AHR

EQ504 targets the aryl hydrocarbon receptor, a clinically validated pathway in the treatment of both skin and gastrointestinal diseases EQ504 has a unique, multi-modal, non-immunosuppressive mechanism of action that is complementary to other immuno-inflammatory therapeutics EQ504 data to be presented in three poster presentations next week at the annual meeting of the American Association of Immunologists (AAI) LA JOLLA, Calif.--(BUSINESS WIRE)-- Equillium, Inc. (Nasdaq: EQ), a clinical-stage biotechnology company leveraging a deep understanding of immunobiology to develop novel therapeutics to treat severe autoimmune and inflammatory disorders, today announced the advancement of a novel and potent aryl hydrocarbon receptor (AhR) modulator (EQ504), which was acquired through the acquisition of Ariagen, a biotechnology company that was majority owned by Equillium’s largest investor, Decheng Capital. AhR is critical to barrier organ tissue physiology and immunology, where it maintains barrier function, promotes tissue repair and regeneration, and regulates resident immune cells and anti-inflammatory responses. Modulation of AhR is a clinically validated pathway in the treatment of both skin and gastrointestinal diseases demonstrating high levels of clinical efficacy. “We’re excited to announce the addition of this promising AhR modulator, representing a target of high strategic interest, to our portfolio of differentiated immunology assets,” said Bruce Steel, chief executive officer at Equillium. “Decheng had been looking for a team to advance development of this asset and believe Equillium is an excellent fit based on our immunology expertise and development capabilities. Aligning both parties’ interests the program was acquired on favorable terms – there was no upfront payment and milestone payments commence upon FDA approval.” “Decades of research has identified the AhR pathway as an important physiological regulator of immune homeostasis in barrier tissues,” said Francisco J. Quintana, Ph.D., Professor of Neurology at the Ann Romney Center for Neurologic Diseases, at Brigham and Women’s Hospital, Harvard Medical School. “Unique to AhR is that its activation can promote both barrier function and anti-inflammatory pathways highlighting it as an attractive therapeutic target. Indeed, the first AhR-activating drug tapinarof (VTAMA®) was recently approved for the treatment of psoriasis and atopic dermatitis while clinical trials are underway to evaluate the effects of AhR modulators in other inflammatory diseases.” Despite