Design and syntheses of a bimolecular STING agonist based on the covalent STING antagonist

Discovery of novel rigid STING PROTAC degraders as potential therapeutics for acute kidney injury

Acute kidney injury (AKI) is a critical condition resulting from intrinsic immune overactivation for which no ideal therapeutic agent is available. The development of therapeutic drugs with new targets and mechanism has become one of the important challenges in the pharmaceutical field. The interferon gene stimulating protein (STING) directly regulates the intrinsic immune processes and is a potential target for AKI therapy. Herein, we designed synthesized and evaluated a series of novel STING-PROTAC degraders via a rigid strategy. Among them, compound ST9 performed the highest degradation capacity with a DC50 of 0.62 μM in THP-1 cells. In a cisplatin-induced HK-2 cell model, ST9 could down-regulate the STING/NF-κB signaling axis and thus inhibit the expression of inflammatory factors. Additionally, ST9 showed a significantly improved metabolic stability profile. Furthermore, ST9 displayed favorable in vivo anti-AKI efficacy and has no toxic side effects on other organs. These results suggest that the novel rigid STING-PROTAC ST9 has clinical potential as a renoprotective agent for the treatment/prevention of acute kidney injury.

Design, synthesis, and activity evaluation of novel STING inhibitors based on C170 and H151

Stimulating the STING signaling pathway for immune system activation is considered a promising strategy for cancer treatment. However, activating the STING pathway can lead to adverse effects, as aberrant activation or specific mutations in STING may result in autoimmune and inflammatory diseases. Therefore, the development of STING inhibitors is equally important. In this study, we first introduced hydroxyl groups into the STING inhibitors C170 and H151, creating functional sites for further modification. Then the introduction of various substituents resulted in the identification of more potent inhibitors, Y2 and HY2, which effectively suppressed the activation of the STING pathway in THP1 and RAW264.7 cells. Compounds Y2 and HY2 demonstrated potent anti-inflammatory effects in mice cisplatin-induced acute kidney injury models by inhibiting the STING pathway. Collectively, Y2 and HY2 warrant further investigation as novel anti-inflammatory agents.

Oligomerization of STING and Chemical Regulatory Strategies

Stimulator of interferon genes (STING) plays a crucial role in innate immunity. Upon the recognition of cytosolic dsDNA, STING undergoes several structural changes, with oligomerization playing a key role in initiating a cascade of immune responses. Therefore, controlling the STING pathway by manipulating STING oligomerization is a practical strategy. This review focuses on the detailed mechanism of STING oligomerization, highlighting its decisive role. It also describes oligomerization-based strategies to regulate STING protein, such as the use of small-molecule agonists and biomacromolecules, highlighting their interaction modes and potential therapeutic applications. This knowledge may lead to the development of innovative approaches for treating cancer and immune disorders.

Design, Synthesis, and Biological Assessment of Novel Aminobenzidazole Agonists Targeting the Stimulator of Interferon Genes (STING) Receptor Signaling Pathway for Oncology Immunotherapy

The activation of the STING-mediated signaling pathway leads to the secretion of type I interferon (IFN) and the activation of tumor-specific T cells. STING, a pattern recognition receptor located on the endoplasmic reticulum membrane of immune cells, binds with endogenous cyclic dinucleotides. STING undergoes phosphorylation, triggering the STING-TBK1-IRF3 pathway and NF-κB pathway, resulting in the release of IFN-β and other pro-inflammatory cytokines, ultimately enhancing the activation of tumor-specific T cells. This mechanism serves to complement the limitations of immune checkpoint inhibitors and enhances the efficiency of the immune response. This study selected benzimidazole compounds GSK and SR-717, which exhibit promising potential as patented medicines, as our lead compounds. Aiming to address the challenges associated with the short half-life of benzimidazole compounds and the limited molecular activity of SR-717, we designed and synthesized a series of STING agonists (compounds 6~29). The compound 17 showed excellent agonistic activity on hSTING protein in vitro. The cytotoxicity tests of all the synthesized compounds were performed in vitro. Performed in vivo pharmacokinetic studies on the most promising compounds and conducted molecular docking analyses.

