In Situ Vaccination with a TLR9 Agonist and Local Low-Dose Radiation Induces Systemic Responses in Untreated Indolent Lymphoma

Neoadjuvant vidutolimod and nivolumab in high-risk resectable melanoma: A prospective phase II trial

Intratumoral TLR9 agonists and anti-PD-1 produce clinical responses and broad immune activation. We conducted a single-arm study of neoadjuvant TLR9 agonist vidutolimod combined with anti-PD-1 nivolumab in high-risk resectable melanoma. In 31 evaluable patients, 55% major pathologic response (MPR) was observed, meeting primary endpoint. MPR was associated with necrosis, and melanophagocytosis with increased CD8+ tumor-infiltrating lymphocytes and plasmacytoid dendritic cells (pDCs) in the tumor microenvironment, and increased frequencies of Ki67+CD8+ T cells peripherally. MPRs had an enriched pre-treatment gene signature of myeloid cells, and response to therapy was associated with gene signatures of immune cells, pDCs, phagocytosis, and macrophage activation. MPRs gut microbiota were enriched for Gram-negative bacteria belonging to the Bacteroidaceae and Enterobacteriaceae families and the small subgroup of Gram-negative Firmicutes. Our findings support that combined vidutolimod and nivolumab stimulates a broad anti-tumor immune response and is associated with distinct baseline myeloid gene signature and gut microbiota. ClinicalTrials.gov identifier: NCT03618641.

Molecular Biomarkers in Prediction of High-Grade Transformation and Outcome in Patients with Follicular Lymphoma: A Comprehensive Systemic Review

Follicular lymphoma (FL) is the most prevalent indolent B-cell lymphoma entity, often characterized by the t(14;18) BCL2-IGH translocation. The malignancy represents a clinically and biologically highly heterogeneous disease. Most patients have favorable prognoses; however, despite therapeutic advancements, the disease remains incurable, with recurrent relapses or early disease progression. Moreover, transformation to an aggressive histology, most often diffuse large-B-cell lymphoma, remains a critical event in the disease course, which is associated with poor outcomes. Understanding the individual patient's risk of transformation remains challenging, which has motivated much research on novel biomarkers within the past four decades. This review systematically assessed the research on molecular biomarkers in FL transformation and outcome. Following the PRISMA guidelines for systemic reviews, the PubMed database was searched for English articles published from January 1984 through September 2024, yielding 6769 results. The identified publications were carefully screened and reviewed, of which 283 original papers met the inclusion criteria. The included studies focused on investigating molecular biomarkers as predictors of transformation or as prognostic markers of time-related endpoints (survival, progression, etc.). The effects of each biomarker were categorized based on their impact on prognosis or risk of transformation as none, favorable, or inferior. The biomarkers included genetic abnormalities, gene expression, microRNAs, markers of B cells/FL tumor cells, markers of the tumor microenvironment, and soluble biomarkers. This comprehensive review provides an overview of the research conducted in the past four decades, underscoring the persistent challenge in risk anticipation of FL patients.

Mechanism of immune activation mediated by genomic instability and its implication in radiotherapy combined with immune checkpoint inhibitors

Various genetic and epigenetic changes associated with genomic instability (GI), including DNA damage repair defects, chromosomal instability, and mitochondrial GI, contribute to development and progression of cancer. These alterations not only result in DNA leakage into the cytoplasm, either directly or through micronuclei, but also trigger downstream inflammatory signals, such as the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway. Apart from directly inducing DNA damage to eliminate cancer cells, radiotherapy (RT) exerts its antitumor effects through intracellular DNA damage sensing mechanisms, leading to the activation of downstream inflammatory signaling pathways. This not only enables local tumor control but also reshapes the immune microenvironment, triggering systemic immune responses. The combination of RT and immunotherapy has emerged as a promising approach to increase the probability of abscopal effects, where distant tumors respond to treatment due to the systemic immunomodulatory effects. This review emphasizes the importance of GI in cancer biology and elucidates the mechanisms by which RT induces GI remodeling of the immune microenvironment. By elucidating the mechanisms of GI and RT-induced immune responses, we aim to emphasize the crucial importance of this approach in modern oncology. Understanding the impact of GI on tumor biological behavior and therapeutic response, as well as the possibility of activating systemic anti-tumor immunity through RT, will pave the way for the development of new treatment strategies and improve prognosis for patients.

Biomaterial-Based In Situ Cancer Vaccines

Cancer immunotherapies have reshaped the paradigm for cancer treatment over the past decade. Among them, therapeutic cancer vaccines that aim to modulate antigen-presenting cells and subsequent T cell priming processes are among the first FDA-approved cancer immunotherapies. However, despite showing benign safety profiles and the capability to generate antigen-specific humoral and cellular responses, cancer vaccines have been limited by the modest therapeutic efficacy, especially for immunologically cold solid tumors. One key challenge lies in the identification of tumor-specific antigens, which involves a costly and lengthy process of tumor cell isolation, DNA/RNA extraction, sequencing, mutation analysis, epitope prediction, peptide synthesis, and antigen screening. To address these issues, in situ cancer vaccines have been actively pursued to generate endogenous antigens directly from tumors and utilize the generated tumor antigens to elicit potent cytotoxic T lymphocyte (CTL) response. Biomaterials-based in situ cancer vaccines, in particular, have achieved significant progress by taking advantage of biomaterials that can synergize antigens and adjuvants, troubleshoot delivery issues, home, and manipulate immune cells in situ. This review will provide an overview of biomaterials-based in situ cancer vaccines, either living or artificial materials, under development or in the clinic, and discuss the design criteria for in situ cancer vaccines.

Integrative Approaches in Non-Small Cell Lung Cancer Management: The Role of Radiotherapy

Treatment guidelines for non-small cell lung cancer (NSCLC) vary by several factors including pathological stage, patient candidacy, and goal of treatment. With many therapeutics and even more combinations available in the NSCLC clinician's toolkit, a multitude of questions remain unanswered vis-a-vis treatment optimization. While some studies have begun exploring the interplay among the many pillars of NSCLC treatment-surgical resection, radiotherapy, chemotherapy, and immunotherapy-the vast number of combinations and permutations of different therapy modalities in addition to the modulation of each constituent therapy leaves much to be desired in a field that is otherwise rapidly evolving. Given NSCLC's high incidence and lethality, the experimentation of synergistic benefits that combinatorial treatment may confer presents a ripe target for advancement and increased understanding without the cost and burden of novel drug development. This review introduces, synthesizes, and compares prominent NSCLC therapies, placing emphasis on the interplay among types of therapies and the synergistic benefits some combinatorial therapies have demonstrated over the past several years.

Radioactive Hydroxyapatite Microspheres Empower Sustainable In Situ Tumor Vaccination

Tumor in situ vaccination (ISV) strategies have emerged in clinical trials as promising approaches, involving the release of tumor antigens through local radiotherapy and intratumorally adjuvant injections. However, the current fabrication strategy for achieving a sustainable immune response to ISV remains a pressing challenge. In this study, we present an empowered sustainable ISV method for antitumor therapy using 177Lu-labeled manganese-doped mesoporous hydroxyapatite (177Lu/Mn-HAP) microspheres. The ISV enables the sustained utilization of tumor antigens, leading to the activation of dendritic cells and polarization of macrophages toward the M1 subtype. Consequently, it facilitates the generation of potent CD8+ T-cell responses, enhancing the antitumor effects of internal radiation in both primary and distant tumors. Importantly, this approach achieves complete remission in all tumor-bearing mice and stimulates immune memory to prevent tumor recurrence. Our study highlights a universal and safe ISV strategy capable of inducing potent tumor-specific and sustainable immune response.

