Anti-CTLA-4 Immunotherapy Does Not Deplete FOXP3+ Regulatory T Cells (Tregs) in Human Cancers

Immunotherapies and Combination Strategies for Immuno-Oncology

The advent of novel immunotherapies in the treatment of cancers has dramatically changed the landscape of the oncology field. Recent developments in checkpoint inhibition therapies, tumor-infiltrating lymphocyte therapies, chimeric antigen receptor T cell therapies, and cancer vaccines have shown immense promise for significant advancements in cancer treatments. Immunotherapies act on distinct steps of immune response to augment the body's natural ability to recognize, target, and destroy cancerous cells. Combination treatments with immunotherapies and other modalities intend to activate immune response, decrease immunosuppression, and target signaling and resistance pathways to offer a more durable, long-lasting treatment compared to traditional therapies and immunotherapies as monotherapies for cancers. This review aims to briefly describe the rationale, mechanisms of action, and clinical efficacy of common immunotherapies and highlight promising combination strategies currently approved or under clinical development. Additionally, we will discuss the benefits and limitations of these immunotherapy approaches as monotherapies as well as in combination with other treatments.

Molecular Pathways of Colon Inflammation Induced by Cancer Immunotherapy

Checkpoint blockade with antibodies specific for the PD-1 and CTLA-4 inhibitory receptors can induce durable responses in a wide range of human cancers. However, the immunological mechanisms responsible for severe inflammatory side effects remain poorly understood. Here we report a comprehensive single-cell analysis of immune cell populations in colitis, a common and severe side effect of checkpoint blockade. We observed a striking accumulation of CD8 T cells with highly cytotoxic and proliferative states and no evidence of regulatory T cell depletion. T cell receptor (TCR) sequence analysis demonstrated that a substantial fraction of colitis-associated CD8 T cells originated from tissue-resident populations, explaining the frequently early onset of colitis symptoms following treatment initiation. Our analysis also identified cytokines, chemokines, and surface receptors that could serve as therapeutic targets for colitis and potentially other inflammatory side effects of checkpoint blockade.

STAT3 Modulation of Regulatory T Cells in Response to Radiation Therapy in Head and Neck Cancer

BACKGROUND

Radioresistance represents a major problem in the treatment of head and neck cancer (HNC) patients. To improve response, understanding tumor microenvironmental factors that contribute to radiation resistance is important. Regulatory T cells (Tregs) are enriched in numerous cancers and can dampen the response to radiation by creating an immune-inhibitory microenvironment. The purpose of this study was to investigate mechanisms of Treg modulation by radiation in HNC.

METHODS

We utilized an orthotopic mouse model of HNC. Anti-CD25 was used for Treg depletion. Image-guided radiation was delivered to a dose of 10 Gy. Flow cytometry was used to analyze abundance and function of intratumoral immune cells. Enzyme-linked immunosorbent assay was performed to assess secreted factors. For immune-modulating therapies, anti-PD-L1, anti-CTLA-4, and STAT3 antisense oligonucleotide (ASO) were used. All statistical tests were two-sided.

RESULTS

Treatment with anti-CD25 and radiation led to tumor eradication (57.1%, n = 4 of 7 mice), enhanced T-cell cytotoxicity compared with RT alone (CD4 effector T cells [Teff]: RT group mean = 5.37 [ 0.58] vs RT + αCD25 group mean =10.71 [0.67], P = .005; CD8 Teff: RT group mean = 9.98 [0.81] vs RT + αCD25 group mean =16.88 [2.49], P = .01) and induced tumor antigen-specific memory response (100.0%, n = 4 mice). In contrast, radiation alone or when combined with anti-CTLA4 did not lead to durable tumor control (0.0%, n = 7 mice). STAT3 inhibition in combination with radiation, but not as a single agent, improved tumor growth delay, decreased Tregs, myeloid-derived suppressor cells, and M2 macrophages and enhanced effector T cells and M1 macrophages. Experiments in nude mice inhibited the benefit of STAT3 ASO and radiation.

CONCLUSION

We propose that STAT3 inhibition is a viable and potent therapeutic target against Tregs. Our data support the design of clinical trials integrating STAT3 ASO in the standard of care for cancer patients receiving radiation.

Combined Anti-Cancer Strategies Based on Anti-Checkpoint Inhibitor Antibodies

Therapeutic monoclonal antibodies for the treatment of cancer came of age in 1997, with the approval of anti-CD20 Rituximab. Since then, a wide variety of antibodies have been developed with many different formats and mechanisms of action. Among these, antibodies blocking immune checkpoint inhibitors (ICI) have revolutionized the field, based on the novelty of their concept and their demonstrated efficacy in several types of cancer otherwise lacking effective immunotherapy approaches. ICI are expressed by tumor, stromal or immune cells infiltrating the tumor microenvironment, and negatively regulate anti-tumor immunity. Antibodies against the first discovered ICI, CTLA-4, PD-1 and PD-L1, have shown significant activity in phase III studies against melanoma and other solid cancers, alone or in combination with chemotherapy or radiotherapy. However, not all cancers and not all patients respond to these drugs. Therefore, novel antibodies targeting additional ICI are currently being developed. In addition, CTLA-4, PD-1 and PD-L1 blocking antibodies are being combined with each other or with other antibodies targeting novel ICI, immunostimulatory molecules, tumor antigens, angiogenic factors, complement receptors, or with T cell engaging bispecific antibodies (BsAb), with the aim of obtaining synergistic effects with minimal toxicity. In this review, we summarize the biological aspects behind such combinations and review some of the most important clinical data on ICI-specific antibodies.

The Tumor Microenvironment in the Response to Immune Checkpoint Blockade Therapies

Tumor cells constantly interact with their microenvironment, which comprises a variety of immune cells together with endothelial cells and fibroblasts. The composition of the tumor microenvironment (TME) has been shown to influence response to immune checkpoint blockade (ICB). ICB takes advantage of immune cell infiltration in the tumor to reinvigorate an efficacious antitumoral immune response. In addition to tumor cell intrinsic biomarkers, increasing data pinpoint the importance of the TME in guiding patient selection and combination therapies. Here, we review recent efforts in determining how various components of the TME can influence response and resistance to ICB. Although a large body of evidence points to the extent and functional orientation of the T cell infiltrate as important in therapy response, recent studies also confirm a role for other components of the TME, such as B cells, myeloid lineage cells, cancer-associated fibroblasts, and vasculature. If the ultimate goal of curative cancer therapies is to induce a long-term memory T cell response, the other components of the TME may positively or negatively modulate the induction of efficient antitumor immunity. The emergence of novel high-throughput methods for analyzing the TME, including transcriptomics, has allowed tremendous developments in the field, with the expansion of patient cohorts, and the identification of TME-based markers of therapy response. Together, these studies open the possibility of including TME-based markers for selecting patients that are likely to respond to specific therapies, and pave the way to personalized medicine in oncology.

Immune-related adverse events of checkpoint inhibitors

Cancer immunotherapies have changed the landscape of cancer treatment during the past few decades. Among them, immune checkpoint inhibitors, which target PD-1, PD-L1 and CTLA-4, are increasingly used for certain cancers; however, this increased use has resulted in increased reports of immune-related adverse events (irAEs). These irAEs are unique and are different to those of traditional cancer therapies, and typically have a delayed onset and prolonged duration. IrAEs can involve any organ or system. These effects are frequently low grade and are treatable and reversible; however, some adverse effects can be severe and lead to permanent disorders. Management is primarily based on corticosteroids and other immunomodulatory agents, which should be prescribed carefully to reduce the potential of short-term and long-term complications. Thoughtful management of irAEs is important in optimizing quality of life and long-term outcomes.

