PD-1 and LAG-3 blockade improve anti-tumor vaccine efficacy

PD-1: A critical player and target for immune normalization

Immune system imbalances contribute to the pathogenesis of several different diseases, and immunotherapy shows great therapeutic efficacy against tumours and infectious diseases with immune-mediated derivations. In recent years, molecules targeting the programmed cell death protein 1 (PD-1) immune checkpoint have attracted much attention, and related signalling pathways have been studied clearly. At present, several inhibitors and antibodies targeting PD-1 have been utilized as anti-tumour therapies. However, increasing evidence indicates that PD-1 blockade also has different degrees of adverse side effects, and these new explorations into the therapeutic safety of PD-1 inhibitors contribute to the emerging concept that immune normalization, rather than immune enhancement, is the ultimate goal of disease treatment. In this review, we summarize recent advancements in PD-1 research with regard to immune normalization and targeted therapy.

A novel LAG3 neutralizing antibody improves cancer immunotherapy by dual inhibition of MHC-II and FGL1 ligand binding

LAG3 is an inhibitory immune checkpoint expressed on activated T and NK cells. Blocking the interaction of LAG3 with its ligands MHC-II and FGL1 renders T cells improved cytotoxicity to cancer cells. Current study generated a panel of LAG3 monoclonal antibodies (mAbs) through immunization of mice followed by phage display. Some of them bound to the D1-D2 domain of LAG3, which is known for the engagement of its ligands FGL1 and MHC-II. Three outperformers, M208, M226, and M234, showed stronger blocking activity than Relatlimab in the FGL1 binding. Furthermore, M234 showed dual inhibition of FGL1 (IC50 of 20.6 nM) and MHC-II binding (IC50 of 6.2 nM) to LAG3. In vitro functional tests showed that M234 significantly stimulated IFN-γ secretion from activated PBMC cells. In vivo studies in a mouse model of hepatocellular carcinoma xenografts demonstrated that combining M234 IgG with GPC3-targeted bispecific antibodies significantly improved efficacy. In addition, GPC3-targeted CAR-T cells secreting IL-21-M234 scFv fusion protein exhibited enhanced activity in inhibiting tumor growth and greatly increased the survival rate of mice. Taken together, M234 has potential in cancer immunotherapy and warrants further clinical trial.

Combining toll-like receptor agonists with immune checkpoint blockade affects antitumor vaccine efficacy

BACKGROUND

T cell checkpoint receptors are expressed when T cells are activated, and modulation of the expression or signaling of these receptors can alter the function of T cells and their antitumor efficacy. We previously found that T cells activated with cognate antigen had increases in the expression of PD-1, and this was attenuated in the presence of multiple toll-like receptor (TLR) agonists, notably TLR3 plus TLR9. In the current report, we sought to investigate whether combining TLR agonists with immune checkpoint blockade can further augment vaccine-mediated T cell antitumor immunity in murine tumor models.

METHODS

TLR agonists (TLR3 plus TLR9) and immune checkpoint inhibitors (antibodies targeting PD-1, CTLA-4, LAG-3, TIM-3 or VISTA) were combined and delivered with vaccines or vaccine-activated CD8+T cells to E.G7-OVA or MyC-CaP tumor-bearing mice. Tumors were assessed for growth and then collected and analyzed by flow cytometry.

RESULTS

Immunization of E.G7-OVA tumor-bearing mice with SIINFEKL peptide vaccine, coadministered with TLR agonists and αCTLA-4, demonstrated greater antitumor efficacy than immunization with TLR agonists or αCTLA-4 alone. Conversely, the antitumor efficacy was abrogated when vaccine and TLR agonists were combined with αPD-1. TLR agonists suppressed PD-1 expression on regulatory T cells (Tregs) and activated this population. Depletion of Tregs in tumor-bearing mice led to greater antitumor efficacy of this combination therapy, even in the presence of αPD-1. Combining vaccination with TLR agonists and αCTLA-4 or αLAG-3 showed greater antitumor than with combinations with αTIM-3 or αVISTA.