Enhancing radiotherapy response via intratumoral injection of a TLR9 agonist in autochthonous murine sarcomas

Radiation therapy (RT) is frequently used to treat cancers, including soft-tissue sarcomas. Prior studies established that the toll-like receptor 9 (TLR9) agonist cytosine-phosphate-guanine oligodeoxynucleotide (CpG) enhances the response to RT in transplanted tumors, but the mechanisms of this enhancement remain unclear. Here, we used CRISPR/Cas9 and the chemical carcinogen 3-methylcholanthrene (MCA) to generate autochthonous soft-tissue sarcomas with high tumor mutation burden. Treatment with a single fraction of 20 Gy RT and 2 doses of CpG significantly enhanced tumor response, which was abrogated by genetic or immunodepletion of CD8+ T cells. To characterize the immune response to CpG+RT, we performed bulk RNA-Seq, single-cell RNA-Seq, and mass cytometry. Sarcomas treated with 20 Gy and CpG demonstrated increased CD8 T cells expressing markers associated with activation and proliferation, such as Granzyme B, Ki-67, and IFN-γ. CpG+RT also upregulated antigen presentation pathways on myeloid cells. Furthermore, in sarcomas treated with CpG+RT, TCR clonality analysis suggests an increase in clonal T cell dominance. Collectively, these findings demonstrate that CpG+RT significantly delays tumor growth in a CD8 T cell-dependent manner. These results provide a strong rationale for clinical trials evaluating CpG or other TLR9 agonists with RT in patients with soft-tissue sarcoma.

DNA sensing of dendritic cells in cancer immunotherapy

Dendritic cells (DCs) are involved in the initiation and maintenance of immune responses against malignant cells by recognizing conserved pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs) through pattern recognition receptors (PRRs). According to recent studies, tumor cell-derived DNA molecules act as DAMPs and are recognized by DNA sensors in DCs. Once identified by sensors in DCs, these DNA molecules trigger multiple signaling cascades to promote various cytokines secretion, including type I IFN, and then to induce DCs mediated antitumor immunity. As one of the potential attractive strategies for cancer therapy, various agonists targeting DNA sensors are extensively explored including the combination with other cancer immunotherapies or the direct usage as major components of cancer vaccines. Moreover, this review highlights different mechanisms through which tumor-derived DNA initiates DCs activation and the mechanisms through which the tumor microenvironment regulates DNA sensing of DCs to promote tumor immune escape. The contributions of chemotherapy, radiotherapy, and checkpoint inhibitors in tumor therapy to the DNA sensing of DCs are also discussed. Finally, recent clinical progress in tumor therapy utilizing agonist-targeted DNA sensors is summarized. Indeed, understanding more about DNA sensing in DCs will help to understand more about tumor immunotherapy and improve the efficacy of DC-targeted treatment in cancer.

Engineered Bacteriophage-Based In Situ Vaccine Remodels a Tumor Microenvironment and Elicits Potent Antitumor Immunity

In situ vaccines (ISVs) utilize the localized delivery of chemotherapeutic agents or radiotherapy to stimulate the release of endogenous antigens from tumors, thereby eliciting systemic and persistent immune activation. Recently, a bioinspired ISV strategy has attracted tremendous attention due to its features such as an immune adjuvant effect and genetic plasticity. M13 bacteriophages are natural nanomaterials with intrinsic immunogenicity, genetic flexibility, and cost-effectiveness for large-scale production, demonstrating the potential for application in cancer vaccines. In this study, we propose an ISV based on the engineered M13 bacteriophage targeting CD40 (M13CD40) for dendritic cell (DC)-targeted immune stimulation, named H-GM-M13CD40. We induce immunogenic cell death and release tumor antigens through local delivery of (S)-10-hydroxycamptothecin (HCPT), followed by intratumoral injection of granulocyte-macrophage colony stimulating factor (GM-CSF) and M13CD40 to enhance DC recruitment and activation. We demonstrate that this ISV strategy can result in significant accumulation and activation of DCs at the tumor site, reversing the immunosuppressive tumor microenvironment. In addition, H-GM-M13CD40 can synergize with the PD-1 blockade and induce abscopal effects in cold tumor models. Overall, our study verifies the immunogenicity of the engineered M13CD40 bacteriophage and provides a proof of concept that the engineered M13CD40 phage can function as an adjuvant for ISVs.

When will the immune-stimulating antibody conjugates (ISACs) be transferred from bench to bedside?

Immunostimulatory antibody conjugates (ISACs) as a promising new generation of targeted therapeutic antibody-drug conjugates (ADCs), that not only activate innate immunity but also stimulate adaptive immunity, providing a dual therapeutic effect to eliminate tumor cells. However, several ISACs are still in the early stages of clinical development or have already failed. Therefore, it is crucial to design ISACs more effectively to overcome their limitations, including high toxicity, strong immunogenicity, long development time, and poor pharmacokinetics. This review aims to summarize the composition and function of ISACs, incorporating current design considerations and ongoing clinical trials. Additionally, the review delves into the current issues with ISACs and potential solutions, such as adjusting the drug-antibody ratio (DAR) to improve the bioavailability of ISACs. By leveraging the affinity and bioavailability-enhancing properties of bispecific antibodies, the utility between antibodies and immunostimulatory agents can be balanced. Commonly used immunostimulatory agents may induce systemic immune reactions, and BTK (Bruton's tyrosine kinase) inhibitors can regulate immunogenicity. Finally, the concept of grafting ADC's therapeutic principles is simple, but the combination of payload, linker, and targeted functional molecules is not a simple permutation and combination problem. The development of conjugate drugs faces more complex pharmacological and toxicological issues. Standing on the shoulders of ADC, the development and application scenarios of ISAC are endowed with broader space.

Low-dose radiation therapy mobilizes antitumor immunity: New findings and future perspectives

Radiotherapy has unique immunostimulatory and immunosuppressive effects. Although high-dose radiotherapy has been found to have systemic antitumor effects, clinically significant abscopal effects were uncommon on the basis of irradiating single lesion. Low-dose radiation therapy (LDRT) emerges as a novel approach to enhance the antitumor immune response due to its role as a leverage to reshape the tumor immune microenvironment (TIME). In this article, from bench to bedside, we reviewed the possible immunomodulatory role of LDRT on TIME and systemic tumor immune environment, and outlined preclinical evidence and clinical application. We also discussed the current challenges when LDRT is used as a combination therapy, including the optimal dose, fraction, frequency, and combination of drugs. The advantage of low toxicity makes LDRT potential to be applied in multiple lesions to amplify antitumor immune response in polymetastatic disease, and its intersection with other disciplines might also make it a direction for radiotherapy-combined modalities.

Radiotherapy Combined with Intralesional Immunostimulatory Agents for Soft Tissue Sarcomas

Immunotherapy has shifted the treatment paradigm for many types of cancer. Unfortunately, the most commonly used immunotherapies, such as immune checkpoint inhibitors (ICI), have yielded limited benefit for most types of soft tissue sarcoma (STS). Radiotherapy (RT) is a mainstay of sarcoma therapy and can induce immune modulatory effects. Combining immunotherapy and RT in STS may be a promising strategy to improve sarcoma response to RT and increase the efficacy of immunotherapy. Most combination strategies have employed immunotherapies, such as ICI, that derepress immune suppressive networks. These have yielded only modest results, possibly due to the limited immune stimulatory effects of RT. Combining RT with immune stimulatory agents has yielded promising preclinical and clinical results but can be limited by the toxic nature of systemic administration of immune stimulants. Using intralesional immune stimulants may generate stronger RT immune modulation and less systemic toxicity, which may be a feasible strategy in accessible tumors such as STS. In this review, we summarize the immune modulatory effects of RT, the mechanism of action of various immune stimulants, including toll-like receptor agonists, and data for combinatorial strategies utilizing these agents.

Advances and Challenges in Interventional Immuno-Oncology Locoregional Therapies

Interventional immuno-oncology is making strides in locoregional therapies to address complex tumor microenvironments. Long-standing interventional radiology cancer therapies, such as tumor ablation and embolization, are being recharacterized in the context of immunotherapy. Intratumoral injections, such as those of genetically engineered or unaltered viruses, and the delivery of immune cells, antibodies, proteins, or cytokines into targeted tumors, along with advancements in delivery techniques, have produced promising results in preliminary studies, indicating their antitumor effectiveness. Emerging strategies using DNA scaffolding, polysaccharides, glycan, chitosan, and natural products are also showing promise in targeted cancer therapy. The future of interventional immuno-oncology lies in personalized immunotherapies that capitalize on individual immune profiles and tumor characteristics, along with the exploration of combination therapies. This study will review various interventional immuno-oncology strategies and emerging technologies to enhance delivery of therapeutics and response to immunotherapy.