a paradigm shift in our understanding of modulating AhR and the growing level of clinical validation, drug development efforts have been hampered by lack of suitable clinical development candidates. EQ504 is a potent and selective AhR modulator with excellent drug-like properties making it amenable to be formulated for targeted, local delivery such as enteric coating for the treatment of ulcerative colitis or inhaled formulations for the treatment of inflammatory lung diseases. “There is significant clinical evidence that AhR modulators are impactful in treating gastrointestinal inflammation where they can resolve inflammation and promote mucosal healing. We believe EQ504 may represent a powerful monotherapy or combination approach to treating ulcerative colitis, where poor mucosal healing limits the majority of patients achieving full clinical remission,” said Dr. Stephen Connelly, chief scientific officer at Equillium. “Subject to additional capital, we plan to initiate a phase 1 study to demonstrate targeted proof of mechanism.” Additional data will be presented next week at the annual meeting of the American Association of Immunologists (AAI) in Honolulu, Hawaii. About EQ504 EQ504 is a potent and selective AhR modulator with a unique, multi-modal, non-immunosuppressive mechanism of action that is complementary to other inflammation and immunology agents. AhR is critical to barrier organ tissue physiology and immunology, maintaining barrier function and promoting tissue repair and regeneration, while regulating resident immune cells with anti-inflammatory responses. EQ504 has excellent drug-like properties making it amenable to be formulated for targeted, local delivery such as enteric coating for the treatment of ulcerative colitis or inhaled formulations for the treatment of inflammatory lung diseases. About Equillium Equillium is a clinical-stage biotechnology company leveraging a deep understanding of immunobiology to develop novel therapeutics to treat severe autoimmune and inflammatory disorders with high unmet medical need. The company’s pipeline consists of several novel immunomodulatory assets and product platform targeting immuno-inflammatory pathways. For more information, visit www.equilliumbio.com. Forward Looking Statements Statements contained in this press release regarding matters that are not historical facts are “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995. Forward-looking statements may be identified by the use of words such as “anticipate”, “believe”, “could”, “continue”, “expect”, “estimate”, “may”, “plan”, “outlook”, “future”, “potential” and “project” and other similar expressions that predict or indicate future events or trends or that are not statements of historical matters. These statements include, but are not limited to, statements regarding Equillium’s plans and strategies with respect to developing EQ504, including the initiation of clinical studies and the reporting of data therefrom; the expected timeline for initiating and reporting data from a Phase 1 study of EQ504; the ability to raise additional capital to fund development of EQ504; and the potential benefits of EQ504. Because such statements are subject to risks and uncertainties, many of which are outside of Equillium’s control, actual results may differ materially from those expressed or implied by such forward-looking statements. Risks that contribute to the uncertain nature of the forward-looking statements include: Equillium’s ability to execute its plans and strategies; Equillium’s ability to continue as a going concern; risks related to performing clinical and pre-clinical studies; whether the results from clinical and pre-clinical studies will validate and support the safety and efficacy of Equillium’s product candidates; changes in the competitive landscape; and Equillium’s ability to raise sufficient financing, which may not be available on acceptable terms or at all, to advance EQ504 and fund Equillium’s strategic plans. These and other risks and uncertainties are described more fully under the caption "Risk Factors" and elsewhere in Equillium's filings and reports, which may be accessed for free by visiting the Securities and Exchange Commission’s website and on Equillium’s website under the heading “Investors.” Investors should take such risks into account and should not rely on forward-looking statements when making investment decisions. All forward-looking statements contained in this press release speak only as of the date on which they were made. Equillium undertakes no obligation to update such statements to reflect events that occur or circumstances that exist after the date on which they were made, except as required by law. Corporate Contact Michael Moore Vice President, Investor Relations Officer & Head of Corporate Communications 619-302-4431 ir@equilliumbio.com