CONCLUSION

The combination of TLR agonists and αCTLA-4 or αLAG-3 can further improve the efficacy of a cancer vaccine, an effect not observed using αPD-1 due to activation of Tregs when αPD-1 was combined with TLR3 and TLR9 agonists. These data suggest that optimal combinations of TLR agonists and immune checkpoint blockade may improve the efficacy of human anticancer vaccines.

Treatment advances in high-grade gliomas

High-grade gliomas (HGG) pose significant challenges in modern tumour therapy due to the distinct biological properties and limitations of the blood-brain barrier. This review discusses recent advancements in HGG treatment, particularly in the context of immunotherapy and cellular therapy. Initially, treatment strategies focus on targeting tumour cells guided by the molecular characteristics of various gliomas, encompassing chemotherapy, radiotherapy and targeted therapy for enhanced precision. Additionally, technological enhancements are augmenting traditional treatment modalities. Furthermore, immunotherapy, emphasising comprehensive tumour management, has gained widespread attention. Immune checkpoint inhibitors, vaccines and CAR-T cells exhibit promising efficacy against recurrent HGG. Moreover, emerging therapies such as tumour treating fields (TTFields) offer additional treatment avenues for patients with HGG. The combination of diverse treatments holds promise for improving the prognosis of HGG, particularly in cases of recurrence.

Recent applications of RNA therapeutic in clinics

Ribonucleic acid (RNA) therapy has been extensively researched for several decades and has garnered significant attention in recent years owing to its potential in treating a broad spectrum of diseases. It falls under the domain of gene therapy, leveraging RNA molecules as a therapeutic approach in medicine. RNA can be targeted using small-molecule drugs, or RNA molecules themselves can serve as drugs by interacting with proteins or other RNA molecules. While several RNA drugs have been granted clinical approval, numerous RNA-based therapeutics are presently undergoing clinical investigation or testing for various conditions, including genetic disorders, viral infections, and diverse forms of cancer. These therapies offer several advantages, such as high specificity, enabling precise targeting of disease-related genes or proteins, cost-effectiveness, and a relatively straightforward manufacturing process. Nevertheless, successful translation of RNA therapies into widespread clinical use necessitates addressing challenges related to delivery, stability, and potential off-target effects. This chapter provides a comprehensive overview of the general concepts of various classes of RNA-based therapeutics, the mechanistic basis of their function, as well as recent applications of RNA therapeutic in clinics.

A phase 2, multicenter, open-label study of anti-LAG-3 ieramilimab in combination with anti-PD-1 spartalizumab in patients with advanced solid malignancies

Ieramilimab, a humanized anti-LAG-3 monoclonal antibody, was well tolerated in combination with the anti-PD-1 antibody spartalizumab in a phase 1 study. This phase 2 study aimed to further investigate the efficacy and safety of combination treatment in patients with selected advanced (locally advanced or metastatic) solid malignancies. Eligible patients with non-small cell lung cancer (NSCLC), melanoma, renal cell carcinoma (RCC), mesothelioma, and triple-negative breast cancer (TNBC) were grouped depending on prior anti-PD-1/L1 therapy (anti-PD-1/L1 naive or anti-PD-1/L1 pretreated). Patients received ieramilimab (400 mg) followed by spartalizumab (300 mg) every 3 weeks. The primary endpoint was objective response rate (ORR), along with safety, pharmacokinetics, and biomarker assessments. Of 235 patients, 142 were naive to anti-PD-1/L1 and 93 were pretreated with anti-PD-1/L1 antibodies. Durable responses (>24 months) were seen across all indications for patients naive to anti-PD-1/L1 and in melanoma and RCC patients pretreated with anti-PD1/L1. The most frequent study drug-related AEs were pruritus (15.5%), fatigue (10.6%), and rash (10.6%) in patients naive to anti-PD-1/L1 and fatigue (18.3%), rash (14.0%), and nausea (10.8%) in anti-PD-1/L1 pretreated patients. Biomarker assessment indicated higher expression of T-cell-inflamed gene signature at baseline among responding patients. Response to treatment was durable (>24 months) in some patients across all enrolled indications, and safety findings were in accordance with previous and current studies exploring LAG-3/PD-1 blockade.