A novel CpG ODN compound adjuvant enhances immune response to spike subunit vaccines of porcine epidemic diarrhea virus

CpG oligodeoxynucleotides (CpG ODNs) boost the humoral and cellular immune responses to antigens through interaction with Toll-like receptor 9 (TLR9). These CpG ODNs have been extensively utilized in human vaccines. In our study, we evaluated five B-type CpG ODNs that have stimulatory effects on pigs by measuring the proliferation of porcine peripheral blood mononuclear cells (PBMCs) and assessing interferon gamma (IFN-γ) secretion. Furthermore, this study examined the immunoenhancing effects of the MF59 and CpG ODNs compound adjuvant in mouse and piglet models of porcine epidemic diarrhea virus (PEDV) subunit vaccine administration. The in vitro screening revealed that the CpG ODN named CpG5 significantly stimulated the proliferation of porcine PBMCs and elevated IFN-γ secretion levels. In the mouse vaccination model, CpG5 compound adjuvant significantly bolstered the humoral and cellular immune responses to the PEDV subunit vaccines, leading to Th1 immune responses characterized by increased IFN-γ and IgG2a levels. In piglets, the neutralizing antibody titer was significantly enhanced with CpG5 compound adjuvant, alongside a considerable increase in CD8+ T lymphocytes proportion. The combination of MF59 adjuvant and CpG5 exhibits a synergistic effect, resulting in an earlier, more intense, and long-lasting immune response in subunit vaccines for PEDV. This combination holds significant promise as a robust candidate for the development of vaccine adjuvant.

Augmenting regulatory T cells: new therapeutic strategy for rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic, systemic autoimmune condition marked by inflammation of the joints, degradation of the articular cartilage, and bone resorption. Recent studies found the absolute and relative decreases in circulating regulatory T cells (Tregs) in RA patients. Tregs are a unique type of cells exhibiting immunosuppressive functions, known for expressing the Foxp3 gene. They are instrumental in maintaining immunological tolerance and preventing autoimmunity. Increasing the absolute number and/or enhancing the function of Tregs are effective strategies for treating RA. This article reviews the studies on the mechanisms and targeted therapies related to Tregs in RA, with a view to provide better ideas for the treatment of RA.

Radiotherapy-Triggered In Situ Tumor Vaccination Boosts Checkpoint Blockaded Immune Response via Antigen-Capturing Nanoadjuvants

In situ vaccination (ISV) formed with the aid of intratumorally injected adjuvants has shed bright light on enhancing the abscopal therapeutic effects of radiotherapy. However, the limited availability of antigens resulting from the radiotherapy-induced immunogenic cell death largely hampers the clinical outcome of ISV. To maximally utilize the radiotherapy-induced antigen, we herein developed a strategy by capturing the radiotherapy-induced antigen in situ with a nanoadjuvant comprised of CpG-loaded Fe3O4 nanoparticles. The highly efficient click reaction between the maleimide residue on the nanoadjuvant and sulfhydryl group on the antigen maximized the bioavailability of autoantigens and CpG adjuvant in vivo. Importantly, combined immune checkpoint blockade can reverse T cell exhaustion after treatment with radiotherapy-induced ISV, thereby largely suppressing the treated and distant tumor. Mechanistically, metabolomics reveals the intratumorally injected nanoadjuvants disrupt redox homeostasis in the tumor microenvironment, further inducing tumor ferroptosis after radiotherapy. Overall, the current study highlights the immense potential of the innovative antigen-capturing nanoadjuvants for synergistically enhancing the antitumor effect.

A clinical trial of therapeutic vaccination in lymphoma with serial tumor sampling and single-cell analysis

ABSTRACT

In situ vaccination (ISV) triggers an immune response to tumor-associated antigens at 1 tumor site, which can then tackle the disease throughout the body. Here, we report clinical and biological results of a phase 1/2 ISV trial in patients with low-grade lymphoma, combining an intratumoral toll-like receptor 9 (TLR9) agonist with local low-dose radiation and ibrutinib (an inhibitor of B- and T-cell kinases). Adverse events were predominately low grade. The overall response rate was 50%, including 1 complete response. All patients experienced tumor reduction at distant sites. Single-cell analyses of serial fine needle aspirates from injected and uninjected tumors revealed correlates of clinical response, such as lower CD47 and higher major histocompatibility complex class II expression on tumor cells, enhanced T-cell and natural killer cell effector function, and reduced immune suppression from transforming growth factor β and inhibitory T regulatory 1 cells. Although changes at the local injected site were more pronounced, changes at distant uninjected sites were more often associated with clinical responses. Functional immune response assays and tracking of T-cell receptor sequences provided evidence of treatment-induced tumor-specific T-cell responses. Induction of immune effectors and reversal of negative regulators were both important in producing clinically meaningful tumor responses. The trial was registered at www.clinicaltrials.gov as #NCT02927964.

Enhancing radiotherapy response via intratumoral injection of the TLR9 agonist CpG to stimulate CD8 T cells in an autochthonous mouse model of sarcoma

Radiation therapy is frequently used to treat cancers including soft tissue sarcomas. Prior studies established that the toll-like receptor 9 (TLR9) agonist cytosine-phosphate-guanine oligodeoxynucleotide (CpG) enhances the response to radiation therapy (RT) in transplanted tumors, but the mechanism(s) remain unclear. Here, we used CRISPR/Cas9 and the chemical carcinogen 3-methylcholanthrene (MCA) to generate autochthonous soft tissue sarcomas with high tumor mutation burden. Treatment with a single fraction of 20 Gy RT and two doses of CpG significantly enhanced tumor response, which was abrogated by genetic or immunodepletion of CD8+ T cells. To characterize the immune response to RT + CpG, we performed bulk RNA-seq, single-cell RNA-seq, and mass cytometry. Sarcomas treated with 20 Gy and CpG demonstrated increased CD8 T cells expressing markers associated with activation and proliferation, such as Granzyme B, Ki-67, and interferon-γ. CpG + RT also upregulated antigen presentation pathways on myeloid cells. Furthermore, in sarcomas treated with CpG + RT, TCR clonality analysis suggests an increase in clonal T-cell dominance. Collectively, these findings demonstrate that RT + CpG significantly delays tumor growth in a CD8 T cell-dependent manner. These results provide a strong rationale for clinical trials evaluating CpG or other TLR9 agonists with RT in patients with soft tissue sarcoma.

Molecular determinants of immunogenic cell death elicited by radiation therapy

Cancer cells undergoing immunogenic cell death (ICD) can initiate adaptive immune responses against dead cell-associated antigens, provided that (1) said antigens are not perfectly covered by central tolerance (antigenicity), (2) cell death occurs along with the emission of immunostimulatory cytokines and damage-associated molecular patterns (DAMPs) that actively engage immune effector mechanisms (adjuvanticity), and (3) the microenvironment of dying cells is permissive for the initiation of adaptive immunity. Finally, ICD-driven immune responses can only operate and exert cytotoxic effector functions if the microenvironment of target cancer cells enables immune cell infiltration and activity. Multiple forms of radiation, including non-ionizing (ultraviolet) and ionizing radiation, elicit bona fide ICD as they increase both the antigenicity and adjuvanticity of dying cancer cells. Here, we review the molecular determinants of ICD as elicited by radiation as we critically discuss strategies to reinforce the immunogenicity of cancer cells succumbing to clinically available radiation strategies.

Toll-Like Receptor 4 Agonist Injection With Concurrent Radiotherapy in Patients With Metastatic Soft Tissue Sarcoma: A Phase 1 Nonrandomized Controlled Trial

Importance

Metastatic soft tissue sarcomas (STSs) have limited systemic therapy options, and immunomodulation has not yet meaningfully improved outcomes. Intratumoral (IT) injection of the toll-like receptor 4 (TLR4) agonist glycopyranosyl lipid A in stable-emulsion formulation (GLA-SE) has been studied as immunotherapy in other contexts.

Objective

To evaluate the safety, efficacy, and immunomodulatory effects of IT GLA-SE with concurrent radiotherapy in patients with metastatic STS with injectable lesions.

