In situ vaccination against mycosis fungoides by intratumoral injection of a TLR9 agonist combined with radiation: a phase 1/2 study. Blood. 2012;119:355-363. [PMID: 22045986 DOI: 10.1182/blood-2011-05-355222]

In situ Vaccination by Direct Dendritic Cell Inoculation: The Coming of Age of an Old Idea?

For more than 25 years, dendritic cell (DC) based vaccination has flashily held promises to represent a therapeutic approach for cancer treatment. While the vast majority of studies has focused on the use of antigen loaded DC, the intratumoral delivery of unloaded DC aiming at in situ vaccination has gained much less attention. Such approach grounds on the ability of inoculated DC to internalize and process antigens directly released by tumor (usually in combination with cell-death-inducing agents) to activate broad patient-specific antitumor T cell response. In this review, we highlight the recent studies in both solid and hematological tumors showing promising clinical results and discuss the main pitfalls and advantages of this approach for endogenous cancer vaccination. Lastly, we discuss how in situ vaccination by DC inoculation may fit with current immunotherapy approaches to expand and prolong patient response.

Immunotherapy for Cutaneous T-Cell Lymphoma: Current Landscape and Future Developments

Mycosis fungoides (MF) and Sézary syndrome (SS) are chronic, progressive primary cutaneous T-cell lymphomas (CTCLs) for which there are no curative treatments. Skin-directed therapies, such as phototherapy, radiation therapy, or topical nitrogen mustard, provide only short-term remissions. Numerous attempts with different chemotherapeutic regimes failed to achieve meaningful clinical responses. Immunotherapy seems to be a promising avenue to achieve long-term disease control in CTCL. There is compelling evidence indicating that MF and SS are immunogenic lymphomas, which can be recognized by the patient's immune system. However, CTCL uses different strategies to impair host's immunity, eg, via repolarizing the T-cell differentiation from type I to type II, recruiting immunosuppressive regulatory T-cells, and limiting the repertoire of lymphocytes in the circulation. Many currently used therapies, such as interferon-α, imiquimod, extracorporeal phototherapy, and allogeneic bone marrow transplant, seem to exert their therapeutic effect via activation of the antitumor cytotoxic response and reconstitution of the host's immune system. It is likely that novel immunotherapies such as immune checkpoint inhibitors, cancer vaccines, and chimeric antigen receptor-T cells will help to manage CTCL more efficiently. We also discuss how current genomic techniques, such as estimating the mutational load by whole genome sequencing and neoantigen calling, are likely to provide clinically useful information facilitating personalized immunotherapy of CTCL.

Novel Immunotherapies for T Cell Lymphoma and Leukemia

PURPOSE OF REVIEW

Novel immunotherapies such as checkpoint inhibitors, bispecific antibodies, and chimeric antigen receptor T cells are leading to promising responses when treating solid tumors and hematological malignancies. T cell neoplasms include leukemia and lymphomas that are derived from T cells and overall are characterized by poor clinical outcomes. This review describes the rational and preliminary results of immunotherapy for patients with T cell lymphoma and leukemia.

RECENT FINDINGS

For T cell neoplasms, despite significant research effort, only few agents, such as monoclonal antibodies and allogeneic stem cell transplantation, showed some clinical activity. One of the major hurdles to targeting T cell neoplasms is that activation or elimination of T cells, either normal or neoplastic, can cause significant toxicity. A need to develop novel safe and effective immunotherapies for T cell neoplasms exists. In this review, we will discuss the rationale for immunotherapy of T cell leukemia and lymphoma and present the most recent therapeutic approaches.

Systemic clinical tumor regressions and potentiation of PD1 blockade with in situ vaccination

Indolent non-Hodgkin's lymphomas (iNHLs) are incurable with standard therapy and are poorly responsive to checkpoint blockade. Although lymphoma cells are efficiently killed by primed T cells, in vivo priming of anti-lymphoma T cells has been elusive. Here, we demonstrate that lymphoma cells can directly prime T cells, but in vivo immunity still requires cross-presentation. To address this, we developed an in situ vaccine (ISV), combining Flt3L, radiotherapy, and a TLR3 agonist, which recruited, antigen-loaded and activated intratumoral, cross-presenting dendritic cells (DCs). ISV induced anti-tumor CD8⁺ T cell responses and systemic (abscopal) cancer remission in patients with advanced stage iNHL in an ongoing trial ( NCT01976585 ). Non-responding patients developed a population of PD1⁺CD8⁺ T cells after ISV, and murine tumors became newly responsive to PD1 blockade, prompting a follow-up trial of the combined therapy. Our data substantiate that recruiting and activating intratumoral, cross-priming DCs is achievable and critical to anti-tumor T cell responses and PD1-blockade efficacy.

Immunology of Plasmacytoid Dendritic Cells in Solid Tumors: A Brief Review

The immune response, both innate and adaptive, is a key player in cancer development and progression. Plasmacytoid dendritic cells (pDCs) are a subset of dendritic cells that play one of the central roles in the immune system. They are known mostly as the major IFN type I-producing cells upon stimulation of Toll-like receptors 7 and 9. However, based on current knowledge, the functionality of pDCs is very complex, as they have the ability to affect many other cell types. In the context of the tumor tissue, pDCs were mostly described to show substantial functional defects and therefore contribute to the establishement of immunosuppressive tumor microenvironment. Immunotherapeutic approaches have proven to be one of the most promising treatment strategies in the last decade. In view of this fact, it is crucial to map the complexity of the tumor microenvironment in detail, including less numerous cell types. This review focuses on pDCs in relation to solid tumors. We provide a summary of current data on the role of pDCs in different tumor types and suggest their possible clinical applications.

