TL-532, a novel specific Toll-like receptor 3 agonist rationally designed for targeting cancers: discovery process and biological characterization

ARNAX, but not conventional adjuvants, alum and squalene, induces antigen-specific CD8+ T cell proliferation in vaccination with influenza split vaccine

The influenza split vaccine (ISV) is generally administered without adjuvant via intra-muscular (i.m.) or intranasal route. Research has demonstrated that SV alone exhibits no capacity to elicit a Th1 (T helper-1) response and cellular immunity represented by cytotoxic T lymphocytes (CTL) induction. This finding is consistent with the observation that SV merely up-regulates antibody (Ab) production in the pre-disposed population. This tendency is reproduced in the SV model in conjunction with conventional adjuvants, including alum or squalene. These adjuvants amplify the Th2 shift, consequently stimulating Th2-dependent Ab production in mice. Conventional adjuvants, when employed with SV in animal studies, demonstrate a limited capacity to stimulate cellular immune activation. The present study aims to demonstrate the efficacy of a Th1-inducing adjuvant, ARNAX, in promoting antigen-presenting DC and subsequent Ag-specific CTL proliferation, culminating in Th1 polarization. Consequently, the synthesis of the two effectors, CTL and Ab, is augmented by the incorporation of ARNAX in SV. The enhanced SV-mediated protective immunity may be further augmented by the induction of antigen-specific CTL and the unique profile of Th1-mediated Ab production.

Toll-like receptor 3 activation enhances antitumor immune response in lung adenocarcinoma through NF-κB signaling pathway

Background

Toll-like receptor 3 (TLR3) is a pattern recognition receptor known to play a crucial role in the immune response to cancer. However, its effect on the efficacy of immunotherapy in lung adenocarcinoma (LUAD) remains unclear. This study aims to investigate the role of TLR3 in LUAD by examining its expression levels, prognostic significance, and impact on immune signaling pathways.

Methods

We analyzed the impact of TLR3 expression on the prognosis of lung adenocarcinoma patients using data from the Cancer Genome Atlas (TCGA) database and four additional cohorts (GSE72094, GSE30219, GSE50081 and GSE31210). Functional enrichment analyses were performed to compare molecular features between low and high TLR3 expression groups using gene set variation analysis (GSVA). We also examined the correlation between TLR3 and tumor mutation burden (TMB), immune infiltration, and PD-L1 expression. Further experimental validation was conducted using co-culture systems of LUAD cells and peripheral blood mononuclear cells (PBMCs) with PD1 inhibitors, and Western blot analysis to investigate the involvement of NF-κB signaling.

Results

TLR3 expression was significantly lower in LUAD tissues compared to normal tissues, with high TLR3 expression correlating with better survival outcomes across multiple cohorts. High TLR3 expression was associated with increased TMB and enhanced immune activation. Patients with high TLR3 expression exhibited higher immune checkpoint expression and immune cell infiltration. Experimental results showed that TLR3 agonists increased the susceptibility of LUAD cells to activated PBMCs under PD1 inhibitor therapy, inhibiting cell proliferation, migration, and invasion. Additionally, TLR3 has a strong positive correlation with MHC molecules and upregulated PD-L1 expression. NF-κB was identified as a key regulator of PD-L1 expression, with TLR3 agonists enhancing NF-κB and PD-L1 activity.

Conclusion

TLR3 enhances the anti-tumor immune response in LUAD by modulating NF-κB signaling and PD-L1 expression, making it a promising prognostic biomarker and therapeutic target. This study highlights the potential of TLR3 to improve immunotherapy outcomes, providing a comprehensive analysis of its role in LUAD and paving the way for novel therapeutic strategies targeting TLR3-mediated pathways.

Targeting the tumor microenvironment to improve clinical outcomes in triple negative breast cancer patients and bridge the current disparity gap

Triple negative breast cancer (TNBC) is a heterogenous disease that disproportionately affects Black women. TNBC outcomes among Black women are dismal secondary to multiple factors, such as poor healthcare accessibility resulting in delays in diagnosis, and aggressive disease biology in addition to a pro-tumor immune microenvironment (TME). Black women with breast cancer exhibit elevated levels of serum pro-inflammatory cytokines, and a pro-tumorigenic TME with higher immunosuppressive regulatory T cells (Tregs), M2 macrophages and exhausted CD8+ T cells. We have shown that the combined use of toll-like receptor 3 (TLR3) ligands with interferon-α (chemokine modulation: CKM) is able to enrich the tumor with CD8+ T cells, while not increasing immunosuppressive cells. Recent clinical trials have revealed the efficacy of immune checkpoint inhibitors (ICI) in rejuvenizing exhausted CD8+ T cells. We hypothesize that strategies to modulate the TME by enriching chemokines that attract CD8+T cells followed by reversal of CD8+ T cell exhaustion (ICI), when added to standard treatment, could potentially improve clinical outcomes, and mitigate the racial disparities in TNBC outcomes between Black and White Women.

