In vitro studies show that SLC15A4 inhibition results in the intracellular degradation of the TASL adapter protein and blockade of inflammatory cytokine production in response to TLR7/8/9 agonists, and these results highlight the early progress developing novel, drug-like inhibitors of SLC15A4.
Abstract
Recent studies have revealed that nucleic acid sensing by the endolysosomal TLRs (TLR7, TLR8, and TLR9) requires coordinated activity of the lysosomal peptide transporter SLC15A4. This peptide transporter interacts with the adaptor protein TASL and is necessary for the recruitment and activation of the transcription factor IRF5. The importance of this signaling pathway in the pathogenesis of autoimmune disease has been highlighted by human genetic variants in SLC15A4, TASL, and IRF5 that are associated with elevated risk of developing systemic lupus erythematosus (SLE), while pre-clinical studies in mouse have shown that genetic knock-out of these genes is protective in multiple autoimmune or inflammatory disease models.
Using structure-based drug design, we have developed a series of novel small molecule SLC15A4 inhibitors. Further optimization of the potency and drug-like properties of these molecules has led to discovery of potential first-in-class lead compounds that exhibit nanomolar cellular potency, favorable in vitro ADME and off-target profiles, and suitable PK properties in mouse that allow for once-daily oral dosing.
In vitro studies show that SLC15A4 inhibition results in the intracellular degradation of the TASL adapter protein and blockade of inflammatory cytokine production in response to TLR7/8/9 agonists. Using in vivo mouse models of TLR-driven acute cytokine production, treatment with an advanced tool compound NTX-348 results in complete suppression of IRF5 phosphorylation and type I interferon production in response to TLR7 or TLR9 agonist treatment.
These results highlight our early progress developing novel, drug-like inhibitors of SLC15A4. SLC15A4 inhibition represent a novel therapeutic approach that may provide clinical benefit as an oral therapy for SLE and other immune-mediated diseases.
All authors are employees or contractors of Nimbus Therapeutics
Therapeutic Approaches to Autoimmunity (THER)
SLC15A4 is a member of the solute carrier superfamily that has been strongly linked to the pathogenesis of the auto‐immune disease SLE. The endo‐lysosomally localized SLC15A4 has traditionally been considered a proton‐dependent histidine and peptide transporter, but has also been shown to facilitate TLR7, 8, and 9 induced IFN‐alpha signaling in B cells and pDCs. New research has shown that SLC15A4 facilitates endo‐lysosomal TLR signaling through a scaffolding interaction with a newly identified signal transducer, termed TASL. This interaction enables TLR7, 8, and 9 induced IRF5 activation, which is a crucial pathway in the pathogenesis of lupus. SLC15A4 is therefore an attractive target for the development of drugs for the treatment of SLE, and several small molecule SLC15A4 binders have now been reported which are capable of inhibiting TLR7, 8, or 9 signaling. This review summarizes the SLC15A4:TASL complex, its link to SLE, existing evidence for the transporter activity of SLC15A4, the current small molecule binders, and tools available for further drug discovery efforts.
Alex L Wilkinson, Dillon Popat, Kathy Sengmany et al.· Pharmacology Research & Pers...· 0 citations
Deletion of MEX3B inhibited caspase-4 and gasdermin D activation, pyroptosis, and secretion of inflammasome-dependent inflammatory cytokines in human cell lines and murine primary macrophages and suggested that MEX3B is a pan-inflammasome regulator targeting inflammatory caspases.
Penghua Wang, Jason G. Cahoon, Duomeng Yang et al.· Journal of Immunology· 0 citations
The TL1A/DR3 and IL-23 pathways exhibit well-documented synergy in driving chronic intestinal inflammation, with TL1A enhancing IFN-γ and IL-17 production in a T cell-intrinsic manner and IL-23 stabilizing the Th17 lineage. We hypothesize that simultaneously co-targeting these two non-redundant axes with a single bispecific agent will deliver superior efficacy by fundamentally reshaping the dysregulated immune landscape in conditions like inflammatory bowel disease (IBD).
We developed a fully human, symmetric 1 + 1 IgG-formatted BsAb. And the Fc portion was engineered to extend serum half-life. Binding affinity for both TL1A and IL-23p19 were determined by surface plasmon resonance (SPR). The dual functionality was assessed using cell-based reporter assays: Inhibition of TL1A-induced NF-κB activation and IL-23-induced STAT3 phosphorylation as well as IL17 secretion from PBMCs. The immune complex formation was assessed by SEC-MALS. In vivo efficacy was determined in human TL1A/IL-23 KI mice using TNBS-induced colitis model. Developability was assessed and PK profile was evaluated in FcRn transgenic mice.
The ES302 demonstrated high-affinity binding to both targets. It potently neutralized both TL1A and IL-23 functionality from in vitro assays. In animal model, the ES302 showed significantly superior efficacy over monospecific therapies, markedly reducing disease activity, histopathological scoring, and pro-inflammatory cytokines. The molecule exhibited low immunogenicity risk, and excellent developability properties, including high Tm value, low viscosity, and superior stability under stress conditions, compatible with high-concentration formulation for subcutaneous administration. Furthermore, ES302 exhibited excellent PK profile (e.g. very long in vivo half-life) in humanized FcRn mice and NHP.
ES302 is a highly differentiated antibody with strong potential for the treatment of inflammatory bowel diseases.