Design, Setting, and Participants

This phase 1 nonrandomized controlled trial of patients with STS was performed at a single academic sarcoma specialty center from November 17, 2014, to March 16, 2016. Data analysis was performed from August 2016 to September 2022.

Interventions

Two doses of IT GLA-SE (5 μg and 10 μg for 8 weekly doses) were tested for safety in combination with concurrent radiotherapy of the injected lesion.

Main Outcomes and Measures

Primary end points were safety and tolerability. Secondary and exploratory end points included local response rates as well as measurement of antitumor immunity with immunohistochemistry and T-cell receptor (TCR) sequencing of tumor-infiltrating and circulating lymphocytes.

Results

Twelve patients (median [range] age, 65 [34-78] years; 8 [67%] female) were treated across the 2 dose cohorts. Intratumoral GLA-SE was well tolerated, with only 1 patient (8%) experiencing a grade 2 adverse event. All patients achieved local control of the injected lesion after 8 doses, with 1 patient having complete regression (mean regression, -25%; range, -100% to 4%). In patients with durable local response, there were detectable increases in tumor-infiltrating lymphocytes. In 1 patient (target lesion -39% at 259 days of follow-up), TCR sequencing revealed expansion of preexisting and de novo clonotypes, with convergence of numerous rearrangements coding for the same binding sequence (suggestive of clonal convergence to antitumor targets). Single-cell sequencing identified these same expanded TCR clones in peripheral blood after treatment; these T cells had markedly enhanced Tbet expression, suggesting TH1 phenotype.

Conclusions and Relevance

In this nonrandomized controlled trial, IT GLA-SE with concurrent radiotherapy was well tolerated and provided more durable local control than radiotherapy alone. Patients with durable local response demonstrated enhanced IT T-cell clonal expansion, with matched expansion of these clonotypes in the circulation. Additional studies evaluating synergism of IT GLA-SE and radiotherapy with systemic immune modulation are warranted.

Trial Registration

ClinicalTrials.gov Identifier: NCT02180698.

Modulation of CD8+ T Cell Responses by Radiotherapy-Current Evidence and Rationale for Combination with Immune Checkpoint Inhibitors

Radiotherapy for cancer has been known to affect the responses of immune cells, especially those of CD8+ T cells that play a pivotal role in anti-tumor immunity. Clinical success of immune checkpoint inhibitors led to an increasing interest in the ability of radiation to modulate CD8+ T cell responses. Recent studies that carefully analyzed CD8+ T cell responses following radiotherapy suggest the beneficial roles of radiotherapy on anti-tumor immunity. In addition, numerous clinical trials to evaluate the efficacy of combining radiotherapy with immune checkpoint inhibitors are currently undergoing. In this review, we summarize the current status of knowledge regarding the changes in CD8+ T cells following radiotherapy from various preclinical and clinical studies. Furthermore, key biological mechanisms that underlie such modulation, including both direct and indirect effects, are described. Lastly, we discuss the current evidence and essential considerations for harnessing radiotherapy as a combination partner for immune checkpoint inhibitors.

Radiation dose, schedule, and novel systemic targets for radio-immunotherapy combinations

Immunotherapy combinations are being investigated to expand the benefit of immune checkpoint blockade across many cancer types. Radiation combinations, in particular using stereotactic body radiotherapy, are of keen interest because of underlying mechanistic rationale, safety, and availability as a standard of care in certain cancers. In addition to direct tumor cytotoxicity, radiation therapy has immunomodulatory effects such as induction of immunogenic cell death, enhancement of antigen presentation, and expansion of the T-cell receptor repertoire as well as recruitment and increased activity of tumor-specific effector CD8+ cells. Combinations of radiation with cytokines and/or chemokines and anti-programmed death 1 and anticytotoxic T-lymphocyte antigen 4 therapies have demonstrated safety and feasibility, as well as the potential to improve long-term outcomes and possibly induce out of irradiated field or abscopal responses. Novel immunoradiotherapy combinations represent a promising therapeutic approach to overcome radioresistance and further enhance systemic immunotherapy. Potential benefits include reversing CD8+ T-cell exhaustion, inhibiting myeloid-derived suppressor cells, and reversing M2 macrophage polarization as well as decreasing levels of colony-stimulating factor-1 and transforming growth factor-β. Here, we discuss current data and mechanistic rationale for combining novel immunotherapy agents with radiation therapy.

Intraperitoneal administration of a modified vaccinia virus Ankara confers single-chain interleukin-12 expression to the omentum and achieves immune-mediated efficacy against peritoneal carcinomatosis

BACKGROUND

Peritoneal carcinomatosis is an advanced stage of cancer in which the disease has spread to the peritoneal cavity. In order to restore antitumor immunity subverted by tumor cells in this location, we evaluated intraperitoneal administrations of modified vaccinia virus Ankara (MVA) engineered to express single-chain interleukin 12 (scIL-12) to increase antitumor immune responses.

METHODS

MVA encoding scIL-12 (MVA.scIL-12) was evaluated against peritoneal carcinomatosis models based on intraperitoneal engraftment of tumor cells. CD8-mediated immune responses, elucidated antitumor efficacy, and safety were evaluated following intravenous, intratumoral, or intraperitoneal administration of the viral vector. The immune response was measured by ELISpot (enzyme-linked immunosorbent spot), RNA sequencing, flow cytometry, intravital microscopy, and depletion of lymphocyte subsets with monoclonal antibodies. Safety was assessed by body-weight follow-up and blood testing. Tissue tropism on intravenous or intraperitoneal administration was assessed by bioluminescence analysis using a reporter MVA encoding luciferase.

RESULTS

Intraperitoneal or locoregional administration, but not other routes of administration, resulted in a potent immune response characterized by increased levels of tumor-specific CD8+ T lymphocytes with the ability to produce both interferon-γ and tumor necrosis factor-α. The antitumor immune response was detectable not only in the peritoneal cavity but also systemically. As a result of intraperitoneal treatment, a single administration of MVA.scIL-12 encoding scIL-12 completely eradicated MC38 tumors implanted in the peritoneal cavity and also protected cured mice from subsequent subcutaneous rechallenges. Bioluminescence imaging using an MVA encoding luciferase revealed that intraperitoneal administration targets transgene to the omentum. The omentum is considered a key tissue in immune protection of the peritoneal cavity. The safety profile of intraperitoneal administration was also better than that following intravenous administration since no weight loss or hematological toxicity was observed when the vector was locally delivered into the peritoneal cavity.

CONCLUSION

Intraperitoneal administration of MVA vectors encoding scIL-12 targets the omentum, which is the tissue where peritoneal carcinomatosis usually begins. MVA.scIL-12 induces a potent tumor-specific immune response that often leads to the eradication of experimental tumors disseminated to the peritoneal cavity.

Anti-CD79b/CD3 bispecific antibody combined with CAR19-T cells for B-cell lymphoma treatment

CD19 CAR-T (chimeric antigen receptor-T) cell immunotherapy achieves a remission rate of approximately 70% in recurrent and refractory lymphoma treatment. However, the loss or reduction of CD19 antigen on the surface of lymphoma cells results in the escape of tumor cells from the immune killing of CD19 CAR-T cells (CAR19-T). Therefore, novel therapeutic strategies are urgently required. In this study, an anti-CD79b/CD3 bispecific antibody (BV28-OKT3) was constructed and combined with CAR19-T cells for B-cell lymphoma treatment. When the CD19 antigen was lost or reduced, BV28-OKT3 redirected CAR19-T cells to CD79b+ CD19- lymphoma cells; therefore, BV28-OKT3 overcomes the escape of CD79b+ CD19- lymphoma cells by the killing action of CAR19-T cells in vitro and in vivo. Furthermore, BV28-OKT3 triggered the antitumor function of CAR- T cells in the infusion product and boosted the antitumor immune response of bystander T cells, markedly improving the cytotoxicity of CAR19-T cells to lymphoma cells in vitro and in vivo. In addition, BV28-OKT3 elicited the cytotoxicity of donor-derived T cells toward lymphoma cells in vitro, which depended on the presence of tumor cells. Therefore, our findings provide a new clinical treatment strategy for recurrent and refractory B-cell lymphoma by combining CD79b/CD3 BsAb with CAR19-T cells.

