Novel CRBN-Recruiting Proteolysis-Targeting Chimeras as Degraders of Stimulator of Interferon Genes with In Vivo Anti-Inflammatory Efficacy

Discovery of an Orally Bioavailable STING Inhibitor with In Vivo Anti-Inflammatory Activity in Mice with STING-Mediated Inflammation

The cyclic GMP-AMP synthase (cGAS)-stimulator of the interferon genes (STING) pathway plays a key role in triggering interferon and inflammatory responses against microbial invasion or tumor. However, aberrant activation of the cGAS-STING pathway is associated with a variety of inflammatory and autoimmune diseases, and thus inhibition of STING is regarded as a potential new approach to treating these diseases. Herein, we report a series of novel indolyl-urea derivatives as STING inhibitors. The representative compound 42 exhibited potent STING inhibitory activity, acceptable pharmacokinetic properties, and good in vivo safety profiles. Mechanistically, 42 could block the palmitoylation of the STING protein and STING downstream signaling. Importantly, oral administration of 42 could effectively suppress STING-mediated inflammation in 10-carboxymethyl-9-acridanone (CMA)-treated mouse and Trex1-/- mouse. Together, compound 42 represents a promising STING inhibitor for treating STING-associated inflammatory and autoimmune diseases.

The STING antagonist SN-011 ameliorates cisplatin induced acute kidney injury via suppression of STING/NF-κB-mediated inflammation

Acute kidney injury (AKI) is a critical clinical syndrome associated with both innate and adaptive immune responses and thus increases mortality. Nevertheless, specific therapeutics for AKI are scarce so far. Recent studies have revealed that knockout of STING alleviate AKI, suggesting that STING could be an attractive target for AKI therapy. SN-011, a promising STING inhibitor, has not been reported in studies of its anti-AKI activity. In this study, we sought to examine the effects of SN-011 on AKI and explore its underlying mechanism. Our findings indicate that SN-011 could modulate the NF-κB and MAPK pathways, suppress the expression of inflammatory factors, and decrease ROS release in the cisplatin-induced cell model. In addition, SN-011 blocked the nuclear translocation of NF-κB p65, further mitigating the inflammatory response. In vivo, SN-011 enhanced survival rates and alleviated renal dysfunction. According to gene set enrichment analysis of sequencing data from mouse kidneys, we further confirm that SN-011 modulates the NF-κB and MAPK pathways. Our study suggests that SN-011 could be an attractive anti-inflammatory agent for further anti-AKI research.

Unleashing the Power of Covalent Drugs for Protein Degradation

Targeted protein degradation (TPD) has emerged as a significant therapeutic approach for a variety of diseases, including cancer. Advances in TPD techniques, such as molecular glue (MG) and lysosome-dependent strategies, have shown substantial progress since the inception of the first PROTAC in 2001. The PROTAC methodology represents the forefront of TPD technology, with ongoing evaluation in more than 20 clinical trials for the treatment of diverse medical conditions. Two prominent PROTACs, ARV-471 and ARV-110, are currently undergoing phase III and II clinical trials, respectively. Traditional PROTACs are encountering obstacles such as limited binding affinity and a restricted range of E3 ligase ligands for facilitating the protein of interest (POI) degradation. Covalent medicines offer the potential to enhance PROTAC efficacy by enabling the targeting of previously considered "undruggable" shallow binding sites. Strategic alterations allow PROTAC to establish covalent connections with particular target proteins, including Kirsten rat sarcoma viral oncogene homolog (KRAS), Bruton's tyrosine kinase (BTK), epidermal growth factor receptor (EGFR), as well as E3 ligases such as DDB1 and CUL4 associated factor 16 (DCAF16) and Kelch-like ECH-associated protein 1 (Keap1). The concept of covalent degradation has also been utilized in various new forms of degraders, including covalent molecule glue (MG), in-cell click-formed proteolysis targeting chimera (CLIPTAC), HaloPROTAC, lysosome-targeting chimera (LYTAC) and GlueTAC. This review focuses on recent advancements in covalent degraders beyond covalent PROTACs and examines obstacles and future directions pertinent to this field.

STING in cancer immunoediting: Modeling tumor-immune dynamics throughout cancer development

Cancer immunoediting is a dynamic process of tumor-immune system interaction that plays a critical role in cancer development and progression. Recent studies have highlighted the importance of innate signaling pathways possessed by both cancer cells and immune cells in this process. The STING molecule, a pivotal innate immune signaling molecule, mediates DNA-triggered immune responses in both cancer cells and immune cells, modulating the anti-tumor immune response and shaping the efficacy of immunotherapy. Emerging evidence has shown that the activation of STING signaling has dual opposing effects in cancer progression, simultaneously provoking and restricting anti-tumor immunity, and participating in every phase of cancer immunoediting, including immune elimination, equilibrium, and escape. In this review, we elucidate the roles of STING in the process of cancer immunoediting and discuss the dichotomous effects of STING agonists in the cancer immunotherapy response or resistance. A profound understanding of the sophisticated roles of STING signaling pathway in cancer immunoediting would potentially inspire the development of novel cancer therapeutic approaches and overcome the undesirable protumor effects of STING activation.

Journey of PROTAC: From Bench to Clinical Trial and Beyond

Proteolysis-targeting chimeras (PROTACs) represent a transformative advancement in drug discovery, offering a method to degrade specific intracellular proteins. Unlike traditional inhibitors, PROTACs are bifunctional molecules that target proteins for elimination, enabling the potential treatment of previously "undruggable" proteins. This concept, pioneered by Crews and his team, introduced the use of small molecules to link a target protein to an E3 ubiquitin ligase, inducing ubiquitination and subsequent degradation of the target protein. By promoting protein degradation rather than merely inhibiting function, PROTACs present a novel therapeutic strategy with enhanced specificity and effectiveness, especially in areas such as cancer and neurodegenerative diseases. Since their initial discovery, the field of PROTAC research has rapidly expanded with numerous PROTACs now designed to target a wide range of disease-relevant proteins. The substantial research, investment, and collaboration across academia and the pharmaceutical industry reflect the growing interest in PROTACs. This Review discusses the journey of PROTACs from initial discovery to clinical trials, highlighting advancements and challenges. Additionally, recent developments in fluorescent and photogenic PROTACs, used for real-time tracking of protein degradation, are presented, showcasing the evolving potential of PROTACs in targeted therapy.

