 vs 0), G4 hyperglycemia (0 vs 1), G3-4 neutropenia (3 vs 0), G3 thrombocytopenia (1 vs 0), G3-4 lymphopenia (2 vs 1); a G5 pneumonitis occurred in the P arm. Response rates were 56% (95% CI, 31-78%) and 69% (95% CI, 38-91%) on the V and P arms, respectively. PFS at 1 year was 47% (95% CI, 23% - 68%) with V and 46% (95% CI, 19% - 70%) with P. Overall survival (OS) at 1 year was 89% (95% CI, 61%-97%) with V and 54% (95% CI, 25%-76%) with P. Adding the 6 patients treated at 120 mg in the phase I part, 1-year with V was 91% (95% CI, 69%-98%). Conclusions: V in combination with CRT was tolerable with expected toxicities that relate to the backbone regimen. In the small number of randomized patients there was a suggestion of promising survival with V that may provide rationale for future trials of PARP inhibitors with CRT. Clinical trial information: NCT01386385.

Phase 1 study of AMG 119, a chimeric antigen receptor (CAR) T cell therapy targeting DLL3, in patients with relapsed/refractory small cell lung cancer (SCLC)

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Background: SCLC is an aggressive neuroendocrine tumor, with initial sensitivity to chemotherapy and radiotherapy often followed by chemoresistant disease progression. Notch signaling is a key regulator of neuroendocrine differentiation in SCLC, and delta-like ligand 3 (DLL3) is an inhibitory ligand of Notch receptors. DLL3 is expressed in most SCLC tumors but minimally expressed in normal tissues, suggesting that it may be a promising target for cancer immunotherapy. AMG 119 is an adoptive cellular therapy that consists of a patient’s autologous T cells that have been genetically modified ex vivo to express a transmembrane CAR that targets DLL3 and redirects cytotoxic T cell specificity to DLL3-positive cells. AMG 119 CAR T cells show potent killing of SCLC cells expressing DLL3 in vitro and inhibit tumor growth in an SCLC xenograft model in vivo. Methods: This phase 1 study will evaluate the safety and tolerability of AMG 119 administered as a single infusion in adult patients with relapsed/refractory SCLC who have progressed after at least 1 platinum-based chemotherapy regimen. The primary objectives are to evaluate safety and tolerability and determine the maximum tolerated cell dose (MTCD) or recommended phase 2 cell dose (RP2CD). Secondary objectives are to evaluate preliminary evidence of antitumor activity, expansion and persistence of AMG 119, and trafficking of AMG 119 to the tumor in post-treatment biopsy. Key inclusion criteria include histologically confirmed SCLC with radiographically documented disease progression or recurrence after at least 1 platinum-based regimen, ECOG performance status 0–1, at least 2 measurable lesions per modified RECIST 1.1, no untreated or symptomatic brain metastases, and adequate organ function. In the cell dose exploration phase, 3–4 patients will receive a single IV infusion of AMG 119 at each cell dose. Cell dose escalation/de-escalation decisions will be guided by a modified toxicity probability interval design. The dose expansion phase will seek to confirm the MTCD or RP2CD and obtain further safety and efficacy data. Clinical trial information: NCT03392064.

Molecular subtypes of small cell lung cancer: a synthesis of human and mouse model data

Small cell lung cancer (SCLC) is an exceptionally lethal malignancy for which more effective therapies are urgently needed. Several lines of evidence, from SCLC primary human tumours, patient-derived xenografts, cancer cell lines and genetically engineered mouse models, appear to be converging on a new model of SCLC subtypes defined by differential expression of four key transcription regulators: achaete-scute homologue 1 (ASCL1; also known as ASH1), neurogenic differentiation factor 1 (NeuroD1), yes-associated protein 1 (YAP1) and POU class 2 homeobox 3 (POU2F3). In this Perspectives article, we review and synthesize these recent lines of evidence and propose a working nomenclature for SCLC subtypes defined by relative expression of these four factors. Defining the unique therapeutic vulnerabilities of these subtypes of SCLC should help to focus and accelerate therapeutic research, leading to rationally targeted approaches that may ultimately improve clinical outcomes for patients with this disease.

