T-Cell redirecting bispecific antibodies: a review of a novel class of immuno-oncology for advanced prostate cancer

Novel T-cell immunotherapies such as bispecific T-cell engagers (BiTEs) are emerging as promising therapeutic strategies for prostate cancer. BiTEs are engineered bispecific antibodies containing two distinct binding domains that allow for concurrent binding to tumor-associated antigens (TAAs) as well as immune effector cells, thus promoting an immune response against cancer cells. Prostate cancer is rich in tumor associated antigens such as, but not limited to, PSMA, PSCA, hK2, and STEAP1 and there is strong biologic rationale for employment of T-cell redirecting BiTEs within the prostate cancer disease space. Early generation BiTE constructs employed in clinical study have demonstrated meaningful antitumor activity, but challenges related to drug delivery, immunogenicity, and treatment-associated adverse effects limited their success. The ongoing development of novel BiTE constructs continues to address these barriers and to yield promising results in terms of efficacy and safety. This review will highlight some of most recent developments of BiTE therapies for patients with advanced prostate cancer and the evolving data surrounding BiTE constructs undergoing clinical evaluation.

Dual blockade immunotherapy targeting PD-1/PD-L1 and CTLA-4 in lung cancer

Cancer immunotherapies, represented by immune checkpoint inhibitors (ICIs), have reshaped the treatment paradigm for both advanced non-small cell lung cancer and small cell lung cancer. Programmed death receptor-1/programmed death receptor ligand-1 (PD-1/PD-L1) and cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) are some of the most common and promising targets in ICIs. Compared to ICI monotherapy, which occasionally demonstrates treatment resistance and limited efficacy, the dual blockade immunotherapy targeting PD-1/PD-L1 and CTLA-4 operates at different stages of T cell activation with synergistically enhancing immune responses against cancer cells. This emerging dual therapy heralds a new direction for cancer immunotherapy, which, however, may increase the risk of drug-related adverse reactions while improving efficacy. Previous clinical trials have explored combination therapy strategy of anti-PD-1/PD-L1 and anti-CTLA-4 agents in lung cancer, yet its efficacy remains to be unclear with the inevitable incidence of immune-related adverse events. The recent advent of bispecific antibodies has made this sort of dual targeting more feasible, aiming to alleviate toxicity without compromising efficacy. Thus, this review highlights the role of dual blockade immunotherapy targeting PD-1/PD-L1 and CTLA-4 in treating lung cancer, and further elucidates its pre-clinical mechanisms and current advancements in clinical trials. Besides, we also provide novel insights into the potential combinations of dual blockade therapies with other strategies to optimize the future treatment mode for lung cancer.

Circulating tumor cells: advancing personalized therapy in small cell lung cancer patients

Small cell lung cancer (SCLC) is a highly aggressive cancer with a dismal 5-year survival of < 7%, despite the addition of immunotherapy to first-line chemotherapy. Specific tumor biomarkers, such as delta-like ligand 3 (DLL3) and schlafen11 (SLFN11), may enable the selection of more efficacious, novel immunomodulating targeted treatments like bispecific T-cell engaging monoclonal antibodies (tarlatamab) and chemotherapy with PARP inhibitors. However, obtaining a tissue biopsy sample can be challenging in SCLC. Circulating tumor cells (CTCs) have the potential to provide molecular insights into a patient's cancer through a "simple" blood test. CTCs have been studied for their prognostic ability in SCLC; however, their value in guiding treatment decisions is yet to be elucidated. This review explores novel and promising targeted therapies in SCLC, summarizes current knowledge of CTCs in SCLC, and discusses how CTCs can be utilized for precision medicine.

