A DLL3-targeted antibody-drug conjugate eradicates high-grade pulmonary neuroendocrine tumor-initiating cells in vivo

Unbiased Proteomic Profiling Uncovers a Targetable GNAS/PKA/PP2A Axis in Small Cell Lung Cancer Stem Cells

Using unbiased kinase profiling, we identified protein kinase A (PKA) as an active kinase in small cell lung cancer (SCLC). Inhibition of PKA activity genetically, or pharmacologically by activation of the PP2A phosphatase, suppresses SCLC expansion in culture and in vivo. Conversely, GNAS (G-protein α subunit), a PKA activator that is genetically activated in a small subset of human SCLC, promotes SCLC development. Phosphoproteomic analyses identified many PKA substrates and mechanisms of action. In particular, PKA activity is required for the propagation of SCLC stem cells in transplantation studies. Broad proteomic analysis of recalcitrant cancers has the potential to uncover targetable signaling networks, such as the GNAS/PKA/PP2A axis in SCLC.

A Bispecific DLL3/CD3 IgG-Like T-Cell Engaging Antibody Induces Antitumor Responses in Small Cell Lung Cancer

PURPOSE

Small cell lung cancer (SCLC) is the most lethal and aggressive subtype of lung carcinoma characterized by highly chemotherapy-resistant recurrence in the majority of patients. To effectively treat SCLC, we have developed a unique and novel IgG-like T-cell engaging bispecific antibody (ITE) that potently redirects T-cells to specifically lyse SCLC cells expressing Delta-like ligand 3 (DLL3), an antigen that is frequently expressed on the cell surface of SCLC cells, with no to very little detectable expression in normal tissues.

EXPERIMENTAL DESIGN

The antitumor activity and mode of action of DLL3/CD3 ITE was evaluated in vitro using SCLC cell lines and primary human effector cells and in vivo in an SCLC xenograft model reconstituted with human CD3⁺ T-cells.

RESULTS

Selective binding of DLL3/CD3 ITE to DLL3-positive tumor cells and T-cells induces formation of an immunological synapse resulting in tumor cell lysis and activation of T-cells. In a human T-cell engrafted xenograft model, the DLL3/CD3 ITE leads to an increase in infiltration of T-cells into the tumor tissue resulting in apoptosis of the tumor cells and tumor regression. Consistent with the mode of action, the DLL3/CD3 ITE treatment led to upregulation of PD-1, PD-L1, and LAG-3.

CONCLUSIONS

This study highlights the ability of the DLL3/CD3 ITE to induce strictly DLL3-dependent T-cell redirected lysis of tumor cells and recruitment of T-cells into noninflamed tumor tissues leading to tumor regression in a preclinical in vivo model. These data support clinical testing of the DLL3/CD3 ITE in patients with SCLC.

Antibody-drug conjugates (ADCs) delivering pyrrolobenzodiazepine (PBD) dimers for cancer therapy

INTRODUCTION

The rationally designed pyrrolobenzodiazepine (PBD) dimers emerged around ten years ago as a new class of drug component for antibody-drug conjugates (ADC). They produce highly cytotoxic DNA cross-links, exploiting a completely different cellular target to the auristatin and maytansinoid tubulin inhibitor classes and a different mode of DNA damage to other DNA interacting warheads such as calicheamicin.

AREAS COVERED

The properties which make the PBD dimers suitable warheads for ADCs, and the development of the two main payload structures talirine and tesirine, are discussed. The clinical experience with the twenty PBD dimer-containing ADCs to enter the clinic is reviewed, with a focus on vadastuximab talirine and rovalpituzumab tesirine, both of which were discontinued following pivotal studies, and loncastuximab tesirine and camidanlumab tesirine which are progressing towards approval.

EXPERT OPINION

Reviewing the clinical efficacy and safety data from almost forty clinical trials of PBD dimer-containing ADCs highlights the complexities and challenges of ADC early clinical development. It enables some conclusions to be made about reasons for failure and suggests strategies to optimise the future clinical development of this promising class of ADCs in a rapidly expanding field.

ASCL1-regulated DARPP-32 and t-DARPP stimulate small cell lung cancer growth and neuroendocrine tumour cell proliferation

Background

Small cell lung cancer (SCLC) is the most aggressive form of lung cancer, and new molecular insights are necessary for prognostic and therapeutic advances.

Methods

Dopamine and cAMP-regulated phosphoprotein, Mr 32000 (DARPP-32) and its N-terminally truncated splice variant, t-DARPP, were stably overexpressed or ablated in human DMS-53 and H1048 SCLC cells. Functional assays and immunoblotting were used to assess how DARPP-32 isoforms regulate SCLC cell growth, proliferation, and apoptosis. DARPP-32-modulated SCLC cells were orthotopically injected into the lungs of SCID mice to evaluate how DARPP-32 and t-DARPP regulate neuroendocrine tumour growth. Immunostaining for DARPP-32 proteins was performed in SCLC patient-derived specimens. Bioinformatics analysis and subsequent transcription assays were used to determine the mechanistic basis of DARPP-32-regulated SCLC growth.

Results

We demonstrate in mice that DARPP-32 and t-DARPP promote SCLC growth through increased Akt/Erk-mediated proliferation and anti-apoptotic signalling. DARPP-32 isoforms are overexpressed in SCLC patient-derived tumour tissue, but undetectable in physiologically normal lung. Achaete-scute homologue 1 (ASCL1) transcriptionally activates DARPP-32 isoforms in human SCLC cells.

Conclusions

We reveal new regulatory mechanisms of SCLC oncogenesis that suggest DARPP-32 isoforms may represent a negative prognostic indicator for SCLC and serve as a potential target for the development of new therapies.

Influence of preanalytical variables on performance of delta-like protein 3 (DLL3) predictive immunohistochemistry

DLL3 might become a predictive immunohistochemical marker in small cell carcinoma of the lung (SCLC). We investigated the influence of pre-analytical handling of samples on the performance of DLL3 immunohistochemistry (IHC) using DLL3 SP347 ready to use assay (Ventana). DLL3 positive cell lines were subjected to different experimental conditions mimicking the pre-analytical variation in daily clinical practice. Formalin fixation of 24 h led to the most optimal results of DLL3 IHC. Longstanding fixation in Cytolyt, methanol-based fixative for cytology samples, but also decalcification using a mix of formic- and hydrochloracid resulted in decreased DLL3 staining. Postponed staining of blanc slides for 3 months also decreased DLL3 IHC. Postponed fixation of the SCLC cell lines did not influence the performance of DLL3 IHC, although this might be different in the tissues than in the cell lines. In conclusion, different pre-analytical variables decrease the performance of DLL3 IHC. These findings are essential for implementing novel predictive immunohistochemical biomarkers in daily pathology practice.

Mechanisms of drugs-resistance in small cell lung cancer: DNA-related, RNA-related, apoptosis-related, drug accumulation and metabolism procedure

Small-cell lung cancer (SCLC), the highest malignant cancer amongst different types of lung cancer, has the feature of lower differentiation, rapid growth, and poor survival rate. Despite the dramatically initial sensitivity of SCLC to various types of treatment methods, including chemotherapy, radiotherapy and immunotherapy, the emergence of drugs-resistance is still a grandly clinical challenge. Therefore, in order to improve the prognosis and develop new therapeutic approaches, having a better understanding of the complex mechanisms of resistance in SCLC is of great clinical significance. This review summarized recent advances in understanding of multiple mechanisms which are involved in the resistance during SCLC treatment, including DNA-related process, RNA-related process, apoptosis-related mechanism, and the process of drug accumulation and metabolism.