CD38-Mediated Immunosuppression as a Mechanism of Tumor Cell Escape from PD-1/PD-L1 Blockade

Although treatment with immune checkpoint inhibitors provides promising benefit for patients with cancer, optimal use is encumbered by high resistance rates and requires a thorough understanding of resistance mechanisms. We observed that tumors treated with PD-1/PD-L1 blocking antibodies develop resistance through the upregulation of CD38, which is induced by all-trans retinoic acid and IFNβ in the tumor microenvironment. In vitro and in vivo studies demonstrate that CD38 inhibits CD8⁺ T-cell function via adenosine receptor signaling and that CD38 or adenosine receptor blockade are effective strategies to overcome the resistance. Large data sets of human tumors reveal expression of CD38 in a subset of tumors with high levels of basal or treatment-induced T-cell infiltration, where immune checkpoint therapies are thought to be most effective. These findings provide a novel mechanism of acquired resistance to immune checkpoint therapy and an opportunity to expand their efficacy in cancer treatment.Significance: CD38 is a major mechanism of acquired resistance to PD-1/PD-L1 blockade, causing CD8⁺ T-cell suppression. Coinhibition of CD38 and PD-L1 improves antitumor immune response. Biomarker assessment in patient cohorts suggests that a combination strategy is applicable to a large percentage of patients in whom PD-1/PD-L1 blockade is currently indicated. Cancer Discov; 8(9); 1156-75. ©2018 AACR.See related commentary by Mittal et al., p. 1066This article is highlighted in the In This Issue feature, p. 1047.

Abstract 2822: ATR inhibitors are active as single agents and in combination with PARP1 and ATM inhibitors in molecularly distinct subsets of small cell lung cancer models

Small cell lung cancer (SCLC) is an aggressive form of lung cancer, notable for rapid emergence of drug resistance following initial chemotherapy. Rates of five-year overall survival are only 7% across all stages and only one drug, topotecan, is approved by the FDA for recurrent SCLC. As a result, the National Cancer Institute has named identifying novel vulnerabilities in SCLC as an urgent area of need. Increased expression, relative to non-small cell lung cancer (NSCLC), of numerous components of the DNA damage response (DDR) pathway, including poly (ADP-Ribose) polymerase 1 (PARP1) and ataxia telangiectasia mutated (ATM), is observed in SCLC. Thus, targeting DDR has emerged as an attractive therapeutic strategy in SCLC, bolstered by recent data demonstrating activity of PARP1 inhibitors (PARPi) in SCLC patients. Interestingly, data suggest that PARPi resistant models from other tumors may rely on another DDR component, ataxia telangiectasia and Rad3 related protein (ATR), for survival. ATR/ATR is also highly expressed in SCLC compared to NSCLC and normal lung tissue. Preclinical data have shown that treatment with ATR inhibitors (ATRi) is especially effective in p53- and ATM-deficient tumor models, a notable fact given that SCLC is universally p53-mutant and that ATM-mutant and ATM-deficient SCLC is a small, but significant proportion of all SCLC. We treated 22 human-derived SCLC cell line models with two clinically relevant ATRi, VX-970 (formerly VE-822) and AZD-6738, and observed single agent activity of both ATR inhibitors in a significant number of cell lines, with half-maximal inhibitory concentrations (IC50s) as low as 30 nM and &gt;100-fold difference in IC50s between the most and least sensitive cell lines. Utilizing extensive genomic, transcriptomic and proteomic characterization of these cell lines, we then identified predictive biomarkers of response to ATRi in SCLC, including low ATM expression. As low ATM was associated with ATRi sensitivity, we tested whether the addition of an ATM inhibitor (AZD-0156) may further sensitize SCLC models to ATRi. We treated 12 SCLC cell lines with AZD-6738 and AZD-0156 in combination and identified a subset of lines in which synergy is observed between the two agents. Similarly, as targeting ATR has been shown to overcome PARPi resistance in other cancer types, we treated 12 SCLC cell lines with the ATRi AZD-6738 and the PARPi olaparib in combination and again observed a subset of lines in which the two agents acted synergistically. Interestingly, the lines in which ATRi+ATMi and ATRi+PARPi synergy is observed are distinct and include lines that were the most resistant to single-agent AZD-6738. Together, these data support further investigation of ATRi in SCLC and suggest that via the use of ATRi alone or in combination with ATMi or PARPi, multiple molecularly distinct subsets of SCLC can be effectively targeted.

