Agonist of stimulator of interferon genes as antitumor agents: a patent review (2008-2020)

cGAS-STING pathway agonists are promising vaccine adjuvants

Adjuvants are of critical value in vaccine development as they act on enhancing immunogenicity of antigen and inducing long-lasting immunity. However, there are only a few adjuvants that have been approved for clinical use, which highlights the need for exploring and developing new adjuvants to meet the growing demand for vaccination. Recently, emerging evidence demonstrates that the cGAS-STING pathway orchestrates innate and adaptive immunity by generating type I interferon responses. Many cGAS-STING pathway agonists have been developed and tested in preclinical research for the treatment of cancer or infectious diseases with promising results. As adjuvants, cGAS-STING agonists have demonstrated their potential to activate robust defense immunity in various diseases, including COVID-19 infection. This review summarized the current developments in the field of cGAS-STING agonists with a special focus on the latest applications of cGAS-STING agonists as adjuvants in vaccination. Potential challenges were also discussed in the hope of sparking future research interests to further the development of cGAS-STING as vaccine adjuvants.

Unraveling the Binding Mode of Cyclic Adenosine-Inosine Monophosphate (cAIMP) to STING through Molecular Dynamics Simulations

The stimulator of interferon genes (STING) plays a significant role in immune defense and protection against tumor proliferation. Many cyclic dinucleotide (CDN) analogues have been reported to regulate its activity, but the dynamic process involved when the ligands activate STING remains unclear. In this work, all-atom molecular dynamics simulations were performed to explore the binding mode between human STING (hSTING) and four cyclic adenosine-inosine monophosphate analogs (cAIMPs), as well as 2',3'-cGMP-AMP (2',3'-cGAMP). The results indicate that these cAIMPs adopt a U-shaped configuration within the binding pocket, forming extensive non-covalent interaction networks with hSTING. These interactions play a significant role in augmenting the binding, particularly in interactions with Tyr167, Arg238, Thr263, and Thr267. Additionally, the presence of hydrophobic interactions between the ligand and the receptor further contributes to the overall stability of the binding. In this work, the conformational changes in hSTING upon binding these cAIMPs were also studied and a significant tendency for hSTING to shift from open to closed state was observed after binding some of the cAIMP ligands.

An updated patent review of stimulator of interferon genes agonists (2021 - present)

INTRODUCTION

Stimulator of Interferon Genes (STING) is an innate immune sensor. Activation of STING triggers a downstream response that results in the expression of proinflammatory cytokines (TNF-α, IL-1β) via nuclear factor kappa-B (NF-κB) or the expression of type I interferons (IFNs) via an interferon regulatory factor 3 (IRF3). IFNs can eventually result in promotion of the adaptive immune response including activation of tumor-specific CD8+ T cells to abolish the tumor. Consequently, activation of STING has been considered as a potential strategy for cancer treatment.

AREAS COVERED

This article provides an overview on structures and pharmacological data of CDN-like and non-nucleotide STING agonists acting as anticancer agents (January 2021 to October 2023) from a medicinal chemistry perspective. The data in this review come from EPO, WIPO, RCSB PDB, CDDI.

EXPERT OPINION

In recent years, several structurally diverse STING agonists have been identified. As an immune enhancer, they are used in the treatment of tumors, which has received extensive attention from scientific community and pharmaceutical companies. Despite the multiple challenges that have appeared, STING agonists may offer opportunities for immunotherapy.

18F-FDG PET Visualizes Systemic STING Agonist-Induced Lymphocyte Activation in Preclinical Models