Biomarkers for Pancreatic Neuroendocrine Neoplasms (PanNENs) Management-An Updated Review

Pancreatic neuroendocrine tumors (PanNENs) are rare sporadic cancers or develop as part of hereditary syndromes. PanNENs can be both functioning and non-functioning based on whether they produce bioactive peptides. Some PanNENs are well differentiated while others-poorly. Symptoms, thus, depend on both oncological and hormonal causes. PanNEN diagnosis and treatment benefit from and in some instances are guided by biomarker monitoring. However, plasmatic monoanalytes are only suggestive of PanNEN pathological status and their positivity is typically followed by deepen diagnostic analyses through imaging techniques. There is a strong need for new biomarkers and follow-up modalities aimed to improve the outcome of PanNEN patients. Liquid biopsy follow-up, i.e., sequential analysis on tumor biomarkers in body fluids offers a great potential, that need to be substantiated by additional studies focusing on the specific markers and the timing of the analyses. This review provides the most updated panorama on PanNEN biomarkers.

SC-002 in patients with relapsed or refractory small cell lung cancer and large cell neuroendocrine carcinoma: Phase 1 study

OBJECTIVES

This phase 1 study investigated safety/tolerability, pharmacokinetics, and preliminary efficacy of SC-002, a delta-like ligand 3-directed antibody-drug conjugate, in advanced small cell lung cancer and large cell neuroendocrine carcinoma.

MATERIALS AND METHODS

Eligible patients received SC-002 at 1 of 7 dose levels during the dose-escalation portion of the study.

RESULTS

Thirty-five enrolled patients received ≥1 dose of SC-002. Twenty-three (66%) patients experienced serious adverse events (AEs), 37% considered related to SC-002. Grade 3/4 AEs occurred in 21 (60%) and 2 (6%) patients; the most common were effusion and hypoalbuminemia. One grade 5 AE occurred in 1 patient. Five (14%) patients achieved a partial response and no patients achieved a complete response.

CONCLUSION

SC-002 treatment was associated with systemic toxicity and limited efficacy.

Targeted Therapies and Biomarkers in Small Cell Lung Cancer

Small cell lung cancer (SCLC) is an aggressive malignancy characterized by rapid growth, early metastasis, and acquired therapeutic resistance. A majority of patients with SCLC have extensive-stage (ES) disease, defined as the presence of metastatic disease outside the hemithorax at first diagnosis. SCLC has been considered “a graveyard for drug development,” with chemotherapy remaining the standard treatment for first- and second-line management until quite recently. In contrast to NSCLC, identifying therapeutic targets in SCLC has been challenging, partly because driver mutations are primarily loss of function, involving the tumor suppressor genes RB1 and TP53 or currently untargetable (e.g., amplification of MYC family members). Recent gene expression profiling of SCLC cells lines, patient samples and representative murine models, have led to a proposed delineation of four major subtypes for SCLC distinguished by differential expression of four key transcriptional regulators (ASCL1, NEUROD1, POU2F3, and YAP1). Our understanding of the biology of SCLC has indeed significantly improved recently due to the continued efforts of the dedicated investigators in this field, but the therapeutic options remain dismal. While recent results from immunotherapy trials are encouraging, most patients demonstrate either primary or rapid acquired resistance to current regimens, highlighting the clear need to improve the effectiveness and expand the scope of current therapeutic strategies. In this opinion article, we will discuss recent developments in the treatment of SCLC, focused on current understanding of the signaling pathways, the role of immunotherapy and targeted therapy, and emerging biomarkers of response to therapy in SCLC.

Delta-Like Protein 3 Expression and Targeting in Merkel Cell Carcinoma

PURPOSE

Delta-like protein 3 (DLL3) is being developed as a predictive biomarker for DLL3-targeting antibody-drug conjugate and other therapies. Given the neuroendocrine features of Merkel cell carcinoma (MCC), we sought to evaluate DLL3 expression and its role in MCC.

EXPERIMENTAL DESIGN

Formalin-fixed and paraffin-embedded MCC cases were consecutively selected. Immunohistochemistry was performed for DLL3 (SC16.65 antibody) and polyomavirus large T-antigen (sc-136172 antibody). Slides were read out for percentage of positive tumor cells. Cox proportional hazards model was applied to assess the association between DLL3 expression and overall survival (OS). A patient with a DLL3-expressing MCC was treated with rovalpituzumab tesirine (Rova-T) in the "other tumor" cohort of NCT02709889 and assessed for response.

RESULTS

The median H-score of DLL3 expression of 65 patients included was 60 (interquartile range, 30-100). Fifty-eight cases (89%) had ≥1% tumor cells positive for DLL3 expression with any intensity, of which the median DLL3 expression was 50% (interquartile range, 25%-70%). Thirty-four cases (52%) had ≥50% tumor cells positive for DLL3 expression with any intensity. Higher H-score of DLL3 expression was associated with higher polyomavirus nuclear expression (p = .003) when it was dichotomized to negative versus positive. H-score of DLL3 expression did not predict OS of patients with MCC (p = .4) after being adjusted for common clinicopathological factors. A patient treated with Rova-T for refractory metastatic MCC achieved partial response.

CONCLUSIONS

DLL3 overexpression is very common in MCC by immunohistochemistry. The response to treatment suggests that DLL3 expression may have predictive relevance for DLL3-targeting therapies in MCC.

IMPLICATIONS FOR PRACTICE

Delta-like protein 3 (DLL3) is being developed as a predictive biomarker to identify patients for treatment with DLL3-targeting agents. Merkel cell carcinoma (MCC) is an aggressive neuroendocrine carcinoma of the skin. It was found that DLL3 overexpression is very common in MCC by immunohistochemistry and significantly associated with Merkel cell polyomavirus expression. Despite the lack of prognostic significance in this cohort, DLL3 expression may have predictive relevance for DLL3-targeting therapies in MCC. The high levels of DLL3 expression in a subset of MCC may potentially be used to select patients to receive DLL3-targeting therapies.

The Role of DLLs in Cancer: A Novel Therapeutic Target

Delta-like ligands (DLLs) control Notch signaling. DLL1, DLL3 and DLL4 are frequently deregulated in cancer and influence tumor growth, the tumor vasculature and tumor immunity, which play different roles in cancer progression. DLLs have attracted intense research interest as anti-cancer therapeutics. In this review, we discuss the role of DLLs in cancer and summarize the emerging DLL-relevant targeting methods to aid future studies.

ImmunoPET: Concept, Design, and Applications

Immuno-positron emission tomography (immunoPET) is a paradigm-shifting molecular imaging modality combining the superior targeting specificity of monoclonal antibody (mAb) and the inherent sensitivity of PET technique. A variety of radionuclides and mAbs have been exploited to develop immunoPET probes, which has been driven by the development and optimization of radiochemistry and conjugation strategies. In addition, tumor-targeting vectors with a short circulation time (e.g., Nanobody) or with an enhanced binding affinity (e.g., bispecific antibody) are being used to design novel immunoPET probes. Accordingly, several immunoPET probes, such as 89Zr-Df-pertuzumab and 89Zr-atezolizumab, have been successfully translated for clinical use. By noninvasively and dynamically revealing the expression of heterogeneous tumor antigens, immunoPET imaging is gradually changing the theranostic landscape of several types of malignancies. ImmunoPET is the method of choice for imaging specific tumor markers, immune cells, immune checkpoints, and inflammatory processes. Furthermore, the integration of immunoPET imaging in antibody drug development is of substantial significance because it provides pivotal information regarding antibody targeting abilities and distribution profiles. Herein, we present the latest immunoPET imaging strategies and their preclinical and clinical applications. We also emphasize current conjugation strategies that can be leveraged to develop next-generation immunoPET probes. Lastly, we discuss practical considerations to tune the development and translation of immunoPET imaging strategies.