Recruiting In Vitro Transcribed mRNA against Cancer Immunotherapy: A Contemporary Appraisal of the Current Landscape

Over 100 innovative in vitro transcribed (IVT)-mRNAs are presently undergoing clinical trials, with a projected substantial impact on the pharmaceutical market in the near future. Τhe idea behind this is that after the successful cellular internalization of IVT-mRNAs, they are subsequently translated into proteins with therapeutic or prophylactic relevance. Simultaneously, cancer immunotherapy employs diverse strategies to mobilize the immune system in the battle against cancer. Therefore, in this review, the fundamental principles of IVT-mRNA to its recruitment in cancer immunotherapy, are discussed and analyzed. More specifically, this review paper focuses on the development of mRNA vaccines, the exploitation of neoantigens, as well as Chimeric Antigen Receptor (CAR) T-Cells, showcasing their clinical applications and the ongoing trials for the development of next-generation immunotherapeutics. Furthermore, this study investigates the synergistic potential of combining the CAR immunotherapy and the IVT-mRNAs by introducing our research group novel, patented delivery method that utilizes the Protein Transduction Domain (PTD) technology to transduce the IVT-mRNAs encoding the CAR of interest into the Natural Killer (NK)-92 cells, highlighting the potential for enhancing the CAR NK cell potency, efficiency, and bioenergetics. While IVT-mRNA technology brings exciting progress to cancer immunotherapy, several challenges and limitations must be acknowledged, such as safety, toxicity, and delivery issues. This comprehensive exploration of IVT-mRNA technology, in line with its applications in cancer therapeutics, offers valuable insights into the opportunities and challenges in the evolving landscape of cancer immunotherapy, setting the stage for future advancements in the field.

Anti-PD-1 immunotherapy with androgen deprivation therapy induces robust immune infiltration in metastatic castration-sensitive prostate cancer

When compared to other malignancies, the tumor microenvironment (TME) of primary and castration-resistant prostate cancer (CRPC) is relatively devoid of immune infiltrates. While androgen deprivation therapy (ADT) induces a complex immune infiltrate in localized prostate cancer, the composition of the TME in metastatic castration-sensitive prostate cancer (mCSPC), and the effects of ADT and other treatments in this context are poorly understood. Here, we perform a comprehensive single-cell RNA sequencing (scRNA-seq) profiling of metastatic sites from patients participating in a phase 2 clinical trial (NCT03951831) that evaluated standard-of-care chemo-hormonal therapy combined with anti-PD-1 immunotherapy. We perform a longitudinal, protein activity-based analysis of TME subpopulations, revealing immune subpopulations conserved across multiple metastatic sites. We also observe dynamic changes in these immune subpopulations in response to treatment and a correlation with clinical outcomes. Our study uncovers a therapy-resistant, transcriptionally distinct tumor subpopulation that expands in cell number in treatment-refractory patients.

The upregulation of immune checkpoints after photodynamic therapy reducing immune effect for treating breast cancer

The immune effect induced by photodynamic therapy (PDT) has a limited effect on breast tumor. This study hypothesized that suppressive immune checkpoints on T cells might upregulate after PDT, which may reduce the antitumor effect of PDT for treating breast tumor. This study explored the alteration of immune checkpoint for the first time. A bilateral subcutaneous transplanted breast tumor mice model was established, and right tumors imitated primary tumors, and left tumors imitated distant tumors. Primary tumors were treated with PDT mediated by hematoporphyrin derivatives (HpD-PDT). Costimulatory molecules (ICOS, OX40, and 4-1BB) and immune checkpoints (PD1, LAG-3, CTLA-4, TIM-3, TIGIT) on tumor infiltrating T cells after HpD-PDT were analyzed by flow cytometry. Antitumor and immune effects were also assessed after HpD-PDT combined with anti-PD1 and LAG-3 antibodies. Primary tumors were suppressed, but distant tumors could not be inhibited after HpD-PDT. The number of T cells was increased, but function did not enhance after HpD-PDT. Additionally, costimulatory molecules (ICOS, OX40, and 4-1BB) were not elevated, but the suppressive immune checkpoints on tumor infiltrating T cells were upregulated after HpD-PDT. Notably, PD1+ LAG-3+ CD4+ T and PD1+ LAG-3+ CD8+ T cells were significantly increased. When PD1 and LAG-3 blockade combined with HpD-PDT, both primary and distant tumors were significantly suppressed, and antitumor immune effects were significantly enhanced. HpD-PDT could upregulate the PD1+ LAG-3+ CD4+ T and PD1+ LAG-3+ CD8+ T cells. Dual blockade of PD1 and LAG-3 immune checkpoints can enhance the antitumor effect of HpD-PDT.