Citation Format: Carl M. Gay, Pan Tong, Lerong Li, C. Allison Stewart, Triparna Sen, Bonnie S. Glisson, John V. Heymach, Jing Wang, Lauren Averett Byers. ATR inhibitors are active as single agents and in combination with PARP1 and ATM inhibitors in molecularly distinct subsets of small cell lung cancer models [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 2822.

Randomized, Double-Blind, Phase II Study of Temozolomide in Combination With Either Veliparib or Placebo in Patients With Relapsed-Sensitive or Refractory Small-Cell Lung Cancer

Purpose Both temozolomide (TMZ) and poly (ADP-ribose) polymerase (PARP) inhibitors are active in small-cell lung cancer (SCLC). This phase II, randomized, double-blind study evaluated whether addition of the PARP inhibitor veliparib to TMZ improves 4-month progression-free survival (PFS). Patients and Methods A total of 104 patients with recurrent SCLC were randomly assigned 1:1 to oral veliparib or placebo 40 mg twice daily, days 1 to 7, and oral TMZ 150 to 200 mg/m²/day, days 1 to 5, of a 28-day cycle until disease progression, unacceptable toxicity, or withdrawal of consent. Response was determined by imaging at weeks 4 and 8, and every 8 weeks thereafter. Improvement in PFS at 4 months was the primary end point. Secondary objectives included overall response rate (ORR), overall survival (OS), and safety and tolerability of veliparib with TMZ. Exploratory objectives included PARP-1 and SLFN11 immunohistochemical expression, MGMT promoter methylation, and circulating tumor cell quantification. Results No significant difference in 4-month PFS was noted between TMZ/veliparib (36%) and TMZ/placebo (27%; P = .19); median OS was also not improved significantly with TMZ/veliparib (8.2 months; 95% CI, 6.4 to 12.2 months; v 7.0 months; 95% CI, 5.3 to 9.5 months; P = .50). However, ORR was significantly higher in patients receiving TMZ/veliparib compared with TMZ/placebo (39% v 14%; P = .016). Grade 3/4 thrombocytopenia and neutropenia more commonly occurred with TMZ/veliparib: 50% versus 9% and 31% versus 7%, respectively. Significantly prolonged PFS (5.7 v 3.6 months; P = .009) and OS (12.2 v 7.5 months; P = .014) were observed in patients with SLFN11-positive tumors treated with TMZ/veliparib. Conclusion Four-month PFS and median OS did not differ between the two arms, whereas a significant improvement in ORR was observed with TMZ/veliparib. SLFN11 expression was associated with improved PFS and OS in patients receiving TMZ/veliparib, suggesting a promising biomarker of PARP-inhibitor sensitivity in SCLC.

Poly ADP-ribose polymerase-1 as a potential therapeutic target in Merkel cell carcinoma

BACKGROUND

Patients with metastatic Merkel cell carcinoma are treated similarly to small cell lung cancer (SCLC). Poly ADP-ribose polymerase-1 (PARP1) is overexpressed in SCLC and response to PARP inhibitors have been reported in patients with SCLC. Our study explores PARP as a therapeutic target in Merkel cell carcinoma.

METHODS

We evaluated PARP1 expression and Merkel cell polyomavirus (MCPyV) in 19 patients with Merkel cell carcinoma. Target exome-sequencing was performed in 14 samples. Sensitivity to olaparib was tested in 4 Merkel cell carcinoma cell lines.