Covalent Proximity Inducers

Molecules that are able to induce proximity between two proteins are finding ever increasing applications in chemical biology and drug discovery. The ability to introduce an electrophile and make such proximity inducers covalent can offer improved properties such as selectivity, potency, duration of action, and reduced molecular size. This concept has been heavily explored in the context of targeted degradation in particular for bivalent molecules, but recently, additional applications are reported in other contexts, as well as for monovalent molecular glues. This is a comprehensive review of reported covalent proximity inducers, aiming to identify common trends and current gaps in their discovery and application.

Regulation of STING G-quadruplex for rescuing cellular senescence and Aβ phagocytic capacity of microglia

Alzheimer's disease (AD), the most common form of dementia, affects millions of people worldwide and its cause is very complicated. Besides the classical amyloid cascade hypothesis, oxidative stress, metal ion imbalance, cellular senescence and neuroinflammation are also considered crucial triggers of AD. Therefore, therapeutic strategies other than inhibiting Aβ deposition are very promising. As a crucial innate immune pathway, the abnormal activation of the cGAS-STING pathway in AD has attracted much attention and become a promising target for AD treatment. Here, we identify a highly conserved and stable G-quadruplex (G4) in the STING promoter region, and further verify its function in transcriptional inhibition of STING by using CRISPR technology to precisely target STING G4. Intriguingly, down-regulation of STING expression can alleviate cellular senescence and restore the Aβ phagocytic capacity of microglia. Our results highlight the compelling therapeutic potential of STING promoter G4 for regulation of the abnormal activation of the cGAS-STING pathway in AD. Different from the existing therapeutic strategies for AD, this work provides an alternative way of targeting the functional gene secondary structure, such as the STING promoter region, which may promote the design and synthesis of drug candidates for AD.

Design, synthesis and biological evaluation of novel TMPRSS2-PROTACs with florosubstituted 4-guanidino-N-phenylbenzamide derivative ligands

Transmembrane Serine Protease 2 (TMPRSS2) plays a critical role in tumorigenesis and progression, making its degradation a promising therapeutic strategy. In this study, we designed and synthesized TMPRSS2-PROTACs, including VPOT64 and VPOT76, based on camostat. Both compounds exhibited superior inhibitory effects on HT-29 colorectal and Calu-3 lung cancer cells compared to paclitaxel. Notably, VPOT76 effectively degraded TMPRSS2, significantly inhibiting the proliferation of TMPRSS2-positive HT-29 cells and inducing apoptosis with an IC50 of 0.39 ± 0.01 μM. Flow cytometry analysis demonstrated that VPOT76 increased early apoptotic cells in a dose-dependent manner and caused G2 phase arrest at 0.8 μM. Colony formation assays showed that VPOT76 inhibited HT-29 colony formation, even at low concentrations, further confirming its anti-proliferative effect. Additionally, wound healing assays indicated that VPOT76 reduced the migration of HT-29 cells after 48 h, suggesting its potential to impair tumor cell invasion and metastasis. These findings highlight the multifaceted anticancer activities of VPOT76, including apoptosis induction, cell cycle arrest, colony formation inhibition, and migration suppression. Overall, this study establishes VPOT76 as a potent TMPRSS2-degrading PROTAC with strong therapeutic potential, laying the groundwork for further development of TMPRSS2-targeting treatments for colorectal and other cancers.

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.

The application of PROTACs in immune-inflammation diseases

Immune-inflammatory diseases are a class of conditions with high prevalence that severely impact the quality of life. Current treatment strategies include immunosuppressants, glucocorticoids, and monoclonal antibodies. However, these approaches have certain limitations, such as poor membrane permeability, immunogenicity, and the requirement for injection in large molecule drugs. Small molecule compounds, on the other hand, suffer from issues like poor selectivity, inability to inhibit non-enzymatic functions, and biological compensation. These factors constrain the effectiveness of current therapeutic strategies in immune-inflammatory diseases. As a novel small molecule drug development technology, proteolysis-targeting chimeras (PROTACs) regulate protein levels by inducing interactions between target proteins and E3 ubiquitin ligases, leading to the selective degradation of target proteins. This technology has already shown promising therapeutic effects in the treatment of immune-inflammatory diseases. This review aims to comprehensively summarize the application of PROTAC technology in the field of immune inflammation and provide insights into its potential in treating immune-inflammatory diseases.

The cross-talk between the cGAS-STING signaling pathway and chronic inflammation in the development of musculoskeletal disorders

Musculoskeletal disorders (MSDs) comprise diverse conditions affecting bones, joints, and muscles, leading to pain and loss of function, and are one of the most prevalent and major global health concerns. One of the hallmarks of MSDs is DNA damage. Once accumulated in the cytoplasm, the damaged DNA is sensed by the cyclic GMP-AMP synthase (cGAS)/stimulator of interferon genes (STING) pathway, which triggers the induction of type I interferons and inflammatory cytokines. Thus, this pathway connects the musculoskeletal and immune systems. Inhibitors of cGAS or STING have shown promising therapeutic effects in the pre-clinical models of several MSDs. Systemic, chronic, low-grade inflammation (SCLGI) underlies the development and maintenance of many MSDs. Failure to resolve SCLGI has been hypothesized to play a critical role in the development of chronic diseases, suggesting that the successful resolution of SCLGI will result in the alleviation of their related symptomatology. The process of inflammation resolution is feasible by specialized pro-resolving mediators (SPMs), which are enzymatically generated from dietary essential polyunsaturated fatty acids (PUFAs). The supplementation of SPMs or their stable, small-molecule mimetics and receptor agonists has revealed beneficial effects in inflammation-related animal models, including arthropathies, osteoporosis, and muscle dystrophy, suggesting a translational potential in MSDs. In this review, we substantiate the hypothesis that the use of cGAS-STING signaling pathway inhibitors together with SCLG-resolving compounds may serve as a promising new therapeutic approach for MSDs.