Breaking the Impasse: Advances in Treatment of Small Cell Lung Cancer

Small cell lung cancer (SCLC) is an aggressive malignancy and carries a poor prognosis with limited effective treatments in the advanced setting. SCLC is characterized by a high tumor mutation burden and alterations in Notch signaling and DNA damage repair pathways, providing rationale for the use of immunotherapy and targeted therapies. Immunotherapies have led to the most significant advances in treating SCLC in decades, and several promising targeted approaches have emerged from the increased understanding of the biology of SCLC. However, responses to these novel approaches are far from universal, and efforts to refine these therapies are ongoing.

New Approaches to SCLC Therapy: From the Laboratory to the Clinic

The outcomes of patients with SCLC have not yet been substantially impacted by the revolution in precision oncology, primarily owing to a paucity of genetic alterations in actionable driver oncogenes. Nevertheless, systemic therapies that include immunotherapy are beginning to show promise in the clinic. Although, these results are encouraging, many patients do not respond to, or rapidly recur after, current regimens, necessitating alternative or complementary therapeutic strategies. In this review, we discuss ongoing investigations into the pathobiology of this recalcitrant cancer and the therapeutic vulnerabilities that are exposed by the disease state. Included within this discussion, is a snapshot of the current biomarker and clinical trial landscapes for SCLC. Finally, we identify key knowledge gaps that should be addressed to advance the field in pursuit of reduced SCLC mortality. This review largely summarizes work presented at the Third Biennial International Association for the Study of Lung Cancer SCLC Meeting.

Dysregulated Pyrimidine Biosynthesis Contributes to 5-FU Resistance in SCLC Patient-Derived Organoids but Response to a Novel Polymeric Fluoropyrimidine, CF10

Chemo-immunotherapy is central to the treatment of small cell lung cancer (SCLC). Despite modest progress made with the addition of immunotherapy, current cytotoxic regimens display minimal survival benefit and new treatments are needed. Thymidylate synthase (TS) is a well-validated anti-cancer drug target, but conventional TS inhibitors display limited clinical efficacy in refractory or recurrent SCLC. We performed RNA-Seq analysis to identify gene expression changes in SCLC biopsy samples to provide mechanistic insight into the potential utility of targeting pyrimidine biosynthesis to treat SCLC. We identified systematic dysregulation of pyrimidine biosynthesis, including elevated TYMS expression that likely contributes to the lack of efficacy for current TS inhibitors in SCLC. We also identified E2F1-3 upregulation in SCLC as a potential driver of TYMS expression that may contribute to tumor aggressiveness. To test if TS inhibition could be a viable strategy for SCLC treatment, we developed patient-derived organoids (PDOs) from human SCLC biopsy samples and used these to evaluate both conventional fluoropyrimidine drugs (e.g., 5-fluorouracil), platinum-based drugs, and CF10, a novel fluoropyrimidine polymer with enhanced TS inhibition activity. PDOs were relatively resistant to 5-FU and while moderately sensitive to the front-line agent cisplatin, were relatively more sensitive to CF10. Our studies demonstrate dysregulated pyrimidine biosynthesis contributes to drug resistance in SCLC and indicate that a novel approach to target these pathways may improve outcomes.

Advances in Antibody–Drug Conjugate Design: Current Clinical Landscape and Future Innovations

The targeted delivery of potent cytotoxic molecules into cancer cells is considered a promising anticancer strategy. The design of clinically effective antibody–drug conjugates (ADCs), in which biologically active drugs are coupled through chemical linkers to monoclonal antibodies, has presented challenges for pharmaceutical researchers. After 30 years of intensive research and development activities, only seven ADCs have been approved for clinical use; two have received fast-track designation and two breakthrough therapy designation from the Food and Drug Administration. There is continued interest in the field, as documented by the growing number of candidates in clinical development. This review aims to summarize the most recent innovations that have been applied to the design of ADCs undergoing early- and late-stage clinical trials. Discovery and rational optimization of new payloads, chemical linkers, and antibody formats have improved the therapeutic index of next-generation ADCs, ultimately resulting in improved clinical benefit for the patients.

Lineage plasticity in cancer: a shared pathway of therapeutic resistance

Lineage plasticity, the ability of cells to transition from one committed developmental pathway to another, has been proposed as a source of intratumoural heterogeneity and of tumour adaptation to an adverse tumour microenvironment including exposure to targeted anticancer treatments. Tumour cell conversion into a different histological subtype has been associated with a loss of dependency on the original oncogenic driver, leading to therapeutic resistance. A well-known pathway of lineage plasticity in cancer - the histological transformation of adenocarcinomas to aggressive neuroendocrine derivatives - was initially described in lung cancers harbouring an EGFR mutation, and was subsequently reported in multiple other adenocarcinomas, including prostate cancer in the presence of antiandrogens. Squamous transformation is a subsequently identified and less well-characterized pathway of adenocarcinoma escape from suppressive anticancer therapy. The increased practice of tumour re-biopsy upon disease progression has increased the recognition of these mechanisms of resistance and has improved our understanding of the underlying biology. In this Review, we provide an overview of the impact of lineage plasticity on cancer progression and therapy resistance, with a focus on neuroendocrine transformation in lung and prostate tumours. We discuss the current understanding of the molecular drivers of this phenomenon, emerging management strategies and open questions in the field.

Pre-clinical models of small cell lung cancer and the validation of therapeutic targets

Introduction: Small-cell lung cancer (SCLC) is an aggressive form of lung cancer that has a dismal prognosis. One of the factors hindering therapeutic developments for SCLC is that most SCLC is not surgically resected resulting in a paucity of material for analysis. To address this, significant efforts have been made by investigators to develop pre-clinical models of SCLC allowing for downstream target identification in this difficult to treat cancer.Areas covered: In this review, we describe the current pre-clinical models that have been developed to interrogate SCLC, and outline the benefits and limitations associated with each. Using examples we show how each has been used to (i) improve our knowledge of this intractable cancer, and (ii) identify and validate potential therapeutic targets that (iii) are currently under development and testing within the clinic.Expert opinion: The large numbers of preclinical models that have been developed have dramatically improved the ways in which we can examine SCLC and test therapeutic targets/interventions. The newer models are rapidly providing novel avenues for the design and testing of new therapeutics. Despite this many of these models have inherent flaws that limit the possibility of their use for individualized therapy decision-making for SCLC.

Integrin αvβ6-specific therapy for pancreatic cancer developed from foot-and-mouth-disease virus

Goals of investigation: The 5-year survival rate for pancreatic ductal adenocarcinoma (PDAC) has remained at <5% for decades because no effective therapies have been identified. Integrin αvβ6 is overexpressed in most PDAC and represents a promising therapeutic target. Thus, we attempted to develop an αvβ6-specific peptide-drug conjugate (PDC) for therapy of PDAC. Methodology: We conjugated the DNA-binding pyrrolobenzodiazepine (PBD)-based payload SG3249 (tesirine) to an αvβ6-specific 20mer peptide from the VP1 coat protein of foot-and-mouth-disease virus (FMDV) (forming conjugate SG3299) or to a non-targeting peptide (forming conjugate SG3511). PDCs were tested for specificity and toxicity on αvβ6-negative versus-positive PDAC cells, patient-derived cell lines from tumor xenografts, and on two different in vivo models of PDAC. Immunohistochemical analyses were performed to establish therapeutic mechanism. Results: The αvβ6-targeted PDC SG3299 was significantly more toxic (up to 78-fold) for αvβ6-expressing versus αvβ6-negative PDAC cell lines in vitro, and achieved significantly higher toxicity at equal dose than the non-targeted PDC SG3511 (up to 15-fold better). Moreover, SG3299 eliminated established (100mm3) Capan-1 PDAC human xenografts, extending the lifespan of mice significantly (P=0.005). Immunohistochemistry revealed SG3299 induced DNA damage and apoptosis (increased γH2AX and cleaved caspase 3, respectively) associated with significant reductions in proliferation (Ki67), β6 expression and PDAC tumour growth. Conclusions: The FMDV-peptide drug conjugate SG3299 showed αvβ6-selectivity in vitro and in vivo and can specifically eliminate αvβ6-positive cancers, providing a promising new molecular- specific therapy for pancreatic cancer.