Immunogenic cell death (ICD) enhancers-Drugs that enhance the perception of ICD by dendritic cells

The search for immunostimulatory drugs applicable to cancer immunotherapy may profit from target-agnostic methods in which agents are screened for their functional impact on immune cells cultured in vitro without any preconceived idea on their mode of action. We have built a synthetic mini-immune system in which stressed and dying cancer cells (derived from standardized cell lines) are confronted with dendritic cells (DCs, derived from immortalized precursors) and CD8+ T-cell hybridoma cells expressing a defined T-cell receptor. Using this system, we can identify three types of immunostimulatory drugs: (i) pharmacological agents that stimulate immunogenic cell death (ICD) of malignant cells; (ii) drugs that act on DCs to enhance their response to ICD; and (iii) drugs that act on T cells to increase their effector function. Here, we focus on strategies to develop drugs that enhance the perception of ICD by DCs and to which we refer as "ICD enhancers." We discuss examples of ICD enhancers, including ligands of pattern recognition receptors (exemplified by TLR3 ligands that correct the deficient function of DCs lacking FPR1) and immunometabolic modifiers (exemplified by hexokinase-2 inhibitors), as well as methods for target deconvolution applicable to the mechanistic characterization of ICD enhancers.

The Defined TLR3 Agonist, Nexavant, Exhibits Anti-Cancer Efficacy and Potentiates Anti-PD-1 Antibody Therapy by Enhancing Immune Cell Infiltration

Nexavant was reported as an alternative to the TLR3 agonist of Poly(I:C) and its derivatives. The physicochemical properties, signaling pathways, anti-cancer effects, and mechanisms of Nexavant were investigated. The distinctive characteristics of Nexavant compared to that of Poly(I:C) were demonstrated by precise quantification, enhanced thermostability, and increased resistance to RNase A. Unlike Poly(I:C), which activates TLR3, RIG-I, and MDA5, Nexavant stimulates signaling through TLR3 and RIG-I but not through MDA5. Compared to Poly(I:C), an intratumoral Nexavant treatment led to a unique immune response, immune cell infiltration, and suppression of tumor growth in various animal cancer models. Nexavant therapy outperformed anti-PD-1 antibody treatment in all the tested models and showed a synergistic effect in combinational therapy, especially in well-defined cold tumor models. The effect was similar to that of nivolumab in a humanized mouse model. Intranasal instillation of Nexavant led to the recruitment of immune cells (NK, CD4+ T, and CD8+ T) to the lungs, suppressing lung metastasis and improving animal survival. Our study highlighted Nexavant's defined nature for clinical use and unique signaling pathways and its potential as a standalone anti-cancer agent or in combination with anti-PD-1 antibodies.

A Chemically Defined TLR3 Agonist with Anticancer Activity

Toll-like receptor 3 (TLR3) agonists such as polyinosinic:polycytidylic acid (poly(I:C)) have immunostimulatory effects that can be taken advantage of to induce anticancer immune responses in preclinical models. In addition, poly(I:C) has been introduced into clinical trials to demonstrate its efficacy as an adjuvant and to enhance the immunogenicity of locally injected tumors, thus reverting resistance to PD-L1 blockade in melanoma patients. Here, we report the pharmacokinetic, pharmacodynamic, mechanistic and toxicological profile of a novel TLR3 agonist, TL-532, a chemically synthesized double-stranded RNA that is composed by blocks of poly(I:C) and poly(A:U) (polyadenylic - polyuridylic acid). In preclinical models, we show that TL-532 is bioavailable after parenteral injection, has an acceptable toxicological profile, and stimulates the production of multiple chemokines and interleukins that constitute pharmacodynamic markers of its immunostimulatory action. When given at a high dose, TL-532 monotherapy reduced the growth of bladder cancers growing on mice. In addition, in immunodeficient mice lacking formylpeptide receptor-1 (FPR1), TL-532 was able to restore the response of orthotopic subcutaneous fibrosarcoma to immunogenic chemotherapy. Altogether, these findings may encourage further development of TL-532 as an immunotherapeutic anticancer agent.