PROTAC based STING degrader attenuates acute colitis by inhibiting macrophage M1 polarization and intestinal epithelial cells pyroptosis mediated by STING-NLRP3 axis

Inflammatory bowel diseases (IBDs) are chronic, relapsing, and inflammatory disorders of the gastrointestinal tract characterized by abnormal immune responses. Recently, STING has emerged as a promising therapeutic target for various autoinflammatory diseases. However, few STING-selective small molecules have been investigated as novel strategies for IBD. In this study, we sought to examine the effects of PROTAC-based STING degrader SP23 on acute colitis and explore its underlying mechanism. SP23 treatment notably alleviates dextran sulfate sodium (DSS)-induced colitis. Pharmacological degradation of STING significantly reduced the production of inflammatory cytokines, such as TNF-α, IL-1β, and IL-6, and inhibited macrophage polarization towards the M1 type. Furthermore, SP23 administration decreased the loss of tight junction proteins, including ZO-1, occludin, and claudin-1, and downregulated STING and NLRP3 signaling pathways in intestinal inflammation. In vitro, STING activated NLRP3 inflammasome-mediated pyroptosis in intestinal epithelial cells, which could be abrogated by SP23 and STING siRNA intervention. In conclusion, these findings provide new evidence for STING as a novel therapeutic target for IBD, and reveal that hyperactivation of STING could exaggerate colitis by inducing NLRP3/Caspase-1/GSDMD axis mediated intestinal epithelial cells pyroptosis.

Bendamustine-rituximab elicits dual tumoricidal and immunomodulatory responses via cGAS-STING activation in diffuse large B-cell lymphoma

BACKGROUND

Bendamustine-rituximab (BR) therapy stands out as a promising alternative for elderly patients with diffuse large B-cell lymphoma (DLBCL), demonstrating notable efficacy when conventional regimens pose challenges. Despite its clinical success, the intricate mechanisms underlying BR therapy have remained elusive.

METHODS

DLBCL cell lines were used to investigate the mechanism of BR therapy in vitro. RNA-seq and Western blot were used to explore the target pathways of BR therapy. STING was knocked out using Crispr-cas9 and inhibited using H-151 to investigate its role in BR therapy. Bulk RNA-seq and single-cell RNA-seq data from patients were analyzed to investigate the association between STING and pyroptosis pathways, validated using STING downregulated cells. Flow cytometry, transwell experiments and co-culture experiments were performed to investigate the inflammatory phenotype of DLBCL cells after BR treatment and its effect on T-cell recruitment and activation.

RESULTS

This study elucidates that BR elicits direct tumoricidal effects by promoting apoptosis and inducing cell cycle arrest. The synergistic impact with rituximab is further potentiated by complement addition, demonstrating the pivotal role of in vivo antibody-dependent cellular cytotoxicity. Moreover, our investigation reveals that, through a cGAS-STING-dependent pathway, prolonged exposure to BR induces pyroptosis in DLBCL cells. Activation of the cGAS-STING pathway by BR therapy triggers the release of inflammatory factors and upregulates major histocompatibility complex molecules, shaping an immunologically hot tumor microenvironment.

CONCLUSIONS

This unique dual influence not only directly targets DLBCL cells but also engages the patient's immune system, paving the way for innovative combination therapies. The study provides comprehensive insights into the multifaceted actions of BR in DLBCL, offering a foundation for refined and personalized treatment strategies in elderly patients.

Targeted protein degradation: advances in drug discovery and clinical practice

Targeted protein degradation (TPD) represents a revolutionary therapeutic strategy in disease management, providing a stark contrast to traditional therapeutic approaches like small molecule inhibitors that primarily focus on inhibiting protein function. This advanced technology capitalizes on the cell's intrinsic proteolytic systems, including the proteasome and lysosomal pathways, to selectively eliminate disease-causing proteins. TPD not only enhances the efficacy of treatments but also expands the scope of protein degradation applications. Despite its considerable potential, TPD faces challenges related to the properties of the drugs and their rational design. This review thoroughly explores the mechanisms and clinical advancements of TPD, from its initial conceptualization to practical implementation, with a particular focus on proteolysis-targeting chimeras and molecular glues. In addition, the review delves into emerging technologies and methodologies aimed at addressing these challenges and enhancing therapeutic efficacy. We also discuss the significant clinical trials and highlight the promising therapeutic outcomes associated with TPD drugs, illustrating their potential to transform the treatment landscape. Furthermore, the review considers the benefits of combining TPD with other therapies to enhance overall treatment effectiveness and overcome drug resistance. The future directions of TPD applications are also explored, presenting an optimistic perspective on further innovations. By offering a comprehensive overview of the current innovations and the challenges faced, this review assesses the transformative potential of TPD in revolutionizing drug development and disease management, setting the stage for a new era in medical therapy.

cGAS/STING signalling pathway in senescence and oncogenesis

The cGAS/STING signaling pathway is a crucial component of the innate immune system, playing significant roles in sensing cytosolic DNA, regulating cellular senescence, and contributing to oncogenesis. Recent advances have shed new lights into the molecular mechanisms governing pathway activation in multiple pathophysiological settings, the indispensable roles of cGAS/STING signaling in cellular senescence, and its context-dependent roles in cancer development and suppression. This review summarizes current knowledge related to the biology of cGAS/STING signaling pathway and its participations into senescence and oncogenesis. We further explore the clinical implications and therapeutic potential for cGAS/STING targeted therapies, and faced challenges in the field. With a focus on molecular mechanisms and emerging pharmacological targets, this review underscores the importance of future studies to harness the therapeutic potential of the cGAS/STING pathway in treating senescence-related disorders and cancer. Advanced understanding of the regulatory mechanisms of cGAS/STING signaling, along with the associated deregulations in diseases, combined with the development of new classes of cGAS/STING modulators, hold great promises for creating novel and effective therapeutic strategies. These advancements could address current treatment challenges and unlock the full potential of cGAS/STING in treating senescence-related disorders and oncogenesis.

The STING signaling pathways and bacterial infection

As antibiotic-resistant bacteria continue to emerge frequently, bacterial infections have become a significant and pressing challenge to global public health. Innate immunity triggers the activation of host responses by sensing "non-self" components through various pattern recognition receptors (PRRs), serving as the first line of antibacterial defense. Stimulator of interferon genes (STING) is a PRR that binds with cyclic dinucleotides (CDN) to exert effects against bacteria, viruses, and cancer by inducing the production of type I interferon and inflammatory cytokines, and facilitating regulated cell death. Currently, drugs targeting the STING signaling pathway are predominantly applied in the fields of modulating host immune defense against cancer and viral infections, with relatively limited application in treating bacterial infections. Given the significant immunomodulatory functions of STING in the interaction between bacteria and hosts, this review summarizes the research progress on STING signaling pathways and their roles in bacterial infection, as well as the novel functions of STING modulators, aiming to offer insights for the development of antibacterial drugs.