Application of toll-like receptors (TLRs) and their agonists in cancer vaccines and immunotherapy

Toll-like receptors (TLRs) are pattern recognition receptors (PRRs) expressed in various immune cell types and perform multiple purposes and duties involved in the induction of innate and adaptive immunity. Their capability to propagate immunity makes them attractive targets for the expansion of numerous immunotherapeutic approaches targeting cancer. These immunotherapeutic strategies include using TLR ligands/agonists as monotherapy or combined therapeutic strategies. Several TLR agonists have demonstrated significant efficacy in advanced clinical trials. In recent years, multiple reports established the applicability of TLR agonists as adjuvants to chemotherapeutic drugs, radiation, and immunotherapies, including cancer vaccines. Cancer vaccines are a relatively novel approach in the field of cancer immunotherapy and are currently under extensive evaluation for treating different cancers. In the present review, we tried to deliver an inclusive discussion of the significant TLR agonists and discussed their application and challenges to their incorporation into cancer immunotherapy approaches, particularly highlighting the usage of TLR agonists as functional adjuvants to cancer vaccines. Finally, we present the translational potential of rWTC-MBTA vaccination [irradiated whole tumor cells (rWTC) pulsed with phagocytic agonists Mannan-BAM, TLR ligands, and anti-CD40 agonisticAntibody], an autologous cancer vaccine leveraging membrane-bound Mannan-BAM, and the immune-inducing prowess of TLR agonists as a probable immunotherapy in multiple cancer types.

Radiotherapy remodels the tumor microenvironment for enhancing immunotherapeutic sensitivity

Cancer immunotherapy has transformed traditional treatments, with immune checkpoint blockade being particularly prominent. However, immunotherapy has minimal benefit for patients in most types of cancer and is largely ineffective in some cancers (such as pancreatic cancer and glioma). A synergistic anti-tumor response may be produced through the combined application with traditional tumor treatment methods. Radiotherapy (RT) not only kills tumor cells but also triggers the pro-inflammatory molecules' release and immune cell infiltration, which remodel the tumor microenvironment (TME). Therefore, the combination of RT and immunotherapy is expected to achieve improved efficacy. In this review, we summarize the effects of RT on cellular components of the TME, including T cell receptor repertoires, different T cell subsets, metabolism, tumor-associated macrophages and other myeloid cells (dendritic cells, myeloid-derived suppressor cells, neutrophils and eosinophils). Meanwhile, non-cellular components such as lactate and extracellular vesicles are also elaborated. In addition, we discuss the impact of different RT modalities on tumor immunity and issues related to the clinical practice of combination therapy.

Targeting innate immune pathways for cancer immunotherapy

The innate immune system is critical for inducing durable and protective T cell responses to infection and has been increasingly recognized as a target for cancer immunotherapy. In this review, we present a framework wherein distinct innate immune signaling pathways activate five key dendritic cell activities that are important for T cell-mediated immunity. We discuss molecular pathways that can agonize these activities and highlight that no single pathway can agonize all activities needed for durable immunity. The immunological distinctions between innate immunotherapy administration to the tumor microenvironment versus administration via vaccination are examined, with particular focus on the strategies that enhance dendritic cell migration, interferon expression, and interleukin-1 family cytokine production. In this context, we argue for the importance of appreciating necessity vs. sufficiency when considering the impact of innate immune signaling in inflammation and protective immunity and offer a conceptual guideline for the development of efficacious cancer immunotherapies.

Enhanced systemic tumor suppression by in situ vaccine combining radiation and OX40 agonist with CpG therapy

BACKGROUND

In situ tumor vaccine has been gradually becoming a hot research field for its advantage of achieving personalized tumor therapy without prior antigen identification. Various in situ tumor vaccine regimens have been reported to exert considerable antitumor efficacy in preclinical and clinical studies. However, the design of in situ tumor vaccines still needs further optimization and the underlying immune mechanism also waits for deeper investigation.

METHODS

A novel triple in situ vaccine strategy that combining local radiation with intratumoral injection of TLR9 agonist CpG and OX40 agonist was established in this sturdy. Local and abscopal antitumor efficacy as well as survival benefit were evaluated in the bilateral tumors and pulmonary metastasis model of B16F10 melanoma. In situ vaccine-induced immune responses and immune-associated variation in tumor environment were further investigated using multiparameter flow cytometry and RNA sequencing. Base on the analysis, the RT + CpG + αOX40 triple in situ vaccine was combined with checkpoint blockade therapy to explore the potential synergistic antitumor efficacy.

RESULTS

Enhanced tumor suppression was observed with minimal toxicity in both treated and untreated abscopal tumors after receiving RT + CpG + αOX40 triple vaccine. The introduction of local radiation and OX40 agonist benefit more to the inhibition of local and abscopal lesions respectively, which might be partially attributed to the increase of effector memory T cells in the tumor microenvironment. Further analysis implied that the triple in situ vaccine did not only activate the microenvironment of treated tumors, with the upregulation of multiple immune-associated pathways, but also enhanced systemic antitumor responses, thus achieved superior systemic tumor control and survival benefit. Moreover, the triple in situ vaccine synergized with checkpoint blockade therapy, and significantly improved the therapeutic effect of anti-programmed cell death protein (PD)-1 antibody.

CONCLUSION

This triple combining in situ vaccine induced intensive antitumor responses, mediated effective systemic tumor control and survival benefit, and displayed impressive synergistic antitumor effect with checkpoint blockade therapy. These data preliminary confirmed the efficacy, feasibility and safety of the triple combining in situ vaccine, suggesting its great application potential as both monotherapy and a part of combined immunotherapeutic regimens in clinical scenario.

Dendritic Cell Vaccines: A Shift from Conventional Approach to New Generations

In the emerging era of cancer immunotherapy, immune checkpoint blockades (ICBs) and adoptive cell transfer therapies (ACTs) have gained significant attention. However, their therapeutic efficacies are limited due to the presence of cold type tumors, immunosuppressive tumor microenvironment, and immune-related side effects. On the other hand, dendritic cell (DC)-based vaccines have been suggested as a new cancer immunotherapy regimen that can address the limitations encountered by ICBs and ACTs. Despite the success of the first generation of DC-based vaccines, represented by the first FDA-approved DC-based therapeutic cancer vaccine Provenge, several challenges remain unsolved. Therefore, new DC vaccine strategies have been actively investigated. This review addresses the limitations of the currently most adopted classical DC vaccine and evaluates new generations of DC vaccines in detail, including biomaterial-based, immunogenic cell death-inducing, mRNA-pulsed, DC small extracellular vesicle (sEV)-based, and tumor sEV-based DC vaccines. These innovative DC vaccines are envisioned to provide a significant breakthrough in cancer immunotherapy landscape and are expected to be supported by further preclinical and clinical studies.

Tumor-associated macrophage-related strategies for glioma immunotherapy

High-grade glioma is one of the deadliest primary tumors of the central nervous system. Despite the many novel immunotherapies currently in development, it has been difficult to achieve breakthrough results in clinical studies. The reason may be due to the suppressive tumor microenvironment of gliomas that limits the function of specific immune cells (e.g., T cells) which are currently the primary targets of immunotherapy. However, tumor-associated macrophage, which are enriched in tumors, plays an important role in the development of GBM and is becoming a research hotspot for immunotherapy. This review focuses on current research advances in the use of macrophages as therapeutic targets or therapeutic tools for gliomas, and provides some potential research directions.

Challenges and opportunities in the development of combination immunotherapy with OX40 agonists

INTRODUCTION

Costimulatory members of the tumor necrosis factor receptor family, such as OX40 (CD134), provide essential survival and differentiation signals that enhance T cell function. Specifically, OX40 (CD134) agonists stimulate potent anti-tumor immunity in a variety of preclinical models but their therapeutic impact in patients with advanced malignancies has been limited thus far.

AREAS COVERED

In this review, we discuss the current state of combination immunotherapy with OX40 agonists including preclinical studies and recent clinical trials. We also discuss the strengths and limitations of these approaches and provide insight into alternatives that may help enhance the efficacy of combination OX40 agonist immunotherapy.