Vaccines as treatments for prostate cancer

Prostate cancer is a leading cause of death in men worldwide. For over 30 years, growing interest has focused on the development of vaccines as treatments for prostate cancer, with the goal of using vaccines to activate immune cells capable of targeting prostate cancer to either eradicate recurrent disease or at least delay disease progression. This interest has been prompted by the prevalence and long natural history of the disease and by the fact that the prostate is an expendable organ. Thus, an immune response elicited by vaccination might not need to target the tumour uniquely but could theoretically target any prostate tissue. To date, different vaccine approaches and targets for prostate cancer have been evaluated in clinical trials. Overall, five approaches have been assessed in randomized phase III trials and sipuleucel-T was approved as a treatment for metastatic castration-resistant prostate cancer, being the only vaccine approved to date by the FDA as a treatment for cancer. Most vaccine approaches showed safety and some evidence of immunological activity but had poor clinical activity when used as monotherapies. However, increased activity has been observed when these vaccines were used in combination with other immune-modulating therapies. This evidence suggests that, in the future, prostate cancer vaccines might be used to activate and expand tumour-specific T cells as part of combination approaches with agents that target tumour-associated immune mechanisms of resistance.

B cells require licensing by dendritic cells to serve as primary antigen-presenting cells for plasmid DNA

DNA vaccines have been an attractive approach for treating cancer patients, however have demonstrated modest immunogenicity in human clinical trials. Dendritic cells (DCs) are known to cross-present DNA-encoded antigens expressed in bystander cells. However, we have previously reported that B cells, and not DCs, serve as primary antigen-presenting cells (APCs) following passive uptake of plasmid DNA. Here we sought to understand the requirements for B cells to present DNA-encoded antigens, to ultimately increase the immunogenicity of plasmid DNA vaccines. Using ovalbumin-specific OT-1 CD8+ T cells and isolated APC populations, we demonstrated that following passive uptake of plasmid DNA, B cells but not DC, can translate the encoded antigen. However, CD8 T cells were only activated by B cells when they were co-cultured with DCs. We found that a cell-cell contact is required between B cells and DCs. Using MHCI KO and re-purification studies, we demonstrated that B cells were the primary APCs and DCs serve to license this function. We further identified that the gene expression profiles of B cells that have been licensed by DCs, compared to the B cells that have not, are vastly different and have signatures similar to B cells activated with a TLR7/8 agonist. Our data demonstrate that B cells transcribe and translate antigens encoded by plasmid DNA following passive uptake, however require licensing by live DC to present antigen to CD8 T cells. Further study of the role of B cells as APCs will be important to improve the immunological efficacy of DNA vaccines.

mRNA therapeutics: new vaccination and beyond

The idea of mRNA therapy had been conceived for decades before it came into reality during the Covid-19 pandemic. The mRNA vaccine emerges as a powerful and general tool against new viral infections, largely due to its versatility and rapid development. In addition to prophylactic vaccines, mRNA technology also offers great promise for new applications as a versatile drug modality. However, realizing the conceptual potential faces considerable challenges, such as minimal immune stimulation, high and long-term expression, and efficient delivery to target cells and tissues. Here we review the applications of mRNA-based therapeutics, with emphasis on the innovative design and future challenges/solutions. In addition, we also discuss the next generation of mRNA therapy, including circular mRNA and self-amplifying RNAs. We aim to provide a conceptual overview and outlook on mRNA therapeutics beyond prophylactic vaccines.