Role of cyclic guanosine monophosphate-adenosine monophosphate synthase-stimulator of interferon genes pathway in diabetes and its complications

Diabetes mellitus (DM) is one of the major causes of mortality worldwide, with inflammation being an important factor in its onset and development. This review summarizes the specific mechanisms of the cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)-stimulator of interferon genes (STING) pathway in mediating inflammatory responses. Furthermore, it comprehensively presents related research progress and the subsequent involvement of this pathway in the pathogenesis of early-stage DM, diabetic gastroenteropathy, diabetic cardiomyopathy, non-alcoholic fatty liver disease, and other complications. Additionally, the role of cGAS-STING in autonomic dysfunction and intestinal dysregulation, which can lead to digestive complications, has been discussed. Altogether, this study provides a comprehensive analysis of the research advances regarding the cGAS-STING pathway-targeted therapeutic agents and the prospects for their application in the precision treatment of DM.

Selective and Orally Bioavailable c-Met PROTACs for the Treatment of c-Met-Addicted Cancer

c-Met is an attractive therapeutic target in multiple tumors. Previous studies have discovered some effective proteolysis-targeting chimeras (PROTACs) able to degrade c-Met; however, the structure-activity relationship (SAR), degradation selectivity, and pharmacokinetic profiles of c-Met PROTACs have, to date, remained largely unknown. Herein, through extensive SAR studies on various warheads, linkers, and E3 ligase ligands, a novel potent c-Met PROTAC Met-DD4 was identified. Our results suggested that Met-DD4 could induce robust c-Met degradation with excellent selectivity (DC50 = 6.21 nM), substantially killing the c-Met-addicted cancer cells (IC50 = 4.37 nM). Furthermore, in vivo studies showed that Met-DD4 could achieve excellent oral bioavailability and c-Met degradation, strongly retarding tumor growth with minute organ toxicity. Overall, this study reveals that targeted degradation of c-Met is a promising strategy for the treatment of c-Met-addicted cancers and provides novel lead compounds for the clinical translation of c-Met PROTACs.

Recent Advances in Smart Self-Assembled Bioinspired Hydrogels: A Bridging Weapon for Emerging Health Care Applications from Bench to Bedside

Stimuli-responsive low molecular weight hydrogel interventions for Biomedical challenges are a rapidly evolving paradigm in the bottom-up approach recently. Peptide-based self-assembled nano biomaterials present safer alternatives to their non-degradable counterparts as demanded for today's most urged clinical needs.Although a plethora of work has already been accomplished, programming hydrogelators with appropriate functionalities requires a better understanding as the impact of the macromolecular structure of the peptides and subsequently, their self-assembled nanostructures remain unidentified. Henceforth this review focuses on two aspects: Firstly, the underlying guidelines for building biomimetic strategies to tailor scaffolds leading to hydrogelation along with the role of non-covalent interactions that are the key components of various self-assembly processes. In the second section, it is aimed to bring together the recent achievements with designer assembly concerning their self-aggregation behaviour and applications mainly in the biomedical arena like drug delivery carrier design, antimicrobial, anti-inflammatory as well as wound healing materials. Furthermore, it is anticipated that this article will provide a conceptual demonstration of the different approaches taken towards the construction of these task-specific designer hydrogels. Finally, a collective effort among the material scientists is required to pave the path for the entrance of these intelligent materials into medicine from bench to bedside.

Recent insights of PROTAC developments in inflammation-mediated and autoimmune targets: a critical review

According to the mounting evidence in the literature, pro-inflammatory mediators/targets activate multiple signalling pathways to trigger illnesses that are ultimately responsible for acute pain, chronic inflammatory diseases, and several auto-immune disorders. Conventional drugs have been ruled out since proteolysis-targeting chimeras (PROTACs) are poised to overcome the limitations of traditional therapies. These heterobifunctional molecules help to degrade the targeted proteins of interest through ubiquitination. This review encompasses current and future aspects of PROTACs in inflammation-mediated and autoimmune targets. Different key points are highlighted and discussed, such as why PROTACs are preferred in this disease area, drawbacks and lessons learnt from the past, the role of linkers in establishing crucial degradation, in vitro findings, pharmacokinetics, in silico parameters, limitations of PROTACs in clinical settings, and future outcomes.

The balance of STING signaling orchestrates immunity in cancer

Over the past decade, it has become clear that the stimulator of interferon genes (STING) pathway is critical for a variety of immune responses. This endoplasmic reticulum-anchored adaptor protein has regulatory functions in host immunity across a spectrum of conditions, including infectious diseases, autoimmunity, neurobiology and cancer. In this Review, we outline the central importance of STING in immunological processes driven by expression of type I and III interferons, as well as inflammatory cytokines, and we look at therapeutic options for targeting STING. We also examine evidence that challenges the prevailing notion that STING activation is predominantly beneficial in combating cancer. Further exploration is imperative to discern whether STING activation in the tumor microenvironment confers true benefits or has detrimental effects. Research in this field is at a crossroads, as a clearer understanding of the nuanced functions of STING activation in cancer is required for the development of next-generation therapies.

Small molecule induced STING degradation facilitated by the HECT ligase HERC4

Stimulator of interferon genes (STING) is a central component of the cytosolic nucleic acids sensing pathway and as such master regulator of the type I interferon response. Due to its critical role in physiology and its' involvement in a variety of diseases, STING has been a focus for drug discovery. Targeted protein degradation (TPD) has emerged as a promising pharmacology for targeting previously considered undruggable proteins by hijacking the cellular ubiquitin proteasome system (UPS) with small molecules. Here, we identify AK59 as a STING degrader leveraging HERC4, a HECT-domain E3 ligase. Additionally, our data reveals that AK59 is effective on the common pathological STING mutations, suggesting a potential clinical application of this mechanism. Thus, these findings introduce HERC4 to the fields of TPD and of compound-induced degradation of STING, suggesting potential therapeutic applications.