Engineering CD3/CD137 Dual Specificity into a DLL3-Targeted T-Cell Engager Enhances T-Cell Infiltration and Efficacy against Small-Cell Lung Cancer

Small-cell lung cancer (SCLC) is an aggressive cancer for which immune checkpoint inhibitors (ICI) have had only limited success. Bispecific T-cell engagers are promising therapeutic alternatives for ICI-resistant tumors, but not all patients with SCLC are responsive. Herein, to integrate CD137 costimulatory function into a T-cell engager format and thereby augment therapeutic efficacy, we generated a CD3/CD137 dual-specific Fab and engineered a DLL3-targeted trispecific antibody (DLL3 trispecific). The CD3/CD137 dual-specific Fab was generated to competitively bind to CD3 and CD137 to prevent DLL3-independent cross-linking of CD3 and CD137, which could lead to systemic T-cell activation. We demonstrated that DLL3 trispecific induced better tumor growth control and a marked increase in the number of intratumoral T cells compared with a conventional DLL3-targeted bispecific T-cell engager. These findings suggest that DLL3 trispecific can exert potent efficacy by inducing concurrent CD137 costimulation and provide a promising therapeutic option for SCLC.

Treating patients with platinum-sensitive extensive-stage small-cell lung cancer in a real-world setting

Extensive-stage small-cell lung cancer (ES-SCLC) is an aggressive disease with poor 5-year survival. The first-line standard-of-care for ES-SCLC is platinum plus etoposide, along with 1 of the immune checkpoint inhibitors atezolizumab or durvalumab. Although SCLC first-line therapy often leads to rapid responses, treatment becomes more challenging at progression, particularly for those with a chemotherapy-free interval (CTFI) of ≤6 months. The NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines®) for SCLC no longer specify treatment recommendations in this setting, but options approved by the US Food and Drug Administration include topotecan and lurbinectedin. Participation in a clinical trial is recommended as an option regardless of CTFI. Other NCCN-recommended regimens are paclitaxel, irinotecan, temozolomide, and cyclophosphamide/doxorubicin/vincristine, among others. Nivolumab and pembrolizumab are options in those not previously treated with a checkpoint inhibitor. For patients with platinum-sensitive SCLC (CTFI >6 months), preferred treatment per the NCCN Guidelines® for SCLC is retreatment with platinum and etoposide, although the use of immune checkpoint inhibitors is discouraged if there is progression on a drug in this class. Further research on immunotherapies and combination regimens is ongoing, and continuing work on the subcharacterization of SCLC may lead to better precision of therapies that promote more durable responses in individual patients with ES-SCLC.

Advancing immunotherapy in small cell lung cancer

Small cell lung cancer (SCLC) is a rapidly progressive neuroendocrine carcinoma that, until recently, had a very small armamentarium of effective treatments. Advances in DNA sequencing and whole transcriptomics have delineated key subtypes; therefore, SCLC is no longer viewed as a homogeneous cancer. Chemoimmunotherapy with PD1 blockade is now the standard of care for advanced disease, and ongoing research efforts are moving this strategy into the limited stage setting. Combination strategies of immunotherapy with radiation are also under active clinical trial in both limited and extensive stage disease. PLAIN LANGUAGE SUMMARY: Small cell lung cancer (SCLC) is a rapidly progressive neuroendocrine carcinoma that, until recently, had a very small armamentarium of effective treatments. Chemoimmunotherapy with immune check point inhibitors is now the standard of care for advanced disease. This comprehensive review provides an overview of current treatment strategies for SCLC, unmet needs in this patient population, and emerging treatment strategies incorporating immunotherapy that will hopefully further improve outcomes for patients.

Conformation-selective rather than avidity-based binding to tumor associated antigen derived peptide-MHC enables targeting of WT1-pMHC low expressing cancer cells by anti-WT1-pMHC/CD3 T cell engagers