EXPERT OPINION

OX40 agonist immunotherapy has not yet demonstrated significant clinical activity as a monotherapy or in combination with immune checkpoint blockade (ICB), likely due to several factors including the timing of administration, drug potency, and selection of agents for combination therapy clinical trials. We believe that careful consideration of the biological mechanisms regulating OX40 expression and function may help inform new approaches, particularly in combination with novel agents, capable of increasing the therapeutic efficacy of this approach.

Rewiring innate and adaptive immunity with TLR9 agonist to treat osteosarcoma

BACKGROUND

Osteosarcoma (OS) is the most common primary bone tumor in children and adolescent. Surgery and multidrug chemotherapy are the standard of treatment achieving 60-70% of event-free survival for localized disease at diagnosis. However, for metastatic disease, the prognosis is dismal. Exploiting immune system activation in the setting of such unfavorable mesenchymal tumors represents a new therapeutic challenge.

METHODS

In immune competent OS mouse models bearing two contralateral lesions, we tested the efficacy of intralesional administration of a TLR9 agonist against the treated and not treated contralateral lesion evaluating abscopal effect. Multiparametric flow cytometry was used to evaluate changes of the tumor immune microenviroment. Experiments in immune-deficient mice allowed the investigation of the role of adaptive T cells in TLR9 agonist effects, while T cell receptor sequencing was used to assess the expansion of specific T cell clones.

RESULTS

TLR9 agonist strongly impaired the growth of locally-treated tumors and its therapeutic effect also extended to the contralateral, untreated lesion. Multiparametric flow cytometry showed conspicuous changes in the immune landscape of the OS immune microenvironment upon TLR9 engagement, involving a reduction in M2-like macrophages, paralleled by increased infiltration of dendritic cells and activated CD8 T cells in both lesions. Remarkably, CD8 T cells were needed for the induction of the abscopal effect, whereas they were not strictly necessary for halting the growth of the treated lesion. T cell receptor (TCR) sequencing of tumor infiltrating CD8 T cells showed the expansion of specific TCR clones in the treated tumors and, remarkably, their selected representation in the contralateral untreated lesions, providing the first evidence of the rewiring of tumor-associated T cell clonal architectures.

CONCLUSIONS

Overall these data indicate that the TLR9 agonist acts as an in situ anti-tumor vaccine, activating an innate immune response sufficient to suppress local tumor growth while inducing a systemic adaptive immunity with selective expansion of CD8 T cell clones, which are needed for the abscopal effect.

Mechanistic rationales for combining immunotherapy with radiotherapy

Immunotherapy consisted mainly of immune checkpoint inhibitors (ICIs) has led to significantly improved antitumor response. However, such response has been observed only in tumors possessing an overall responsive tumor immune micro-environment (TIME), in which the presence of functional tumor-infiltrating lymphocytes (TILs) is critical. Various mechanisms of immune escape from immunosurveillance exist, leading to different TIME phenotypes in correlation with primary or acquired resistance to ICIs. Radiotherapy has been shown to induce antitumor immunity not only in the irradiated primary tumor, but also at unirradiated distant sites of metastases. Such antitumor immunity is mainly elicited by radiation's stimulatory effects on antigenicity and adjuvanticity. Furthermore, it may be significantly augmented when irradiation is combined with immunotherapy, such as ICIs. Therefore, radiotherapy represents one potential therapeutic strategy to restore anti-tumor immunity in tumors presenting with an unresponsive TIME. In this review, the generation of anti-tumor immunity, its impairment, radiation's immunogenic properties, and the antitumor effects of combining radiation with immunotherapy will be comprehensively discussed.

Exploring low-dose radiotherapy to overcome radio-immunotherapy resistance

Immune checkpoint inhibitors (ICIs) have revolutionized the current treatment landscape for cancer, yet the response rates of ICIs remain unmet. Synergistic with immunotherapy, low-dose radiotherapy (LDRT) has been demonstrated to activate anti-tumor immunity - a transition from traditional radiation therapy geared toward local radical treatment to a type of immunological adjuvant. As such, studies utilizing LDRT to enhance the efficacy of immunotherapy have been increasing preclinically and clinically. This paper reviews the recent strategies of using LDRT to overcome the resistance of ICIs, as well as providing potential opportunities in cancer treatment. Despite the potential of LDRT in immunotherapy is recognized, the mechanisms behind this form of treatment remain largely elusive. Thus, we reviewed history, mechanisms and challenges associated with this form of treatment, as well as different modes of its application, to provide relatively accurate practice standards for LDRT as a sensitizing treatment when combined with immunotherapy or radio-immunotherapy.

Radiation-induced tumor immune microenvironments and potential targets for combination therapy

As one of the four major means of cancer treatment including surgery, radiotherapy (RT), chemotherapy, immunotherapy, RT can be applied to various cancers as both a radical cancer treatment and an adjuvant treatment before or after surgery. Although RT is an important modality for cancer treatment, the consequential changes caused by RT in the tumor microenvironment (TME) have not yet been fully elucidated. RT-induced damage to cancer cells leads to different outcomes, such as survival, senescence, or death. During RT, alterations in signaling pathways result in changes in the local immune microenvironment. However, some immune cells are immunosuppressive or transform into immunosuppressive phenotypes under specific conditions, leading to the development of radioresistance. Patients who are radioresistant respond poorly to RT and may experience cancer progression. Given that the emergence of radioresistance is inevitable, new radiosensitization treatments are urgently needed. In this review, we discuss the changes in irradiated cancer cells and immune cells in the TME under different RT regimens and describe existing and potential molecules that could be targeted to improve the therapeutic effects of RT. Overall, this review highlights the possibilities of synergistic therapy by building on existing research.

Opportunities and challenges of low-dose radiation to enable immunotherapy efficacy

Therapeutic monoclonal antibodies blocking different immune checkpoints, have demonstrated efficacy against a wide variety of solid tumors. The exclusion or absence of lymphocytes within the tumor microenvironment (TME) is one of the main resistance mechanisms to immune checkpoint inhibitor (ICI)-based therapies. Therefore, there is a growing interest in identifying novel approaches to promote T cell infiltration on immune-deserted (cold) and immune-excluded tumors to turn them into inflamed (hot) tumors. Here, we provide a comprehensive overview of the recently published studies showing the potential of low-dose radiation (LDRT) to reprogram the TME to allow and promote T-cell infiltration and thus, improve currently approved ICI-based therapies.

Osmani R, Hani U, Yoonus Thajudeen K, Kiran Raj G, Gowda DV. Recent advances in the liposomal nanovesicles based immunotherapy in the treatment of cancer: A review

Immunotherapy, along with chemotherapy, targeted delivery, radiation and surgery has become one of the most common cancer treatments. The aim of cancer immunology is to use the bodys immune system to combat tumors and develop a robust antitumor immune response. In the last few years, immune checkpoint inhibitors and chimeric antigen receptor-modified T cells have made substantial advancements in cancer immunotherapy. By boosting cell type-specific delivery and immunological responses, nanocarriers like liposomes have the ability to enhance greater immune responses. The efficacy of anti-tumor therapeutics is being significantly improved as liposomes can assist in resolving a number of issues that can arise from a variety of cancer immunotherapies. Since, liposomes can be loaded with both hydrophilic and hydrophobic drugs and protect the immunotherapeutic agents loaded inside the core, they offer significant advantages over other nano delivery systems. The use of liposomes for accurate and timely delivery of immunotherapies to particular targeted neoplasms, with little or no injury to healthy cells, maximizes immunotherapy efficacy. Liposomes are also suitable vehicles for delivering medications simultaneously with other therapies such as chemotherapy, radiation, and phototherapy. Liposomal nanoparticles will be introduced and used as an objective immunotherapy delivery system for great precision, making them a viable cancer treatment approach.With an emphasis on dendritic cells, T cells, tumor and natural killer cells, and macrophages; outline of many forms of immune-therapies in oncology and cutting-edge advances in liposomal nanovesicles for cancer immunotherapy are covered in this review.