Mechanisms of Primary and Secondary Resistance to Immune Checkpoint Inhibitors in Cancer

Immune checkpoint inhibitors (ICPis) have revolutionized cancer therapy with broad activities against a wide range of malignancies. However, in many malignancies their efficacy remains limited due to the primary resistance. Furthermore, a high percentage of patients develop progression due to the secondary resistance even after obtaining a response or achieving a stable disease. In this review, we will discuss the mechanisms that underlie the primary and secondary resistance to ICPis in cancer immunotherapy and provide an overview to impart a broad understanding of the critical issues that are encountered in clinical oncology practice.

Combining Radiotherapy With Anti-angiogenic Therapy and Immunotherapy; A Therapeutic Triad for Cancer?

Radiotherapy has been used for the treatment of cancer for over a century. Throughout this period, the therapeutic benefit of radiotherapy has continuously progressed due to technical developments and increased insight in the biological mechanisms underlying the cellular responses to irradiation. In order to further improve radiotherapy efficacy, there is a mounting interest in combining radiotherapy with other forms of therapy such as anti-angiogenic therapy or immunotherapy. These strategies provide different opportunities and challenges, especially with regard to dose scheduling and timing. Addressing these issues requires insight in the interaction between the different treatment modalities. In the current review, we describe the basic principles of the effects of radiotherapy on tumor vascularization and tumor immunity and vice versa. We discuss the main strategies to combine these treatment modalities and the hurdles that have to be overcome in order to maximize therapeutic effectivity. Finally, we evaluate the outstanding questions and present future prospects of a therapeutic triad for cancer.

Radiotherapy as a New Player in Immuno-Oncology

Recent development in radiation biology has revealed potent immunogenic properties of radiotherapy in cancer treatments. However, antitumor immune effects of radiotherapy are limited by the concomitant induction of radiation-dependent immunosuppressive effects. In the growing era of immunotherapy, combining radiotherapy with immunomodulating agents has demonstrated enhancement of radiation-induced antitumor immune activation that correlated with improved treatment outcomes. Yet, how to optimally deliver combination therapy regarding dose-fractionation and timing of radiotherapy is largely unknown. Future prospective testing to fine-tune this promising combination of radiotherapy and immunotherapy is warranted.

Trial Watch: Toll-like receptor agonists in cancer immunotherapy

Toll-like receptor (TLR) agonists demonstrate therapeutic promise as immunological adjuvants for anticancer immunotherapy. To date, three TLR agonists have been approved by US regulatory agencies for use in cancer patients. Additionally, the potential of hitherto experimental TLR ligands to mediate clinically useful immunostimulatory effects has been extensively investigated over the past few years. Here, we summarize recent preclinical and clinical advances in the development of TLR agonists for cancer therapy.

Combining radiation therapy and cancer immune therapies: From preclinical findings to clinical applications

Besides its direct cytotoxic effect on the tumor cells, radiation therapy is also able to elicit an immune-mediated systemic anti-tumor response, resulting in tumor regression in irradiated sites but also within distant out of field secondary lesions and providing a long-term anti-tumor response. It is now clear that associating ionizing radiation with immune therapies can enhance radio-induced anti-tumor immune responses. Over the last decade, such a combination aroused considerable interest among the scientific community, with many preclinical models and clinical trials, using many types of immune therapies and radiation regimens. In this article, we summarize the main mechanisms underlying radio-induced anti-tumor responses. We will then present an extended overview of the recent preclinical and clinical research built on this background of combined radiation and immune therapy, shedding light on what we know so far about such a promising strategy.

PD-1 blockade enhances radio-immunotherapy efficacy in murine tumor models

PURPOSE

It has become increasingly clear in cancer treatment that radiotherapy can be enhanced by immunotherapy. In the present study, we evaluated a novel triple combination therapy consisting of local radiotherapy, intratumoral CpG, and systemic PD-1 blockade in lung cancer models.

METHODS

The efficacy of a novel triple therapy was examined by recording tumor volume and survival time. The immunologic effects of this novel triple therapy were evaluated by the frequency and percentage of immune cells and cytokines using flow cytometry.

RESULTS

This triple combination proved more effective than its subcomponents and its positive antitumor effects included reducing tumor growth and improving host survival. The antitumor effect was not only observed in directly irradiated tumors but also in at distant tumor sites in a CD8⁺ T-cell-dependent fashion. Phenotypic analyses of CD8⁺ T cells revealed that the triple combination therapy increased the percentage of effector memory T cells in the spleen. Furthermore, the combination therapy significantly increased the frequency of IFN-γ and TNF-α-positive-CD8⁺ tumor-infiltrating lymphocytes (TIL) and mature-activated dendritic cells (DCs) within treated tumors, indicating that the antitumor effects likely depend on the activation of a DC subset specialized in antigen crosspriming to induce cytotoxic lymphocyte (CTLs). In addition, the triple therapy reduced immunosuppressive factors, like regulatory T cells (Tregs) in the spleen and tumor microenvironment while inducing the robust systemic antitumor effect. Finally, the triple treatment was, indeed, well tolerated and had a little effect on the hemogram and lung.

CONCLUSIONS

These results suggest that this triple therapy promotes a local antitumor immune response with systemic consequences. The efficacy and limited toxicity of this strategy are attractive for clinical translation.

Deciphering molecular consequences of the proprotein convertase 1/3 inhibition in macrophages for application in anti-tumour immunotherapy

During tumour development, macrophages are recruited to the tumour site and orientated towards an anti-inflammatory phenotype. Due to their immunosuppressive function, tumour associated macrophages (TAMs) are recognized as major components in tumour progression. Changing these macrophages to a pro-inflammatory phenotype is thus extensively studied as a potential means for developing novel anti-tumour therapy. In this context, we found that the Proprotein convertase 1/3 (PC1/3) is a relevant target. Proteomic analysis reveals that PC1/3 knockdown (KD) macrophages present all the characteristic of activated pro-inflammatory macrophages. Moreover, in PC1/3 KD macrophages, TLR4 and TLR9 signaling pathways can be enhanced leading to the secretion of pro-inflammatory factors and anti-tumour factors. To develop an efficient anti-tumour immunotherapy, we may (i) target TAMs directly inside the tumour site for PC1/3 inhibition and TLR activation and used them as "Trojan macrophages" or (ii) directly take advantage of PC1/3 inhibited macrophages and use them as "drone macrophages" by activating them "at distance" with a TLR ligand. Therefore, PC1/3 inhibited macrophages constitute an innovative cell therapy to treat tumours efficiently.