Bacterial lipopolysaccharide-related genes are involved in the invasion and recurrence of prostate cancer and are related to immune escape based on bioinformatics analysis

Background

The composition of the tumor microbial microenvironment participates in the whole process of tumor disease. However, due to the limitations of the current technical level, the depth and breadth of the impact of microorganisms on tumors have not been fully recognized, especially in prostate cancer (PCa). Therefore, the purpose of this study is to explore the role and mechanism of the prostate microbiome in PCa based on bacterial lipopolysaccharide (LPS)-related genes by means of bioinformatics.

Methods

The Comparative Toxicogenomics Database (CTD) was used to find bacterial LPS- related genes. PCa expression profile data and clinical data were acquired from TCGA, GTEx, and GEO. The differentially expressed LPS-related hub genes (LRHG) were obtained by Venn diagram, and gene set enrichment analysis (GSEA) was used to investigate the putative molecular mechanism of LRHG. The immune infiltration score of malignancies was investigated using single-sample gene set enrichment analysis (ssGSEA). Using univariate and multivariate Cox regression analysis, a prognostic risk score model and nomogram were developed.

Results

6 LRHG were screened. LRHG were involved in functional phenotypes such as tumor invasion, fat metabolism, sex hormone response, DNA repair, apoptosis, and immunoregulation. And it can regulate the immune microenvironment in the tumor by influencing the antigen presentation of immune cells in the tumor. And a prognostic risk score and the nomogram, which were based on LRHG, showed that the low-risk score has a protective effect on patients.

Conclusion

Microorganisms in the PCa microenvironment may use complex mechanism and networks to regulate the occurrence and development of PCa. Bacterial lipopolysaccharide-related genes can help build a reliable prognostic model and predict progression-free survival in patients with prostate cancer.

Role of B cells as antigen presenting cells

B cells have been long studied for their role and function in the humoral immune system. Apart from generating antibodies and an antibody-mediated memory response against pathogens, B cells are also capable of generating cell-mediated immunity. It has been demonstrated by several groups that B cells can activate antigen-specific CD4 and CD8 T cells, and can have regulatory and cytotoxic effects. The function of B cells as professional antigen presenting cells (APCs) to activate T cells has been largely understudied. This, however, requires attention as several recent reports have demonstrated the importance of B cells within the tumor microenvironment, and B cells are increasingly being evaluated as cellular therapies. Antigen presentation through B cells can be through antigen-specific (B cell receptor (BCR) dependent) or antigen non-specific (BCR independent) mechanisms and can be modulated by a variety of intrinsic and external factors. This review will discuss the pathways and mechanisms by which B cells present antigens, and how B cells differ from other professional APCs.

The Cellular and Molecular Immunotherapy in Prostate Cancer

In recent history, immunotherapy has become a viable cancer therapeutic option. However, over many years, its tenets have changed, and it now comprises a range of cancer-focused immunotherapies. Clinical trials are currently looking into monotherapies or combinations of medicines that include immune checkpoint inhibitors (ICI), CART cells, DNA vaccines targeting viruses, and adoptive cellular therapy. According to ongoing studies, the discipline should progress by incorporating patient-tailored immunotherapy, immune checkpoint blockers, other immunotherapeutic medications, hormone therapy, radiotherapy, and chemotherapy. Despite significantly increasing morbidity, immunotherapy can intensify the therapeutic effect and enhance immune responses. The findings for the immunotherapy treatment of advanced prostate cancer (PCa) are compiled in this study, showing that is possible to investigate the current state of immunotherapy, covering new findings, PCa treatment techniques, and research perspectives in the field’s unceasing evolution.