T cell engagers, a category of T cell-retargeting immunotherapy, are rapidly transforming clinical cancer care. However, the lack of tumor-specific targets poses a significant roadblock for broad adaptation of this therapeutic modality in many indications, often resulting in systemic on-target off-tumor toxicity. Though various tumor-derived intracellular mutations provide a massive pool of potential tumor-specific antigens, targeting them is extremely challenging, partly due to the low copy number of tumor associated antigen (TAA)-derived pMHC on tumor cell surface. Further, the interplay of binding geometry and format valency in relation to the capacity of a T cell engager to efficiently target low density cell-surface pMHC is not well understood. Using the Wilms' tumor 1 (WT1) oncoprotein as a proof-of-principle TAA, combined with an array of IgG-like T cell engager modalities that differ in their anti-TAA valency and binding geometry, we show that the ability to induce an immunological synapse formation, resulting in potent killing of WT1 positive cancer cell lines is primarily dependent on the distinct geometrical conformations between the Fab arms of anti-WT1-HLA-A*02:01 and anti-CD3. The augmented avidity conferred by the binding of two anti-WT1-HLA-A*02:01 Fab arms has only minimal influence on cell killing potency. These findings demonstrate the need for careful examination of key design parameters for the development of next-generation T cell engagers targeting low density TAA-pMHCs on tumor cells.

Bispecific Antibodies in Lung Cancer: A State-of-the-Art Review

Bispecific antibodies have emerged as a promising class of therapeutics in the field of oncology, offering an innovative approach to target cancer cells while sparing healthy tissues. These antibodies are designed to bind two different antigens, enabling them to bridge immune cells with cancer cells, resulting in enhanced tumor cell killing and improved treatment responses. This review article summarizes the current landscape of bispecific antibodies in lung cancer, including their mechanisms of action, clinical development, and potential applications in other solid tumor malignancies. Additionally, the challenges and opportunities associated with their use in the clinic are discussed, along with future directions for research and development in this exciting area of cancer immunotherapy.

Potent molecular-targeted therapies for gastro-entero-pancreatic neuroendocrine carcinoma

Neuroendocrine neoplasms (NENs), which are characterized by neuroendocrine differentiation, can arise in various organs. NENs have been divided into well-differentiated neuroendocrine tumors (NETs) and poorly differentiated neuroendocrine carcinomas (NECs) based on morphological differentiation, each of which has a distinct etiology, molecular profile, and clinicopathological features. While the majority of NECs originate in the pulmonary organs, extrapulmonary NECs occur most predominantly in the gastro-entero-pancreatic (GEP) system. Although platinum-based chemotherapy is the main therapeutic option for recurrent or metastatic GEP-NEC patients, the clinical benefits are limited and associated with a poor prognosis, indicating the clinically urgent need for effective therapeutic agents. The clinical development of molecular-targeted therapies has been hampered due to the rarity of GEP-NECs and the paucity of knowledge on their biology. In this review, we summarize the biology, current treatments, and molecular profiles of GEP-NECs based on the findings of pivotal comprehensive molecular analyses; we also highlight potent therapeutic targets for future precision medicine based on the most recent results of clinical trials.

Considerations for the clinical development of immuno-oncology agents in cancer

Targeting of the immune system has shown to be a successful therapeutic approach in cancer, with the development of check point inhibitors (ICI) or T-cell engagers (TCE). As immuno-oncology agents modulate the immune system to attack cancer cells and do not act directly on oncogenic vulnerabilities, specific characteristics of these compounds should be taken in consideration during clinical development. In this review we will discuss relevant concepts including limitations of preclinical models, special pharmacologic boundaries, clinical development strategies such as the selection of clinical indication, line of treatment and backbone partner, as well as the endpoints and expected magnitude of benefit required at different stages of the drug development. In addition, future directions for early and late trial designs will be reviewed. Examples from approved drugs or those currently in clinical development will be discussed and options to overcome these limitations will be provided.

Current Indications and Future Landscape of Bispecific Antibodies for the Treatment of Lung Cancer

Bispecific antibodies are a promising type of therapy for the treatment of cancer due to their ability to simultaneously inhibit different proteins playing a role in cancer progression. The development in lung cancer has been singularly intense because of the increasingly vast knowledge of the underlying molecular routes, in particular, in oncogene-driven tumors. In this review, we present the current landscape of bispecific antibodies for the treatment of lung cancer and discuss potential scenarios where the role of these therapeutics might expand in the near future.