Discovery of Selective Proteolysis-Targeting Chimera Degraders Targeting PTP1B as Long-Term Hypoglycemic Agents

PTP1B, a promising target for insulin sensitizers in type 2 diabetes treatment, can be effectively degraded using proteolysis-targeting chimera (PROTAC). This approach offers potential for long-acting antidiabetic agents. We report potent bifunctional PROTACs targeting PTP1B through the E3 ubiquitin ligase cereblon. Western blot analysis showed significant PTP1B degradation by PROTACs at concentrations from 5 nM to 5 μM after 48 h. Evaluation of five highly potent PROTACs revealed compound 75 with a longer PEG linker (23 atoms), displaying remarkable degradation activity after 48 and 72 h, with DC50 values of 250 nM and 50 nM, respectively. Compound 75 induced selective degradation of PTP1B, requiring engagement with both the target protein and CRBN E3 ligase, in a ubiquitination and proteasome-dependent manner. It significantly reduced blood glucose AUC0-2h to 29% in an oral glucose tolerance test and activated the IRS-1/PI3K/Akt signaling pathway in HepG2 cells, showing promise for long-term antidiabetic therapy.

Application of covalent modality in proximity-induced drug pharmacology: Early development, current strategy, and feature directions

With a growing number of covalent drugs securing FDA approval as successful therapies across various indications, particularly in the realm of cancer treatment, the covalent modulating strategy is undergoing a resurgence. The renewed interest in covalent bioactive compounds has captured significant attention from both the academic and biopharmaceutical industry sectors. Covalent chemistry presents several advantages over traditional noncovalent proximity-induced drugs, including heightened potency, reduced molecular size, and the ability to target "undruggable" entities. Within this perspective, we have compiled a comprehensive overview of current covalent modalities applied to proximity-induced molecules, delving into their advantages and drawbacks. Our aim is to stimulate more profound insights and ideas within the scientific community, guiding future research endeavors in this dynamic field.

Targeting STING elicits GSDMD-dependent pyroptosis and boosts anti-tumor immunity in renal cell carcinoma

While Stimulator-of-interferon genes (STING) is an innate immune adapter cruicial for sensing cytosolic DNA and modulating immune microenvironment, its tumor-promoting role in tumor survival and immune evasion remains largely unknown. Here we reported that renal cancer cells are exceptionally dependent on STING for survival and evading immunosurveillance via suppressing ER stress-mediated pyroptosis. We found that STING is significantly amplified and upregulated in clear cell renal cell carcinoma (ccRCC), and its elevated expression is associated with worse clinical outcomes. Mechanically, STING depletion in RCC cells specifically triggers activation of the PERK/eIF2α/ATF4/CHOP pathway and activates cleavage of Caspase-8, thereby inducing GSDMD-mediated pyroptosis, which is independent of the innate immune pathway of STING. Moreover, animal study revealed that STING depletion promoted infiltration of CD4+ and CD8+ T cells, consequently boosting robust antitumor immunity via pyroptosis-induced inflammation. From the perspective of targeted therapy, we found that Compound SP23, a PROTAC STING degrader, demonstrated comparable efficacy to STING depletion both in vitro and in vivo for treatment of ccRCC. These findings collectively unveiled an unforeseen function of STING in regulating GSDMD-dependent pyroptosis, thus regulating immune response in RCC. Consequently, pharmacological degradation of STING by SP23 may become an attractive strategy for treatment of advanced RCC.

Design, synthesis, and evaluation of thiazolecarboxamide derivatives as stimulator of interferon gene inhibitors

Stimulator of interferon gene (STING) plays critical roles in the cytoplasmic DNA-sensing pathway and in the induction of inflammatory response. Aberrant cytoplasmic DNA accumulation and STING activation are implicated in numerous inflammatory and autoimmune diseases. Here, we reported the discovery of a series of thiazolecarboxamide-based STING inhibitors through a molecular planarity/symmetry disruption strategy. The privileged compound 15b significantly inhibited STING signaling and suppressed immune-inflammatory cytokine levels in both human and murine cells. In vivo experiments demonstrated 15b effectively ameliorated immune-inflammatory cytokines upregulation in MSA-2-stimulated and Trex1-D18N mice. Furthermore, compound 15b exhibited enhanced efficacy in suppressing interferon-stimulated gene 15 (ISG15), a critical positive feedback regulator of STING. Overall, compound 15b deserves further development for the treatment of STING-associated inflammatory and autoimmune diseases.

Development of STING degrader with double covalent ligands

Stimulator of interferon genes (STING), a homodimeric membrane receptor localized in the endoplasmic reticulum, plays a pivotal role in signaling innate immune responses. Inhibitors and proteolysis-targeting chimeras (PROTACs) targeting STING are promising compounds for addressing autoinflammatory and autoimmune disorders. In this study, we used a minimal covalent handle recently developed as the ligand portion of an E3 ligase. The engineered STING degrader with a low molecular weight compound covalently binds to STING and E3 ligase. Degrader 2 showed sustained STING degradation activity at lower concentrations (3 µM, 48 h, about 75 % degradation) compared to a reported STING PROTAC, SP23. This discovery holds significance for its potential in treating autoinflammatory and autoimmune diseases, offering promising avenues for developing more efficacious STING-targeted therapies.

Design, synthesis and anti-necroptosis activity of fused heterocyclic MLKL inhibitors

Necroptosis is an important form of programmed cell death (PCD), which is mediated by a death receptor and independent of the caspase proteolytic enzyme. Mixed lineage kinase domain-like (MLKL) is the final effector of necroptosis, playing an irreplaceable role in the execution of necroptosis. However, the studies on MLKL inhibitors are in their infancy. Necrosulfonamide (NSA) is an early-discovered covalent MLKL inhibitor, possessing medium anti-necroptosis activity and a structure-activity relationship (SAR) not widely disclosed. In this study, with the covalent motif maintained, we aim to improve the activity by introducing the terminal fused heterocycles and meanwhile revealing the SAR on the part. As a result, compounds 9 and 14 showed the best activity (EC50 = 148.4 and 595.9 nM) against necroptosis among the analogues by covalently binding to MLKL. The SAR was also concluded to guide further structural optimization in this field.

Proteolysis Targeting Chimera Degraders of the METTL3-14 m6A-RNA Methyltransferase

Methylation of adenine N6 (m6A) is the most frequent RNA modification. On mRNA, it is catalyzed by the METTL3-14 heterodimer complex, which plays a key role in acute myeloid leukemia (AML) and other types of blood cancers and solid tumors. Here, we disclose the first proteolysis targeting chimeras (PROTACs) for an epitranscriptomics protein. For designing the PROTACs, we made use of the crystal structure of the complex of METTL3-14 with a potent and selective small-molecule inhibitor (called UZH2). The optimization of the linker started from a desfluoro precursor of UZH2 whose synthesis is more efficient than that of UZH2. The first nine PROTAC molecules featured PEG- or alkyl-based linkers, but only the latter showed cell penetration. With this information in hand, we synthesized 26 PROTACs based on UZH2 and alkyl linkers of different lengths and rigidity. The formation of the ternary complex was validated by a FRET-based biochemical assay and an in vitro ubiquitination assay. The PROTACs 14, 20, 22, 24, and 30, featuring different linker types and lengths, showed 50% or higher degradation of METTL3 and/or METTL14 measured by Western blot in MOLM-13 cells. They also showed substantial degradation on three other AML cell lines and prostate cancer cell line PC3.