Near infrared photoimmunotherapy targeting DLL3 for small cell lung cancer

BACKGROUND

Small cell lung cancer (SCLC) has a poor prognosis, and its treatment options are limited. Delta-like protein 3 (DLL3) is expressed specifically in SCLC and is considered a promising therapeutic target for patients with this disease. Rovalpituzumab tesirine (Rova-T) was the first antibody-drug conjugate targeting DLL3. Although Rova-T development was unfortunately terminated, DLL3 remains an ideal target for SCLC. Near infrared photoimmunotherapy (NIR-PIT) is a new form of cancer treatment that employs an antibody-photosensitiser conjugate followed by NIR light exposure and damage target cells specifically. In this study, we demonstrate DLL3-targeted NIR-PIT to develop a novel molecularly targeted treatment for SCLC.

METHODS

The anti-DLL3 monoclonal antibody rovalpituzumab was conjugated to an IR700 photosensitiser (termed 'rova-IR700'). SCLC cells overexpressing DLL3 as well as non-DLL3-expressing controls were incubated with rova-IR700 and then exposed to NIR-light. Next, mice with SCLC xenografts were injected with rova-IR700 and irradiated with NIR-light.

FINDINGS

DLL3-overexpressing cells underwent immediate destruction upon NIR-light exposure, whereas the control cells remained intact. The xenograft in mice treated with rova-IR700 and NIR-light shrank markedly, whereas neither rova-IR700 injection nor NIR-light irradiation alone affected tumour size.

INTERPRETATION

Our data suggest that targeting of DLL3 using NIR-PIT could be a novel and promising treatment for SCLC.

FUNDING

Research supported by grants from the Program for Developing Next-generation Researchers (Japan Science and Technology Agency), KAKEN (18K15923, JSPS), Medical Research Encouragement Prize of The Japan Medical Association, The Nitto Foundation, Kanae Foundation for the Promotion of Medical Science.

Precision medicine for human cancers with Notch signaling dysregulation (Review)

NOTCH1, NOTCH2, NOTCH3 and NOTCH4 are transmembrane receptors that transduce juxtacrine signals of the delta‑like canonical Notch ligand (DLL)1, DLL3, DLL4, jagged canonical Notch ligand (JAG)1 and JAG2. Canonical Notch signaling activates the transcription of BMI1 proto‑oncogene polycomb ring finger, cyclin D1, CD44, cyclin dependent kinase inhibitor 1A, hes family bHLH transcription factor 1, hes related family bHLH transcription factor with YRPW motif 1, MYC, NOTCH3, RE1 silencing transcription factor and transcription factor 7 in a cellular context‑dependent manner, while non‑canonical Notch signaling activates NF‑κB and Rac family small GTPase 1. Notch signaling is aberrantly activated in breast cancer, non‑small‑cell lung cancer and hematological malignancies, such as T‑cell acute lymphoblastic leukemia and diffuse large B‑cell lymphoma. However, Notch signaling is inactivated in small‑cell lung cancer and squamous cell carcinomas. Loss‑of‑function NOTCH1 mutations are early events during esophageal tumorigenesis, whereas gain‑of‑function NOTCH1 mutations are late events during T‑cell leukemogenesis and B‑cell lymphomagenesis. Notch signaling cascades crosstalk with fibroblast growth factor and WNT signaling cascades in the tumor microenvironment to maintain cancer stem cells and remodel the tumor microenvironment. The Notch signaling network exerts oncogenic and tumor‑suppressive effects in a cancer stage‑ or (sub)type‑dependent manner. Small‑molecule γ‑secretase inhibitors (AL101, MRK‑560, nirogacestat and others) and antibody‑based biologics targeting Notch ligands or receptors [ABT‑165, AMG 119, rovalpituzumab tesirine (Rova‑T) and others] have been developed as investigational drugs. The DLL3‑targeting antibody‑drug conjugate (ADC) Rova‑T, and DLL3‑targeting chimeric antigen receptor‑modified T cells (CAR‑Ts), AMG 119, are promising anti‑cancer therapeutics, as are other ADCs or CAR‑Ts targeting tumor necrosis factor receptor superfamily member 17, CD19, CD22, CD30, CD79B, CD205, Claudin 18.2, fibroblast growth factor receptor (FGFR)2, FGFR3, receptor‑type tyrosine‑protein kinase FLT3, HER2, hepatocyte growth factor receptor, NECTIN4, inactive tyrosine‑protein kinase 7, inactive tyrosine‑protein kinase transmembrane receptor ROR1 and tumor‑associated calcium signal transducer 2. ADCs and CAR‑Ts could alter the therapeutic framework for refractory cancers, especially diffuse‑type gastric cancer, ovarian cancer and pancreatic cancer with peritoneal dissemination. Phase III clinical trials of Rova‑T for patients with small‑cell lung cancer and a phase III clinical trial of nirogacestat for patients with desmoid tumors are ongoing. Integration of human intelligence, cognitive computing and explainable artificial intelligence is necessary to construct a Notch‑related knowledge‑base and optimize Notch‑targeted therapy for patients with cancer.

Common and distinct features of potentially predictive biomarkers in small cell lung carcinoma and large cell neuroendocrine carcinoma of the lung by systematic and integrated analysis

BACKGROUND

Large-cell neuroendocrine carcinoma of the lung (LCNEC) and small-cell lung carcinoma (SCLC) are neuroendocrine neoplasms. However, the underlying mechanisms of common and distinct genetic characteristics between LCNEC and SCLC are currently unclear. Herein, protein expression profiles and possible interactions with miRNAs were provided by integrated bioinformatics analysis, in order to explore core genes associated with tumorigenesis and prognosis in SCLC and LCNEC.

METHODS

GSE1037 gene expression profiles were obtained from the Gene Expression Omnibus (GEO) database. Differentially expressed genes (DEGs) in LCNEC and SCLC, as compared with normal lung tissues, were selected using the GEO2R online analyzer and Venn diagram software. Gene ontology (GO) analysis was performed using Database for Annotation, Visualization and Integrated Discovery. The biological pathway analysis was performed using the FunRich database. Subsequently, a protein-protein interaction (PPI) network of DEGs was generated using Search Tool for the Retrieval of Interacting Genes and displayed via Cytoscape software. The PPI network was analyzed by the Molecular Complex Detection app from Cytoscape, and 16 upregulated hub genes were selected. The Oncomine database was used to detect expression patterns of hub genes for validation. Furthermore, the biological pathways of these 16 hub genes were re-analyzed, and potential interactions between these genes and miRNAs were explored via FunRich.