Immune Checkpoint Inhibitors for Vaccine Improvements: Current Status and New Approaches

In recent years, the use of immune checkpoint inhibitors (ICIs) in combination with approved or experimental vaccines has proven to be a promising approach to improve vaccine immunogenicity and efficacy. This strategy seeks to overcome the immunosuppressive mechanisms associated with the vaccine response, thereby achieving increased immunogenicity and efficacy. Most of the information on the use of ICIs combined with vaccines derives from studies on certain anti-tumor vaccines combined with monoclonal antibodies (mAbs) against either cytotoxic T lymphocyte-associated protein 4 (CTLA-4), programmed cell death protein 1 (PD-1), or programmed death-ligand 1 (PD-L1). However, over the past few years, emerging strategies to use new-generation ICIs as molecular adjuvants are paving the way for future advances in vaccine research. Here, we review the current state and future directions of the use of ICIs in experimental and clinical settings, including mAbs and alternative new approaches using antisense oligonucleotides (ASOs), small non-coding RNAs, aptamers, peptides, and other small molecules for improving vaccine efficacy. The scope of this review mainly includes the use of ICIs in therapeutic antitumor vaccines, although recent research on anti-infective vaccines will also be addressed.

Dual Blockade of PD-1 and LAG3 Immune Checkpoints Increases Dendritic Cell Vaccine Mediated T Cell Responses in Breast Cancer Model

PURPOSE

Increasing the efficiency of unsuccessful immunotherapy methods is one of the most important research fields. Therefore, the use of combination therapy is considered as one of the ways to increase the effectiveness of the dendritic cell (DC) vaccine. In this study, the inhibition of immune checkpoint receptors such as LAG3 and PD-1 on T cells was investigated to increase the efficiency of T cells in response to the DC vaccine.

METHODS

We used trimethyl chitosan-dextran sulfate-lactate (TMC-DS-L) nanoparticles (NPs) loaded with siRNA molecules to quench the PD-1 and LAG3 checkpoints' expression.

RESULTS

Appropriate physicochemical characteristics of the generated NPs led to efficient inhibition of LAG3 and PD-1 on T cells, which was associated with increased survival and activity of T cells, ex vivo. Also, treating mice with established breast tumors (4T1) using NPs loaded with siRNA molecules in combination with DC vaccine pulsed with tumor lysate significantly inhibited tumor growth and increased survival in mice. These ameliorative effects were associated with increased anti-tumor T cell responses and downregulation of immunosuppressive cells in the tumor microenvironment and spleen.

CONCLUSION

These findings strongly suggest that TMC-DS-L NPs loaded with siRNA could act as a novel tool in inhibiting the expression of immune checkpoints in the tumor microenvironment. Also, combination therapy based on inhibition of PD-1 and LAG3 in combination with DC vaccine is an effective method in treating cancer that needs to be further studied.

Immunotherapy: Reshape the Tumor Immune Microenvironment

Tumor immune microenvironment (TIME) include tumor cells, immune cells, cytokines, etc. The interactions between these components, which are divided into anti-tumor and pro-tumor, determine the trend of anti-tumor immunity. Although the immune system can eliminate tumor through the cancer-immune cycle, tumors appear to eventually evade from immune surveillance by shaping an immunosuppressive microenvironment. Immunotherapy reshapes the TIME and restores the tumor killing ability of anti-tumor immune cells. Herein, we review the function of immune cells within the TIME and discuss the contribution of current mainstream immunotherapeutic approaches to remolding the TIME. Changes in the immune microenvironment in different forms under the intervention of immunotherapy can shed light on better combination treatment strategies.