Intratumoral immunotherapy: using the tumor as the remedy

Immune checkpoint-targeted monoclonal antibodies directed at Programmed Death Receptor 1 (PD-1), Programmed Death Ligand 1 (PD-L1) and Cytotoxic T-Lymphocyte Associated Protein 4 (CTLA-4) are currently revolutionizing the prognosis of many cancers. By blocking co-inhibitory receptors expressed by antitumor T cells, these antibodies can break the immune tolerance against tumor cells and allow the generation of durable cancer immunity. Benefits in overall survival over conventional therapies have been demonstrated for patients treated with these immunotherapies, leading to multiple approvals of such therapies by regulatory authorities. However, only a minority of patients develop an objective tumor response with long-term survival benefits. Moreover, the systemic delivery of immunotherapies can be responsible for severe auto-immune toxicities. This risk increases dramatically with anti-PD(L)1 and anti-CTLA-4 combinations and currently hampers the development of triple combination immunotherapies. In addition, the price of these novel treatments is probably too high to be reimbursed by health insurances for all the potential indications where immunotherapy has shown activity (i.e. in more than 30 different cancer types). Intratumoral immunotherapy is a therapeutic strategy which aims to use the tumor as its own vaccine. Upon direct injections into the tumor, a high concentration of immunostimulatory products can be achieved in situ, while using small amounts of drugs. Local delivery of immunotherapies allows multiple combination therapies, while preventing significant systemic exposure and off-target toxicities. Despite being uncertain of the dominant epitopes of a given cancer, one can therefore trigger an immune response against the relevant neo-antigens or tumor-associated antigens without the need for their characterization. Such immune stimulation can induce a strong priming of the cancer immunity locally while generating systemic (abscopal) tumor responses, thanks to the circulation of properly activated antitumor immune cells. While addressing many of the current limitations of cancer immunotherapy development, intratumoral immunotherapy also offers a unique opportunity to better understand the dynamics of cancer immunity by allowing sequential and multifocal biopsies at every tumor injection.

Methods for improving the immunogenicity and efficacy of cancer vaccines

INTRODUCTION

Cancer vaccines represent one of the oldest immunotherapy strategies. A variety of tumor-associated antigens have been exploited to investigate their immunogenicity as well as multiple strategies for vaccine administration. These efforts have led to the development of several clinical trials in tumors with different histological origins to test the clinical efficacy of cancer vaccines. However, suboptimal clinical results have been reported mainly due to the lack of optimized strategies to induce strong and sustained systemic tumor antigen-specific immune responses.

AREAS COVERED

We provide an overview of different types of cancer vaccines that have been developed and used in the context of clinical studies. Moreover, we review different preclinical and clinical strategies pursued to enhance the immunogenicity, stability, and targeting at tumor site of cancer vaccines.

EXPERT OPINION

Additional and appropriate preclinical studies are warranted to optimize the immunogenicity and delivery of cancer vaccines. The appropriate choice of target antigens is challenging; however, the exploitation of neoantigens generated from somatic mutations of tumor cells represents a promising approach to target highly immunogenic tumor-specific antigens. Remarkably, the investigation of the combination of cancer vaccines with immunomodulating agents able to skew the tumor microenvironment from immunosuppressive to immunostimulating will dramatically improve their clinical efficacy.

Immunotherapy Plus Cryotherapy: Potential Augmented Abscopal Effect for Advanced Cancers

Since the 1920s the gold standard for treating cancer has been surgery, which is typically preceded or followed with chemotherapy and/or radiation, a process that perhaps contributes to the destruction of a patient’s immune defense system. Cryosurgery ablation of a solid tumor is mechanistically similar to a vaccination where hundreds of unique antigens from a heterogeneous population of tumor cells derived from the invading cancer are released. However, releasing tumor-derived self-antigens into circulation may not be sufficient enough to overcome the checkpoint escape mechanisms some cancers have evolved to avoid immune responses. The potentiated immune response caused by blocking tumor checkpoints designed to prevent programmed cell death may be the optimal treatment method for the immune system to recognize these new circulating cryoablated self-antigens. Preclinical and clinical evidence exists for the complementary roles for Cytotoxic T-lymphocyte-associated protein (CTLA-4) and PD-1 antagonists in regulating adaptive immunity, demonstrating that combination immunotherapy followed by cryosurgery provides a more targeted immune response to distant lesions, a phenomenon known as the abscopal effect. We propose that when the host’s immune system has been “primed” with combined anti-CTLA-4 and anti-PD-1 adjuvants prior to cryosurgery, the preserved cryoablated tumor antigens will be presented and processed by the host’s immune system resulting in a robust cytotoxic CD8⁺ T-cell response. Based on recent investigations and well-described biochemical mechanisms presented herein, a polyvalent autoinoculation of many tumor-specific antigens, derived from a heterogeneous population of tumor cancer cells, would present to an unhindered yet pre-sensitized immune system yielding a superior advantage in locating, recognizing, and destroying tumor cells throughout the body.