-01-引言1976年，美国科学家Poland与Glover在研究剧毒污染物二噁英（TCDD）时，意外发现了一种能与毒素特异性结合的蛋白——芳香烃受体（AHR）。自此近50年间，AHR因介导环境毒素的致癌、致畸作用而被视为"危险分子"，药物研发领域对其避之不及。 然而，近年研究揭示了AHR的另一面：它不仅参与免疫调控，更是连接肠道菌群代谢、膳食营养与疾病机制的核心枢纽。2016年，首个AHR激活剂Tapinarof获批治疗银屑病，标志着这一靶点从"毒理噩梦"正式逆袭为"免疫治疗新星"。-02-一、AHR的结构AHR是含bHLH-PAS结构域的配体依赖性转录因子。AHR在氨基末端包含一个bHLH结构域，这对DNA结合至关重要，其次是两个PAS结构域，PAS-a和PAS-B，以及羧基末端的一个转录激活结构域（TAD）。bHLH结构域介导AHR与特定DNA基序的结合，以控制靶基因的转录活性；它还促进了与ARNT的二聚化。PAS-A参与AHR-ARNT异二聚体的稳定。PAS-B含有一个配体结合口袋，激动剂通过诱导构象变化来结合和激活AHR，从而暴露核定位信号，促进AHR易位到核中。一旦与DNA结合，AHR的C末端TAD就会与转录调节因子和辅激活因子相互作用，激活靶基因的表达。PAS-A和PAS-B结构域之间的铰链区是灵活的，在配体诱导的构象变化中起着至关重要的作用。-03- 二、AHR的配体和信号通路AHR激动剂包括多种外源性和内源性分子。外源配体主要由二恶英等环境污染物组成，二恶英通常是工业过程和燃烧的产物。内源性配体包括几种代谢副产物和天然化合物，如色氨酸衍生物和微生物代谢物。在激动剂结合后，AHR信号机制可分为经典和非经典信号途径。重要的是，AHR信号模式的多样性使细胞能够对各种刺激做出反应，从而促进对细胞环境的适应。典型的AHR信号通路是由激动剂与细胞质中的AHR-伴侣复合物结合启动的。这种相互作用诱导AHR的构象变化，导致AIP从AHR复合物中解离，并暴露出N端核定位信号。AHR激动剂复合物随后与转运蛋白和输入蛋白-β相互作用，后者介导其核输入。一旦进入细胞核，AHR激动剂复合物就会与ARNT异二聚体化。这种异二聚是AHR转录活性的关键步骤，涉及AHR和ARNT的构象变化。AHR–ARNT复合物与特定的DNA序列结合，这些DNA序列包含一个共有的5′-TNGCGG-3′序列，其中AHR与5′-TGCG相互作用，ARNT与序列的GTG-3′半位点相互作用。在多种AHR靶基因中，有异生物质代谢酶，细胞因子IL-10和IL-21以及参与细胞代谢的酶。非典型AHR信号转导涉及核和/或细胞质途径。在核机制中，AHR激动剂复合物与其他转录因子相互作用并调节其活性。例如，AHR通过直接相互作用和间接机制控制核因子-κB（NF-κB）的活性。此外，AHR促进Krüppel样因子4（KLF4）和KLF6驱动的转录程序的表达，而抑制信号转导子和转录激活子（STAT）信号。-04-三、AHR信号的免疫调控作用AHR通过多层次的调控网络（代谢、转录、表观）平衡免疫激活与抑制，其在维持屏障稳态、调控适应性/固有免疫细胞分化及应答中具有重要作用。AHR在免疫系统中的免疫调节作用机制可归纳为以下方面：一、免疫稳态的维持AHR通过调控树突状细胞（DCs）功能，维持肠道上皮细胞的完整性。AHR激活的DCs通过诱导IL-10和IL-22的表达，促进调节性T细胞（Treg）分化，抑制促炎性T细胞（TH17），从而减轻结肠炎等炎症反应。此外，肠道共生菌代谢色氨酸（Trp）生成AHR配体（如吲哚类化合物），AHR激活后增强肠道抗菌肽表达，维持微生物群稳态。二、免疫细胞分化的调控树突状细胞（DCs）：AHR激活的DCs下调MHC II类分子和共刺激分子（CD80/CD86），减少促炎因子（IL-6、IL-12、TNF），并诱导吲哚胺2,3-双加氧酶（IDO1/IDO2）生成色氨酸代谢产物，促进Treg分化。 AHR激动剂（如TCDD）诱导DCs分泌TGF-β和IL-27，增强Tr1细胞生成，Tr1细胞是不表达转录因子Foxp3但产生高水平IL-10的调节性T细胞，从而抑制TH17细胞介导的自身免疫反应。T淋巴细胞：AHR信号通过配体特异性（如TCDD与FICZ）调控T细胞分化。例如： TGF-β联合TCDD诱导Foxp3+ Treg分化，抑制自身免疫；FICZ激活AHR驱动TH17分化，加重实验性自身脑脊髓炎（EAE）等疾病。此外，AHR通过色氨酸代谢生成犬尿氨酸（Kyn），抑制STAT1磷酸化，促进SMAD1介导的免疫抑制。先天性淋巴细胞（ILCs）：AHR对肠道ILC3的存活与功能至关重要，通过诱导IL-7R、Bcl-2和Notch表达，促进IL-22分泌，抵抗病原体（如Citrobacter rodentium）。AHR协同RORγt调控ILC3在感染中的抗菌反应。-05-四、靶向AHR的药物开发自身免疫疾病Tapinarof是一种天然鉴定的具有AHR激动剂活性的二苯乙烯化合物，由Dermavant Sciences开发，并于2022年获得FDA批准，用于治疗成人斑块状银屑病。临床前研究证实，tapinarof是一种直接与AHR-ARNT异二聚体结合的AHR激动剂。它诱导角质形成细胞中CYP1A1和皮肤屏障成分角蛋白、聚丝蛋白、外皮蛋白的表达，以及表皮屏障的神经酰胺脂质成分的表达，并抑制T细胞中促炎细胞因子的表达，包括IL-17A和IL-17F。在治疗成人斑块状银屑病的III期试验中，与赋形剂对照组相比，tapinarof局部用药显示出临床意义和统计学上的显著优势。此外，还观察到持续使用的持久效果和缓解效果。在一项长期扩展研究（PSOARING 3）中，41%接受tapinarof治疗的患者实现了疾病的完全清除，并且在停药后能够维持疾病控制，中位时间为4个月。tapinarof抑制了记忆T细胞在体外的产生、活性和持久性，这些效应可能有助于临床研究中观察到的缓解。DMVT-506是一种与tapinarof具有相似药理学特征的AHR激动剂，Dermavant Sciences正在开发用于其他炎症性疾病的药物。除了局部制剂外，DMVT-506还被开发为IBD的口服缓释剂型，以及哮喘和慢性阻塞性肺病等呼吸系统疾病的干粉吸入剂。Azora Therapeutics正在开发天然AHR激动剂靛玉红的局部和口服制剂，用于治疗过敏性皮炎，Galileo Biosystems正在开发治疗性AHR调节剂，用于治疗炎症和自身免疫性疾病。礼来公司最近为AHR激动剂颁发了两项专利，表明其对炎症领域的积极兴趣。癌症此外，AHR拮抗剂正在癌症患者中进行临床评估。