RESULTS

A total of 384 DEGs were identified. A Venn diagram determined 88 common DEGs. The PPI network was constructed with 48 nodes and 221 protein pairs. Among them, 16 hub genes were extracted, 14 of which were upregulated in SCLC samples, as compared with normal lung specimens, and 10 were correlated with the cell cycle pathway. Furthermore, 57 target miRNAs for 8 hub genes were identified, among which 31 miRNAs were correlated with the progression of carcinoma, drug-resistance, radio-sensitivity, or autophagy in lung cancer.

CONCLUSION

This study provided effective biomarkers and novel therapeutic targets for diagnosis and prognosis of SCLC and LCNEC.

An Overview of the Current ADC Discovery Landscape

The prototypical ADC mechanism involving antigen-mediated uptake and lysosomal release is both elegantly simple and scientifically compelling. However, recent clinical-stage failures have prompted a reevaluation of this delivery paradigm and have resulted in an array of new technologies that have the potential to improve the safety and efficacy of up and coming programs. These innovations can generally be categorized into seven areas that will be elaborated on in this chapter: (1) Exploiting new payload mechanisms; (2) Increasing the drug-antibody ratio (DAR); (3) Increasing the antibody penetration; (4) Overcoming ADC resistance mechanisms; (5) Increasing the efficiency of ADC uptake and processing; (6) Mitigating off-target payload exposure; and (7) Employment of noncytotoxic payloads. It is our belief that these seven areas capture the current "landscape" of innovations that are taking place in the design of next-generation ADCs. Together, these advancements are reshaping the ADC field and providing a path forward in the face of the recent clinical setbacks.

Antibody-drug conjugates for lung cancer in the era of personalized oncology

With 9.6 million deaths in 2018, cancer represents one of the most common causes of death, both in men and women. Despite recent advances in the understanding of molecular mechanisms involved in cancer development and progression, treatment options are still limited. Limitations of traditional chemotherapy include the lack of selectivity and the unfavorable safety profile. The efficacy of targeted therapies (e.g., tyrosine kinase inhibitors) is also limited by their cytostatic action, which inhibits tumor cell proliferation without inducing tumor cell death, and by the risk of acquired resistance. Antibody-drug conjugates (ADCs), a newly developed class of engineered anticancer drugs, consist of recombinant monoclonal antibodies against tumor-specific antigens that are covalently bound to cytotoxic agents. They have been designed to overcome the limitations of traditional chemotherapy and targeted therapies by combining the target selectivity of monoclonal antibodies with the high potency of cytotoxic drugs. Currently, ADCs that have received regulatory approval include brentuximab vedotin for CD30-positive Hodgkin lymphoma and trastuzumab emtansine for human epidermal growth factor receptor 2-positive breast cancer. However, over 80 novel ADCs are actively being investigated in preclinical studies and early-phase clinical trials. In this review, we will provide a comprehensive overview of the biological rational, efficacy and safety of ADCs as therapeutic agents against non-small cell lung cancer and small cell lung cancer.

Axon-like protrusions promote small cell lung cancer migration and metastasis

Metastasis is the main cause of death in cancer patients but remains a poorly understood process. Small cell lung cancer (SCLC) is one of the most lethal and most metastatic cancer types. SCLC cells normally express neuroendocrine and neuronal gene programs but accumulating evidence indicates that these cancer cells become relatively more neuronal and less neuroendocrine as they gain the ability to metastasize. Here we show that mouse and human SCLC cells in culture and in vivo can grow cellular protrusions that resemble axons. The formation of these protrusions is controlled by multiple neuronal factors implicated in axonogenesis, axon guidance, and neuroblast migration. Disruption of these axon-like protrusions impairs cell migration in culture and inhibits metastatic ability in vivo. The co-option of developmental neuronal programs is a novel molecular and cellular mechanism that contributes to the high metastatic ability of SCLC.

Comparative expression analysis in small cell lung carcinoma reveals neuroendocrine pattern change in primary tumor versus lymph node metastases

Background

Recent preclinical data suggest that neuroendocrine (NE) subtype of small cell lung cancer (SCLC) has strong therapeutic relevance. NE high tumors are associated with immune desert and NE low tumors are considered to have an immune oasis phenotype. Our aim was to investigate the NE phenotypes of surgically resected SCLC tumors according to inter-tumor heterogeneity.

Methods

Expression analysis for 2,560 genes was performed in 32 surgically resected SCLC patients' primary tumors and corresponding lymph node (LN) metastases. To analyze tumor heterogeneity, we examined the differences in the gene expression of primary tumors versus LN metastases. We performed cluster analysis and heat map to divide patients into NE high and low subtypes by using the top NE-associated genes described in preclinical studies.

Results

We found 6% (n=154) genes with significant differences and only 13.1% (n=336) of all genes in the panel had a strong correlation between the primary tumor and LN metastases. Cluster analysis clearly distinguished SCLC NE high versus low subtypes both in primary tumor (20 vs. 12, respectively) and LNs (23 vs. 9, respectively). As for inter-tumor heterogeneity, in case of five patients, a change in the NE pattern was observed. Specifically, we found significant downregulation of the NE-associated genes CAV1 (P=0.004), CAV2 (P=0.029) and ANXA3 (P=0.035) in their LN metastases compared to their primary tumor.

Conclusions

Our data confirm the results of preclinical studies and clearly distinguish NE low and high differentiation clusters in SCLC. Moreover, they highlight the gene expression discordance between primary tumors and corresponding LN metastases suggesting that the NE pattern of metastatic LNs might not reflect that of the primary tumor. Altogether, by shedding light on the diversity of SCLC, the current study might help to improve patient selection and treatment in this devastating disease.

Keywords

Small cell lung cancer (SCLC); neuroendocrine tumor; lymph node metastasis; tumor heterogeneity; RNA sequencing.

Immunotherapeutic maintenance treatment with toll-like receptor 9 agonist lefitolimod in patients with extensive-stage small-cell lung cancer: results from the exploratory, controlled, randomized, international phase II IMPULSE study

Background

The immune surveillance reactivator lefitolimod (MGN1703), a DNA-based TLR9 agonist, might foster innate and adaptive immune response and thus improve immune-mediated control of residual cancer disease. The IMPULSE phase II study evaluated the efficacy and safety of lefitolimod as maintenance treatment in extensive-stage small-cell lung cancer (ES-SCLC) after objective response to first-line chemotherapy, an indication with a high unmet medical need and stagnant treatment improvement in the last decades.

Patients and methods

103 patients with ES-SCLC and objective tumor response (as per RECIST 1.1) following four cycles of platinum-based first-line induction therapy were randomized to receive either lefitolimod maintenance therapy or local standard of care at a ratio of 3 : 2 until progression or unacceptable toxicity.

Results

From 103 patients enrolled, 62 were randomized to lefitolimod, 41 to the control arm. Patient demographics and response patterns to first-line therapy were balanced. Lefitolimod exhibited a favorable safety profile and pharmacodynamic assessment confirmed the mode-of-action showing a clear activation of monocytes and production of interferon-gamma-induced protein 10 (IP-10). While in the intent-to-treat (ITT) population no relevant effect of lefitolimod on progression-free and overall survival (OS) could be observed, two predefined patient subgroups indicated promising results, favoring lefitolimod with respect to OS: in patients with a low frequency of activated CD86⁺ B cells (hazard ratio, HR 0.53, 95% CI: 0.26–1.08; n = 38 of 88 analyzed) and in patients with reported chronic obstructive pulmonary disease (COPD) (HR 0.48, 95% CI: 0.20–1.17, n = 25 of 103).

Conclusions

The IMPULSE study showed no relevant effect of lefitolimod on the main efficacy end point OS in the ITT, but (1) the expected pharmacodynamic response to lefitolimod, (2) positive OS efficacy signals in two predefined subgroups and (3) a favorable safety profile. These data support further exploration of lefitolimod in SCLC.