Radiation and Anti-Cancer Vaccines: A Winning Combination

The emerging combination of radiation therapy with vaccines is a promising new treatment plan in the fight against cancer. While many cancer vaccines such as MUC1, p53 CpG oligodeoxynucleotide, and SOX2 may be great candidates for antitumor vaccination, there still remain many investigations to be done into possible vaccine combinations. One fruitful partnership that has emerged are anti-tumor vaccines in combination with radiation. Radiation therapy was previously thought to be only a tool for directly or indirectly damaging DNA and therefore causing cancer cell death. Now, with much preclinical and clinical data, radiation has taken on the role of an in situ vaccine. With both cancer vaccines and radiation at our disposal, more and more studies are looking to combining vaccine types such as toll-like receptors, viral components, dendritic-cell-based, and subunit vaccines with radiation. While the outcomes of these combinatory efforts are promising, there is still much work to be covered. This review sheds light on the current state of affairs in cancer vaccines and how radiation will bring its story into the future.

Radiation effects on antitumor immune responses: current perspectives and challenges

Radiotherapy (RT) is currently used in more than 50% of cancer patients during the course of their disease in the curative, adjuvant or palliative setting. RT achieves good local control of tumor growth, conferring DNA damage and impacting tumor vasculature and the immune system. Formerly regarded as a merely immunosuppressive treatment, pre- and clinical observations indicate that the therapeutic effect of RT is partially immune mediated. In some instances, RT synergizes with immunotherapy (IT), through different mechanisms promoting an effective antitumor immune response. Cell death induced by RT is thought to be immunogenic and results in modulation of lymphocyte effector function in the tumor microenvironment promoting local control. Moreover, a systemic immune response can be elicited or modulated to exert effects outside the irradiation field (so called abscopal effects). In this review, we discuss the body of evidence related to RT and its immunogenic potential for the future design of novel combination therapies.

New developments in immunotherapy for lymphoma

The development of immunotherapies for lymphoma has undergone a revolutionary evolution over the past decades. Since the advent of rituximab as the first successful immunotherapy for B-cell non-Hodgkin lymphoma over two decades ago, a plethora of new immunotherapeutic approaches to treat lymphoma has ensued. Four of the most exciting classes of immunotherapies include: chimeric antigen receptor T-cells, bispecific antibodies, immune checkpoint inhibitors, and vaccines. However, with addition of these novel therapies the appropriate timing of treatment, optimal patient population, duration of therapy, toxicity, and cost must be considered. In this review, we describe the most-promising immunotherapeutic approaches for the treatment of lymphoma in clinical development, specifically focusing on clinical trials performed to date and strategies for improvement.

The role of macrophage phenotype in regulating the response to radiation therapy

Increasing experimental and clinical evidence has revealed a critical role for myeloid cells in the development and progression of cancer. The ability of monocytes and macrophages to regulate inflammation allows them to manipulate the tumor microenvironment to support the growth and development of malignant cells. Recent studies have shown that macrophages can exist in several functional states depending on the microenvironment they encounter in the tissue. These functional phenotypes influence not only the genesis and propagation of tumors, but also the efficacy of cancer therapies, particularly radiation. Early classification of the macrophage phenotypes, or "polarization states," identified 2 major states, M1 and M2, that have cytotoxic and wound repair capacity, respectively. In the context of tumors, classically activated or M1 macrophages driven by interferon-gamma support antitumor immunity while alternatively activated or M2 macrophages generated in part from interleukin-4 exposure hinder antitumor immunity by suppressing cytotoxic responses against a tumor. In this review, we discuss the role that the functional phenotype of a macrophage population plays in tumor development. We will then focus specifically on how macrophages and myeloid cells regulate the tumor response to radiation therapy.

Radiation-enhanced delivery of systemically administered amphiphilic-CpG oligodeoxynucleotide

Along with vaccines and checkpoint blockade, immune adjuvants may have an important role in tumor immunotherapy. Oligodeoxynucleotides containing unmethylated cytidyl guanosyl dinucleotide motifs (CpG ODN) are TLR9 ligands with attractive immunostimulatory properties, but intratumoral administration has been required to induce an effective anti-tumor immune response. Following on recent studies with radiation-targeted delivery of nanoparticles, we examined enhanced tumor-specific delivery of amphiphile-CpG, an albumin-binding analog of CpG ODN, following systemic administration 3days after tumor irradiation. The combination of radiation and CpG displayed superior tumor control over either treatment alone. Intravital imaging of fluorescently labeled amphiphilic-CpG revealed increased accumulation in irradiated tumors along with decreased off-target accumulation in visceral organs. Within 48h after amphiphile-CpG administration, immune activation could be detected by increased Granzyme B and Interferon gamma activity in the tumor as well as in circulating monocytes and activated CD8⁺ T cells. Using radiotherapy to enhance the targeting of CpG to tumors may help advance this once promising therapy to clinical relevance.

Stimulating Innate Immunity to Enhance Radiation Therapy-Induced Tumor Control

Novel ligands that target Toll-like receptors and other innate recognition pathways represent a potent strategy for modulating innate immunity to generate antitumor immunity. Although many of the current clinically successful immunotherapies target adaptive T-cell responses, both preclinical and clinical studies suggest that adjuvants have the potential to enhance the scope and efficacy of cancer immunotherapy. Radiation may be a particularly good partner to combine with innate immune therapies, because it is a highly efficient means to kill cancer cells but may fail to send the appropriate inflammatory signals needed to act as an efficient endogenous vaccine. This may explain why although radiation therapy is a highly used cancer treatment, true abscopal effects-regression of disease outside the field without additional systemic therapy-are extremely rare. This review focuses on efforts to combine innate immune stimuli as adjuvants with radiation, creating a distinct and complementary approach from T cell-targeted therapies to enhance antitumor immunity.