Novel therapeutic strategies for recurrent SCLC

Therapeutic options for patients with relapsed SCLC are limited, and the prognosis in this setting remains poor. While clinical outcomes for frontline treatment have modestly improved with the introduction of immunotherapy, treatment in the second-line setting persists almost unchanged. In this review, current treatment options and recent advances in molecular biology are described. Emerging therapeutic options in this setting and potential strategies to improve clinical outcomes of these patients are also addressed.

Spotlight on Small-Cell Lung Cancer and Other Lung Neuroendocrine Neoplasms

Lung neuroendocrine neoplasms (NENs) encompass a spectrum of neoplasms that are subdivided into the well-differentiated neuroendocrine tumors comprising the low- and intermediate-grade typical and atypical carcinoids, respectively, and the poorly differentiated, high-grade neuroendocrine carcinomas including large-cell neuroendocrine carcinomas and small-cell lung carcinoma (SCLC). Here, we review the current morphological and molecular classifications of the NENs on the basis of the updated WHO Classification of Thoracic Tumors and discuss the emerging subclassifications on the basis of molecular profiling and the potential therapeutic implications. We focus on the efforts in subtyping SCLC, a particularly aggressive tumor with few treatment options, and the recent advances in therapy with the adoption of immune checkpoint inhibitors in the frontline setting for patients with extensive-stage SCLC. We further highlight the promising immunotherapy strategies in SCLC that are currently under investigation.

What Is New in Small Cell Lung Cancer

Small cell lung cancer (SCLC) is a rare yet aggressive lung cancer subtype with an extremely poor prognosis of around 1 year. SCLC accounts for 15% of all newly diagnosed lung cancers and is characterized by rapid growth with high potential for metastatic spread and treatment resistance. In the article the authors review some of the most notable efforts to improve outcomes, including trials of novel immunotherapy agents, novel disease targets, and multiple drug combinations.

Rare thoracic cancers: a comprehensive overview of diagnosis and management of small cell lung cancer, malignant pleural mesothelioma and thymic epithelial tumours

Despite the progress in outcomes seen with immunotherapy in various malignancies, including nonsmall cell lung cancer, the benefits are less in small cell lung cancer, malignant pleural mesothelioma and thymic epithelial tumours. New effective treatment options are needed, guided via more in-depth insights into the pathophysiology of these rare malignancies. This review comprehensively presents an overview of the clinical presentation, diagnostic tools, staging systems, pathophysiology and treatment options for these rare thoracic cancers. In addition, opportunities for further improvement of therapies are discussed.

Bispecific T-Cell Engagers Therapies in Solid Tumors: Focusing on Prostate Cancer

Over the past decade, immunotherapy has demonstrated an impressive improvement in treatment outcomes for multiple cancers. Following the landmark approvals for use of immune checkpoint inhibitors, new challenges emerged in various clinical settings. Not all tumor types harbor immunogenic characteristics capable of triggering responses. Similarly, many tumors' immune microenvironment allows them to become evasive, leading to resistance and, thus, limiting the durability of responses. To overcome this limitation, new T-cell redirecting strategies such as bispecific T-cell engager (BiTE) have become attractive and promising immunotherapies. Our review provides a comprehensive perspective of the current evidence of BiTE therapies in solid tumors. Considering that immunotherapy has shown modest results in advanced prostate cancer to date, we review the biologic rationale and promising results of BiTE therapy in this clinical setting and discuss potential tumor-associated antigens that may be integrated into BiTE construct designs. Our review also aims to evaluate the advances of BiTE therapies in prostate cancer, illustrate the major obstacles and underlying limitations, and discuss directions for future research.

Current status and future perspectives of bispecific antibodies in the treatment of lung cancer

ABSTRACT

Monoclonal antibodies have been successfully incorporated into the current therapeutical landscape of lung cancer in the last decades. Recently, with technological advances, bispecific antibodies (bsAbs) have also shown robust efficacy in the treatment of malignant cancers, including lung cancer. These antibodies target two independent epitopes or antigens and have been extensively explored in translational and clinical studies in lung cancer. Here, we outline the mechanisms of action of bsAbs, related clinical data, ongoing clinical trials, and potent novel compounds of various types of bsAbs in clinical studies, especially in lung cancer. We also propose future directions for the clinical development of bsAbs, which might bring a new era of treatment for patients with lung cancer.