RESULTS

Most Merkel cell carcinomas (74%) express PARP1 at high levels. Mutations in DNA-damage repair genes were identified in 9 samples (64%), occurred exclusively in head neck primaries, and correlated with TP53/RB1 mutations. The TP53/RB1 mutations were more frequent in MCPyV-negative tumors. Sensitivity to olaparib was seen in the Merkel cell carcinoma line with highest PARP1 expression.

CONCLUSION

Based on PARP1 overexpression, DNA-damage repair gene mutations, platinum sensitivity, and activity of olaparib in a Merkel cell carcinoma line, clinical trials with PARP inhibitors are warranted in Merkel cell carcinoma.

Integrative proteomic and transcriptomic analysis provides evidence for TrkB (NTRK2) as a therapeutic target in combination with tyrosine kinase inhibitors for non-small cell lung cancer

While several molecular targets have been identified for adenocarcinoma (ACA) of the lung, similar drivers with squamous cell carcinoma (SCC) are sparse. We compared signaling pathways and potential therapeutic targets in lung SCC and ACA tumors using reverse phase proteomic arrays (RPPA) from two independent cohorts of resected early stage NSCLC patients: a testing set using an MDACC cohort (N=140) and a validation set using the Cancer Genome Atlas (TCGA) cohorts. We identified multiple potentially targetable proteins upregulated in SCC, including NRF2, Keap1, PARP, TrkB, and Chk2. Of these potential targets, we found that TrkB also had significant increases in gene expression in SCC as compared to adenocarcinoma. Thus, we next validated the upregulation of TrkB both in vitro and in vivo and found that it was constitutively expressed at high levels in a subset of SCC cell lines. Furthermore, we found that TrkB inhibition suppressed tumor growth, invasiveness and sensitized SCC cells to tyrosine kinase EGFR inhibition in a cell-specific manner.

Dynamic variations in epithelial-to-mesenchymal transition (EMT), ATM, and SLFN11 govern response to PARP inhibitors and cisplatin in small cell lung cancer

Small cell lung cancer (SCLC) is one of the most aggressive forms of cancer, with a 5-year survival <7%. A major barrier to progress is the absence of predictive biomarkers for chemotherapy and novel targeted agents such as PARP inhibitors. Using a high-throughput, integrated proteomic, transcriptomic, and genomic analysis of SCLC patient-derived xenografts (PDXs) and profiled cell lines, we identified biomarkers of drug sensitivity and determined their prevalence in patient tumors. In contrast to breast and ovarian cancer, PARP inhibitor response was not associated with mutations in homologous recombination (HR) genes (e.g., BRCA1/2) or HRD scores. Instead, we found several proteomic markers that predicted PDX response, including high levels of SLFN11 and E-cadherin and low ATM. SLFN11 and E-cadherin were also significantly associated with in vitro sensitivity to cisplatin and topoisomerase1/2 inhibitors (all commonly used in SCLC). Treatment with cisplatin or PARP inhibitors downregulated SLFN11 and E-cadherin, possibly explaining the rapid development of therapeutic resistance in SCLC. Supporting their functional role, silencing SLFN11 reduced in vitro sensitivity and drug-induced DNA damage; whereas ATM knockdown or pharmacologic inhibition enhanced sensitivity. Notably, SCLC with mesenchymal phenotypes (i.e., loss of E-cadherin and high epithelial-to-mesenchymal transition (EMT) signature scores) displayed striking alterations in expression of miR200 family and key SCLC genes (e.g., NEUROD1, ASCL1, ALDH1A1, MYCL1). Thus, SLFN11, EMT, and ATM mediate therapeutic response in SCLC and warrant further clinical investigation as predictive biomarkers.