How to select IgG subclasses in developing anti-tumor therapeutic antibodies

The intact antibody of human immunoglobulin (IgG) is composed of the fragment for antigen binding (Fab) and the crystallizable fragment (Fc) for binding of Fcγ receptors. Among the four subclasses of human IgG (IgG1, IgG2, IgG3, IgG4), which differ in their constant regions, particularly in their hinges and CH2 domains, IgG1 has the highest FcγR-binding affinity, followed by IgG3, IgG2, and IgG4. As a result, different subclasses have different effector functions such as antibody-dependent cell-mediated cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP). Fcγ receptors include six subtypes (FcγRI, FcγRIIA, FcγRIIB, FcγRIIC, FcγRIIIA, FcγRIIIB) which differ in cellular distribution, binding affinity to Fc, and the resulting biological activity. Therefore, when developing anti-tumor therapeutic antibodies, including single-targeted antibodies, bi-specific antibodies (BsAbs), and antibody-drug conjugates (ADCs), many factors, such as target biology, cellular distribution of the targets, the environments of particular tumor types, as well as the proposed mechanism of action (MOA), must be taken into consideration. This review outlines fundamental strategies that are required to select IgG subclasses in developing anti-tumor therapeutic antibodies.

Harnessing neoantigen specific CD4 T cells for cancer immunotherapy

The goal of precision immunotherapy is to direct a patient's T cell response against the immunogenic mutations expressed on their tumors. Most immunotherapy approaches to-date have focused on MHC class I-restricted peptide epitopes by which cytotoxic CD8+ T lymphocytes (CTL) can directly recognize tumor cells. This strategy largely overlooks the critical role of MHC class II-restricted CD4+ T cells as both positive regulators of CTL and other effector cell types, and as direct effectors of antitumor immunity. In this review, we will discuss the role of neoantigen specific CD4+ T cells in cancer immunotherapy and how existing treatment modalities may be leveraged to engage this important T cell subset.

Targeting T cell activation in immuno-oncology

The years since 2009 have seen tremendous progress in unlocking the curative potential of the immune system for the treatment of cancer. Much of that revolution in immuno-oncology has been fueled by the clinical success of immune checkpoint inhibitors, particularly those targeting the PD-1 axis. Unfortunately, many patients still fail to benefit from checkpoint blockade or other immunotherapies. An inability to fully activate antitumour T cells contributes in part to the failure of those therapies. Here, we review the basic biology of T cell activation, with particular emphasis on the essential role of the dendritic cell and the innate immune system in T cell activation. The current understanding of the multiple factors that govern T cell activation and how they impinge on tumour immunotherapy are also discussed. Lastly, treatment strategies to potentially overcome barriers to T cell activation and to enhance the efficacy of immunotherapy are addressed.

Modern Aspects of Immunotherapy with Checkpoint Inhibitors in Melanoma

Although melanoma is one of the most immunogenic tumors, it has an ability to evade anti-tumor immune responses by exploiting tolerance mechanisms, including negative immune checkpoint molecules. The most extensively studied checkpoints represent cytotoxic T lymphocyte-associated protein-4 (CTLA-4) and programmed cell death protein 1 (PD-1). Immune checkpoint inhibitors (ICI), which were broadly applied for melanoma treatment in the past decade, can unleash anti-tumor immune responses and result in melanoma regression. Patients responding to the ICI treatment showed long-lasting remission or disease control status. However, a large group of patients failed to respond to this therapy, indicating the development of resistance mechanisms. Among them are intrinsic tumor properties, the dysfunction of effector cells, and the generation of immunosuppressive tumor microenvironment (TME). This review discusses achievements of ICI treatment in melanoma, reasons for its failure, and promising approaches for overcoming the resistance. These methods include combinations of different ICI with each other, strategies for neutralizing the immunosuppressive TME and combining ICI with other anti-cancer therapies such as radiation, oncolytic viral, or targeted therapy. New therapeutic approaches targeting other immune checkpoint molecules are also discussed.

Characteristics of Tumor-Infiltrating Lymphocytes Prior to and During Immune Checkpoint Inhibitor Therapy

The tumor immune contexture plays a major role for the clinical outcome of patients. High densities of CD45RO⁺ T helper 1 cells and CD8⁺ T cells are associated with improved survival of patients with various cancer entities. In contrast, a higher frequency of tumor-infiltrating M2 macrophages is correlated with poor prognosis. Recent studies provide evidence that the tumor immune architecture also essentially contributes to the clinical efficacy of immune checkpoint inhibitor (CPI) therapy in patients. Pretreatment melanoma samples from patients who experienced a clinical response to anti-programmed cell death protein 1 (PD-1) treatment show higher densities of infiltrating CD8⁺ T cells compared to samples from patients that progressed during therapy. Anti-PD-1 therapy results in an increased density of tumor-infiltrating T lymphocytes in treatment responders. In addition, elevated frequencies of melanoma-infiltrating TCF7⁺CD8⁺ T cells are correlated with beneficial clinical outcome of anti-PD-1-treated patients. In contrast, a high density of tumor-infiltrating, dysfunctional PD-1⁺CD38^hi CD8⁺ cells in melanoma patients is associated with anti-PD-1 resistance. Such findings indicate that comprehensive tumor immune contexture profiling prior to and during CPI therapy may lead to the identification of underlying mechanisms for treatment response or resistance, and the design of improved immunotherapeutic strategies. Here, we focus on studies exploring the impact of intratumoral T and B cells at baseline on the clinical outcome of CPI-treated cancer patients. In addition, recent findings demonstrating the influence of CPIs on tumor-infiltrating lymphocytes are summarized.

Sensitizing the Tumor Microenvironment to Immune Checkpoint Therapy

Immune checkpoint blockade (ICB) has revolutionized cancer treatment, providing remarkable clinical responses in some patients. However, the majority of patients do not respond. It is therefore crucial both to identify predictive biomarkers of response and to increase the response rates to immune checkpoint therapy. In this review we explore the current literature about the predictive characteristics of the tumor microenvironment and discuss therapeutic approaches that aim to change this toward a milieu that is conducive to response. We propose a personalized biomarker-based adaptive approach to immunotherapy, whereby a sensitizing therapy is tailored to the patient's specific tumor microenvironment, followed by on-treatment verification of a change in the targeted biomarker, followed by immune checkpoint therapy. By incorporating detailed knowledge of the immunological tumor microenvironment, we may be able to sensitize currently non-responsive tumors to respond to immune checkpoint therapy.