Prevalence of DLL3, CTLA-4 and MSTN Expression in Patients with Small Cell Lung Cancer

Introduction

Immune-based and antibody-drug conjugate therapies have shown promise in the treatment of patients with small cell lung cancer (SCLC). However, better predictive biomarkers are needed for selection of the appropriate SCLC patients for these advanced therapies and also for evaluation of the efficacy of these treatments.

Objective

The aim of this study was to examine the expression of delta-like protein 3 (DLL3), cytotoxic T lymphocyte-associated protein 4 (CTLA-4), and mesothelin (MSTN) in patients with SCLC and compare them with those patients’ clinical characteristics.

Methods

Immunohistochemical analyses of DLL3, CTLA-4 and MSTN expression were performed in 38 samples from patients with SCLC.

Results

We found that positive expression in patients of the biomarkers was as follows: for DLL3, 100% (38/38), for CTLA-4, 89.5% (36/38) and for MSTN 81.5% (31/38). The median survival time was 17.9 months in the DLL3 high expression group and 23 months in the DLL3 low expression group. Patients with a high expression of DLL3 showed a poorer prognosis than those with a low expression of DLL3 (HR=3.4; 95% CI, 1.34–8.6; p=0.01).

Conclusion

The expression of DLL3, CTLA-4 and MSTN was not correlated with patients’ age, sex, smoking status, stage, and tumor metastasis. The fact that there was a higher expression of DLL3, CTLA-4, and MSTN in SCLC suggested that these molecules could be used as predictive biomarkers for SCLC.

Heterogeneity of Vascular Endothelial Cells, De Novo Arteriogenesis and Therapeutic Implications in Pancreatic Neuroendocrine Tumors

Arteriogenesis supplies oxygen and nutrients in the tumor microenvironment (TME), which may play an important role in tumor growth and metastasis. Pancreatic neuroendocrine tumors (pNETs) are the second most common pancreatic malignancy and are frequently metastatic on presentation. Nearly a third of pNETs secrete bioactive substances causing debilitating symptoms. Current treatment options for metastatic pNETs are limited. Importantly, these tumors are highly vascularized and heterogeneous neoplasms, in which the heterogeneity of vascular endothelial cells (ECs) and de novo arteriogenesis may be critical for their progression. Current anti-angiogenetic targeted treatments have not shown substantial clinical benefits, and they are poorly tolerated. This review article describes EC heterogeneity and heterogeneous tumor-associated ECs (TAECs) in the TME and emphasizes the concept of de novo arteriogenesis in the TME. The authors also emphasize the challenges of current antiangiogenic therapy in pNETs and discuss the potential of tumor arteriogenesis as a novel therapeutic target. Finally, the authors prospect the clinical potential of targeting the FoxO1-CD36-Notch pathway that is associated with both pNET progression and arteriogenesis and provide insights into the clinical implications of targeting plasticity of cancer stem cells (CSCs) and vascular niche, particularly the arteriolar niche within the TME in pNETs, which will also provide insights into other types of cancer, including breast cancer, lung cancer, and malignant melanoma.

Investigating Tumor Heterogeneity in Mouse Models

Cancer arises from a single cell through a series of acquired mutations and epigenetic alterations. Tumors gradually develop into a complex tissue comprised of phenotypically heterogeneous cancer cell populations, as well as noncancer cells that make up the tumor microenvironment. The phenotype, or state, of each cancer and stromal cell is influenced by a plethora of cell-intrinsic and cell-extrinsic factors. The diversity of these cellular states promotes tumor progression, enables metastasis, and poses a challenge for effective cancer treatments. Thus, the identification of strategies for the therapeutic manipulation of tumor heterogeneity would have significant clinical implications. A major barrier in the field is the difficulty in functionally investigating heterogeneity in tumors in cancer patients. Here we review how mouse models of human cancer can be leveraged to interrogate tumor heterogeneity and to help design better therapeutic strategies.

Polymorphism in ASCL1 target gene DDC is associated with clinical outcomes of small cell lung cancer patients

BACKGROUND

Achaete-scute homolog 1 (ASCL1) is a basic helix-loop-helix transcription factor and is essential in the differentiation of neuroendocrine cells and neural tissues. ASCL1 is frequently overexpressed in small cell lung cancer (SCLC) and plays a crucial role in the pathogenesis of SCLC.

METHODS

This study was conducted to identify the association between single nucleotide polymorphisms (SNPs) in ASCL1 target genes and clinical outcomes of patients with SCLC after chemotherapy. A total of 261 patients diagnosed with SCLC were enrolled in this study. The association between 103 SNPs in 58 ASCL1 target genes and the response to chemotherapy and survival of patients with SCLC were analyzed.

RESULTS

Among the 103 SNPs, 10 SNPs were significantly associated with the response to chemotherapy, and 19 SNPs were associated with OS in multivariate analyses. Among these, Dopa Decarboxylase (DDC) rs12666409A>T was significantly associated with both a worse response to chemotherapy and worse OS (adjusted odds ratio [aOR] = 0.40, 95% CI = 0.18-0.90, P = 0.03; adjusted hazard ratio [aHR] = 1.52, 95% CI = 1.10-2.10, P = 0.01, respectively, under a dominant model). In a stage-stratified analysis, the association was significant only in the extensive disease subgroup (aOR = 0.19, 95% CI = 0.06-0.60, P = 0.01; aHR = 1.73, 95% CI = 1.16-2.56, P = 0.01, respectively, under a dominant model), but not in the limited disease subgroup.

CONCLUSION

The results of our study suggest that DDC rs12666409A>T may be useful markers for predicting the clinical outcomes of patients with SCLC undergoing chemotherapy.

Role of Focal Adhesion Kinase in Small-Cell Lung Cancer and Its Potential as a Therapeutic Target

Small-cell lung cancer (SCLC) represents 15% of all lung cancers and it is clinically the most aggressive type, being characterized by a tendency for early metastasis, with two-thirds of the patients diagnosed with an extensive stage (ES) disease and a five-year overall survival (OS) as low as 5%. There are still no effective targeted therapies in SCLC despite improved understanding of the molecular steps leading to SCLC development and progression these last years. After four decades, the only modest improvement in OS of patients suffering from ES-SCLC has recently been shown in a trial combining atezolizumab, an anti-PD-L1 immune checkpoint inhibitor, with carboplatin and etoposide, chemotherapy agents. This highlights the need to pursue research efforts in this field. Focal adhesion kinase (FAK) is a non-receptor protein tyrosine kinase that is overexpressed and activated in several cancers, including SCLC, and contributing to cancer progression and metastasis through its important role in cell proliferation, survival, adhesion, spreading, migration, and invasion. FAK also plays a role in tumor immune evasion, epithelial-mesenchymal transition, DNA damage repair, radioresistance, and regulation of cancer stem cells. FAK is of particular interest in SCLC, being known for its aggressiveness. The inhibition of FAK in SCLC cell lines demonstrated significative decrease in cell proliferation, invasion, and migration, and induced cell cycle arrest and apoptosis. In this review, we will focus on the role of FAK in cancer cells and their microenvironment, and its potential as a therapeutic target in SCLC.