CAR-Based Immunotherapy of Solid Tumours-A Survey of the Emerging Targets

Immunotherapy with CAR T-cells has revolutionised the treatment of B-cell and plasma cell-derived cancers. However, solid tumours present a much greater challenge for treatment using CAR-engineered immune cells. In a partner review, we have surveyed data generated in clinical trials in which patients with solid tumours that expressed any of 30 discrete targets were treated with CAR-based immunotherapy. That exercise confirms that efficacy of this approach falls well behind that seen in haematological malignancies, while significant toxic events have also been reported. Here, we consider approximately 60 additional candidates for which such clinical data are not available yet, but where pre-clinical data have provided support for their advancement to clinical evaluation as CAR target antigens.

Immunotherapeutic Targeting and PET Imaging of DLL3 in Small-Cell Neuroendocrine Prostate Cancer

Effective treatments for de novo and treatment-emergent small-cell/neuroendocrine (t-SCNC) prostate cancer represent an unmet need for this disease. Using metastatic biopsies from patients with advanced cancer, we demonstrate that delta-like ligand 3 (DLL3) is expressed in de novo and t-SCNC and is associated with reduced survival. We develop a PET agent, [89Zr]-DFO-DLL3-scFv, that detects DLL3 levels in mouse SCNC models. In multiple patient-derived xenograft models, AMG 757 (tarlatamab), a half-life-extended bispecific T-cell engager (BiTE) immunotherapy that redirects CD3-positive T cells to kill DLL3-expressing cells, exhibited potent and durable antitumor activity. Late relapsing tumors after AMG 757 treatment exhibited lower DLL3 levels, suggesting antigen loss as a resistance mechanism, particularly in tumors with heterogeneous DLL3 expression. These findings have been translated into an ongoing clinical trial of AMG 757 in de novo and t-SCNC, with a confirmed objective partial response in a patient with histologically confirmed SCNC. Overall, these results identify DLL3 as a therapeutic target in SCNC and demonstrate that DLL3-targeted BiTE immunotherapy has significant antitumor activity in this aggressive prostate cancer subtype.

SIGNIFICANCE

The preclinical and clinical evaluation of DLL3-directed immunotherapy, AMG 757, and development of a PET radiotracer for noninvasive DLL3 detection demonstrate the potential of targeting DLL3 in SCNC prostate cancer.

Evolving role of immunotherapy in small cell lung cancer

Small cell lung cancer (SCLC) is a highly lethal subtype of lung cancer with a particularly poor prognosis. For decades, the best available systemic therapy was platinum plus etoposide chemotherapy, which offered frequent but transient responses. Survival gains were finally realized with the addition of immune checkpoint inhibitors to first-line chemotherapy. The phase III IMpower 133 trial showed that the addition of atezolizumab to chemotherapy improved survival. The subsequent CASPIAN trial demonstrated a similar benefit with durvalumab. These results quickly established chemo-immunotherapy as the preferred initial treatment for advanced SCLC, but outcomes remain poor for most patients. Here, we review the current and evolving role of immunotherapy in SCLC and outline emerging strategies poised to further elevate the standard of care.