Combining microenvironment normalization strategies to improve cancer immunotherapy

Advances in immunotherapy have revolutionized the treatment of multiple cancers. Unfortunately, tumors usually have impaired blood perfusion, which limits the delivery of therapeutics and cytotoxic immune cells to tumors and also results in hypoxia-a hallmark of the abnormal tumor microenvironment (TME)-that causes immunosuppression. We proposed that normalization of TME using antiangiogenic drugs and/or mechanotherapeutics can overcome these challenges. Recently, immunotherapy with checkpoint blockers was shown to effectively induce vascular normalization in some types of cancer. Although these therapeutic approaches have been used in combination in preclinical and clinical studies, their combined effects on TME are not fully understood. To identify strategies for improved immunotherapy, we have developed a mathematical framework that incorporates complex interactions among various types of cancer cells, immune cells, stroma, angiogenic molecules, and the vasculature. Model predictions were compared with the data from five previously reported experimental studies. We found that low doses of antiangiogenic treatment improve immunotherapy when the two treatments are administered sequentially, but that high doses are less efficacious because of excessive vessel pruning and hypoxia. Stroma normalization can further increase the efficacy of immunotherapy, and the benefit is additive when combined with vascular normalization. We conclude that vessel functionality dictates the efficacy of immunotherapy, and thus increased tumor perfusion should be investigated as a predictive biomarker of response to immunotherapy.

Insights Into Lung Cancer Immune-Based Biology, Prevention, and Treatment

Lung cancer is the number one cause of cancer-related deaths. The malignancy is characterized by dismal prognosis and poor clinical outcome mostly due to advanced-stage at diagnosis, thereby inflicting a heavy burden on public health worldwide. Recent breakthroughs in immunotherapy have greatly benefited a subset of lung cancer patients, and more importantly, they are undauntedly bringing forth a paradigm shift in the drugs approved for cancer treatment, by introducing "tumor-type agnostic therapies". Yet, and to fulfill immunotherapy's potential of personalized cancer treatment, demarcating the immune and genomic landscape of cancers at their earliest possible stages will be crucial to identify ideal targets for early treatment and to predict how a particular patient will fare with immunotherapy. Recent genomic surveys of premalignant lung cancer have shed light on early alterations in the evolution of lung cancer. More recently, the advent of immunogenomic technologies has provided prodigious opportunities to study the multidimensional landscape of lung tumors as well as their microenvironment at the molecular, genomic, and cellular resolution. In this review, we will summarize the current state of immune-based therapies for cancer, with a focus on lung malignancy, and highlight learning outcomes from clinical and preclinical studies investigating the naïve immune biology of lung cancer. The review also collates immunogenomic-based evidence from seminal reports which collectively warrant future investigations of premalignancy, the tumor-adjacent normal-appearing lung tissue, pulmonary inflammatory conditions such as chronic obstructive pulmonary disease, as well as systemic microbiome imbalance. Such future directions enable novel insights into the evolution of lung cancers and, thus, can provide a low-hanging fruit of targets for early immune-based treatment of this fatal malignancy.

Single-cell genomic approaches for developing the next generation of immunotherapies

Recent progress in single-cell genomics urges its application in drug development, particularly of cancer immunotherapies. Current immunotherapy pipelines are focused on functional outcome and simple cellular and molecular readouts. A thorough mechanistic understanding of the cells and pathways targeted by immunotherapy agents is lacking, which limits the success rate of clinical trials. A large leap forward can be made if the immunotherapy target cells and pathways are characterized at high resolution before and after treatment, in clinical cohorts and model systems. This will enable rapid development of effective immunotherapies and data-driven design of synergistic drug combinations. In this Perspective, we discuss how emerging single-cell genomic technologies can serve as an engine for target identification and drug development.

[Which immunoglobulin heavy chains for which immunostimulatory antibodies?]

Immunostimulatory antibodies in cancer rely on different mechanisms of action, simple blocking of immune checkpoints, depletion of tumour-infiltrating regulatory T cells, agonistic action on lymphocyte activatory receptors, etc. Choosing the relevant heavy chain isotype or the adequate engineering variant of this heavy chain is critical for the therapeutic efficacy, since the aforementioned properties sometimes bring into play the Fc region and the hinge region. This short review tries to learn the lessons from the clinical experience.

Janus or Hydra: The Many Faces of T Helper Cells in the Human Tumour Microenvironment

CD4+ T helper (T_H) cells are key regulators in the tumour immune microenvironment (TIME), mediating the adaptive immunological response towards cancer, mainly through the activation of cytotoxic CD8+ T cells. After antigen recognition and proper co-stimulation, naïve T_H cells are activated, undergo clonal expansion, and release cytokines that will define the differentiation of a specific effector T_H cell subtype. These different subtypes have different functions, which can mediate both anti- and pro-tumour immunological responses. Here, we present the dual role of T_H cells restraining or promoting the tumour, the factors controlling their homing and differentiation in the TIME, their influence on immunotherapy, and their use as prognostic indicators.

Depleting tumor-associated Tregs via nanoparticle-mediated hyperthermia to enhance anti-CTLA-4 immunotherapy

Aim: We aim to demonstrate that a local nanoparticle-mediated hyperthermia can effectively eliminate tumor-associated Tregs and thereby boost checkpoint blockade-based immunotherapy. Materials & methods: Photothermal therapy (PTT), mediated with systemically administered stealthy iron-oxide nanoparticles, was applied to treat BALB/c mice bearing 4T1 murine breast tumors. Flow cytometry was applied to evaluate both Treg and CD8+ T-cell population. Tumor growth following combination therapy of both PTT and anti-CTLA-4 was further evaluated. Results: Our data reveal that tumor-associated Tregs can be preferentially depleted via iron-oxide nanoparticles-mediated PTT. When combining PTT with anti-CTLA-4 immunotherapy, we demonstrate a significant inhibition of syngeneic 4T1 tumor growth. Conclusion: This study offers a novel strategy to overcome Treg-mediated immunosuppression and thereby to boost cancer immunotherapy.

Efficacy and Tolerability of Tremelimumab in Locally Advanced or Metastatic Urothelial Carcinoma Patients Who Have Failed First-Line Platinum-Based Chemotherapy

PURPOSE

Patients with advanced urothelial carcinoma who fail platinum-containing chemotherapy (treatment fails) have a poor prognosis and limited treatment options. Recent approvals of immune-checkpoint inhibitors confirmed the value of immunomodulatory therapy in urothelial carcinoma. Tremelimumab is a selective human immunoglobulin G2 (IgG2) monoclonal antibody against cytotoxic T-lymphocyte-associated antigen 4 with demonstrated durable response rate in metastatic melanoma. This is the first study to report the efficacy and safety of tremelimumab in urothelial carcinoma.

PATIENTS AND METHODS

We report the results of the urothelial carcinoma cohort from a phase II, open-label, multicenter study of patients with advanced solid tumors (NCT02527434). Patients with locally advanced/metastatic urothelial carcinoma were treated with tremelimumab monotherapy (750 mg via intravenous infusion every 4 weeks for seven cycles, then every 12 weeks for two additional cycles) for up to 12 months or until disease progression, initiation of other anticancer therapy, unacceptable toxicity, or consent withdrawal.

RESULTS

In 32 evaluable patients with metastatic urothelial carcinoma, objective response rate was 18.8% (95% confidence interval, 7.2-36.4), including complete response (CR) in 2 (6.3%), and partial response in 4 patients (12.5%). Median duration of response has not been reached. Stable disease of ≥12 months was reported in 1 patient (3.1%), yielding a disease control rate at 12 months of 21.9%. Overall, tremelimumab was generally well tolerated; safety results were consistent with the known safety profile.

CONCLUSIONS

Tremelimumab monotherapy demonstrated clinical activity and durable responses in patients with metastatic urothelial carcinoma. This study is the first in which CR has been observed with tremelimumab as a single agent in urothelial carcinoma.