Discovery of novel nitrofuran PROTAC-like compounds as dual inhibitors and degraders targeting STING

Aberrant activation of the innate immune molecule STING can initiate inflammation and autoimmune diseases. Small molecule inhibitors targeting STING have demonstrated therapeutic efficacy against these conditions. Moreover, employing degradants to target STING represents a novel approach to drug design strategy. Consequently, we have designed and synthesized a series of covalent degradants targeting STING. Among them, compound P8 exhibited the highest degradation capacity, with a 24-h DC50 of 2.58 μM in THP-1 cells. In THP-1 cells, P8 specifically degraded STING proteins through the lysosomal pathway, acting as dual a degrader and inhibitor to manifest anti-inflammatory effects. Conversely, in RAW264.7 cells, P8 solely acted as an inhibitor without exhibiting degradative capacity towards the STING protein level. Additionally, P8 displayed renal-protective properties in a cisplatin-induced acute kidney injury model. These results highlight the significant potential of further investigating compound P8.

piSTING: A Pocket-Independent Agonist Based on Multivalency-Driven STING Oligomerization

The stimulator of interferon genes (STING) pathway is a potent therapeutic target for innate immunity. Despite the efforts to develop pocket-dependent small-molecule STING agonists that mimic the endogenous STING ligand, cyclic guanosine monophosphate-adenosine monophosphate (cGAMP), most of these agonists showed disappointing results in clinical trials owing to the limitations of the STING pocket. In this study, we developed novel pocket-independent STING-activating agonists (piSTINGs), which act through multivalency-driven oligomerization to activate STING. Additionally, a piSTING-adjuvanted vaccine elicited a significant antibody response and inhibited tumour growth in therapeutic models. Moreover, a piSTING-based vaccine combination with aPD-1 showed remarkable potential to enhance the effectiveness of immune checkpoint blockade (ICB) immunotherapy. In particular, piSTING can strengthen the impact of STING pathway in immunotherapy and accelerate the clinical translation of STING agonists.

The cGAS-STING pathway: a therapeutic target in diabetes and its complications

Diabetic wound healing (DWH) represents a major complication of diabetes where inflammation is a key impediment to proper healing. The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway has emerged as a central mediator of inflammatory responses to cell stress and damage. However, the contribution of cGAS-STING activation to impaired healing in DWH remains understudied. In this review, we examine the evidence that cGAS-STING-driven inflammation is a critical factor underlying defective DWH. We summarize studies revealing upregulation of the cGAS-STING pathway in diabetic wounds and discuss how this exacerbates inflammation and senescence and disrupts cellular metabolism to block healing. Partial pharmaceutical inhibition of cGAS-STING has shown promise in damping inflammation and improving DWH in preclinical models. We highlight key knowledge gaps regarding cGAS-STING in DWH, including its relationships with endoplasmic reticulum stress and metal-ion signaling. Elucidating these mechanisms may unveil new therapeutic targets within the cGAS-STING pathway to improve healing outcomes in DWH. This review synthesizes current understanding of how cGAS-STING activation contributes to DWH pathology and proposes future research directions to exploit modulation of this pathway for therapeutic benefit.

Chemical Biology Perspectives on STING Agonists as Tumor Immunotherapy

Stimulator of interferon genes (STING) is a crucial adaptor protein in the innate immune response. STING activation triggers cytokine secretion, including type I interferon and initiates T cell-mediated adaptive immunity. The activated immune system converts "cold tumors" into "hot tumors" that are highly responsive to T cells by recruiting them to the tumor microenvironment, ultimately leading to potent and long-lasting antitumor effects. Unlike most immune checkpoint inhibitors, STING agonists represent a groundbreaking class of innate immune agonists that hold great potential for effectively targeting various cancer populations and are poised to become a blockbuster in tumor immunotherapy. This review will focus on the correlation between the STING signaling pathway and tumor immunity, as well as explore the impact of STING activation on other biological processes. Ultimately, we will summarize the development and optimization of STING agonists from a medicinal chemistry perspective, evaluate their potential in cancer therapy, and identify possible challenges for future advancement.