Small-molecule PTPN2 Inhibitors Sensitize Resistant Melanoma to Anti-PD-1 Immunotherapy

Although immune checkpoint inhibitors targeting T-cell immunoregulatory proteins have revolutionized cancer treatment, they are effective only in a limited number of patients, and new strategies are needed to enhance tumor responses to immunotherapies. Deletion of protein tyrosine phosphatase non-receptor type 2 (Ptpn2), a regulator of growth factor and cytokine signaling pathways, has been shown to sensitize murine B16F10 melanoma cells to IFNγ and anti-PD-1 immunotherapy. Here, we investigated the potential therapeutic utility of small-molecule PTPN2 inhibitors. Ten inhibitors were synthesized on the basis of in silico modeling and structure-based design and functionally tested in vitro and in vivo. We show that the inhibitors had little effect on B16F10 cells alone, but effectively sensitized the tumor cells to IFNγ treatment in vitro and to anti-PD-1 therapy in vivo. Under both conditions, Ptpn2 inhibitor cotreatment suppressed B16F10 cell growth and enhanced Stat1 phosphorylation and expression of IFNγ response genes. In vivo, PTPN2 inhibitor cotreatment significantly reduced melanoma and colorectal tumor growth and enhanced mouse survival compared with anti-PD-1 treatment alone, and this was accompanied by increased tumor infiltration by granzyme B+ CD8+ T cells. Similar results were obtained with representative murine and human colon cancer and lung cancer cell lines. Collectively, these results demonstrate that small-molecule inhibitors of PTPN2 may have clinical utility as sensitizing agents for immunotherapy-resistant cancers.

Significance

To enhance the effectiveness of immunotherapies in resistant or nonresponsive cancers, it is important to develop inhibitors of enzymes that negatively influence the outcome of treatments. We have designed and evaluated small-molecule inhibitors of PTPN2 demonstrating that these compounds may have clinical utility as sensitizing agents for immunotherapy-resistant cancers.

Intratumoral BO-112 in combination with radiotherapy synergizes to achieve CD8 T-cell-mediated local tumor control

BACKGROUND

Radioimmunotherapy combines irradiation of tumor lesions with immunotherapy to achieve local and abscopal control of cancer. Most immunotherapy agents are given systemically, but strategies for delivering immunotherapy locally are under clinical scrutiny to maximize efficacy and avoid toxicity. Local immunotherapy, by injecting various pathogen-associated molecular patterns, has shown efficacy both preclinically and clinically. BO-112 is a viral mimetic based on nanoplexed double-stranded RNA (poly I:C) which exerts immune-mediated antitumor effects in mice and humans on intratumoral delivery. BO-112 and focal irradiation were used to make the proof-of-concept for local immunotherapy plus radiation therapy combinations.

METHODS

Murine transplantable tumor cell lines (TS/A, MC38 and B16-OVA) were used to show increased immunogenic features under irradiation, as well as in bilateral tumor models in which only one of the lesions was irradiated or/and injected with BO-112. Flow cytometry and multiplex tissue immunofluorescence were used to determine the effects on antitumor immunity. Depletions of immune cell populations and knockout mice for the IFNAR and BATF-3 genes were used to delineate the immune system requirements for efficacy.

RESULTS

In cultures of TS/A breast cancer cells, the combination of irradiation and BO-112 showed more prominent features of immunogenic tumor cell death in terms of calreticulin exposure. Injection of BO-112 into the tumor lesion receiving radiation achieved excellent control of the treated tumor and modest delays in contralateral tumor progression. Local effects were associated with more prominent infiltrates of antitumor cytotoxic tumor lymphocytes (CTLs). Importantly, local irradiation plus BO-112 in one of the tumor lesions that enhanced the therapeutic effects of radiotherapy on distant irradiated lesions that were not injected with BO-112. Hence, this beneficial effect of local irradiation plus BO-112 on a tumor lesion enhanced the therapeutic response to radiotherapy on distant non-injected lesions.

CONCLUSION

This study demonstrates that local BO-112 immunotherapy and focal irradiation may act in synergy to achieve local tumor control. Irradiation plus BO-112 in one of the tumor lesions enhanced the therapeutic effects on distant irradiated lesions that were not injected with BO-112, suggesting strategies to treat oligometastatic patients with lesions susceptible to radiotherapy and with at least one tumor accessible for repeated BO-112 intratumoral injections.

Trial watch: Toll-like receptor ligands in cancer therapy

Accumulating evidence indicates that Toll-like receptor (TLR) agonists proficiently (re)instore cancer immunosurveillance as immunological adjuvants. So far, three TLR agonists have been approved by regulatory agencies for use in oncological applications. Additionally, these immunotherapeutics have been extensively investigated over the past few years. Multiple clinical trials are currently evaluating the combination of TLR agonists with chemotherapy, radiotherapy, or different immunotherapies. Moreover, antibodies targeting tumor-enriched surface proteins that have been conjugated to TLR agonists are being developed to stimulate anticancer immune responses specifically within the tumor microenvironment. Solid preclinical and translational results support the favorable immune-activating effects of TLR agonists. Here, we summarize recent preclinical and clinical advances in the development of TLR agonists for anticancer immunotherapy.

Tilsotolimod Exploits the TLR9 Pathway to Promote Antigen Presentation and Type 1 IFN Signaling in Solid Tumors: A Multicenter International Phase I/II Trial (ILLUMINATE-101)

PURPOSE

Tilsotolimod is an investigational synthetic Toll-like receptor 9 (TLR9) agonist that has demonstrated antitumor activity in preclinical models. The ILLUMINATE-101 phase I study explored the safety, dose, efficacy, and immune effects of intratumoral (it) tilsotolimod monotherapy in multiple solid tumors.

PATIENTS AND METHODS

Patients with a diagnosis of refractory cancer not amenable to curative therapies received tilsotolimod in doses escalating from 8 to 32 mg into a single lesion at weeks 1, 2, 3, 5, 8, and 11. Additional patients with advanced malignant melanoma were enrolled into an expansion cohort at the 8 mg dose. Objectives included characterizing the safety, establishing the dose, efficacy, and immunologic assessment. Blood samples and tumor biopsies of injected and noninjected lesions were obtained at baseline and 24 hours after treatment for immune analyses.

RESULTS

Thirty-eight and 16 patients were enrolled into the dose escalation and melanoma expansion cohorts, respectively. Deep visceral injections were conducted in 91% of patients. No dose-limiting toxicities (DLT) or grade 4 treatment-related adverse events were observed. Biopsies 24 hours after treatment demonstrated an increased IFN pathway signature and dendritic cell maturation. Immunologic profiling revealed upregulation of IFN-signaling genes and modulation of genes for checkpoint proteins. In the dose escalation cohort, 12 (34%) of 35 evaluable patients achieved a best overall response rate (ORR) of stable disease (SD), whereas 3 (19%) of 16 evaluable patients in the melanoma cohort achieved stable disease.

CONCLUSIONS

Overall, tilsotolimod monotherapy was generally well tolerated and induced rapid, robust alterations in the tumor microenvironment. See related commentary by Punekar and Weber, p. 5007.

Tripartite antigen-agnostic combination immunotherapy cures established poorly immunogenic tumors

BACKGROUND

Single-agent immunotherapy has shown remarkable efficacy in selected cancer entities and individual patients. However, most patients fail to respond. This is likely due to diverse immunosuppressive mechanisms acting in a concerted way to suppress the host anti-tumor immune response. Combination immunotherapy approaches that are effective in such poorly immunogenic tumors mostly rely on precise knowledge of antigenic determinants on tumor cells. Creating an antigen-agnostic combination immunotherapy that is effective in poorly immunogenic tumors for which an antigenic determinant is not known is a major challenge.

METHODS

We use multiple cell line and poorly immunogenic syngeneic, autochthonous, and autologous mouse models to evaluate the efficacy of a novel combination immunotherapy named tripartite immunotherapy (TRI-IT). To elucidate TRI-ITs mechanism of action we use immune cell depletions and comprehensive tumor and immune infiltrate characterization by flow cytometry, RNA sequencing and diverse functional assays.