Tumor microenvironmental influences on dendritic cell and T cell function: A focus on clinically relevant immunologic and metabolic checkpoints

Cancer immunotherapy is fast becoming one of the most promising means of treating malignant disease. Cancer vaccines, adoptive cell transfer therapies, and immune checkpoint blockade have all shown varying levels of success in the clinical management of several cancer types in recent years. However, despite the clinical benefits often achieved by these regimens, an ongoing problem for many patients is the inherent or acquired resistance of their cancer to immunotherapy. It is now appreciated that dendritic cells and T lymphocytes both play key roles in antitumor immune responses and that the tumor microenvironment presents a number of barriers to the function of these cells that can ultimately limit the success of immunotherapy. In particular, the engagement of several immunologic and metabolic checkpoints within the hostile tumor microenvironment can severely compromise the antitumor functions of these important immune populations. This review highlights work from both preclinical and clinical studies that has shaped our understanding of the tumor microenvironment and its influence on dendritic cell and T cell function. It focuses on clinically relevant targeted and immunotherapeutic strategies that have emerged from these studies in an effort to prevent or overcome immune subversion within the tumor microenvironment. Emphasis is also placed on the potential of next-generation combinatorial regimens that target metabolic and immunologic impediments to dendritic cell and T lymphocyte function as strategies to improve antitumor immune reactivity and the clinical outcome of cancer immunotherapy going forward.

Preserving the CTLA-4 Checkpoint for Safer and More Effective Cancer Immunotherapy

A major paradigm in cancer immunotherapy is the use of checkpoint inhibitors to break regulatory mechanisms that usually guard the host against autoimmune diseases. CTLA-4-targeting immunotherapy was the first example that helped establish this paradigm. However, the clinically tested anti-CTLA-4 antibodies exhibit suboptimal efficacy but high toxicity. Recent studies have demonstrated that immunotherapy-related adverse events (irAE) and the cancer immunotherapeutic effect (CITE) represent distinct and therapeutically separable activities of anti-CTLA-4 antibodies. The former is attributable to inactivation of the CTLA-4 checkpoint, while the latter is due to selective depletion of regulatory T cells (Treg) in a tumor microenvironment. Here we argue that for safer and more effective CTLA-4-targeting immune therapy, one should preserve rather than inhibit the CTLA-4 checkpoint while enhancing the efficacy and selectivity of Treg depletion in a tumor microenvironment.

Therapeutic Monoclonal Antibodies Targeting Immune Checkpoints for the Treatment of Solid Tumors

Recently, modulation of immune checkpoints has risen to prominence as a means to treat a number of solid malignancies, given the durable response seen in many patients and improved side effect profile compared to conventional chemotherapeutic agents. Several classes of immune checkpoint modulators have been developed. Here, we review current monoclonal antibodies directed against immune checkpoints that are employed in practice today. We discuss the history, mechanism, indications, and clinical data for each class of therapies. Furthermore, we review the challenges to durable tumor responses that are seen in some patients and discuss possible interventions to circumvent these barriers.

Combination anti-CTLA-4 plus anti-PD-1 checkpoint blockade utilizes cellular mechanisms partially distinct from monotherapies

Immune checkpoint blockade therapy has become a critical pillar of cancer therapy. Here, we characterize the cellular mechanisms of monotherapy and combination anti–cytotoxic T lymphocyte antigen-4 plus anti–programmed cell death-1 therapy. Using high-dimensional single-cell profiling, we determine that combination therapy elicits cellular responses that are partially distinct from those induced by either monotherapy. In particular, combination therapy mediates a switch from expansion of phenotypically exhausted cluster of differentiation 8 (CD8) T cells to expansion of activated effector CD8 T cells. In addition, we systematically compare T cell subsets present in matched peripheral blood and tumor tissues to define what aspects of antitumor responses can be observed peripherally. These findings have significant implications for both the cellular mechanisms of action and biomarkers of response to monotherapies and combination therapy.

Immune checkpoint blockade therapy targets T cell-negative costimulatory molecules such as cytotoxic T lymphocyte antigen-4 (CTLA-4) and programmed cell death-1 (PD-1). Combination anti–CTLA-4 and anti–PD-1 blockade therapy has enhanced efficacy, but it remains unclear through what mechanisms such effects are mediated. A critical question is whether combination therapy targets and modulates the same T cell populations as monotherapies. Using a mass cytometry-based systems approach, we comprehensively profiled the response of T cell populations to monotherapy and combination anti–CTLA-4 plus anti–PD-1 therapy in syngeneic murine tumors and clinical samples. Most effects of monotherapies were additive in the context of combination therapy; however, multiple combination therapy-specific effects were observed. Highly phenotypically exhausted cluster of differentiation 8 (CD8) T cells expand in frequency following anti–PD-1 monotherapy but not combination therapy, while activated terminally differentiated effector CD8 T cells expand only following combination therapy. Combination therapy also led to further increased frequency of T helper type 1 (Th1)-like CD4 effector T cells even though anti–PD-1 monotherapy is not sufficient to do so. Mass cytometry analyses of peripheral blood from melanoma patients treated with immune checkpoint blockade therapies similarly revealed mostly additive effects on the frequencies of T cell subsets along with unique modulation of terminally differentiated effector CD8 T cells by combination ipilimumab plus nivolumab therapy. Together, these findings indicate that dual blockade of CTLA-4 and PD-1 therapy is sufficient to induce unique cellular responses compared with either monotherapy.

T Regulatory Cells and Priming the Suppressive Tumor Microenvironment

Treg play a central role in maintenance of self tolerance and homeostasis through suppression of self-reactive T cell populations. In addition to that role, Treg also survey cancers and suppress anti-tumor immune responses. Thus, understanding the unique attributes of Treg-tumor interactions may permit control of this pathologic suppression without interfering with homeostatic self-tolerance. This review will define the unique role of Treg in cancer growth, and the ways by which Treg inhibit a robust anti-tumor immune response. There will be specific focus placed on Treg homing to the tumor microenvironment (TME), TME formation of induced Treg (iTreg), mechanisms of suppression that underpin cancer immune escape, and trophic nonimmunologic effects of Treg on tumor cells.

CTLA-4 Immunohistochemistry and Quantitative Image Analysis for Profiling of Human Cancers

There is an important need in immuno-oncology to develop reliable immunohistochemistry (IHC) to assess the expression of CTLA-4⁺ tumor-infiltrating lymphocytes in human cancers and quantify them with image analysis (IA). We used commercial polyclonal and monoclonal antibodies and characterized three chromogenic cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) assays with suitable specificity and sensitivity for use in formalin-fixed, paraffin-embedded (FFPE) tissues. We found variable numbers of CTLA-4⁺ lymphocytes in multiple types of cancer and secondary lymphoid organs (SLOs) and other normal human tissues. Combining CTLA-4 with CD3, CD4, or CD8 by immunofluorescence showed that CTLA-4⁺ lymphocytes in SLOs and tumors were typically CD3⁺ and CD4⁺, but not CD8⁺. Individual lymphocytes expressed CTLA-4 either as primarily granular cytoplasmic staining or as excentric globular deposits. The CTLA-4/FoxP3 (forkhead box P3 protein) duplex IHC demonstrated that CTLA-4⁺/FoxP3^- lymphocytes predominated in the germinal centers of SLOs and tumor tertiary lymphoid structures (TLSs), whereas CTLA-4⁺/FoxP3⁺ lymphocytes populated the T-cell zone of SLOs and TLSs, plus tumor stroma. IA scoring was highly comparable with pathologist scoring for CTLA-4 and CTLA-4/FoxP3 assays and a FoxP3 single IHC. Our findings show that CTLA-4 IHC can be used to reliably label lymphocytes in FFPE human tissues, making it possible to investigate the role of CTLA-4 in the tumor microenvironment.