STING signaling in the brain: Molecular threats, signaling activities, and therapeutic challenges

Stimulator of interferon genes (STING) is an innate immune signaling protein critical to infections, autoimmunity, and cancer. STING signaling is also emerging as an exciting and integral part of many neurological diseases. Here, we discuss recent advances in STING signaling in the brain. We summarize how molecular threats activate STING signaling in the diseased brain and how STING signaling activities in glial and neuronal cells cause neuropathology. We also review human studies of STING neurobiology and consider therapeutic challenges in targeting STING to treat neurological diseases.

Covalent PROTAC design method based on a sulfonyl pyridone probe

Covalent proteolysis-targeting chimeras (PROTACs) offer enhanced selectivity, prolonged action, and increased efficacy against challenging target proteins. The conventional approach relies on covalent ligands, but our study presents an innovative method employing an N-sulfonyl pyridone warhead to selectively target tyrosine (Tyr) residues. The von Hippel-Lindau (VHL) moiety is transferred from the warhead to the exposed Tyr, allowing us to design a STING degrader (DC50 0.53 μM, Dmax 56.65%). This approach showcases the potential of nucleophilic amino acid labeling probes, particularly for proteins lacking easily accessible cysteine residues, opening new possibilities for covalent PROTAC design and targeted protein degradation therapies.

Microtubule-destabilizing agents enhance STING-mediated innate immune response via biased mechanism in human monocyte cells

The stimulator of the interferon gene (STING) signaling pathway acts as a primary defense system against DNA pathogens. Because of the crucial role of STING in type I interferon (IFN) response and innate immunity, extensive research has been conducted to elucidate the roles of various effector molecules involved in STING-mediated signal transduction. However, despite the substantial contribution of microtubules to the immune system, the association between the STING signaling pathway and microtubules remains unclear. In this study, we revealed that the modulation of STING via microtubule-destabilizing agents (MDAs) specifically induced type I IFN responses rather than inflammatory responses in human monocytes. Co-treatment of MDAs with STING agonists induced the elevation of phospho-TANK-binding kinase 1 (TBK1), amplifying the innate immune response. However, during the deficiency of TBK1, the non-canonical signaling pathway through nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) contributed to MDA-induced STING activation in type I IFN response which suggested the versatile regulation of MDA in STING-mediated immunity.

The role of cGAS-STING signaling in ischemic stroke: From immune response to therapeutic targeting

Stroke, a debilitating condition with limited treatment options, presents a significant therapeutic challenge. A comprehensive grasp of stroke pathophysiology is imperative for designing newer and more effective therapeutic approaches. Notably, the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway has emerged as a central orchestrator of the poststroke immune response. It regulates pivotal processes, including immune cell activation, cytokine production, neuroinflammation, apoptosis, and tissue regeneration. Modulating this pathway shows immense potential in improving stroke outcomes, necessitating the development of selective inhibitors and activators. This review provides an overview of the cGAS-STING pathway's role in ischemic stroke and explores emerging therapies, including cGAS and STING inhibitors and STING agonist preconditioning. It also addresses challenges like specificity, timing, and off-target effects.

The role of cGAS-STING signaling in pulmonary fibrosis and its therapeutic potential

Pulmonary fibrosis is a progressive and ultimately fatal lung disease, exhibiting the excessive production of extracellular matrix and aberrant activation of fibroblast. While Pirfenidone and Nintedanib are FDA-approved drugs that can slow down the progression of pulmonary fibrosis, they are unable to reverse the disease. Therefore, there is an urgent demand to develop more efficient therapeutic approaches for pulmonary fibrosis. The intracellular DNA sensor called cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) synthase (cGAS) plays a crucial role in detecting DNA and generating cGAMP, a second messenger. Subsequently, cGAMP triggers the activation of stimulator of interferon genes (STING), initiating a signaling cascade that leads to the stimulation of type I interferons and other signaling molecules involved in immune responses. Recent studies have highlighted the involvement of aberrant activation of cGAS-STING contributes to fibrotic lung diseases. This review aims to provide a comprehensive summary of the current knowledge regarding the role of cGAS-STING pathway in pulmonary fibrosis. Moreover, we discuss the potential therapeutic implications of targeting the cGAS-STING pathway, including the utilization of inhibitors of cGAS and STING.

Target protein degradation by protacs: A budding cancer treatment strategy

Cancer is one of the most common causes of death. So, its lethal effect increases with time. Near about hundreds of cancers are known in humans. Cancer treatment is done to cure or prolonged remission, and shrinkage of the tumor. Cytotoxic agents, biological agents/targeted drugs, hormonal drugs, surgery, radiotherapy/proton therapy, chemotherapy, immunotherapy, and gene therapy are currently used in the treatment of cancer but their cost is high and cause various side effects. Seeing this, some new targeted strategies such as PROTACs are the need of the time. Proteolysis targeting chimera (PROTAC) has become one of the most discussed topics regarding cancer treatment. Few of the PROTAC molecules are in the trial phases. PROTACs have many advantages over other strategies such as modularity, compatibility, sub-stoichiometric activity, acting on undruggable targets, molecular design, and acts on intracellular targets, selectivity and specificity can be recruited for any cancer, versatility, and others. PROTACs are having some unclear questions on their pharmacokinetics, heavy-molecular weight, etc. PROTACs are anticipated to bring about a conversion in current healthcare and will emerge as booming treatments. In this review article we summarize PROTACs, their mechanism of action, uses, advantages, disadvantages, challenges, and future aspects for the successful development of potent PROTACs as a drug strategy.

Recent trends in STING modulators: Structures, mechanisms, and therapeutic potential

The cyclic GMP-AMP synthase stimulator (cGAS)-stimulator of interferon gene (STING) signaling pathway has an integral role in the host immune response through DNA sensing followed by inducing a robust innate immune defense program. STING has become a promising therapeutic target associated with multiple diseases, including various inflammatory diseases, cancer, and infectious diseases, among others. Thus, modulators of STING are regarded as emerging therapeutic agents. Recent progress has been made in STING research, including recently identified STING-mediated regulatory pathways, the development of a new STING modulator, and the new association of STING with disease. In this review, we focus on recent trends in the development of STING modulators, including structures, mechanisms, and clinical application.