Factors Affecting the Cancer Immunotherapeutic Efficacy of T Cell Bispecific Antibodies and Strategies for Improvement

T-cell bispecific antibodies (T-BsAbs) are a new class of cancer immunotherapy drugs that can simultaneously bind to tumor-associated antigens on target cells and to the CD3 subunit of the T-cell receptor (TCR) on T cells. In the last decade, numerous T-BsAbs have been developed for the treatment of both hematological malignancies and solid tumors. Among them, blinatumomab has been successfully used to treat CD19 positive malignancies and has been approved by the FDA as standard care for acute lymphoblastic leukemia (ALL). However, in many clinical scenarios, the efficacy of T-BsAbs remains unsatisfactory. To further improve T-BsAb therapy, it will be crucial to better understand the factors affecting treatment efficacy and the nature of the T-BsAb-induced immune response. Herein, we first review the studies on the potential mechanisms by which T-BsAbs activate T-cells and how they elicit efficient target killing despite suboptimal costimulatory support. We focus on analyzing reports from clinical trials and preclinical studies, and summarize the factors that have been identified to impact the efficacy of T-BsAbs. Lastly, we review current and propose new approaches to improve the clinical efficacy of T-BsAbs.

Emerging immune checkpoint inhibitors for the treatment of non-small cell lung cancer

INTRODUCTION

Over the last decade, immune checkpoint inhibitors (ICIs) have impacted on the standard therapy for patients with non-small cell lung cancer (NSCLC). ICIs first showed efficacy in patients with advanced disease who had progressed after chemotherapy, later reaching the first-line therapy context alone, in combination with chemotherapy, and/or with dual-immunotherapy regimens.

AREAS COVERED

Most of their benefit is, however, restricted to just 20% of patients due to primary or emergence of acquired resistance. In this review, we will describe the role of new emerging ICIs in the current panorama of NSCLC therapeutic approaches, not only in metastatic disease but also in locally advanced stage disease, with specific focus on those drugs under investigation in Phase 2/3 clinical trials.

EXPERT OPINION

Several new ICIs are now under investigation to optimize NSCLC patient management; these are usually used in combination with other well-known agents, such as 'traditional' ICIs and chemotherapy, or with other newly developed drugs. Identification of better biomarkers will provide personalized treatment approaches to overcome patient-specific immune resistance.

Phase I trial of the DLL3/CD3 bispecific T-cell engager BI 764532 in DLL3-positive small-cell lung cancer and neuroendocrine carcinomas

Poorly differentiated neuroendocrine carcinomas such as small-cell lung cancer (SCLC) have poor survival and high relapse rates. DLL3 is found on these carcinomas and has become a target of increasing interest in recent years. The bispecific DLL3/CD3 T-cell engager BI 764532 has been shown to induce complete tumor regression in a human T cell-engrafted mouse model. Here, we describe the study design of a first-in-human, phase I, multicenter, open-label, non-randomized, dose-escalation study in patients with SCLC or other DLL3-positive neuroendocrine carcinomas. The study will determine the maximum tolerated dose and evaluate safety, tolerability, pharmacokinetics and preliminary efficacy of BI 764532 monotherapy.

[Small cell lung cancer-Established standards and new approaches]

BACKGROUND

Although the treatment and prognosis of many solid tumor types in the metastatic situation could be considerably improved during the last decade, for a long time no significant progress in the treatment of small cell lung cancer (SCLC) could be achieved.

OBJECTIVE

The aim of this article is to describe the current treatment standard for SCLC and to discuss potential approaches for further improvement.

METHODS

A selective literature search was carried out in PubMed and abstract lists of relevant conferences.

RESULTS

Given the recent approval of two immunochemotherapy regimens based on the combination of anti-PD-L1 antibodies with platinum-etoposide, the therapeutic standard in the first line treatment of metastasized SCLC has finally been improved for the first time in three decades; however, the overall survival benefit has been modest with an improvement of just 2-3 months. In advanced lines of treatment no new approaches could so far show improved outcome compared with established chemotherapy protocols, such as topotecan and combinations of anthracycline, cyclophosphamide and vincristine. The slow progress in SCLC compared to non-SCLC, has been attributed to the complex biology, the exceptionally high proliferation rate and rapid development of resistance to chemotherapy. Increasing knowledge on the molecular and immunological principles of SCLC is increasingly opening up novel treatment approaches.

CONCLUSION

There has finally been a slow but clinically meaningful progress in the treatment of SCLC. Patients should be included in clinical trials at the latest after second line treatment, in order to accelerate the speed of the expansion of treatment options.