Demystifying the manipulation of host immunity, metabolism, and extraintestinal tumors by the gut microbiome

The trillions of microorganisms in the gut microbiome have attracted much attention recently owing to their sophisticated and widespread impacts on numerous aspects of host pathophysiology. Remarkable progress in large-scale sequencing and mass spectrometry has increased our understanding of the influence of the microbiome and/or its metabolites on the onset and progression of extraintestinal cancers and the efficacy of cancer immunotherapy. Given the plasticity in microbial composition and function, microbial-based therapeutic interventions, including dietary modulation, prebiotics, and probiotics, as well as fecal microbial transplantation, potentially permit the development of novel strategies for cancer therapy to improve clinical outcomes. Herein, we summarize the latest evidence on the involvement of the gut microbiome in host immunity and metabolism, the effects of the microbiome on extraintestinal cancers and the immune response, and strategies to modulate the gut microbiome, and we discuss ongoing studies and future areas of research that deserve focused research efforts.

Prognostic Factors and Biomarkers of Responses to Immune Checkpoint Inhibitors in Lung Cancer

Manipulation of the immune response is a game changer in lung cancer treatment, revolutionizing management. PD1 and CTLA4 are dynamically expressed on different T cell subsets that can either disrupt or sustain tumor growth. Monoclonal antibodies (MoAbs) against PD1/PDL1 and CTLA4 have shown that inhibitory signals can be impaired, blocking T cell activation and function. MoAbs, used as both single-agents or in combination with standard therapy for the treatment of advanced non-small cell lung cancer (NSCLC), have exhibited advantages in terms of overall survival and response rate; nivolumab, pembrolizumab, atezolizumab and more recently, durvalumab, have already been approved for lung cancer treatment and more compounds are in the pipeline. A better understanding of signaling elicited by these antibodies on T cell subsets, as well as identification of biological determinants of sensitivity, resistance and correlates of efficacy, will help to define the mechanisms of antitumor responses. In addition, the relevance of T regulatory cells (Treg) involved in immune responses in cancer is attracting increasing interest. A major challenge for future research is to understand why a durable response to immune checkpoint inhibitors (ICIs) occurs only in subsets of patients and the mechanisms of resistance after an initial response. This review will explore current understanding and future direction of research on ICI treatment in lung cancer and the impact of tumor immune microenvironment n influencing clinical responses.

A Neuropilin-1 Antagonist Exerts Antitumor Immunity by Inhibiting the Suppressive Function of Intratumoral Regulatory T Cells

Regulatory T cells (Treg) are targeted for cancer immunotherapy because they suppress antitumor immunity. Although the importance of neuropilin-1 (NRP1) in the stability and function of intratumoral Tregs is well-documented, targeting of NRP1⁺ Tregs for anticancer immunotherapy has not been well explored. Here, we found that an NRP1 antagonist [Fc(AAG)-TPP11], generated by fusion of the NRP1-specific binding peptide TPP11 with the C-terminus of an effector function-deficient immunoglobulin Fc(AAG) variant, inhibits intratumoral NRP1⁺ Treg function and stability. Fc(AAG)-TPP11 triggered the internalization of NRP1, reducing its surface expression on Tregs and thereby inhibiting the suppressive function of Tregs. In two murine syngeneic tumor models, Fc(AAG)-TPP11 retarded tumor growth, comparable with a Treg-depleting anti-CTLA-4 antibody, without noticeable toxicity. Fc(AAG)-TPP11 inhibited NRP1-dependent Treg function, inducing unstable intratumoral Tregs, with reduced expression of Foxp3 and enhanced production of IFNγ, which subsequently increased the functionality and frequency of intratumoral CD8⁺ T cells. We also observed selective expression of NRP1 on Tregs isolated from human tumors, but not from the blood of healthy donors and patients with cancer, as well as ex vivo inhibition of intratumoral NRP1⁺ Treg function by Fc(AAG)-TPP11. Our results suggest that the NRP1 antagonist Fc(AAG)-TPP11 has therapeutic potential for the inhibition of intratumoral NRP1⁺ Tregs with limited unfavorable effects on peripheral Tregs.

Guadecitabine Plus Ipilimumab in Unresectable Melanoma: The NIBIT-M4 Clinical Trial

PURPOSE

The immunomodulatory activity of DNA hypomethylating agents (DHAs) suggests they may improve the effectiveness of cancer immunotherapies. The phase Ib NIBIT-M4 trial tested this hypothesis using the next-generation DHA guadecitabine combined with ipilimumab.

PATIENTS AND METHODS

Patients with unresectable stage III/IV melanoma received escalating doses of guadecitabine 30, 45, or 60 mg/m²/day subcutaneously on days 1 to 5 every 3 weeks, and ipilimumab 3 mg/kg intravenously on day 1 every 3 weeks, starting 1 week after guadecitabine, for four cycles. Primary endpoints were safety, tolerability, and MTD of treatment; secondary were immune-related (ir) disease control rate (DCR) and objective response rate (ORR); and exploratory were changes in methylome, transcriptome, and immune contextures in sequential tumor biopsies, and pharmacokinetics.

RESULTS

Nineteen patients were treated; 84% had grade 3/4 adverse events, and neither dose-limiting toxicities per protocol nor overlapping toxicities were observed. Ir-DCR and ir-ORR were 42% and 26%, respectively. Median CpG site methylation of tumor samples (n = 8) at week 4 (74.5%) and week 12 (75.5%) was significantly (P < 0.05) lower than at baseline (80.3%), with a median of 2,454 (week 4) and 4,131 (week 12) differentially expressed genes. Among the 136 pathways significantly (P < 0.05; Z score >2 or ←2) modulated by treatment, the most frequently activated were immune-related. Tumor immune contexture analysis (n = 11) demonstrated upregulation of HLA class I on melanoma cells, an increase in CD8⁺, PD-1⁺ T cells and in CD20⁺ B cells in posttreatment tumor cores.

CONCLUSIONS

Treatment of guadecitabine combined with ipilimumab is safe and tolerable in advanced melanoma and has promising immunomodulatory and antitumor activity.