BAY2416964是一种旨在抑制AHR的小分子，其目的是增强对癌症的免疫反应。一项I期临床试验正在确定BAY 2416964在晚期癌症患者中的最高耐受剂量（NCT04069026）。此外，BAY2416964与抗PD-1免疫检查点抑制剂pembrolizumab联合用药治疗晚期实体癌患者，如头颈部癌症、肺癌和癌症（NCT04999202）。同样，另一种名为IK-175（Ikena Oncology）的AHR拮抗剂正在早期试验中作为单一药物和与抗PD-1抗体nivolumab联合使用，用于晚期或转移性实体瘤患者，包括尿路上皮癌（NCT04200963）。其它除了以上的临床试验外，还有20项其他临床试验已经完成或正在进行中，以研究使用内源性和膳食配体以及合成小分子调节AHR的临床效果。在内源性配体中，补充l-色氨酸（一种代谢为AHR激动剂的氨基酸）正在评估对无麸质饮食无反应的活检确诊乳糜泻患者的疗效（NCT05576038）。另一项研究评估了内源性AHR激动剂（如Kyn）在识别与阻塞性睡眠呼吸暂停相关的高血压患者方面的鉴别潜力（NCT04646902）。菊粉是一种来自植物的膳食纤维，通过直接与AHR相互作用或增强AHR与XREs的结合来诱导CYP1A的表达。菊粉对慢性肾病患者肠道微生物组、肠道屏障功能、细菌代谢产物和免疫细胞的影响正在研究中（NCT05071131）。临床前和早期临床研究结果都支持这些化合物的治疗潜力，但在对其临床疗效得出明确结论之前，还需要进一步的临床研究。-06-结语AHR的逆袭史，验证了基础研究颠覆性突破的威力——通过解码生物学本质，曾经的"危险分子"也能蜕变为治疗利器。随着首个AHR药物落地，我们正站在免疫代谢治疗的新起点。未来，期待更多跨界创新将AHR的调控潜力转化为普惠疗法，为自身免疫病、肿瘤、感染性疾病患者带来新曙光。参考资料：1.The aryl hydrocarbon receptor: a rehabilitated target for therapeutic immune modulation. Nat Rev Drug Discov.2025 Apr 17.公众号内回复“ADC”或扫描下方图片中的二维码免费下载《抗体偶联药物：从基础到临床》的PDF格式电子书！公众号已建立“小药说药专业交流群”微信行业交流群以及读者交流群，扫描下方小编二维码加入，入行业群请主动告知姓名、工作单位和职务。

买科研服务（代计算、代测试、超算机时），送老李校长“科研理工男士情感课”第一性原理计算解决50年悬而未决难题：半导体中铜为何扩散更快？Ab initio及第一性原理入门参考书介绍《海贼王》告诉你，做科研为什么不能闭门造车……985博导亲测：用DeepSeek写国自然本子，3天完成30天工作量来自公众号：深究科学本文以传播知识为目的，如有侵权请后台联系我们，我们将在第一时间删除。肠道是人体Th17细胞最为富集的部位，这与肠道作为吸收营养的主要器官，每天需要接触大量外界抗原，包括各种病原微生物的特性密切相关。因为，Th17细胞在清除胞外菌和真菌及维持肠道粘膜屏障的完整性中具有重要作用。而肠道菌群直接参与肠道Th17细胞的诱导。目前，主流观点认为分节丝状菌是诱导肠道Th17细胞的主要细菌。然而，分节丝状菌的生长条件极其苛刻，成人肠道是否有分节丝状菌的定植仍存在很大的争议。2025 年 4 月 11 日，蔡志坚团队，在Immunity期刊发表了题为：A. faecalis induces intestinal T helper 17 cells by promoting E3 ubiquitin ligase Trim21-mediated E3 ubiquitin ligase Fbxw7 degradation的研究论文，发现诱导肠道Th17细胞生成的关键细菌，合理解释了Th17细胞在人体肠道中富集的现象。团队研究发现，E3泛素连接酶Fbxw7可通过降解JunB，减少JunB介导的Ahr转录，进而限制AhR介导的Th17细胞关键转录因子基因Rorc的转录，最终抑制Th17细胞分化。有趣的是，肠固有层和肠系膜淋巴结来源的CD4+ T细胞中Fbxw7水平特异下调，这促使课题组进一步探讨肠道菌群在调节CD4+ T细胞中Fbxw7水平的作用。不出所料，肠道菌群裂解物可直接抑制CD4+ T细胞中Fbxw7的水平。通过肠道菌群培养，16S rRNA测序及无菌小鼠定植实验，课题组发现粪产碱菌是诱导肠道Th17细胞的主要细菌。进一步研究发现粪产碱菌的蛋白成分可通过小G蛋白CDC42依赖的方式被CD4+ T细胞内吞，阻止E3泛素连接酶Trim21与其E2泛素结合酶的结合，抑制Trim21的自泛素化降解，导致Trim21蛋白在胞内的积累。随后，Trim21促进了Fbxw7的泛素化降解。此外，粪产碱菌分泌的外膜囊泡可通过巨胞饮而非CDC42依赖的方式进入CD4+ T细胞，并通过Trim21-Fbxw7轴促进Th17细胞的分化。粪产碱菌在人类生活环境中普遍存在，通过粪便检测，团队发现粪产碱菌在成人粪便的检出率为86%（86/100），而分节丝状菌在成人粪便的检出率为0%（0/100）。表明分节丝状菌作为诱导肠道Th17细胞主要细菌的观点很可能是一种生理悖论。相较于分节丝状菌，粪产碱菌更能合理解释Th17细胞在不同种族、年龄、性别及饮食习惯的人群肠道中富集的现象。综上所述，该研究揭示了肠道菌群通过Trim21-Fbxw7轴诱导肠道Th17细胞生成的关键机制，不仅为肠道菌群如何诱导Th17细胞在大多数人群肠道中富集提供了更科学的解释，还首次报道了肠道菌群可通过直接调控CD4+ T细胞内源性分子，决定CD4+ T细胞分化的命运。此外，该研究还提出肠道菌群可以通过外膜囊泡与CD4+ T细胞进行交流，维持肠道免疫稳态的新概念。浙江大学医学院附属邵逸夫医院沈颖颖、马泽宇、王涵靓及浙江大学附属儿童医院陈英虎为论文共同第一作者，浙江大学医学院免疫学研究所蔡志坚教授为论文通讯作者。该研究受到国家自然科学基金重项目、国家重点研发计划及中原院士基金的的支持。