Therapeutic Antibodies to KIR3DL2 and Other Target Antigens on Cutaneous T-Cell Lymphomas

KIR3DL2 is a member of the killer cell immunoglobulin-like receptor (KIR) family that was initially identified at the surface of natural killer (NK) cells. KIR3DL2, also known as CD158k, is expressed as a disulfide-linked homodimer. Each chain is composed of three immunoglobulin-like domains and a long cytoplasmic tail containing two immunoreceptor tyrosine-based inhibitory motifs. Beside its expression on NK cells, it is also found on rare circulating T lymphocytes, mainly CD8⁺. Although the KIR gene number varies between haplotype, KIR3DL2 is a framework gene present in all individuals. Together with the presence of genomic regulatory sequences unique to KIR3DL2, this suggests some particular functions for the derived protein in comparison with other KIR family members. Several ligands have been identified for KIR3DL2. As for other KIRs, binding to HLA class I molecules is essential for NK development by promoting phenomena such as licensing and driving NK cell maturation. For KIR3DL2, this includes binding to HLA-A3 and -A11 and to the free heavy chain form of HLA-B27. In addition, KIR3DL2 binds to CpG oligonucleotides (ODN) and ensures their transport to endosomal toll-like receptor 9 that promotes cell activation. These characteristics have implicated KIR3DL2 in several pathologies: ankylosing spondylitis and cutaneous T-cell lymphomas such as Sézary syndrome, CD30⁺ cutaneous lymphoma, and transformed mycosis fungoides. Consequently, a new generation of humanized monoclonal antibodies (mAbs) directed against KIR3DL2 has been helpful in the diagnosis, follow-up, and treatment of these diseases. In addition, preliminary clinical studies of a novel targeted immunotherapy for cutaneous T-cell lymphomas using the anti-KIR3DL2 mAb IPH4102 are now underway. In this review, we discuss the various aspects of KIR3DL2 on the functions of CD4⁺ T cells and how targeting this receptor helps to develop innovative therapeutic strategies.

Synthetic immune niches for cancer immunotherapy

Cancer immunotherapy can successfully promote long-term anticancer immune responses, although there is still only a limited number of patients who benefit from such treatment, and it can sometimes have severe treatment-associated adverse events. Compared with systemic immunomodulation, local immunomodulation may enable more effective treatment at lower doses and, at the same time, prevent systemic toxicity. Local delivery of engineered three-dimensional scaffolds may fulfil this role by acting as synthetic immune niches that boost anticancer immunity. In this Opinion article, we highlight the potential of scaffold-based adoptive cell transfer and scaffold-based cancer vaccines that, although applied locally, can promote systemic antitumour immunity. Furthermore, we discuss how scaffold-based cancer immunotherapy may contribute to the development of the next generation of cancer treatments.

Brachytherapy attains abscopal effects when combined with immunostimulatory monoclonal antibodies

PURPOSE/OBJECTIVES

Preclinical and clinical evidence indicate that the proimmune effects of radiotherapy can be synergistically augmented with immunostimulatory monoclonal antibodies (mAb) to act both on irradiated tumor lesions and on tumors at distant, nonirradiated sites. We have recently reported that external beam radiotherapy achieves abscopal effects when combined with antagonist anti-PD1 mAbs and agonist anti-CD137 (4-1BB) mAbs. The goal of this work is to study the abscopal effects of radiotherapy instigated by brachytherapy techniques.

METHODS AND MATERIALS

Mice bearing a subcutaneous colorectal carcinoma, MC38 (colorectal cancer), in both flanks were randomly assigned to receive brachytherapy or not (8 Gy × three fractions) to only one of the two grafted tumors, in combination with intraperitoneal immunostimulatory monoclonal antibodies (anti-PD1, anti-CD137, and/or their respective isotype controls). To study the abscopal effects of brachytherapy, we established an experimental set up that permits irradiation of mouse tumors sparing a distant site resembling metastasis. Such second nonirradiated tumor was used as indicator of abscopal effect. Tumor size was monitored every 2 days.

RESULTS

Abscopal effects on distant nonirradiated subcutaneous tumor lesions of transplanted MC38-derived tumors only took place when brachytherapy was combined with immunostimulatory anti-PD1 and/or anti-CD137 mAbs.

CONCLUSIONS

Our results demonstrate that immunotherapy-potentiated abscopal effects can be attained by brachytherapy. Accordingly, immunotherapy plus brachytherapy combinations are suitable for clinical translation.

An Update on the Use of Immunotherapy in the Treatment of Lymphoma

PURPOSE OF REVIEW

Throughout the field of oncology, immunotherapy is moving further towards the first-line setting, and there is encouraging data for the use of these novel therapies in the management of lymphomas, utilizing treatments approved for both solid and hematologic malignancies. Herein, we review promising advances in this rapidly moving field from the past year.

RECENT FINDINGS

In the last year, we have seen promising clinical data on engineered antibody therapies for the treatment of lymphomas, as well as further optimization of engineered antibody fragments fused onto linkers or chimeric T cell receptors, both of the modalities capable of transforming non-specific T cells into tumor-specific, serial killer cells. Here we will review the promising data on these advances in antibody-based therapies, as well as some of the immunomodulators and checkpoint-blocking therapies that shown to have promising results in the treatment of lymphomas within the past year.

Vaccine strategies for the treatment of lymphoma: preclinical progress and clinical trial update

The clonal B-cell immunoglobulin idiotype found on the surface of lymphomas was the first targeted tumor-specific antigen, and combinations of idiotype with classical and novel adjuvants were shown to stimulate robust humoral and cellular responses, though clinical efficacy was more variable. Cellular and in situ vaccination to help target a wider array of tumor-specific antigens have also been able to stimulate tumor-specific cellular responses, though their clinical success has also been limited. Our growing understanding of the role of regulatory cells and the immunosuppressive tumor microenvironment, along with a wide variety of immunomodulatory agents developed as of late, offer promising adjuvants to potentiate the immune responses elicited by these vaccine protocols and to achieve durable remissions.