Bispecific Antibody-Based Immune-Cell Engagers and Their Emerging Therapeutic Targets in Cancer Immunotherapy

Cancer is the second leading cause of death worldwide after cardiovascular diseases. Harnessing the power of immune cells is a promising strategy to improve the antitumor effect of cancer immunotherapy. Recent progress in recombinant DNA technology and antibody engineering has ushered in a new era of bispecific antibody (bsAb)-based immune-cell engagers (ICEs), including T- and natural-killer-cell engagers. Since the first approval of blinatumomab by the United States Food and Drug Administration (US FDA), various bsAb-based ICEs have been developed for the effective treatment of patients with cancer. Simultaneously, several potential therapeutic targets of bsAb-based ICEs have been identified in various cancers. Therefore, this review focused on not only highlighting the action mechanism, design and structure, and status of bsAb-based ICEs in clinical development and their approval by the US FDA for human malignancy treatment, but also on summarizing the currently known and emerging therapeutic targets in cancer. This review provides insights into practical considerations for developing next-generation ICEs.

SCLC Treatment in the Immuno-Oncology Era: Current Evidence and Unmet Needs

Small cell lung cancer (SCLC) represents about 13%-15% of all lung cancers. It has a particularly unfavorable prognosis and in about 70% of cases occurs in the advanced stage (extended disease). Three phase III studies tested the combination of immunotherapy (atezolizumab, durvalumab with or without tremelimumab, and pembrolizumab) with double platinum chemotherapy, with practice-changing results. However, despite the high tumor mutational load and the chronic pro-inflammatory state induced by prolonged exposure to cigarette smoke, the benefit observed with immunotherapy is very modest and most patients experience disease recurrence. Unfortunately, biological, clinical, or molecular factors that can predict this risk have not yet been identified. Thanks to these clinically meaningful steps forward, SCLC is no longer considered an "orphan" disease. Innovative treatment strategies and combinations are currently under investigation to further improve the expected prognosis of patients with SCLC. Following the recent therapeutic innovations, we have reviewed the available literature data about SCLC management, with a focus on current unmet needs and potential predictive factors. In detail, the role of radiotherapy; fragile populations, such as elderly or low-performance status patients (ECOG PS 2), usually excluded from randomized studies; predictive factors of response useful to optimize and guide therapeutic choices; and new molecular targets and future combinations have been explored and revised.

Targeting Solid Tumors with Bispecific T Cell Engager Immune Therapy

T cell engagers (TCEs) are targeted immunotherapies that have emerged as a promising treatment to redirect effector T cells for tumor cell killing. The strong therapeutic value of TCEs, established by the approval of blinatumomab for the treatment of B cell precursor acute lymphoblastic leukemia, has expanded to include other hematologic malignancies, as well as some solid tumors. Successful clinical development of TCEs in solid tumors has proven challenging, as it requires additional considerations such as the selectivity of target expression, tumor accessibility, and the impact of the immunosuppressive tumor microenvironment. In this review, we provide a brief history of blinatumomab, summarize learnings from TCEs in hematologic malignancies, and highlight results from recent TCE trials in solid tumors. Additionally, we examine approaches to improve the efficacy and safety of TCEs in solid tumors, including therapeutic combinations to increase the depth and durability of response.

Cancer cell-intrinsic resistance to BiTE therapy is mediated by loss of CD58 costimulation and modulation of the extrinsic apoptotic pathway

Background

Bispecific T-cell engager (BiTE) molecules induce redirected lysis of cancer cells by T cells and are an emerging modality for solid tumor immunotherapy. While signs of clinical activity have been demonstrated, efficacy of T-cell engagers (TCEs) in solid tumors settings, molecular determinants of response, and underlying mechanisms of resistance to BiTE therapy require more investigation.