STING signaling in inflammaging: a new target against musculoskeletal diseases

Stimulator of Interferon Gene (STING) is a critical signaling linker protein that plays a crucial role in the intrinsic immune response, particularly in the cytoplasmic DNA-mediated immune response in both pathogens and hosts. It is also involved in various signaling processes in vivo. The musculoskeletal system provides humans with morphology, support, stability, and movement. However, its aging can result in various diseases and negatively impact people's lives. While many studies have reported that cellular aging is a leading cause of musculoskeletal disorders, it also offers insight into potential treatments. Under pathological conditions, senescent osteoblasts, chondrocytes, myeloid cells, and muscle fibers exhibit persistent senescence-associated secretory phenotype (SASP), metabolic disturbances, and cell cycle arrest, which are closely linked to abnormal STING activation. The accumulation of cytoplasmic DNA due to chromatin escape from the nucleus following DNA damage or telomere shortening activates the cGAS-STING signaling pathway. Moreover, STING activation is also linked to mitochondrial dysfunction, epigenetic modifications, and impaired cytoplasmic DNA degradation. STING activation upregulates SASP and autophagy directly and indirectly promotes cell cycle arrest. Thus, STING may be involved in the onset and development of various age-related musculoskeletal disorders and represents a potential therapeutic target. In recent years, many STING modulators have been developed and used in the study of musculoskeletal disorders. Therefore, this paper summarizes the effects of STING signaling on the musculoskeletal system at the molecular level and current understanding of the mechanisms of endogenous active ligand production and accumulation. We also discuss the relationship between some age-related musculoskeletal disorders and STING, as well as the current status of STING modulator development.

The Many Ways to Deal with STING

The stimulator of interferon genes (STING) is an adaptor protein involved in the activation of IFN-β and many other genes associated with the immune response activation in vertebrates. STING induction has gained attention from different angles such as the potential to trigger an early immune response against different signs of infection and cell damage, or to be used as an adjuvant in cancer immune treatments. Pharmacological control of aberrant STING activation can be used to mitigate the pathology of some autoimmune diseases. The STING structure has a well-defined ligand binding site that can harbor natural ligands such as specific purine cyclic di-nucleotides (CDN). In addition to a canonical stimulation by CDNs, other non-canonical stimuli have also been described, whose exact mechanism has not been well defined. Understanding the molecular insights underlying the activation of STING is important to realize the different angles that need to be considered when designing new STING-binding molecules as therapeutic drugs since STING acts as a versatile platform for immune modulators. This review analyzes the different determinants of STING regulation from the structural, molecular, and cell biology points of view.

Development of VHL-recruiting STING PROTACs that suppress innate immunity

STING acts as a cytosolic nucleotide sensor to trigger host defense upon viral or bacterial infection. While STING hyperactivation can exert anti-tumor effects by increasing T cell filtrates, in other contexts hyperactivation of STING can contribute to autoimmune and neuroinflammatory diseases. Several STING targeting agonists and a smaller subset of antagonists have been developed, yet STING targeted degraders, or PROTACs, remain largely underexplored. Here, we report a series of STING-agonist derived PROTACs that promote STING degradation in renal cell carcinoma (RCC) cells. We show that our STING PROTACs activate STING and target activated/phospho-STING for degradation. Locking STING on the endoplasmic reticulum via site-directed mutagenesis disables STING translocation to the proteasome and resultingly blocks STING degradation. We also demonstrate that PROTAC treatment blocks downstream innate immune signaling events and attenuates the anti-viral response. Interestingly, we find that VHL acts as a bona fide E3 ligase for STING in RCC; thus, VHL-recruiting STING PROTACs further promote VHL-dependent STING degradation. Our study reveals the design and biological assessment of VHL-recruiting agonist-derived STING PROTACs, as well as demonstrates an example of hijacking a physiological E3 ligase to enhance target protein degradation via distinct mechanisms.

Potential Therapeutic Value of the STING Inhibitors

The stimulator of interferon genes (STING) is a critical protein in the activation of the immune system in response to DNA. It can participate the inflammatory response process by modulating the inflammation-preferred translation program through the STING-PKR-like endoplasmic reticulum kinase (PERK)-eIF2α pathway or by inducing the secretion of type I interferons (IFNs) and a variety of proinflammatory factors through the recruitment of TANK-binding kinase 1 (TBK1) and interferon regulatory factor 3 (IRF3) or the regulation of the nuclear factor kappa-B (NF-κB) pathway. Based on the structure, location, function, genotype, and regulatory mechanism of STING, this review summarizes the potential value of STING inhibitors in the prevention and treatment of infectious diseases, psoriasis, systemic lupus erythematosus, non-alcoholic fatty liver disease, and other inflammatory and autoimmune diseases.

A path towards personalized medicine for autoinflammatory and related diseases

The human genome project led to the advancement of genetic technologies and genomic medicine for a variety of human diseases, including monogenic autoimmune and autoinflammatory diseases. As a result, the genome of an individual can now be rapidly sequenced at a low cost, and this technology is beginning to change the practice of rheumatology. In this Perspective, we describe how new sequencing technologies combined with careful clinical phenotyping have led to the discovery of rare rheumatic diseases and their corresponding disease-causing mutations. Additionally, we explore ways in which single-gene mutations, including somatic mutations, are creating opportunities to develop personalized medicines. To illustrate this idea, we focus on diseases affecting the TREX1-cGAS-STING pathway, which is associated with monogenic autoinflammatory diseases and vasculopathies. For many of the affected patients and families, there is an urgent, unmet need for the development of personalized therapies. New innovations related to small molecular inhibitors and gene therapies have the potential to benefit these families, and might help drive further innovations that could prove useful for patients with more common forms of autoimmunity and autoinflammation.