The effects of local irradiation on circulating lymphocytes in dogs receiving fractionated radiotherapy

Localized radiation therapy can be an effective treatment for cancer but is associated with localized and systemic side effects. Several studies have noted changes in complete blood count (CBC) parameters including decreases in the absolute lymphocyte count (ALC) and increases in the neutrophil:lymphocyte ratio (NLR). These changes could reflect immunosuppression and may contribute to decreased efficacy of immunotherapies used to treat cancer. We hypothesized that dogs would demonstrate decreased ALCs during a course of radiotherapy. A retrospective study was conducted on 203 dogs receiving definitive-intent radiotherapy. Demographic information, CBC values and details of the radiotherapy protocol were collected. The mean lymphocyte count pre-treatment was 1630.68 cells/μL (SD ± 667.56) with a mean NLR of 3.66 (SD ± 4.53). The mean lymphocyte count mid-treatment was 1251.07 cells/μL (SD ± 585.96) and the mean NLR was 6.23 (SD ± 4.99). There was a significant decrease in the mean lymphocyte count by 351.41 lymphocytes/μL (SD ± 592.32) between pre-treatment and mid-treatment (P < .0001), and a corresponding significant increase in the mean NLR of 0.93 (P = .02). Lymphopenia grade increased in 33.5% of dogs and was significant (P = .03). The ALC decrease was not correlated with the volume irradiated (P = .27), but correlated with the irradiated volume:body weight ratio (P = .03). A subset of patients (n = 35) with additional CBCs available beyond the mid-treatment time point demonstrated significant and sustained downward trends in the ALC compared with baseline. Although severe lymphopenia was rare, these decreases, especially if sustained, could impact adjuvant therapy for their cancer.

Blood-brain barrier permeable nano immunoconjugates induce local immune responses for glioma therapy

Brain glioma treatment with checkpoint inhibitor antibodies to cytotoxic T-lymphocyte-associated antigen 4 (a-CTLA-4) and programmed cell death-1 (a-PD-1) was largely unsuccessful due to their inability to cross blood-brain barrier (BBB). Here we describe targeted nanoscale immunoconjugates (NICs) on natural biopolymer scaffold, poly(β-L-malic acid), with covalently attached a-CTLA-4 or a-PD-1 for systemic delivery across the BBB and activation of local brain anti-tumor immune response. NIC treatment of mice bearing intracranial GL261 glioblastoma (GBM) results in an increase of CD8+ T cells, NK cells and macrophages with a decrease of regulatory T cells (Tregs) in the brain tumor area. Survival of GBM-bearing mice treated with NIC combination is significantly longer compared to animals treated with single checkpoint inhibitor-bearing NICs or free a-CTLA-4 and a-PD-1. Our study demonstrates trans-BBB delivery of tumor-targeted polymer-conjugated checkpoint inhibitors as an effective GBM treatment via activation of both systemic and local privileged brain tumor immune response.

Balancing cancer immunotherapy and immune-related adverse events: The emerging role of regulatory T cells

Advances in our understanding οf tumor immunity have prompted a paradigm shift in oncology, with the emergence of immunotherapy, where therapeutic agents are used to target immune cells rather than cancer cells. A real breakthrough in the field of immunotherapy came with the use of immune checkpoint inhibitors (ICI), namely antagonistic antibodies that block key immune regulatory molecules (checkpoint molecules), such as cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4), programmed cell death protein (PD-1) and its ligand PD-L1, that under physiologic conditions suppress T cell effector function. However, despite the enormous success, a significant proportion of patients do not respond, while responses are frequently accompanied by life-threatening autoimmune related adverse events (irAEs). A major impediment in the effectiveness of ICI immunotherapy is the tumoral resistance, which is dependent on the immunosuppressive nature of tumor microenvironment (TME). Regulatory T cells (Tregs) are among the most abundant suppressive cells in the TME and their presence has been correlated with tumor progression, invasiveness as well as metastasis. Tregs are characterized by the expression of the transcription factor Foxp3 and various mechanisms ranging from cell-to-cell contact to secretion of inhibitory molecules have been implicated in their function. Notably, Tregs amply express most of the checkpoint molecules such as CTLA4, PD1 and LAG3 and therefore represent a direct target of ICI immunotherapy. Taking into consideration the critical role of Tregs in maintenance of immune homeostasis and avoidance of autoimmunity it is plausible that targeting of Tregs by ICI immunotherapy results in the development of irAEs. Since the use of ICI becomes common, and new immune checkpoint molecules are currently under clinical trials for the treatment of cancer, the occurrence of irAEs is expected to dramatically rise. Herein we review the current literature focusing on the role of Tregs in cancer evolution, ICI response and development of irAEs. Unraveling the complex mechanisms that hinder the tumor immune surveillance and in particular how ICI immunotherapy imprint on Treg activities to promote cancer regression while avoid development of irAEs, will empower the design of novel immunotherapeutic modalities in cancer with increased efficacy and diminished adverse events.

ICOS Costimulation at the Tumor Site in Combination with CTLA-4 Blockade Therapy Elicits Strong Tumor Immunity

Cytotoxic T lymphocyte-associated protein 4 (CTLA-4) blockade therapy is able to induce long-lasting antitumor responses in a fraction of cancer patients. Nonetheless, there is still room for improvement in the quest for new therapeutic combinations. ICOS costimulation has been underscored as a possible target to include with CTLA-4 blocking treatment. Herein, we describe an ICOS agonistic aptamer that potentiates T cell activation and induces stronger antitumor responses when locally injected at the tumor site in combination with anti-CTLA-4 antibody in different tumor models. Furthermore, ICOS agonistic aptamer was engineered as a bi-specific tumor-targeting aptamer to reach any disseminated tumor lesions after systemic injection. Treatment with the bi-specific aptamer in combination with CTLA-4 blockade showed strong antitumor immunity, even in a melanoma tumor model where CTLA-4 treatment alone did not display any significant therapeutic benefit. Thus, this work provides strong support for the development of combinatorial therapies involving anti-CTLA-4 blockade and ICOS agonist tumor-targeting agents.

Hijacking antibody-induced CTLA-4 lysosomal degradation for safer and more effective cancer immunotherapy

It remains unclear why the clinically used anti-CTLA-4 antibodies, popularly called checkpoint inhibitors, have severe immunotherapy-related adverse effects (irAEs) and yet suboptimal cancer immunotherapeutic effects (CITE). Here we report that while irAE-prone Ipilimumab and TremeIgG1 rapidly direct cell surface CTLA-4 for lysosomal degradation, the non-irAE-prone antibodies we generated, HL12 or HL32, dissociate from CTLA-4 after endocytosis and allow CTLA-4 recycling to cell surface by the LRBA-dependent mechanism. Disrupting CTLA-4 recycling results in robust CTLA-4 downregulation by all anti-CTLA-4 antibodies and confers toxicity to a non-irAE-prone anti-CTLA-4 mAb. Conversely, increasing the pH sensitivity of TremeIgG1 by introducing designed tyrosine-to-histidine mutations prevents antibody-triggered lysosomal CTLA-4 downregulation and dramatically attenuates irAE. Surprisingly, by avoiding CTLA-4 downregulation and due to their increased bioavailability, pH-sensitive anti-CTLA-4 antibodies are more effective in intratumor regulatory T-cell depletion and rejection of large established tumors. Our data establish a new paradigm for cancer research that allows for abrogating irAE while increasing CITE of anti-CTLA-4 antibodies.

Considering B7-CD28 as a family through sequence and structure

With the emergence of immuno-oncology, new therapeutic agents that modulate immune activation and regulation are being used to treat cancer patients with durable response. It is well known that following T-cell receptor (TCR) activation, many co-receptors can augment or suppress the TCR signal, and therapeutically targeting these co-receptors has proven effective. The B7-CD28 family is comprised of such immune-regulatory receptors, and antibodies against its members programmed cell death protein 1 (PD-1), programmed death-ligand 1 (PD-L1), and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) have revolutionized cancer treatment. These therapies promote an immune response against tumor cells, which demonstrated better long-term survival and tolerability compared to traditional cancer treatments. In this review we describe the history of the expanding B7-CD28 family, and by comparison of sequence and structure reveal that it is a non-traditional family. The family has grown to include proteins that share low sequence identity, generally grouped by regulation of immune response, which utilize the common immunoglobulin fold. This low level of commonality has provided additional challenges to the drug discovery process as the mechanisms and therapeutic potency between family members can vary greatly.