The clinical progress of mRNA vaccines and immunotherapies

The emergency use authorizations (EUAs) of two mRNA-based severe acute respiratory syndrome coronavirus (SARS-CoV)-2 vaccines approximately 11 months after publication of the viral sequence highlights the transformative potential of this nucleic acid technology. Most clinical applications of mRNA to date have focused on vaccines for infectious disease and cancer for which low doses, low protein expression and local delivery can be effective because of the inherent immunostimulatory properties of some mRNA species and formulations. In addition, work on mRNA-encoded protein or cellular immunotherapies has also begun, for which minimal immune stimulation, high protein expression in target cells and tissues, and the need for repeated administration have led to additional manufacturing and formulation challenges for clinical translation. Building on this momentum, the past year has seen clinical progress with second-generation coronavirus disease 2019 (COVID-19) vaccines, Omicron-specific boosters and vaccines against seasonal influenza, Epstein-Barr virus, human immunodeficiency virus (HIV) and cancer. Here we review the clinical progress of mRNA therapy as well as provide an overview and future outlook of the transformative technology behind these mRNA-based drugs.

LAG3-PD-1 Combo Overcome the Disadvantage of Drug Resistance

Although PD-1 blockade therapy has been promising in cancer treatment, only 4% (pancreatic cancer) to 70% (melanoma) of patients have a positive response to this blockade therapy, which is one of its important disadvantages. Therefore, it is important to seek out new targets for cancer immunotherapy to improve the overall response rate in patients. Lymphocyte activation gene-3 (LAG-3), an immune checkpoint receptor, is mainly expressed in activated immune cells. LAG-3 maintains the body’s immune homeostasis under physiological conditions while mediating tumour immune escape. Several preclinical and clinical examinations have shown that LAG-3 blockade effectively alleviates the patient’s tolerance to PD-1 immune checkpoint inhibitors. Moreover, the combination of LAG-3 and PD-1 blockade has good clinical efficacy in cancers. Hence, synchronous LAG-3 and PD-1 inhibition may be a potential new strategy for tumour immunotherapy.

Toll-like receptor agonist combinations augment mouse T-cell anti-tumor immunity via IL-12- and interferon ß-mediated suppression of immune checkpoint receptor expression

We previously found that activated CD8+ T-cells increase expression of PD-1, which can be attenuated in the presence of specific Toll-like receptor (TLR) agonists, mediated by IL-12 secreted by professional antigen-presenting cells. While these CD8+ T-cells had greater anti-tumor activity, T-cells stimulated by different TLR had different gene expression profiles. Consequently, we sought to determine whether combinations of TLR agonists might further affect the expression of T-cell checkpoint receptors and improve T-cell anti-tumor immunity. Activation of CD8+ T-cells in the presence of specific TLR ligands resulted in decreased expression of PD-1, LAG-3, and CD160, notably with combinations of TLR1/2, TLR3, and TLR9 agonists. Immunization of E.G7-OVA or TRAMP-C1 tumor-bearing mice with peptide or DNA vaccines, co-administered with combination of TLR3 and TLR9 agonists, showed greater suppression of tumor growth. The anti-tumor effect of TLR1/2 and/or TLR9, but not TLR3, was abrogated in IL-12KO mice. RNA sequencing of TLR-conditioned CD8+ T-cells revealed IL-12 pathway activation, and type 1 IFN pathway activation following TLR3 stimulation. Our results provide a mechanistic rationale for the choice of optimal combinations of TLR ligands to use as adjuvants to improve the efficacy of anti-tumor vaccines.

Phase 2 trial of T-cell activation using MVI-816 and pembrolizumab in patients with metastatic, castration-resistant prostate cancer (mCRPC)

Background

We previously reported a trial using a DNA vaccine encoding prostatic acid phosphatase (MVI-816, pTVG-HP), given over 12 weeks concurrently or sequentially with pembrolizumab, in patients with mCRPC. We report the final analysis of this trial following two additional treatment arms in which patients with mCRPC continued concurrent treatment until progression.

Materials and methods

Patients with mCRPC were treated with MVI-816 and pembrolizumab every 3 weeks (arm 3, n=20) or MVI-816 every 2 weeks and pembrolizumab every 4 weeks (arm 4, n=20). The primary objectives were safety, 6-month progression-free survival (PFS), median time to radiographic progression, and objective response rates. Secondary objectives included immunological evaluations.