Targeting DNA damage repair in small cell lung cancer and the biomarker landscape

Small cell lung cancer (SCLC) is an aggressive malignancy that accounts for 14% of all lung cancer diagnoses. Despite decades of active research, treatment options for SCLC are limited and resistance to the few Food and Drug Administration (FDA) approved therapies develops rapidly. With no approved targeted agents to date, new therapeutic strategies are desperately needed. SCLC is characterized by high mutation burden, ubiquitous loss of TP53 and RB1, mutually exclusive amplification of MYC family members, thereby, high genomic instability. Studies in the past few years have demonstrated the potential of targeting the DNA damage response (DDR) pathway as a promising therapeutic strategy for SCLC. Inhibitors targeting DDR proteins have shown promise in preclinical models, and are under clinical investigation as single agents and in combination with cytotoxic therapies. Recent efforts to expand the therapeutic arsenal toward SCLC have focused in part on immune checkpoint inhibitors, such as agents targeting the receptor-ligand pair programmed cell death protein 1 (PD-1) and programmed death-ligand 1 (PD-L1). Clinical trials have confirmed activity of these agents in extensive stage (ES)-SCLC. However, while several patients had dramatic responses, overall response rates to immune checkpoint blockade (ICB) remain poor. As a result, there is an urgent need to develop rational combination therapies to enhance response rates to immunotherapy in SCLC. Identification of predictive biomarkers for patient stratification, identifying effective combinations to overcome adaptive resistance to DDR-targeted therapies and identifying strategies to enhance response to immunotherapy are areas of active investigation in SCLC.

A phase 2, open-label, multi-center study of amuvatinib in combination with platinum etoposide chemotherapy in platinum-refractory small cell lung cancer patients

Background

Amuvatinib (MP-470) is a multi-targeted kinase inhibitor with potent activity against c-Kit, synergistic with DNA-damaging agents. We evaluated amuvatinib in combination with platinum-etoposide (EP) chemotherapy by objective response rate, survival, and tolerability in platinum-refractory small cell lung cancer (SCLC) patients.

Methods

This study used a Simon 2-stage design requiring ≥3 centrally confirmed responses in the first 21 subjects. Subjects received EP with 300 mg amuvatinib orally three times daily in cycles of 21 days. A three-day amuvatinib run-in period before EP occurred in Cycle 1. Subjects received the same EP chemotherapy regimen given prior to progression/relapse.

Results

Among 23 subjects treated, we observed four PRs (17.4%) per RECIST 1.1, only two of which were centrally confirmed (8.7%, response duration 119, 151 days). Three subjects (13%) had confirmed stable disease. c-Kit H-score was ≥100 in two subjects whose respective durations of disease control were 151 and 256 days.

Conclusions

The addition of amuvatinib to EP chemotherapy in unselected, platinum-refractory SCLC did not meet the primary endpoint of ≥3 confirmed responses in stage 1. However, high c-Kit expression in two subjects with durable disease control suggests the potential for further study of amuvatinib in SCLC patients with high c-Kit expression.

Targeting AXL and mTOR Pathway Overcomes Primary and Acquired Resistance to WEE1 Inhibition in Small-Cell Lung Cancer

Purpose: Drugs targeting DNA repair and cell-cycle checkpoints have emerged as promising therapies for small-cell lung cancer (SCLC). Among these, the WEE1 inhibitor AZD1775 has shown clinical activity in a subset of SCLC patients, but resistance is common. Understanding primary and acquired resistance mechanisms will be critical for developing effective WEE1 inhibitor combinations.Experimental Design: AZD1775 sensitivity in SCLC cell lines was correlated with baseline expression level of 200 total or phosphorylated proteins measured by reverse-phase protein array (RPPA) to identify predictive markers of primary resistance. We further established AZD1775 acquired resistance models to identify mechanism of acquired resistance. Combination regimens were tested to overcome primary and acquired resistance to AZD1775 in in vitro and in vivo SCLC models.Results: High-throughput proteomic profiling demonstrate that SCLC models with primary resistance to AZD1775 express high levels of AXL and phosphorylated S6 and that WEE1/AXL or WEE1/mTOR inhibitor combinations overcome resistance in vitro and in vivo Furthermore, AXL, independently and via mTOR, activates the ERK pathway, leading to recruitment and activation of another G2-checkpoint protein, CHK1. AZD1775 acquired resistance models demonstrated upregulation of AXL, pS6, and MET, and resistance was overcome with the addition of AXL (TP0903), dual-AXL/MET (cabozantinib), or mTOR (RAD001) inhibitors.Conclusions: AXL promotes resistance to WEE1 inhibition via downstream mTOR signaling and resulting activation of a parallel DNA damage repair pathway, CHK1. These findings suggest rational combinations to enhance the clinical efficacy of AZD1775, which is currently in clinical trials for SCLC and other malignancies. Clin Cancer Res; 23(20); 6239-53. ©2017 AACR.