Delivering safer immunotherapies for cancer

Cancer immunotherapy is now a powerful clinical reality, with a steady progression of new drug approvals and a massive pipeline of additional treatments in clinical and preclinical development. However, modulation of the immune system can be a double-edged sword: Drugs that activate immune effectors are prone to serious non-specific systemic inflammation and autoimmune side effects. Drug delivery technologies have an important role to play in harnessing the power of immune therapeutics while avoiding on-target/off-tumor toxicities. Here we review mechanisms of toxicity for clinically-relevant immunotherapeutics, and discuss approaches based in drug delivery technology to enhance the safety and potency of these treatments. These include strategies to merge drug delivery with adoptive cellular therapies, targeting immunotherapies to tumors or select immune cells, and localizing therapeutics intratumorally. Rational design employing lessons learned from the drug delivery and nanomedicine fields has the potential to facilitate immunotherapy reaching its full potential.

Challenges and opportunities for checkpoint blockade in T-cell lymphoproliferative disorders

The T-cell lymphoproliferative disorders are a heterogeneous group of non-Hodgkin’s lymphomas (NHL) for which current therapeutic strategies are inadequate, as most patients afflicted with these NHL will succumb to disease progression within 2 years of diagnosis. Appreciation of the genetic and immunologic landscape of these aggressive NHL, including PD-L1 (B7-H1, CD274) expression by malignant T cells and within the tumor microenvironment, provides a strong rationale for therapeutic targeting this immune checkpoint. While further studies are needed, the available data suggests that responses with PD-1 checkpoint blockade alone will unlikely approach those achieved in other lymphoproliferative disorders. Herein, we review the unique challenges posed by the T-cell lymphoproliferative disorders and discuss potential strategies to optimize checkpoint blockade in these T-cell derived malignancies.

Ameliorating Active Ulcerative Colitis via an Orally Available Toll-Like Receptor-9 Modifier: A Prospective Open-Label, Multicenter Phase II Trial

BACKGROUND

Treatment of active ulcerative colitis is associated with incomplete efficacy, adverse events, and loss of response. Toll-like receptor-9 mediates innate and adaptive immune response toward intestinal microorganisms. The oral synthetic oligonucleotide toll-like receptor-9 modulator has demonstrated anti-inflammatory properties in colitis murine models and a satisfactory safety profile in humans.

AIM

To evaluate the efficacy and safety of BL-7040 (a Toll-like receptor-9 modulator) in patients with moderately active ulcerative colitis.

METHODS

Moderately active ulcerative colitis patients were included in this multicenter, open-label phase IIa trial. Concomitant mesalamine and steroids at a stable dose were allowed. Clinical outcome was evaluated using the Mayo score, histology, and mucosal cytokine levels. Side effects were registered.

RESULTS

Sixteen out of 22 patients completed a 5-week treatment course and 2-week follow-up. Six patients discontinued the study, three of them due to adverse events. Clinical remission was observed in two patients (12.5 %), and clinical response as well as mucosal healing were achieved in half (50 %) of the patients, while all others remained stable. Furthermore, mucosal neutrophil (p = 0.002) and mucosal interleukin-6 levels (p = 0.046) were significantly reduced in responders compared to non-responders. Toll-like receptor-9 was well tolerated with only one unrelated to study drug serious adverse event (hemoglobin decrease) and 29 mild-to-moderate adverse events.

CONCLUSIONS

Oral administration of the Toll-like receptor-9 agonist BL-7040 appeared efficacious, safe and well tolerated in patients with moderately active ulcerative colitis.

Intratumoral injection of a CpG oligonucleotide reverts resistance to PD-1 blockade by expanding multifunctional CD8+ T cells

Despite the impressive rates of clinical response to programmed death 1 (PD-1) blockade in multiple cancers, the majority of patients still fail to respond to this therapy. The CT26 tumor in mice showed similar heterogeneity, with most tumors unaffected by anti-PD-1. As in humans, response of CT26 to anti-PD-1 correlated with increased T- and B-cell infiltration and IFN expression. We show that intratumoral injection of a highly interferogenic TLR9 agonist, SD-101, in anti-PD-1 nonresponders led to a complete, durable rejection of essentially all injected tumors and a majority of uninjected, distant-site tumors. Therapeutic efficacy of the combination was also observed with the TSA mammary adenocarcinoma and MCA38 colon carcinoma tumor models that show little response to PD-1 blockade alone. Intratumoral SD-101 substantially increased leukocyte infiltration and IFN-regulated gene expression, and its activity was dependent on CD8⁺ T cells and type I IFN signaling. Anti-PD-1 plus intratumoral SD-101 promoted infiltration of activated, proliferating CD8⁺ T cells and led to a synergistic increase in total and tumor antigen-specific CD8⁺ T cells expressing both IFN-γ and TNF-α. Additionally, PD-1 blockade could alter the CpG-mediated differentiation of tumor-specific CD8⁺ T cells into CD127^lowKLRG1^high short-lived effector cells, preferentially expanding the CD127^highKLRG1^low long-lived memory precursors. Tumor control and intratumoral T-cell proliferation in response to the combined treatment is independent of T-cell trafficking from secondary lymphoid organs. These findings suggest that a CpG oligonucleotide given intratumorally may increase the response of cancer patients to PD-1 blockade, increasing the quantity and the quality of tumor-specific CD8⁺ T cells.

Tumor-directed immunotherapy can generate tumor-specific T cell responses through localized co-stimulation

The most important goals for the field of immuno-oncology are to improve the response rate and increase the number of tumor indications that respond to immunotherapy, without increasing adverse side effects. One approach to achieve these goals is to use tumor-directed immunotherapy, i.e., to focus the immune activation to the most relevant part of the immune system. This may improve anti-tumor efficacy as well as reduce immune-related adverse events. Tumor-directed immune activation can be achieved by local injections of immune modulators in the tumor area or by directing the immune modulator to the tumor using bispecific antibodies. In this review, we focus on therapies targeting checkpoint inhibitors and co-stimulatory receptors that can generate tumor-specific T cell responses through localized immune activation.