Results

In 25 patients with measurable disease, there were no complete response and one confirmed partial response in a patient who subsequently found to have an MSI^hi tumor. 4/40 patients (10%) had a prostate-specific antigen decline >50%. The estimated overall radiographic PFS rate at 6 months was 47.2% (44.4% arm 3, 61.5% arm 4). Accounting for all off-study events, overall median time on treatment was 5.6 months (95% CI: 5.4 to 10.8 months), 5.6 months for arm 3 and 8.1 months for arm 4 (p=0.64). Thirty-two per cent of patients remained on trial beyond 6 months without progression. Median overall survival was 22.9 (95% CI: 16.2 to 25.6) months. One grade 4 event (hyperglycemia) was observed. Immune-related adverse events (irAEs) >grade 1 were observed in 42% of patients overall. Interferon-γ and/or granzyme B immune response to prostatic acid phosphatase was detected in 2/20 patients in arm 3 and 6/20 patients in arm 4. Plasma cytokines associated with immune activation and CD8+ T-cell recruitment were augmented at weeks 6 and 12. The development of irAE was significantly associated with a prolonged time on treatment (HR=0.42, p=0.003). Baseline DNA homologous recombination repair mutations were not associated with longer time to progression.

Conclusions

Findings here demonstrate that combining programmed cell death 1 blockade with MVI-816 is safe, can augment tumor-specific T cells, and can result in a favorable 6-month disease control rate. Correlative studies suggest T-cell activation by vaccination is critical to the mechanism of action of this combination. Future randomized clinical trials are needed to validate these findings.

Trial registration number

NCT02499835.

Immune Checkpoint LAG3 and Its Ligand FGL1 in Cancer

LAG3 is the most promising immune checkpoint next to PD-1 and CTLA-4. High LAG3 and FGL1 expression boosts tumor growth by inhibiting the immune microenvironment. This review comprises four sections presenting the structure/expression, interaction, biological effects, and clinical application of LAG3/FGL1. D1 and D2 of LAG3 and FD of FGL1 are the LAG3-FGL1 interaction domains. LAG3 accumulates on the surface of lymphocytes in various tumors, but is also found in the cytoplasm in non-small cell lung cancer (NSCLC) cells. FGL1 is found in the cytoplasm in NSCLC cells and on the surface of breast cancer cells. The LAG3-FGL1 interaction mechanism remains unclear, and the intracellular signals require elucidation. LAG3/FGL1 activity is associated with immune cell infiltration, proliferation, and secretion. Cytokine production is enhanced when LAG3/FGL1 are co-expressed with PD-1. IMP321 and relatlimab are promising monoclonal antibodies targeting LAG3 in melanoma. The clinical use of anti-FGL1 antibodies has not been reported. Finally, high FGL1 and LAG3 expression induces EGFR-TKI and gefitinib resistance, and anti-PD-1 therapy resistance, respectively. We present a comprehensive overview of the role of LAG3/FGL1 in cancer, suggesting novel anti-tumor therapy strategies.

Evaluation of single domain antibodies as nuclear tracers for imaging of the immune checkpoint receptor human lymphocyte activation gene-3 in cancer

Recent advancements in the field of immune-oncology have led to a significant increase in life expectancy of patients with diverse forms of cancer, such as hematologic malignancies, melanoma and lung cancer. Unfortunately, these encouraging results are not observed in the majority of patients, who remain unresponsive and/or encounter adverse events. Currently, researchers are collecting more insight into the cellular and molecular mechanisms that underlie these variable responses. As an example, the human lymphocyte activation gene-3 (huLAG-3), an inhibitory immune checkpoint receptor, is increasingly studied as a therapeutic target in immune-oncology. Noninvasive molecular imaging of the immune checkpoint programmed death protein-1 (PD-1) or its ligand PD-L1 has shown its value as a strategy to guide and monitor PD-1/PD-L1-targeted immune checkpoint therapy. Yet, radiotracers that allow dynamic, whole body imaging of huLAG-3 expression are not yet described. We here developed single-domain antibodies (sdAbs) that bind huLAG-3 and showed that these sdAbs can image huLAG-3 in tumors, therefore representing promising tools for further development into clinically applicable radiotracers.