Phase 1/2 study of veliparib (V) combined with carboplatin (Cb) and etoposide (E) in patients (pts) with extensive-stage disease (ED) small cell lung cancer (SCLC) and other solid tumors: Phase 1 results

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Background: The majority of SCLC cases are diagnosed as ED, for which there is a poor prognosis and no curative treatment (Tx). V, a potent PARP inhibitor, has been shown in preclinical studies to enhance the antitumor activity of platinum-based agents and E against SCLC. The presented phase 1 dose-escalation (NCT02289690) evaluated V combined with Cb/E. Methods: Pts (≥18 years) with ED SCLC or other advanced/metastatic solid tumors with ≤1 line of prior cytotoxic therapy and ECOG performance score 0/1 were included. This study followed a 3+3 design. V starting dose and schedule were 80 mg BID PO administered on days (D) –2 to 5 in combination with Cb AUC 5 mg/mL•min administered on D 1 and E 100 mg/m2 administered on D 1 to 3 via intravenous infusion in 21-D cycles. V schedules of D –2 to 12 and continuous dosing were also explored. Primary objectives were to establish the maximum tolerated dose (MTD) and recommended phase 2 dose (RP2D) for V combined with Cb/E, and to evaluate the pharmacokinetic (PK) interaction between V and E. Results: Thirty-nine pts (n = 24 ED SCLC; n = 15 other solid tumors) with median age of 62 years (range 43–79) received study Tx. Most common adverse events (AEs; ≥40%) were nausea (54%), fatigue (51%), alopecia (46%), and anemia (44%); grade 3/4 AEs (≥30%) were decreased neutrophil count, neutropenia (31% each), and anemia (26%). Dose-limiting toxicity occurred in 1 pt (n = 1 grade 3 fatigue) at V 240 mg BID D –2 to 5. The MTD was not reached; RP2D for V was set at 240 mg BID on D –2 to 12 based on long-term tolerability. Continuous dosing of V 240 mg BID with Cb/E resulted in unacceptable Cb/E dose delays due to hematologic toxicity. Coadministration of V (80 to 240 mg BID) with Cb/E exhibited dose-proportional kinetics with no impact on the E PK. Confirmed responses: ED SCLC 63% (15/24 pts) across all dose levels and in 83% (5/6) at RP2D; other tumor types: 13% (2/15) across all dose levels. Conclusions: V + Cb/E had an acceptable safety profile in pts with ED SCLC, with an RP2D of 240 mg BID D –2 to 12. Coadministration of V with Cb/E had no effect on E PK. Responses were seen across all dose levels. A phase 2 study of V with Cb/E in ED SCLC is ongoing. Clinical trial information: NCT02289690.

Response of germline and somatic smoothened (SMO) mutations in non-small cell lung cancer (NSCLC) to hedgehog inhibitor vismodegib