[Radiotherapy and targeted therapy/immunotherapy]

Thanks to recent advances achieved in oncologic systemic and local ablative treatment, the treatments become more and more efficient in term of local control and overall survival. Thus, the targeted therapies, immunotherapy or stereotactic radiotherapy have modified the management of patients, especially in case of oligometastatic disease. Many questions are raised by these innovations, particularly the diagnosis and management of new side effects or that of the combination of these different treatments, depending on the type of primary tumor. Fundamental data are available, while clinical data are still limited. Ongoing trials should help to clarify the clinical management protocols. This manuscript is a review of the combination of radiotherapy and targeted therapy/immunotherapy.

Sensing of dangerous DNA

The presence of damaged and microbial DNA can pose a threat to the survival of organisms. Cells express various sensors that recognize specific aspects of such potentially dangerous DNA. Recognition of damaged or microbial DNA by sensors induces cellular processes that are important for DNA repair and inflammation. Here, we review recent evidence that the cellular response to DNA damage and microbial DNA are tightly intertwined. We also discuss insights into the parameters that enable DNA sensors to distinguish damaged and microbial DNA from DNA present in healthy cells.

Abscopal Effects of Radiotherapy Are Enhanced by Combined Immunostimulatory mAbs and Are Dependent on CD8 T Cells and Crosspriming

Preclinical and clinical evidence indicate that the proimmune effects of radiotherapy can be synergistically augmented with immunostimulatory mAbs to act both on irradiated tumor lesions and on distant, nonirradiated tumor sites. The combination of radiotherapy with immunostimulatory anti-PD1 and anti-CD137 mAbs was conducive to favorable effects on distant nonirradiated tumor lesions as observed in transplanted MC38 (colorectal cancer), B16OVA (melanoma), and 4T1 (breast cancer) models. The therapeutic activity was crucially performed by CD8 T cells, as found in selective depletion experiments. Moreover, the integrities of BATF-3-dependent dendritic cells specialized in crosspresentation/crosspriming of antigens to CD8⁺ T cells and of the type I IFN system were absolute requirements for the antitumor effects to occur. The irradiation regimen induced immune infiltrate changes in the irradiated and nonirradiated lesions featured by reductions in the total content of effector T cells, Tregs, and myeloid-derived suppressor cells, while effector T cells expressed more intracellular IFNγ in both the irradiated and contralateral tumors. Importantly, 48 hours after irradiation, CD8⁺ TILs showed brighter expression of CD137 and PD1, thereby displaying more target molecules for the corresponding mAbs. Likewise, PD1 and CD137 were induced on tumor-infiltrating lymphocytes from surgically excised human carcinomas that were irradiated ex vivo These mechanisms involving crosspriming and CD8 T cells advocate clinical development of immunotherapy combinations with anti-PD1 plus anti-CD137 mAbs that can be synergistically accompanied by radiotherapy strategies, even if the disease is left outside the field of irradiation. Cancer Res; 76(20); 5994-6005. ©2016 AACR.

Circulating nano-particulate TLR9 agonist scouts out tumor microenvironment to release immunogenic dead tumor cells

Recent evidence suggest that a β-glucan derived from mushroom Schizophyllan(SPG) complexed with a humanized TLR9 agonistic CpG DNA, K3 (K3-SPG) is a promising vaccine adjuvant that induces robust CD8 T cell responses to co-administered antigen. However, it has not been investigated whether K3-SPG alone can act as an anti-cancer immunotherapeutic agent or not. Here, we demonstrate that intravenous injection of K3-SPG, but not CpG alone, is accumulated in the tumor microenvironment and triggered immunogenic cell death (ICD) of tumor cells by local induction of type-I interferon (IFN) as well as IL-12. Resultant innate immune activation as well as subsequent tumor-specific CD8 T cell responses were contributed the tumor growth suppression. This anti-tumor effect of K3-SPG monotherapy was also confirmed by using various tumor models including pancreatic cancer peritoneal dissemination model. Taken together, nano-particulate TLR9 agonist injected intravenously can scout out tumor microenvironment to provoke local innate immune activation and release dead tumor cells into circulation that may induce broader and protective tumor antigen-specific CD8 T cells.

Sézary Syndrome and Atopic Dermatitis: Comparison of Immunological Aspects and Targets

Sézary syndrome (SS), an aggressive form of erythrodermic pruritic cutaneous T cell lymphoma (CTCL), from an immunological perspective characterized by increased Th2 cytokine levels, elevated serum IgE and impaired cellular immunity. Not only the clinical appearance but also the hallmark immunological characteristics of SS often share striking similarities with acute flares of atopic dermatitis (AD), a common benign chronic inflammatory skin disease. Given the overlap of several immunological features, the application of similar or even identical therapeutic approaches in certain stages of both diseases may come into consideration. The aim of this review is to compare currently accepted immunological aspects and possible therapeutic targets in AD and SS.

Intravenous administration of the selective toll-like receptor 7 agonist DSR-29133 leads to anti-tumor efficacy in murine solid tumor models which can be potentiated by combination with fractionated radiotherapy

Strategies to augment anti-cancer immune responses have recently demonstrated therapeutic utility. To date clinical success has been achieved through targeting co-inhibitory checkpoints such as CTLA-4, PD-1, and PD-L1. However, approaches that target co-activatory pathways are also being actively being developed. Here we report that the novel TLR7-selective agonist DSR-29133 is well tolerated in mice and leads to acute immune activation. Administration of DSR-29133 leads to the induction of IFNα/γ, IP-10, TNFα, IL-1Ra and IL-12p70, and to a reduction in tumor burden in syngeneic models of renal cancer (Renca), metastatic osteosarcoma (LM8) and colorectal cancer (CT26). Moreover, we show that the efficacy of DSR-29133 was significantly improved when administered in combination with low-dose fractionated radiotherapy (RT). Effective combination therapy required weekly administration of DSR-29133 commencing on day 1 of a fractionated RT treatment cycle, whereas no enhancement of radiation response was observed when DSR-29133 was administered at the end of the fractionated RT cycle. Combined therapy resulted in curative responses in a high proportion of mice bearing established CT26 tumors which was dependent on the activity of CD8+ T-cells but independent of CD4+ T-cells and NK/NKT cells. Moreover, long-term surviving mice originally treated with DSR-29133 and RT were protected by a tumor-specific memory immune response which could prevent tumor growth upon rechallenge. These results demonstrate that DSR-29133 is a potent selective TLR7 agonist that when administered intravenously can induce anti-tumor immune responses that can be further enhanced through combination with low-dose fractionated RT.