Technological and Therapeutic Advances in Advanced Small Cell Lung Cancer

Small cell lung cancer (SCLC) accounts for approximately 10-15% of all lung cancers. The prognosis is poor with median survival in the advanced stage remaining at around 12 months. Despite applying every known therapeutic approach, no major breakthrough has improved the overall survival in the last 30 years. Historically, experiments performed on conventional cell lines may have limitations of not accurately reflecting the complex biological and genomic heterogeneity of this disease. However, additional knowledge gained from recently developed genetically engineered mouse models (GEMMs) and patient derived xenografts (PDXs) have made encouraging inroads. Whole genome sequencing (WGS) data reveals a high mutational burden and a number of genetic alterations but low frequency of targetable mutations. Despite several failures, considerable therapeutic opportunities have recently emerged. Potentially promising therapies include those targeting DNA damage repair, stem cell/renewal and drug resistant mechanisms. Modest success has also been achieved with immune checkpoint inhibitors while therapeutic exploration of various other components of the immune system is underway. However, the complex heterogeneities reflect the need for accurate bio-markers to translate novel discoveries into clinical benefit. Additionally, the molecular mechanisms that differentiate chemo-sensitive from chemo-refractory disease remain unknown. Obtaining reliable tumour samples by utilising novel techniques such as endobronchial ultrasound guided needle aspiration or adopting to liquid biopsies are becoming popular. This review will focus on recent technological and therapeutic advancements to surmount this recalcitrant disease.

DLL3 expression in large cell neuroendocrine carcinoma (LCNEC) and association with molecular subtypes and neuroendocrine profile

OBJECTIVES

For stage IV pulmonary large cell neuroendocrine carcinoma (LCNEC), the only therapeutic option is palliative chemotherapy. DLL3 is a new therapeutic target, which seems to be often expressed in SCLC and LCNEC. It has recently been reported that DLL3 mRNA expression is particularly upregulated in the LCNEC subgroup with STK11/KEAP1 and TP53 co-mutations, in contrast to lower expression levels in RB1 and TP53 co-mutated LCNEC. Our aim was to investigate DLL3 protein expression in stage IV LCNEC and correlate data with mutational profiles (i.e.STK11/KEAP1/RB1), immunostaining results (pRb, NE markers) and clinical characteristics.

MATERIALS AND METHODS

Immunohistochemical analysis for DLL3 (SC16.65) and ASCL1 (SC72.201) was performed on 94 and 51 FFPE tissue sections, respectively, of pathologically reviewed stage IV LCNEC. DLL3 and ASCL1 were scored positive if ≥1% of the tumor cells showed cytoplasmic/membranous or dotlike (DLL3) or nuclear (ASCL1) immunostaining. Data were correlated with available sequencing (TP53, RB1, STK11, KEAP1), immunostaining (pRb, NE markers) and clinical data.

RESULTS

DLL3 was expressed in 70/94 (74%) LCNEC, 56 (80%) of which showed cytoplasmic/membranous staining. Median H-score was 55 (interquartile range 0-160). DLL3 staining was not different in pRb immunohistochemistry negative and positive patients (DLL3+ in 53/70 (76%) vs. 14/21 (67%), p = 0.409) or RB1 mutated and wildtype patients (DLL3+ in 27/34 (79%) vs. 23/33 (70%), p = 0.361). Nevertheless, 6/6 (100%) STK11 mutated, 10/11 (91%) KEAP1 mutated and 9/9 (100%) TP53 wildtype tumors were DLL3+ . Furthermore, DLL3 expression was associated with expression of ASCL1 and at least 2 out of 3 neuroendocrine markers.

CONCLUSION

The high percentage (74%) of DLL3 expression in stage IV LCNEC denotes the potential of DLL3 targeted therapy in this patient group.

A growth model of neuroendocrine tumor surrogates and the efficacy of a novel somatostatin-receptor-guided antibody-drug conjugate: Perspectives on clinical response?

BACKGROUND

As patient-derived xenografts and other preclinical models of neuroendocrine tumors for testing personalized therapeutics are lacking, we have developed a perfused, 3D bioreactor model to culture tumor surrogates from patient-derived neuroendocrine tumors. This work evaluates the duration of surrogate culture and surrogate response to a novel antibody-drug conjugate.

METHODS

Twenty-seven patient-derived neuroendocrine tumors were cultured. Histologic sections of a pancreatic neuroendocrine tumor xenograft (BON-1) tumor were assessed for SSTR2 expression before tumor implantation into 2 bioreactors. One surrogate was treated with an antibody-drug conjugate composed of an anti-mitotic Monomethyl auristatin-E linked to a somatostatin receptor 2 antibody. Viability and therapeutic response were assessed by pre-imaging incubation with IR-783 and the RealTime-Glo AnnexinV Apoptosis and Necrosis Assay (Promega Corporation, Madison, WI) over 6 days. A primary human pancreatic neuroendocrine tumor was evaluated similarly.

RESULTS

Mean surrogate growth duration was 34.8 days. Treated BON-1 surrogates exhibited less proliferation (1.2 vs 1.9-fold) and greater apoptosis (1.5 vs 1.1-fold) than controls, whereas treated patient-derived neuroendocrine tumor bioreactors exhibited greater degrees of apoptosis (13- vs 9-fold) and necrosis (2.5- vs 1.6-fold).

CONCLUSION

Patient-derived neuroendocrine tumor surrogates can be cultured reliably within the bioreactor. This model can be used to evaluate the efficacy of antibody-guided chemotherapy ex vivo and may be useful for predicting clinical responses.

Antibody-Drug Conjugates for Cancer Treatment

The concept of exploiting the specific binding properties of monoclonal antibodies as a mechanism for selective delivery of cytotoxic agents to tumor cells is an attractive solution to the challenge of increasing the therapeutic index of cell-killing agents for treating cancer. All three parts of an antibody-drug conjugate (ADC)-the antibody, the cytotoxic payload, and the linker chemistry that joins them together-as well as the biologic properties of the cell-surface target antigen are important in designing an effective anticancer agent. The approval of brentuximab vedotin in 2011 for treating relapsed Hodgkin's lymphoma and systemic anaplastic large cell lymphoma, and the approval of ado-trastuzumab emtansine in 2013 for treating HER2-positive metastatic breast cancer, have sparked vigorous research in the field, with >65 ADCs currently in clinical evaluation. This review highlights the ADCs that are approved for marketing, in pivotal clinical trials, or in at least phase II clinical development for treating both hematologic malignancies and solid tumors.

Efficacy and Safety of Rovalpituzumab Tesirine in Third-Line and Beyond Patients with DLL3-Expressing, Relapsed/Refractory Small-Cell Lung Cancer: Results From the Phase II TRINITY Study

PURPOSE

Although extensive-stage small-cell lung cancer (SCLC) is highly responsive to first-line therapy, virtually all patients develop resistance with short survival. Rovalpituzumab tesirine (Rova-T) is an antibody-drug conjugate targeting delta-like 3 protein (DLL3). This open-label, single-arm, phase II study (TRINITY) assessed safety and efficacy of Rova-T in patients with DLL3-expressing SCLC in the third-line and beyond (3L+) setting.

PATIENTS AND METHODS

Patients with DLL3-expressing SCLC (determined by mouse antibody immunohistochemistry [IHC] assay), and ≥2 prior regimens, received 0.3 mg/kg Rova-T once every 6 weeks for two cycles. During study, a rabbit antibody IHC assay was developed and used for the final analysis, with DLL3-positive and DLL3-high defined as ≥25% and ≥75% of tumor cells positive for DLL3, respectively. The primary endpoints were objective response rate (ORR) and overall survival (OS).

RESULTS

Among 339 patients enrolled, 261 (77%) had two prior lines of therapy and 78 (23%) had ≥3. DLL3-high and DLL3-positive tumors by rabbit IHC were seen in 238 (70%) and 287 (85%) patients, respectively. The remaining 52 (15%) were DLL3-negative only by rabbit IHC or had missing results. ORR was 12.4%, 14.3%, and 13.2% in all, DLL3-high, and DLL3-positive patients, respectively. Median OS was 5.6 months in all patients and 5.7 months in DLL3-high patients. The most common adverse events (AE) were fatigue, photosensitivity reaction, and pleural effusion. Grade 3-5 AEs were seen in 213 (63%) patients.