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Background: Smoothened (SMO) gene somatic mutations activate hedgehog signaling in basal cell cancers (BCC) and medulloblastomas but have not been reported in NSCLC. We detected somatic and germline SMOmutations in NSCLC patients (A-C) and sought to characterize the mutations further. Methods: We performed tumor/blood germline sequencing of SMO mutations, familial germline mutation testing (saliva specimens), somatic mutation analysis of TCGA lung carcinoma datasets, and germline mutation analysis of the TCGA and 3 additional large cohorts (n = 1933). To evaluate the functional significance of SMOP641A, HCC4011 lung cancer cells were transfected with a wild-type SMO or SMOP641A expression vector and a predictive model was created. Results: NSCLC SMOP641A in vitro activated the hedgehog pathway, and vismodegib/cyclopamine inhibited tumor cell growth. Structural modeling suggests that SMO P641A induces conformational changes and disrupts PTCH-SMO interaction leading to constitutive activation. In the NSCLC TCGA databases, somatic SMO mutations occur 1.7%. In the overall TCGA database, germline SMO P641A occurred in 0.11% of cancer patients (multiple cancers) compared with 0% in cancer-free individuals. Patient A (never-smoking SCC) had a 46% RECIST reduction within 6 weeks for 6 months on vismodegib. His 3-generation family pedigree identified germline SMOP641A in one daughter (who developed BCC early). Two additional NSCLC patients (B – germline P641A and C –M525L received vismodegib; B initially stabilized but stopped vismodegib after 14 weeks for toxicity while patient C had no response. Conclusions: SMO mutations are targetable, potentially heritable, oncogenic drivers in NSCLC and other cancers. Tumor genetic profiling should consider including SMO gene, especially in never-smoking lung SCC patients. Additional studies are needed to define the role of germline/somatic SMO alterations in promoting carcinogenesis, interactions with P53 alterations, and the responsiveness of different SMO mutations to hedgehog inhibitors. Currently, the ongoing ECOG-ACRIN MATCH study (NCT02465060) treats SMO/PTCH mutated patients with vismodegib.

CHK1 Inhibition in Small-Cell Lung Cancer Produces Single-Agent Activity in Biomarker-Defined Disease Subsets and Combination Activity with Cisplatin or Olaparib

Effective targeted therapies for small-cell lung cancer (SCLC), the most aggressive form of lung cancer, remain urgently needed. Here we report evidence of preclinical efficacy evoked by targeting the overexpressed cell-cycle checkpoint kinase CHK1 in SCLC. Our studies employed RNAi-mediated attenuation or pharmacologic blockade with the novel second-generation CHK1 inhibitor prexasertib (LY2606368), currently in clinical trials. In SCLC models in vitro and in vivo, LY2606368 exhibited strong single-agent efficacy, augmented the effects of cisplatin or the PARP inhibitor olaparib, and improved the response of platinum-resistant models. Proteomic analysis identified CHK1 and MYC as top predictive biomarkers of LY2606368 sensitivity, suggesting that CHK1 inhibition may be especially effective in SCLC with MYC amplification or MYC protein overexpression. Our findings provide a preclinical proof of concept supporting the initiation of a clinical efficacy trial in patients with platinum-sensitive or platinum-resistant relapsed SCLC. Cancer Res; 77(14); 3870-84. ©2017 AACR.

CD38 as a novel immune checkpoint and a mechanism of resistance to the blockade of the PD-1/PD-L1 axis