Methods

To uncover cancer cell-intrinsic genetic modifiers of TCE-mediated cytotoxicity, we performed genome-wide CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) loss-of-function and CRISPRa (CRISPR activation) gain-of-function screens using TCEs against two distinct tumor-associated antigens (TAAs). By using in vitro T-cell cytotoxicity assays and in vivo efficacy studies, we validated the roles of two common pathways identified in our screen, T-cell costimulation pathway and apoptosis pathway, as key modifiers of BiTE activity.

Results

Our genetic screens uncovered TAAs-independent cancer cell-intrinsic genes with functions in autophagy, T-cell costimulation, the apoptosis pathway, chromatin remodeling, and cytokine signaling that altered responsiveness to BiTE-mediated killing. Notably, loss of CD58 (the ligand of the CD2 T-cell costimulatory receptor), a gene frequently altered in cancer, led to decreased TCE-mediated cytotoxicity, T-cell activation and antitumor efficacy in vitro and in vivo. Moreover, the effects of CD58 loss were synergistically compounded by concurrent loss of CD80/CD86 (ligands for the CD28 T-cell costimulatory receptor), whereas joint CD2 and CD28 costimulation additively enhanced TCE-mediated killing, indicating non-redundant costimulatory mechanisms between the two pathways. Additionally, loss of CFLAR (Caspase-8 and FADD Like Apoptosis Regulator), BCL2L1, and BID (BH3 Interacting Domain Death Agonist) induced profound changes in sensitivity to TCEs, indicating that key regulators of apoptosis, which are frequently altered in cancer, impact tumor responsiveness to BiTE therapy.

Conclusions

This study demonstrates that genetic alterations central to carcinogenesis and commonly detected in cancer samples lead to significant modulation of BiTE antitumor activity in vitro and in vivo, findings with relevance for a better understanding of patient responses to BiTE therapy and novel combinations that enhance TCE efficacy.

Extensive-Stage Small-Cell Lung Cancer: First-Line and Second-Line Treatment Options

Extensive-stage small-cell lung cancer is a therapeutically challenging disease. After more than two decades without clinical progress, the addition of programmed cell death protein 1 axis blockade to platinum-based chemotherapy has demonstrated sustained overall survival benefit and represents the current standard of care in the first-line setting. Despite this benefit, resistance emerges relatively rapidly in virtually all patients. Although newer treatments are being incorporated in the relapse setting, marked therapeutic resistance is typically observed in patients with relapsed small-cell lung cancer (SCLC), underscoring the need of developing more effective therapies in this setting. Notably, recent progress in the understanding of the molecular biology of SCLC might bring possibilities toward molecularly informed therapeutic strategies for patients with SCLC, which could have a significant impact for improving outcomes in this disease. Here, we review current treatment options and recent progress made in the first-line and relapsed SCLC, including the role of biomarkers and new evolving therapeutic strategies.

Limited-Stage Small-Cell Lung Cancer: Current Progress and the Next Frontier

Limited-stage (LS) small-cell lung cancer (SCLC) is defined as disease confined to a tolerable radiation portal without extrathoracic metastases. Despite clinical research over two decades, the prognosis of LS-SCLC patients remains poor. The current standard of care for LS-SCLC patients is concurrent platinum-based chemotherapy with thoracic radiotherapy (RT). Widespread heterogeneity on the optimal radiation dose and fractionation regimen among physicians highlights the logistical challenges of administering BID regimens. Prophylactic cranial irradiation (PCI) is recommended to patients following a good initial response to chemoradiation due to improved overall survival from historical trials and the propensity for LS-SCLC to recur with brain metastases. However, PCI utilization is being debated due to the greater availability of magnetic resonance imaging (MRI) and data in extensive-stage SCLC regarding close MRI surveillance in lieu of PCI while spurring novel RT techniques, such as hippocampal-avoidance PCI. Additionally, novel treatment combinations incorporating targeted small molecule therapies and immunotherapies with or following radiation for LS-SCLC have seen recent interest and some concepts are being investigated in clinical trials. Here, we review the landscape of progress, limitations, and challenges for LS-SCLC including current standard of care, novel radiation techniques, and the integration of novel therapeutic strategies for LS-SCLC.