RESULTS

We show that combined adoptive cellular therapy (ACT) with lymphokine-activated killer cells, cytokine-induced killer cells, Vγ9Vδ2-T-cells (γδ-T-cells) and T-cells enriched for tumor recognition (CTLs) display synergistic antitumor effects, which are further enhanced by cotreatment with anti-PD1 antibodies. Most strikingly, the full TRI-IT protocol, a combination of this ACT with anti-PD1 antibodies, local immunotherapy of agonists against toll-like receptor 3, 7 and 9 and pre-ACT lymphodepletion, eradicates and induces durable anti-tumor immunity in a variety of poorly immunogenic syngeneic, autochthonous, as well as autologous humanized patient-derived models. Mechanistically, we show that TRI-IT coactivates adaptive cellular and humoral, as well as innate antitumor immune responses to mediate its antitumor effect without inducing off-target toxicity.

CONCLUSIONS

Overall, TRI-IT is a novel, highly effective, antigen-agnostic, non-toxic combination immunotherapy. In this study, comprehensive insights into its preclinical efficacy, even in poorly immunogenic tumors, and mode of action are given, so that translation into clinical trials is the next step.

Macrophages as tools and targets in cancer therapy

Tumour-associated macrophages are an essential component of the tumour microenvironment and have a role in the orchestration of angiogenesis, extracellular matrix remodelling, cancer cell proliferation, metastasis and immunosuppression, as well as in resistance to chemotherapeutic agents and checkpoint blockade immunotherapy. Conversely, when appropriately activated, macrophages can mediate phagocytosis of cancer cells and cytotoxic tumour killing, and engage in effective bidirectional interactions with components of the innate and adaptive immune system. Therefore, they have emerged as therapeutic targets in cancer therapy. Macrophage-targeting strategies include inhibitors of cytokines and chemokines involved in the recruitment and polarization of tumour-promoting myeloid cells as well as activators of their antitumorigenic and immunostimulating functions. Early clinical trials suggest that targeting negative regulators (checkpoints) of myeloid cell function indeed has antitumor potential. Finally, given the continuous recruitment of myelomonocytic cells into tumour tissues, macrophages are candidates for cell therapy with the development of chimeric antigen receptor effector cells. Macrophage-centred therapeutic strategies have the potential to complement, and synergize with, currently available tools in the oncology armamentarium.

Macrophages can promote tumorigenesis and enhance the antitumour response. This Review discusses the molecular mechanisms underlying the reprogramming of macrophages in the tumour microenvironment and provides an overview of macrophage-targeted therapies for the treatment of cancer.

Cancer vaccines: the next immunotherapy frontier

After several decades, therapeutic cancer vaccines now show signs of efficacy and potential to help patients resistant to other standard-of-care immunotherapies, but they have yet to realize their full potential and expand the oncologic armamentarium. Here, we classify cancer vaccines by what is known of the included antigens, which tumors express those antigens and where the antigens colocalize with antigen-presenting cells, thus delineating predefined vaccines (shared or personalized) and anonymous vaccines (ex vivo or in situ). To expedite clinical development, we highlight the need for accurate immune monitoring of early trials to acknowledge failures and advance the most promising vaccines.

Radiotherapy combined with immunotherapy: the dawn of cancer treatment

Radiotherapy (RT) is delivered for purposes of local control, but can also exert systemic effect on remote and non-irradiated tumor deposits, which is called abscopal effect. The view of RT as a simple local treatment has dramatically changed in recent years, and it is now widely accepted that RT can provoke a systemic immune response which gives a strong rationale for the combination of RT and immunotherapy (iRT). Nevertheless, several points remain to be addressed such as the interaction of RT and immune system, the identification of the best schedules for combination with immunotherapy (IO), the expansion of abscopal effect and the mechanism to amplify iRT. To answer these crucial questions, we roundly summarize underlying rationale showing the whole immune landscape in RT and clinical trials to attempt to identify the best schedules of iRT. In consideration of the rarity of abscopal effect, we propose that the occurrence of abscopal effect induced by radiation can be promoted to 100% in view of molecular and genetic level. Furthermore, the “radscopal effect” which refers to using low-dose radiation to reprogram the tumor microenvironment may amplify the occurrence of abscopal effect and overcome the resistance of iRT. Taken together, RT could be regarded as a trigger of systemic antitumor immune response, and with the help of IO can be used as a radical and systemic treatment and be added into current standard regimen of patients with metastatic cancer.

Innate and Adaptive Responses of Intratumoral Immunotherapy with Endosomal Toll-Like Receptor Agonists

Toll-like receptors (TLRs) are natural initial triggers of innate and adaptive immune responses. With the advent of cancer immunotherapy, nucleic acids engineered as ligands of endosomal TLRs have been investigated for the treatment of solid tumors. Despite promising results, their systemic administration, similarly to other immunotherapies, raises safety issues. To overcome these problems, recent studies have applied the direct injection of endosomal TLR agonists in the tumor and/or draining lymph nodes, achieving high local drug exposure and strong antitumor response. Importantly, intratumoral delivery of TLR agonists showed powerful effects not only against the injected tumors but also often against uninjected lesions (abscopal effects), resulting in some cases in cure and antitumoral immunological memory. Herein, we describe the structure and function of TLRs and their role in the tumor microenvironment. Then, we provide our vision on the potential of intratumor versus systemic delivery or vaccination approaches using TLR agonists, also considering the use of nanoparticles to improve their targeting properties. Finally, we collect the preclinical and clinical studies applying intratumoral injection of TLR agonists as monotherapies or in combination with: (a) other TLR or STING agonists; (b) other immunotherapies; (c) radiotherapy or chemotherapy; (d) targeted therapies.

Development of Immunotherapy Strategies Targeting Tumor Microenvironment Is Fiercely Ongoing

Tumor immune microenvironment is a very complex system that is influenced by a wide range of factors; in this microenvironment, various immune cells, stromal cells, and cytokines can interact with tumor cells and jointly regulate this complex ecosystem. During tumor development, the tumor microenvironment (TME) shows the upregulation of inhibitory signals and downregulation of activating signals, which result in an immunosuppressive microenvironment and lead to tumor immune escape. In recent years, a variety of precision immunotherapy strategies have been developed to remodel the TME into a positive immune microenvironment by stimulating or restoring the inherent tumor inhibition ability of the immune system so as to improve anti-tumor therapeutic efficacy. This review focuses on immunotherapy strategies targeting the TME, including those that target the microenvironment to inhibit signaling, activate signaling, and specifically involve many new targets such as physical barriers, immune cells and their surface molecular receptors, cytokines, and metabolic factors. Furthermore, it summarizes the challenges faced while conducting research on the tumor immune microenvironment and the corresponding solutions.

Intratumoural administration of an NKT cell agonist with CpG promotes NKT cell infiltration associated with an enhanced antitumour response and abscopal effect

Intratumoural administration of unmethylated cytosine-phosphate-guanine motifs (CpG) to stimulate toll-like receptor (TLR)-9 has been shown to induce tumour regression in preclinical studies and some efficacy in the clinic. Because activated natural killer T (NKT) cells can cooperate with pattern-recognition via TLRs to improve adaptive immune responses, we assessed the impact of combining a repeated dosing regimen of intratumoural CpG with a single intratumoural dose of the NKT cell agonist α-galactosylceramide (α-GalCer). The combination was superior to CpG alone at inducing regression of established tumours in several murine tumour models, primarily mediated by CD8⁺ T cells. An antitumour effect on distant untreated tumours (abscopal effect) was reliant on sustained activity of NKT cells and was associated with infiltration of KLRG1⁺ NKT cells in tumours and draining lymph nodes at both injected and untreated distant sites. Cytometric analysis pointed to increased exposure to type I interferon (IFN) affecting many immune cell types in the tumour and lymphoid organs. Accordingly, antitumour activity was lost in animals in which dendritic cells (DCs) were incapable of signaling through the type I IFN receptor. Studies in conditional ablation models showed that conventional type 1 DCs and plasmacytoid DCs were required for the response. In tumour models where the combined treatment was less effective, the addition of tumour-antigen derived peptide, preferably conjugated to α-GalCer, significantly enhanced the antitumour response. The combination of TLR ligation, NKT cell agonism, and peptide delivery could therefore be adapted to induce responses to both known and unknown antigens.