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Therapeutic Approaches to Autoimmunity (THER)
Hongtao Lu, Jing Gao, Dawei Sun et al.· Journal of Immunology· 0 citations
Coronavirus disease 2019 (COVID-19) and influenza share key pathogenic mechanisms, including viral invasion, dysregulated innate immune activation, and the development of severe systemic complications. A central mediator of disease progression in both infections is the hyperactivation of the NLRP3 inflammasome, which drives excessive production of pro-inflammatory cytokines, immunothrombosis, multiorgan injury, and increased mortality. Colchicine possesses a unique pharmacokinetic property of preferential accumulation within myeloid cells, where sufficiently high intracellular concentrations inhibit NLRP3 inflammasome activation. This mechanism provides a biological rationale for preventing the cytokine storm and its downstream consequences when colchicine is administered early during infection. Available pharmacokinetic, toxicological, and clinical evidence suggests that loading doses of colchicine up to approximately 0.05 mg/kg body weight can be administered safely in appropriately selected patients, provided that clinically significant drug–drug interactions and hepatic or renal impairment are carefully excluded. The widely accepted belief that total doses of 7–7.5 mg are inherently lethal appears to reflect historical cases complicated by drug interactions and/or hepatic or renal impairment, rather than toxicity attributable to colchicine dose alone. These observations support reconsideration of current guideline recommendations regarding colchicine dosing. In particular, cumulative doses below 0.1 mg/kg appear to be consistently safe, whereas doses between 0.1 and 0.2 mg/kg are associated with only a low risk of toxicity and rarely with severe intoxication. Reassessment of colchicine dosing strategies may therefore be warranted to optimize NLRP3 inflammasome inhibition and improve outcomes in patients with COVID-19 and influenza.
V. Mitev· International Journal of Mol...· 0 citations
Cytosolic innate immune sensing is essential for maintaining the integrity of barrier tissues such as the skin and gut. The pattern-recognition receptors NOD1 and NOD2 detect bacterial peptidoglycan fragments (muropeptides) to trigger antimicrobial and inflammatory responses. However, how these muropeptides gain access to the cytosol of epithelial cells has remained unclear.
Expression of Slc46a2 and Slc46a3 was analyzed by qRT-PCR, immunofluorescence, and RNA-seq datasets. CRISPR-Cas9—mediated knockout and overexpression studies were performed in epithelial cells to assess NOD1/2 activation using NF-κB reporter, cytokine (IL-8) assays, and labeled muropeptide uptake. Slc46a2⁻/⁻, Slc46a3⁻/⁻, Nod1⁻/⁻, and Nod2⁻/⁻ mice were used in imiquimod-induced psoriasis and DSS or Citrobacter rodentium colitis models. Inflammation and barrier integrity were evaluated by histopathology, cytokine profiling, and immune cell analysis.
Our study identifies a family of solute carrier transporters, SLC46s, as key mediators of this process. We demonstrate that SLC46A2 and SLC46A3 selectively transport DAP- and MDP-type muropeptides, respectively, thereby triggering cytosolic NOD1 and NOD2 activation in epithelial cells. SLC46A2 is highly expressed in epidermal keratinocytes, where its loss impairs DAP-muropeptide uptake and NOD1-dependent responses, leading to reduced psoriatic inflammation in mice. Conversely, SLC46A3 is expressed in intestinal epithelial cells and is required for MDP transport and NOD2 activation. Slc46a3-deficient mice exhibit increased susceptibility to DSS-induced and Citrobacter rodentium-associated colitis, mirroring the pathology of Nod2-/- animals
Together, our findings reveal SLC46 transporters as critical gateways for muropeptide entry into epithelial cells, establishing a mechanistic link between microbial sensing and barrier homeostasis, and suggesting novel therapeutic targets for inflammatory skin and intestinal diseases.
NIH
Innate Immune Responses and Host Defense: Molecular Mechanisms (INM)
Ravi Bharadwaj, Neal Silverman· Journal of Immunology· 0 citations
Selinexor (KPT-330), the first oral selective nuclear export inhibitor, simultaneously modulates key signaling pathways, including NF-κB, JAK/STAT, FOXO, Nrf2, and NLRP3, by blocking XPO1-mediated nuclear export, thereby offering a novel multi-target strategy for treating chronic inflammatory diseases. This review systematically integrates existing preclinical and early clinical evidence within the framework of "cytokine signaling networks", focusing on elucidating the molecular mechanisms and biological effects of selinexor in suppressing proinflammatory factor production, mitigating oxidative stress, and regulating inflammatory tissue-remodeling networks. Recent findings further indicate that SINE compounds can remodel proteostasis, including ankyrin repeat and SOCS box-containing protein 8 (ASB8)/Cullin-RING ligase 5 (CRL5)-associated XPO1 degradation and regulation of the ACE2-TMPRSS2-XPO1 coronavirus-entry network. However, current evidence primarily stems from in vitro and animal studies, and randomized controlled trials in human chronic inflammatory diseases are lacking. Moreover, hematopoietic and gastrointestinal toxicities observed in oncology settings suggest a narrow therapeutic window. This review emphasizes a stepwise translational logic from protein turnover and receptor regulation to next-generation XPO1 inhibitors. At present, selinexor is more suitable as a mechanistic tool for exploring the XPO1-inflammation axis, whereas inflammatory-disease translation will require eltanexor or related agents with more favorable tissue distribution and tolerability, together with precisely stratified clinical studies.
Hai Zhang, Xinyi Liu, Yunhua Zhao et al.· International Immunopharmaco...· 0 citations