Impact statement

Immunotherapy as a field has dramatically expanded in the last decade in the area of oncology with efficacy demonstrated by PD-1, PD-L1, and CTLA-4 blockade. With all three “checkpoint blockade” receptors being in the B7-CD28 family, there has been increased interest in targeting other members in this family due to redundancy in immune regulation, i.e., the combination of therapeutic agents targeting multiple co-inhibitory receptors may yield additional antitumor efficacy. Therefore significant resources are being dedicated to developing additional B7-CD28 treatment options.

Expression of costimulatory and inhibitory receptors in FoxP3+ regulatory T cells within the tumor microenvironment: Implications for combination immunotherapy approaches

The unprecedented success of immune checkpoint inhibitors has given rise to a rapidly growing number of immuno-oncology agents undergoing preclinical and clinical development and an exponential increase in possible combinations. Defining a clear rationale for combinations by identifying synergies between immunomodulatory pathways has therefore become a high priority. Immunosuppressive regulatory T cells (Tregs) within the tumor microenvironment (TME) represent a major roadblock to endogenous and therapeutic tumor immunity. However, Tregs are also essential for the maintenance of immunological self-tolerance, and share many molecular pathways with conventional T cells including cytotoxic T cells, the primary mediators of tumor immunity. Hence the inability to specifically target and neutralize Tregs within the TME of cancer patients without globally compromising self-tolerance poses a significant challenge. Here we review recent advances in the characterization of tumor-infiltrating Tregs with a focus on costimulatory and inhibitory receptors. We discuss receptor expression patterns, their functional role in Treg biology and mechanistic insights gained from targeting these receptors in preclinical models to evaluate their potential as clinical targets. We further outline a framework of parameters that could be used to refine the assessment of Tregs in cancer patients and increase their value as predictive biomarkers. Finally, we propose modalities to integrate our increasing knowledge on Treg phenotype and function for the rational design of checkpoint inhibitor-based combination therapies. Such combinations have great potential for synergy, as they could concomitantly enhance cytotoxic T cells and inhibit Tregs within the TME, thereby increasing the efficacy of current cancer immunotherapies.

Regulatory T cells as therapeutic targets and mediators

With the advent of the concept of dominant tolerance and the subsequent discovery of CD4⁺ regulatory T cells expressing the transcription factor FOXP3 (Tregs), almost all productive as well as nonproductive immune responses can be compartmentalized to a binary of immune effector T cells and immune regulatory Treg populations. A beneficial immune response warrants the timely regulation by Tregs, whereas a nonproductive immune response indicates insufficient effector functions or an outright failure of tolerance. There are ample reports supporting role of Tregs in suppressing spontaneous auto-immune diseases as well as promoting immune evasion by cancers. To top up their importance, several non-immune functions like tissue homeostasis and regeneration are also being attributed to Tregs. Hence, after being in the center stage of basic and translational immunological research, Tregs are making the next jump towards clinical studies. Therefore, newer small molecules, biologics as well as adoptive cell therapy (ACT) approaches are being tested to augment or undermine Treg responses in the context of autoimmunity and cancer. In this brief review, we present the strategies to modulate Tregs towards a favorable clinical outcome.

Anti-CTLA-4 synergizes with dendritic cell-targeted vaccine to promote IL-3-dependent CD4+ effector T cell infiltration into murine pancreatic tumors

One successful class of cancer immunotherapies, immune checkpoint inhibitory antibodies, disrupts key pathways that regulate immune checkpoints, such as cytotoxic T lymphocyte-associated antigen-4 (CTLA-4). These agents unleash the potency of antigen-experienced T cells that have already been induced as a consequence of the existing tumor. But only 20% of cancers naturally induce T cells. For most cancers, vaccines are require to induce and mobilize T effector cells (Teffs ) to traffick into tumors. We evaluated the effects of anti-CTLA-4 given in combination with an antigen-specific dendritic cell vaccine on intratumoral Teffs in a murine pancreatic cancer model. The dendritic cell-targeted tumor antigen plus anti-CTLA-4 significantly increased the number of vaccine-induced CD4+ Teffs within the tumor. This increase was accompanied by a reduction in the size of the peripheral CD4+ Teff pool. We also found that IL-3 production by activated CD4+ T cells was significantly increased with this combination. Importantly, the CD4+ Teff response was attenuated in Il3-/- mice, suggesting mediation of the effect by IL-3. Finally, the induced T cell infiltration was associated with activation of the tumor endothelium by T cell-derived IL-3. Our findings collectively provide a new insight into the mechanism driving Teff infiltration and vascular activation in a murine pancreatic cancer model, specifically identifying a new role for IL-3 in the anticancer immune response.

How Does an Anti-CTLA-4 Antibody Promote Cancer Immunity?

Anti-CTLA-4 antibodies can induce lasting protection for some melanoma patients. However, their therapeutic potential is limited by significant immunotherapy-related adverse effects (irAE). Here, we argue that the therapeutic effect may be based on an agonist activity that is fundamentally distinct, and can be therapeutically differentiated, from the antagonist activity responsible for irAE.

TLR1/2 ligand enhances antitumor efficacy of CTLA-4 blockade by increasing intratumoral Treg depletion

Immune checkpoint inhibitors such as anti-CTLA-4 antibody are widely accepted therapeutic options for many cancers, but there is still a considerable gap in achieving their full potential. We explored the potential of activating the innate and adaptive immune pathways together to improve tumor reduction and survival outcomes. We treated a mouse model of melanoma with intratumoral injections of Toll-like receptor 1/2 (TLR1/2) ligand Pam3CSK4 plus i.p. injections of anti-CTLA-4 antibody. This combination treatment enhanced antitumor immune responses both qualitatively and quantitatively over anti-CTLA-4 alone, and its efficacy depended on CD4 T cells, CD8 T cells, Fcγ receptor IV, and macrophages. Interestingly, our results suggest a unique mechanism by which TLR1/2 ligand increased Fcγ receptor IV expression on macrophages, leading to antibody-dependent macrophage-mediated depletion of regulatory T cells in the tumor microenvironment and increasing efficacy of anti-CTLA-4 antibody in the combination treatment. This mechanism could be harnessed to modulate the clinical outcome of anti-CTLA-4 antibodies and possibly other antibody-based immunotherapies.