Immunodynamics: a cancer immunotherapy trials network review of immune monitoring in immuno-oncology clinical trials

The efficacy of PD-1/PD-L1 targeted therapies in addition to anti-CTLA-4 solidifies immunotherapy as a modality to add to the anticancer arsenal. Despite raising the bar of clinical efficacy, immunologically targeted agents raise new challenges to conventional drug development paradigms by highlighting the limited relevance of assessing standard pharmacokinetics (PK) and pharmacodynamics (PD). Specifically, systemic and intratumoral immune effects have not consistently correlated with standard relationships between systemic dose, toxicity, and efficacy for cytotoxic therapies. Hence, PK and PD paradigms remain inadequate to guide the selection of doses and schedules, both starting and recommended Phase 2 for immunotherapies. The promise of harnessing the immune response against cancer must also be considered in light of unique and potentially serious toxicities. Refining immune endpoints to better inform clinical trial design represents a high priority challenge. The Cancer Immunotherapy Trials Network investigators review the immunodynamic effects of specific classes of immunotherapeutic agents to focus immune assessment modalities and sites, both systemic and importantly intratumoral, which are critical to the success of the rapidly growing field of immuno-oncology.

Blocking Indolamine-2,3-Dioxygenase Rebound Immune Suppression Boosts Antitumor Effects of Radio-Immunotherapy in Murine Models and Spontaneous Canine Malignancies

PURPOSE

Previous studies demonstrate that intratumoral CpG immunotherapy in combination with radiotherapy acts as an in-situ vaccine inducing antitumor immune responses capable of eradicating systemic disease. Unfortunately, most patients fail to respond. We hypothesized that immunotherapy can paradoxically upregulate immunosuppressive pathways, a phenomenon we term "rebound immune suppression," limiting clinical responses. We further hypothesized that the immunosuppressive enzyme indolamine-2,3-dioxygenase (IDO) is a mechanism of rebound immune suppression and that IDO blockade would improve immunotherapy efficacy.

EXPERIMENTAL DESIGN

We examined the efficacy and immunologic effects of a novel triple therapy consisting of local radiotherapy, intratumoral CpG, and systemic IDO blockade in murine models and a pilot canine clinical trial.

RESULTS

In murine models, we observed marked increase in intratumoral IDO expression after treatment with radiotherapy, CpG, or other immunotherapies. The addition of IDO blockade to radiotherapy + CpG decreased IDO activity, reduced tumor growth, and reduced immunosuppressive factors, such as regulatory T cells in the tumor microenvironment. This triple combination induced systemic antitumor effects, decreasing metastases, and improving survival in a CD8(+) T-cell-dependent manner. We evaluated this novel triple therapy in a canine clinical trial, because spontaneous canine malignancies closely reflect human cancer. Mirroring our mouse studies, the therapy was well tolerated, reduced intratumoral immunosuppression, and induced robust systemic antitumor effects.

CONCLUSIONS

These results suggest that IDO maintains immune suppression in the tumor after therapy, and IDO blockade promotes a local antitumor immune response with systemic consequences. The efficacy and limited toxicity of this strategy are attractive for clinical translation. Clin Cancer Res; 22(17); 4328-40. ©2016 AACR.

Systemic delivery of chTNT-3/CpG immunoconjugates for immunotherapy in murine solid tumor models

CpG oligodeoxynucleotides (CpG) potently activate the immune system by mimicking microbial DNA. Conjugation of CpG to chTNT-3, an antibody targeting the necrotic centers of tumors, enabled CpG to accumulate in tumors after systemic delivery, where it can activate the immune system in the presence of tumor antigens. CpG chemically conjugated to chTNT-3 (chTNT-3/CpG) were compared to free CpG in their ability to stimulate the immune system in vitro and reduce tumor burden in vivo. In subcutaneous Colon 26 adenocarcinoma and B16-F10 melanoma models in BALB/c and C57BL/6 mice, respectively, chTNT-3/CpG, free CpG, or several different control constructs were administered systemically. Intraperitoneal injections of chTNT-3/CpG delayed tumor growth and improved survival and were comparable to intratumorally administered CpG. Compared to saline-treated mice, chTNT-3/CpG-treated mice had smaller average tumor volumes by as much as 72% in Colon 26-bearing mice and 79% in B16-bearing mice. Systemically delivered free CpG and CpG conjugated to an isotype control antibody did not reduce tumor burden or improve survival. In this study, chTNT-3/CpG retained immunostimulatory activity of the CpG moiety and enabled delivery to tumors. Because systemically administered CpG rapidly clear the body and do not accumulate into tumors, chTNT-3/CpG provide a solution to the limitations observed in preclinical and clinical trials.

In situ vaccination for the treatment of cancer

Vaccination has had a tremendous impact on human health by harnessing the immune system to prevent and eradicate infectious diseases and this same approach might be used in cancer therapy. Cancer vaccine development has been slowed hindered by the paucity of universal tumor-associated antigens and the difficulty in isolating and preparing individualized vaccines ex vivo. Another approach has been to initiate or stimulate an immune response in situ (at the tumor site) and thus exploit the potentially numerous tumor-associated antigens there. Here, we review the many approaches that have attempted to accomplish effective in situ vaccination, using intratumoral administration of immunomodulators to increase the numbers or activation state of either antigen present cells or T cells within the tumor.