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Background: Although immune checkpoint inhibitors including PD-L1 blockade provide significant clinical benefit for patients with lung cancer, barriers to immunotherapy clinical successes have been due to a high rate of resistance. The therapeutic improvement requires a thorough understanding of the biological process of resistance. Until recently, there have been only a few studies reporting the mechanisms of resistance to PD-L1 blockade. The mechanistic basis remains poorly defined. Methods: In multiple immunocompetent syngeneic and K-rasLA1/+p53R172H?g/+ spontaneous animal models of lung cancer, we have explored the resistance mechanisms using pharmacological and genetic approaches (monoclonal antibody treatment and CRISPR/Cas9-mediated editing). The molecular and immune profiles of the tumor microenvironment were evaluated. More importantly, to determine the applicability to patients with lung cancer, we analyzed 259 patients’ specimens with IHC staining and mined many immune markers in TCGA adeno and squamous datasets. Results: We identified the up-regulation of CD38 on tumor cells as well as enrichment of CD38highTregs and CD38highMDSCs in tumor as the markers of treatment resistance. We observed the same resistance mechanism caused by CD38 in PD-L1 KO mice bearing PD-L1 KO Lewis lung tumors edited with the CRISPR/Cas9 system. Furthermore, by manipulating CD38 on a panel of lung cancer cell lines, in vitro and in vivo data demonstrates that CD38 inhibits CD8+ T cell proliferation, antitumor cytokine secretion, and tumor cell killing capability. To test whether CD38 blockade might be therapeutically efficacious to anti-PD-L1 resistance, we applied the combination therapy of anti-CD38 and anti-PD-L1 and demonstrated dramatic therapeutic benefit on primary tumor growth and metastasis. Additionally, in 259 lung patients, 18.5% of cases exhibited positive staining for CD38 on tumor cells, showing a great potential benefit for treating lung patients. Conclusions: CD38 is defined as a novel immune checkpoint and acts as a mechanism of resistance in the context of PD-L1 therapy. Targeting this novel immune checkpoint may broaden the benefit of PD-L1/PD-1 axis blockade for lung cancer treatment.

Phase I, Dose-Escalation, Two-Part Trial of the PARP Inhibitor Talazoparib in Patients with Advanced Germline BRCA1/2 Mutations and Selected Sporadic Cancers

Talazoparib inhibits PARP catalytic activity, trapping PARP1 on damaged DNA and causing cell death in BRCA1/2-mutated cells. We evaluated talazoparib therapy in this two-part, phase I, first-in-human trial. Antitumor activity, MTD, pharmacokinetics, and pharmacodynamics of once-daily talazoparib were determined in an open-label, multicenter, dose-escalation study (NCT01286987). The MTD was 1.0 mg/day, with an elimination half-life of 50 hours. Treatment-related adverse events included fatigue (26/71 patients; 37%) and anemia (25/71 patients; 35%). Grade 3 to 4 adverse events included anemia (17/71 patients; 24%) and thrombocytopenia (13/71 patients; 18%). Sustained PARP inhibition was observed at doses ≥0.60 mg/day. At 1.0 mg/day, confirmed responses were observed in 7 of 14 (50%) and 5 of 12 (42%) patients with BRCA mutation-associated breast and ovarian cancers, respectively, and in patients with pancreatic and small cell lung cancer. Talazoparib demonstrated single-agent antitumor activity and was well tolerated in patients at the recommended dose of 1.0 mg/day.Significance: In this clinical trial, we show that talazoparib has single-agent antitumor activity and a tolerable safety profile. At its recommended phase II dose of 1.0 mg/day, confirmed responses were observed in patients with BRCA mutation-associated breast and ovarian cancers and in patients with pancreatic and small cell lung cancer. Cancer Discov; 7(6); 620-9. ©2017 AACR.This article is highlighted in the In This Issue feature, p. 539.

Giving AXL the axe: targeting AXL in human malignancy

The receptor tyrosine kinase AXL, activated by a complex interaction between its ligand growth arrest-specific protein 6 and phosphatidylserine, regulates various vital cellular processes, including proliferation, survival, motility, and immunologic response. Although not implicated as an oncogenic driver itself, AXL, a member of the TYRO3, AXL, and MERTK family of receptor tyrosine kinases, is overexpressed in several haematologic and solid malignancies, including acute myeloid leukaemia, non-small cell lung cancer, gastric and colorectal adenocarcinomas, and breast and prostate cancers. In the context of malignancy, evidence suggests that AXL overexpression drives wide-ranging processes, including epithelial to mesenchymal transition, tumour angiogenesis, resistance to chemotherapeutic and targeted agents, and decreased antitumor immune response. As a result, AXL is an attractive candidate not only as a prognostic biomarker in malignancy but also as a target for anticancer therapies. Several AXL inhibitors are currently in preclinical and clinical development. This article reviews the structure, regulation, and function of AXL; the role of AXL in the tumour microenvironment; the development of AXL as a therapeutic target; and areas of ongoing and future investigation.