Effect of Cytotoxic T-Lymphocyte Antigen-4 on the Efficacy of the Fatty Acid-Binding Protein Vaccine Against Schistosoma japonicum

The present study evaluated the impact of blocking cytotoxic T-lymphocyte antigen-4 (CTLA-4) activity on the protective effect elicited by the fatty acid binding protein (FABP) vaccine against Schistosoma japonicum infection. Mice were randomly divided into uninfected, infected control, anti-CTLA-4 monoclonal antibody (anti-CTLA-4 mAb), FABP, and combination (anti-CTLA-4 mAb and FABP) groups. An assessment of the S. japonicum worm and egg burden in the infected mice revealed that the worm reduction-rate induced by FABP administration was increased from 26.58 to 54.61% by co-administration of the monoclonal anti-CTLA antibody (anti-CTLA-4 mAb). Furthermore, the regulatory T cell (Treg) percentage was significantly increased in mice after administration of the anti-CTLA-4 mAb, but not the FABP vaccine, and elevated levels of the cytokines interferon (IFN)-γ, interleukin (IL)-2, IL-4, and IL-5 were observed in infected mice that were administered the anti-CTLA-4 mAb. Notably, the diameter of egg granulomas in the anti-CTLA-4 mAb and combination groups was significantly increased compared to that observed in the infected control group. Together, these results suggest that co-administering the FABP vaccine and anti-CTLA-4 treatment may have synergistically increased the immunoprotective effect of the FABP vaccine by promoting T-helper 1-type immune responses, while incurring increased tissue damage.

T cell pathology in skin inflammation

Forming the outer body barrier, our skin is permanently exposed to pathogens and environmental hazards. Therefore, skin diseases are among the most common disorders. In many of them, the immune system plays a crucial pathogenetic role. For didactic and therapeutic reasons, classification of such immune-mediated skin diseases according to the underlying dominant immune mechanism rather than to their clinical manifestation appears to be reasonable. Immune-mediated skin diseases may be mediated mainly by T cells, by the humoral immune system, or by uncontrolled unspecific inflammation. According to the involved T cell subpopulation, T cell-mediated diseases may be further subdivided into T1 cell-dominated (e.g., vitiligo), T2 cell-dominated (e.g., acute atopic dermatitis), T17/T22 cell-dominated (e.g., psoriasis), and Treg cell-dominated (e.g., melanoma) responses. Moreover, T cell-dependent and -independent responses may occur simultaneously in selected diseases (e.g., hidradenitis suppurativa). The effector mechanisms of the respective T cell subpopulations determine the molecular changes in the local tissue cells, leading to specific microscopic and macroscopic skin alterations. In this article, we show how the increasing knowledge of the T cell biology has been comprehensively translated into the pathogenetic understanding of respective model skin diseases and, based thereon, has revolutionized their daily clinical management.

Injectable polypeptide hydrogel-based co-delivery of vaccine and immune checkpoint inhibitors improves tumor immunotherapy

Immunotherapy, an attractive option for cancer treatment, necessitates the direct stimulation of immune cells in vivo and the simultaneous effective inhibition of immunosuppressive tumor microenvironments.

Methods: In the present study, we developed an injectable PEG-b-poly(L-alanine) hydrogel for co-delivery of a tumor vaccine and dual immune checkpoint inhibitors to increase tumor immunotherapy efficacy. Tumor cell lysates, granulocyte-macrophage colony stimulating factor (GM-CSF), and immune checkpoint inhibitors (anti-CTLA-4/PD-1 antibody) were readily encapsulated in the porous hydrogel during the spontaneous self-assembly of polypeptide in aqueous solution.

Results: Sustained release of tumor antigens and GM-CSF persistently recruited and activated dendritic cells (DCs) and induced a strong T-cell response in vivo, which was further enhanced by the immune checkpoint therapy. The hydrogel vaccine also upregulated the production of IgG and the secretion of cytokines including IFN-γ, IL-4, and TNF-α. Importantly, the hydrogel-based combination therapy had superior immunotherapy effects against melanoma and 4T-1 tumor in comparison with the vaccine alone or in addition with a single immune checkpoint blockade. In studying the underlying mechanism, we found that the hydrogel-based combinatorial immunotherapy not only significantly increased the activated effector CD8⁺ T cells within the spleens and tumors of vaccinated mice, but also reduced the ratio of Tregs.

Conclusion: Our findings indicate that the polypeptide hydrogel can be used as an effective sustained delivery platform for vaccines and immune checkpoint inhibitors, providing an advanced combinatorial immunotherapy approach for cancer treatment.

The CTLA-4 x OX40 bispecific antibody ATOR-1015 induces anti-tumor effects through tumor-directed immune activation

BACKGROUND

The CTLA-4 blocking antibody ipilimumab has demonstrated substantial and durable effects in patients with melanoma. While CTLA-4 therapy, both as monotherapy and in combination with PD-1 targeting therapies, has great potential in many indications, the toxicities of the current treatment regimens may limit their use. Thus, there is a medical need for new CTLA-4 targeting therapies with improved benefit-risk profile.

METHODS

ATOR-1015 is a human CTLA-4 x OX40 targeting IgG1 bispecific antibody generated by linking an optimized version of the Ig-like V-type domain of human CD86, a natural CTLA-4 ligand, to an agonistic OX40 antibody. In vitro evaluation of T-cell activation and T regulatory cell (Treg) depletion was performed using purified cells from healthy human donors or cell lines. In vivo anti-tumor responses were studied using human OX40 transgenic (knock-in) mice with established syngeneic tumors. Tumors and spleens from treated mice were analyzed for CD8+ T cell and Treg frequencies, T-cell activation markers and tumor localization using flow cytometry.

RESULTS

ATOR-1015 induces T-cell activation and Treg depletion in vitro. Treatment with ATOR-1015 reduces tumor growth and improves survival in several syngeneic tumor models, including bladder, colon and pancreas cancer models. It is further demonstrated that ATOR-1015 induces tumor-specific and long-term immunological memory and enhances the response to PD-1 inhibition. Moreover, ATOR-1015 localizes to the tumor area where it reduces the frequency of Tregs and increases the number and activation of CD8+ T cells.

CONCLUSIONS

By targeting CTLA-4 and OX40 simultaneously, ATOR-1015 is directed to the tumor area where it induces enhanced immune activation, and thus has the potential to be a next generation CTLA-4 targeting therapy with improved clinical efficacy and reduced toxicity. ATOR-1015 is also expected to act synergistically with anti-PD-1/PD-L1 therapy. The pre-clinical data support clinical development of ATOR-1015, and a first-in-human trial has started (NCT03782467).

Immunotherapy Toxicities

Immune checkpoint inhibitors (ICIs) are therapeutic antibodies that target regulatory molecules on T cells and represent the most widely used FDA-approved class of immunotherapy. ICIs are associated with unique immune-mediated toxicities called immune-related adverse events. These toxicities may affect any organ system, and their precise mechanisms of action remain under investigation. Current evidence suggests that activation of T cells is involved, although other components of the immune response have been implicated. This article summarizes toxicities, potential mechanisms of action, management strategies, and other clinical considerations. Unique mechanisms of action and immune-related toxicities of other FDA-approved classes of immunotherapy are reviewed.

Genomic correlates of response to immune checkpoint blockade

Despite impressive durable responses, immune checkpoint inhibitors do not provide a long-term benefit to the majority of patients with cancer. Understanding genomic correlates of response and resistance to checkpoint blockade may enhance benefits for patients with cancer by elucidating biomarkers for patient stratification and resistance mechanisms for therapeutic targeting. Here we review emerging genomic markers of checkpoint blockade response, including those related to neoantigens, antigen presentation, DNA repair, and oncogenic pathways. Compelling evidence also points to a role for T cell functionality, checkpoint regulators, chromatin modifiers, and copy-number alterations in mediating selective response to immune checkpoint blockade. Ultimately, efforts to contextualize genomic correlates of response into the larger understanding of tumor immune biology will build a foundation for the development of novel biomarkers and therapies to overcome resistance to checkpoint blockade.