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)

TPS8576

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 >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.

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.

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

9062

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.