Stimulator of interferon genes (STING) is a mediator of immune recognition of cytosolic DNA, which plays important roles in cancer, cytotoxic therapies, and infections with certain pathogens. Although pharmacologic STING activation stimulates potent antitumor immune responses in animal models, clinically applicable pharmacodynamic biomarkers that inform of the magnitude, duration, and location of immune activation elicited by systemic STING agonists are yet to be described. We investigated whether systemic STING activation induces metabolic alterations in immune cells that can be visualized by PET imaging. Methods: C57BL/6 mice were treated with systemic STING agonists and imaged with 18F-FDG PET after 24 h. Splenocytes were harvested 6 h after STING agonist administration and analyzed by single-cell RNA sequencing and flow cytometry. 18F-FDG uptake in total splenocytes and immunomagnetically enriched splenic B and T lymphocytes from STING agonist-treated mice was measured by γ-counting. In mice bearing prostate or pancreas cancer tumors, the effects of STING agonist treatment on 18F-FDG uptake, T-lymphocyte activation marker levels, and tumor growth were evaluated. Results: Systemic delivery of structurally distinct STING agonists in mice significantly increased 18F-FDG uptake in the spleen. The average spleen SUVmax in control mice was 1.90 (range, 1.56-2.34), compared with 4.55 (range, 3.35-6.20) in STING agonist-treated mice (P < 0.0001). Single-cell transcriptional and flow cytometry analyses of immune cells from systemic STING agonist-treated mice revealed enrichment of a glycolytic transcriptional signature in both T and B lymphocytes that correlated with the induction of immune cell activation markers. In tumor-bearing mice, STING agonist administration significantly delayed tumor growth and increased 18F-FDG uptake in secondary lymphoid organs. Conclusion: These findings reveal hitherto unknown functional links between STING signaling and immunometabolism and suggest that 18F-FDG PET may provide a widely applicable approach toward measuring the pharmacodynamic effects of systemic STING agonists at a whole-body level and guiding their clinical development.

Recent advances in the development of STING inhibitors: an updated patent review

INTRODUCTION

STING is at the center of the cGAS-STING signaling and acts as the hub of the innate immune system. Hyper-activation of STING has been observed in various severe autoimmune diseases, such as AGS, SLE, and many other diseases including neurological and metabolic disorders. Therefore, STING has been considered as a promising target. In recent years, several STING inhibitors have been claimed in patents.

AREAS COVERED

Small-molecule STING inhibitors reported in patents (disclosed before May 2022 through the public database at https://worldwide.espacenet.com) were summarized in this review and the available structure-activity relationships (SARs) and molecular mechanisms of action were presented.

EXPERT OPINION

Compared with STING agonists, the development of STING inhibitors is still in its infancy and no candidates have entered clinical investigation stage. Fortunately, patent applications are appearing at an increasing rate and a few of them have been validated in vivo, thus providing valuable insights for further structural optimization. More efforts are urgently needed since it is not clear yet that inhibitors targeting STING can solely exert sufficient therapeutic effects on autoimmune diseases, and the toxicity profile of such inhibitors is unknown as well. Therefore, it is extremely important to identify a selective and efficacious STING inhibitor for clinical evaluation to provide proof-of-concept for this approach.

STING as an emerging therapeutic target for drug discovery: Perspectives from the global patent landscape

BACKGROUND

The STimulator of INterferon Genes (STING) plays an essential role in the innate immune system by inducing the expression of type I interferons (IFNs) and inflammatory cytokines upon sensing cytosolic DNA. Although modulating STING has shown promise as a potential treatment for cancers and inflammatory and autoimmune diseases in substantial pre-clinical studies, current preliminary clinical results of STING agonists have demonstrated limited anti-tumor efficacy. Currently, there is ongoing R&D targeting STING and focusing on the delivery of next-generation therapeutics. Whereas no comprehensive analysis on the STING patent landscape has been conducted to fill the gap between basic research progress and drug development and commercialization.

AIM OF REVIEW

This study summarized the current agents in the clinical stage and global patenting profiles to help identify the current status, development trends, and emerging technologies of the nascent field of STING modulation.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Rapidly increasing R&D efforts and outcomes targeting STING were indicated by the recently increasing number and pharmacologic classes of drug candidates in clinic as well as in emergent technological patenting activities. Despite the overall fragmental ownership of patents, several pioneers that have advanced the clinical evaluation of novel STING agonists have established the basis of STING-relevant inventions through their influential patents in the field. These patents also facilitated progress on novel STING modulators, relevant delivery systems, pharmaceutical compositions, and combination strategies with the potential for further enhancing therapeutic outcomes by targeting STING.