Discovery of Novel Protein Degraders Based on Bioorthogonal Reaction-Driven Intracellular Self-Assembly Strategy

Proteolysis targeting chimera (PROTAC) is a promising therapeutic modality capable of degrading undruggable proteins and overcoming the shortcomings of traditional inhibitors. However, the molecular weight and pharmaceutical properties of PROTACs fall outside of a reasonable range. To overcome the inherent poor druggability of PROTACs, an intracellular self-assembly strategy based on bio-orthogonal reaction was proposed and applied in this study. Herein, two novel classes of intracellular precursors that can self-assemble into protein degraders through bio-orthogonal reactions were explored, including a novel class of E3 ubiquitin ligase ligands bearing tetrazine (E3L-Tz) and target protein ligands incorporated with norbornene (TPL-Nb). These two types of precursors could spontaneously undergo bio-orthogonal reactions in living cells, affording novel PROTACs. Among these precursors, the biological activities of PROTACs formed by target protein ligand with norbornene group (S4N-1) were more potent than others and degrade VEGFR-2, PDGFR-β and EphB4. The results demonstrated that a highly specific bio-orthogonal reaction driven intracellular self-assembly strategy in living cells could be utilized to improve the degradation activity of PROTACs.

STING Suppresses Mitochondrial VDAC2 to Govern RCC Growth Independent of Innate Immunity

STING is an innate immune sensor for immune surveillance of viral/bacterial infection and maintenance of an immune-friendly microenvironment to prevent tumorigenesis. However, if and how STING exerts innate immunity-independent function remains elusive. Here, the authors report that STING expression is increased in renal cell carcinoma (RCC) patients and governs tumor growth through non-canonical innate immune signaling involving mitochondrial ROS maintenance and calcium homeostasis. Mitochondrial voltage-dependent anion channel VDAC2 is identified as a new STING binding partner. STING depletion potentiates VDAC2/GRP75-mediated MERC (mitochondria-ER contact) formation to increase mitochondrial ROS/calcium levels, impairs mitochondria function, and suppresses mTORC1/S6K signaling leading to RCC growth retardation. STING interaction with VDAC2 occurs through STING-C88/C91 palmitoylation and inhibiting STING palmitoyl-transferases ZDHHCs by 2-BP significantly impedes RCC cell growth alone or in combination with sorafenib. Together, these studies reveal an innate immunity-independent function of STING in regulating mitochondrial function and growth in RCC, providing a rationale to target the STING/VDAC2 interaction in treating RCC.

The cyclic guanosine monophosphate synthase-stimulator of interferon genes pathway as a potential target for tumor immunotherapy

Cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) synthase (cGAS) detects infections or tissue damage by binding to microbial or self-DNA in the cytoplasm. Upon binding DNA, cGAS produces cGAMP that binds to and activates the adaptor protein stimulator of interferon genes (STING), which then activates the kinases IKK and TBK1 to induce the secretion of interferons and other cytokines. Recently, a series of studies demonstrated that the cGAS-STING pathway, a vital component of host innate immunity, might play an important role in anticancer immunity, though its mechanism remains to be elucidated. In this review, we highlight the latest understanding of the cGAS-STING pathway in tumor development and the advances in combination therapy of STING agonists and immunotherapy.

Development of SOS1 Inhibitor-Based Degraders to Target KRAS-Mutant Colorectal Cancer

Direct blockade of KRAS driver mutations in colorectal cancer (CRC) has been challenging. Targeting SOS1, a guanine nucleotide exchange factor, has arisen as an attractive approach for KRAS-mutant CRC. Here, we describe the development of novel SOS1 degraders and their activity in patient-derived CRC organoids (PDO). The design of these degraders as proteolysis-targeting chimera was based on the crystal structures of cereblon and SOS1. The synthesis used the 6- and 7-OH groups of a quinazoline core as anchor points to connect lenalidomide. Fifteen compounds were screened for SOS1 degradation. P7 was found to have up to 92% SOS1 degradation in both CRC cell lines and PDOs with excellent specificity. SOS1 degrader P7 demonstrated superior activity in inhibiting CRC PDO growth with an IC₅₀ 5 times lower than that of SOS1 inhibitor BI3406. In summary, we developed new SOS1 degraders and demonstrated SOS1 degradation as a feasible therapeutic strategy for KRAS-mutant CRC.

STING Targeting in Lung Diseases

The cGAS-STING pathway displays important functions in the regulation of innate and adaptive immunity following the detection of microbial and host-derived DNA. Here, we briefly summarize biological functions of STING and review recent literature highlighting its important contribution in the context of respiratory diseases. Over the last years, tremendous progress has been made in our understanding of STING activation, which has favored the development of STING agonists or antagonists with potential therapeutic benefits. Antagonists might alleviate STING-associated chronic inflammation and autoimmunity. Furthermore, pharmacological activation of STING displays strong antiviral properties, as recently shown in the context of SARS-CoV-2 infection. STING agonists also elicit potent stimulatory activities when used as an adjuvant promoting antitumor responses and vaccines efficacy.

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.

Inhibitory targeting cGAS-STING-TBK1 axis: Emerging strategies for autoimmune diseases therapy

The cGAS-STING signaling plays an integral role in the host immune response, and the abnormal activation of cGAS-STING is highly related to various autoimmune diseases. Therefore, targeting the cGAS-STING-TBK1 axis has become a promising strategy in therapy of autoimmune diseases. Herein, we summarized the key pathways mediated by the cGAS-STING-TBK1 axis and various cGAS-STING-TBK1 related autoimmune diseases, as well as the recent development of cGAS, STING, or TBK1 selective inhibitors and their potential application in therapy of cGAS-STING-TBK1 related autoimmune diseases. Overall, the review highlights that inhibiting cGAS-STING-TBK1 signaling is an attractive strategy for autoimmune disease therapy.

Homobivalent, Trivalent, and Covalent PROTACs: Emerging Strategies for Protein Degradation

Proteolysis-targeting chimeras (PROTACs) is a fast-growing technology providing many strengths over inhibition of protein activity directly and is attracting increasing interest in new drug discovery and development. However, efficiently identifying potent and drug-like degraders is still challenging in the development of PROTACs. Complementary to traditional PROTACs, several emerging types of PROTACs, such as homobivalent PROTACs based on two E3 ligases (e.g., CRBN, VHL, MDM2, TRIM24), chemical- or biological-based trivalent/multitargeted PROTACs, and covalent PROTACs, are rising for targeted protein degradation. These new types of PROTACs have several advantages over the traditional PROTACs including high selectivity, low toxicity, better therapeutic effects, and so on. In this perspective, we will summarize the latest development of representative PROTACs focusing on research mainly in past 10 years and discuss their advantages and disadvantages. Moreover, the outlook and perspectives on the associated challenges and future directions will be provided.