CONCLUSIONS

Rova-T is the first targeted agent in SCLC to use DLL3, a novel biomarker. However, results demonstrate modest clinical activity in 3L+ SCLC, with associated toxicities.

Updates on the Role of Molecular Alterations and NOTCH Signalling in the Development of Neuroendocrine Neoplasms

Neuroendocrine neoplasms (NENs) comprise a heterogeneous group of rare malignancies, mainly originating from hormone-secreting cells, which are widespread in human tissues. The identification of mutations in ATRX/DAXX genes in sporadic NENs, as well as the high burden of mutations scattered throughout the multiple endocrine neoplasia type 1 (MEN-1) gene in both sporadic and inherited syndromes, provided new insights into the molecular biology of tumour development. Other molecular mechanisms, such as the NOTCH signalling pathway, have shown to play an important role in the pathogenesis of NENs. NOTCH receptors are expressed on neuroendocrine cells and generally act as tumour suppressor proteins, but in some contexts can function as oncogenes. The biological heterogeneity of NENs suggests that to fully understand the role and the potential therapeutic implications of gene mutations and NOTCH signalling in NENs, a comprehensive analysis of genetic alterations, NOTCH expression patterns and their potential role across all NEN subtypes is required.

Delta-like 3 localizes to neuroendocrine cells and plays a pivotal role in gastrointestinal neuroendocrine malignancy

Delta‐like 3 (DLL3) is a member of the Delta/Serrate/Lag2 (DSL) group of Notch receptor ligands. Five DSL ligands are known in mammals, among which DLL3 has a unique structure. In the last few years, DLL3 has attracted attention as a novel molecular targeting gene in neuroendocrine carcinoma of the lung due to its high expression. However, the expression pattern and functions of DLL3 in the gastrointestinal tract and gastrointestinal neuroendocrine carcinoma remain unclear. In this study, we examined the expression and role of DLL3 in the gastrointestinal tract, as well as in gastrointestinal neuroendocrine carcinoma. Immunohistochemical staining of the human normal gastrointestinal tract revealed that DLL3 localized in neuroendocrine cells. DLL3 showed intense staining in chromogranin A‐positive gastric cancer specimens. Real‐time quantitative RT‐PCR and western blotting analyses showed considerable upregulation of DLL3 in gastrointestinal neuroendocrine carcinoma cell lines. Immuno‐electron microscopy demonstrated abundant expression of DLL3 in neurosecretory granules in these cells. Furthermore, gene silencing of DLL3 caused significant growth inhibition through the induction of intrinsic apoptosis. Our findings suggest that DLL3 is expressed in neuroendocrine cells of the gastrointestinal tract and that it has a pivotal role in gastrointestinal neuroendocrine carcinoma cells. Based on these findings, further investigations are required to achieve a breakthrough in developing therapeutic strategies for gastrointestinal neuroendocrine carcinoma.

Molecular Characterization of Circulating Tumor Cells Enriched by A Microfluidic Platform in Patients with Small-Cell Lung Cancer

At initial diagnosis, most patients with small-cell lung cancer (SCLC) present with metastatic disease with a high number of tumor cells (CTCs) circulating in the blood. We analyzed RNA transcripts specific for neuroendocrine and for epithelial cell lineages, and Notch pathway delta-like 3 ligand (DLL3), the actionable target of rovalpituzumab tesirine (Rova-T) in CTC samples. Peripheral blood samples from 48 SCLC patients were processed using the microfluidic Parsortix™ technology to enrich the CTCs. Blood samples from 26 healthy donors processed in the same way served as negative controls. The isolated cells were analyzed for the presence of above-mentioned transcripts using quantitative PCR. In total, 16/51 (31.4%) samples were CTC-positive as determined by the expression of epithelial cell adhesion molecule 1 (EpCAM), cytokeratin 19 (CK19), chromogranin A (CHGA), and/or synaptophysis (SYP). The epithelial cell lineage-specific EpCAM and/or CK19 gene expression was observed in 11 (21.6%) samples, and positivity was not associated with impaired survival. The neuroendocrine cell lineage-specific CHGA and/or SYP were positive in 13 (25.5%) samples, and positivity was associated with poor overall survival. DLL3 transcripts were observed in four (7.8%) SCLC blood samples and DLL3-positivity was similarly associated with poor overall survival (OS). CTCs in SCLC patients can be assessed using epithelial and neuroendocrine cell lineage markers at the molecular level. Thus, the implementation of liquid biopsy may improve the management of lung cancer patients, in terms of a faster diagnosis, patient stratification, and on-treatment therapy monitoring.

The evolving landscape of immunotherapy in small-cell lung cancer: A focus on predictive biomarkers

Small cell lung cancer (SCLC) was defined as a "recalcitrant cancer" because of its dismal prognosis and lack of outcome improvements in the last 30 years. Immunotherapy with checkpoint inhibitors revolutionized treatment in many cancer types and results from the IMpower133 study, a double-blind placebo-controlled phase III trial, showed overall survival benefit for atezolizumab when added to standard platinum-etoposide chemotherapy in first-line SCLC setting for the first time since years. Trials with other checkpoint inhibitors, e.g. pembrolizumab, durvalumab, nivolumab and ipilimumab, are ongoing in various settings, but, to date, there are no defined factors to identify patients who are more likely to benefit from such treatments. This review summarizes results of immunotherapy trials in SCLC for first-line, maintenance and further-line therapies for single-agents and combinations with checkpoint inhibitors. Predictive factors from these trials are reviewed in order to identify their clinical value, with particular emphasis on PD-L1 expression on both tumor cells and in stroma, especially in pembrolizumab-treated patients, and tumor mutational burden, for patients treated with the ipilimumab and nivolumab combination.

Somatostatin receptor 2 targeting in small cell lung carcinoma: perspectives

Small Cell lung carcinoma (SCLC) is the most lethal and aggressive subtype of lung cancer. Novel targeting approaches and agents are desperately needed. In this perspectives, we briefly explore recent data published in the International Journal of Cancer suggesting Somatostatin Receptor 2 (SSTR2) as a viable target for SCLC, summarize the current clinical trial space, and describe promising new research and clinical directions for Somatostatin Receptor 2 targeting in SCLC.

An FDA oncology analysis of toxicities associated with PBD-containing antibody-drug conjugates

With a new generation of antibody-drug conjugates (ADCs) that contain a drug-to-antibody ratio (DAR) of 2, the question remains whether advances in technology have resulted in more stable and tumor-specific ADCs. These ADCs are anticipated to cause minimal systemic exposures of payloads, with toxicities being evident mainly at tumor sites. We examined 15 ADCs with PBD-dimer payloads and a DAR of 2 and concluded that dose limiting toxicities in animals and in humans are generally related to the payload. Both the payloads and the ADCs had pro-inflammatory responses causing severe toxicities that were at times of low incidence, making it difficult to assess a cause-effect relationship. Due to their low incidence, single-patient cohorts may not detect these events and such design may not be suitable in first-in-human (FIH) trials. The commonly proposed approach by the sponsors for FIH dose selection was 1/6^th highest non-severely toxic dose (HNSTD) in monkeys. This approach resulted in an acceptable balance of safety and efficient dose escalation in phase 1 trials, when using data from repeat-dose toxicology studies and body surface area for scaling. No sponsor used the data generated in rodents or proposed novel approaches for FIH dose selection.