ST-00937

近年来，靶向蛋白质降解剂（TPD）逐渐走进人们的视野，以PROTAC、分子胶为代表的靶向蛋白降解技术已发展为小分子药物的重要模式。 从2019年首个PROTAC分子（ARV-110）进入临床开始，层出不穷的蛋白降解剂相继进入临床研究阶段。受益于独特的作用机制，蛋白降解剂不仅能靶向以往难成药的靶点，还为耐药患者提供了可选治疗方案。 图1. 蛋白降解剂发展时间线[1] 根据医药魔方NextPharma®数据库，蛋白降解剂早期研发主要围绕AR、ER、BTK等靶点。如今，蛋白降解领域迎来了新的发展阶段，研究人员正将目光投向更多新颖的靶标领域。 越来越多的蛋白降解剂管线显示，传统上难以成药的靶标（如IKZF1/3、GSPT1、VAV1、WIZ、BCL6等）正变得越来越容易实现（表1）。这一转变标志着靶向蛋白质降解技术的应用范围正在不断扩大，为药物研发带来了新的机遇和挑战。 表1. 靶向蛋白降解领域的靶点[2] 分子胶的新发现 科学家通过对来那度胺（FDA批准的多发性骨髓瘤药物）及其相关免疫调节药物（IMiDs）的作用机制进行深入研究，发现了这些药物能够结合并重塑E3泛素连接酶CRBN，进而促进转录因子IKZF1和IKZF3（IKAROS家族锌指转录因子1/3）的泛素化。研究人员进一步认识到，其他分子胶可能也具备重塑CRBN的潜力，从而能够靶向更多蛋白质。 尽管如此，早期进入临床的项目仍然集中在来那度胺所降解的靶点上。例如，Celgene（2019年被BMS收购）基于来那度胺类似物发现了CC-92480（又名mezigdomide），并对其进行优化，以降解IKZF1和IKZF3。目前，该药物正处于多发性骨髓瘤的III期临床开发阶段。此外，激酶CK1α作为来那度胺的另一个降解靶点，也成为了早期开发的重点。 GSPT1（G1 to S phase transition 1）是一种翻译终止因子，通过与eRF1结合识别终止密码子，迫使蛋白质在翻译后与核糖体分离。GSPT1的下调可导致多种肿瘤细胞中关键蛋白的异常表达，抑制肿瘤细胞增殖或诱导其凋亡。BMS在2016年首次将GSPT1降解剂CC-90009推进到临床阶段，但后来由于未公开的原因终止了该项目。 GSPT1的降解可能会关闭整体蛋白质翻译，并可能引发许多不良事件。为了提高GSPT1降解的有效性和耐受性，BMS转向了抗体-分子胶偶联物策略。BMS-986497分子将GSPT1降解分子胶和CD33靶向抗体结合，这样能更有效地将降解剂递送到癌细胞。 今年7月，诺华在Science杂志发表论文，他们发现了一种基于CRBN的、能够靶向转录因子WIZ的分子胶降解剂。该分子胶可以提高小鼠和灵长类动物体内的胎儿血红蛋白（fetal hemoglobin，HbF）水平。这一发现表明，分子胶有望为开发治疗镰状细胞病（SCD）的新药铺平道路。 新靶点，新征程 Monte Rosa是开发靶向GSPT1分子胶的先驱之一，他们研发的MRT-2359临床表现出色，在MYC驱动的实体瘤患者中具有良好的治疗指数和可耐受的安全性。随着其降解平台的建立，Monte Rosa发现了更多的靶点，VAV1就是其中之一。Monte Rosa首席执行官Markus Warmuth表示：“我确信，在过去10-20年里，大型制药公司的每个免疫学团队都曾关注过VAV1这一靶点。” VAV1是一种鸟嘌呤核苷酸交换因子（GEF），与B细胞和T细胞的信号传导密切相关。Monte Rosa研发的VAV1降解剂MRT-6160在自身免疫性疾病动物模型中显示出临床前疗效，效果与标准治疗（JAK抑制剂和S1P调节剂）相当。目前，这种降解剂已进入临床I期试验，并将在自身免疫性疾病中进一步的试验。 此外，转录因子IKZF1和IKZF3是经典的CRBN的新底物。研究人员指出，数百种转录因子含有G-loop的C2H2锌指结构（包括IKZF2和WIZ），这为分子胶降解剂提供了更多潜在靶点。然而，像GSPT1和CK1α这样的非转录因子蛋白中的CRBN新底物，也携带G-loop降解结构域，使它们也处于IMiDs的作用范围内。 目前，大多数分子胶是偶然发现的。人体内有600多种E3连接酶，但目前的分子胶大多是基于CRBN，所以开发可招募除CRBN外的其他E3连接酶的分子胶，成为理性设计的重要策略。 SEED Therapeutics正在研发一种利用DCAF15连接酶降解剪接因子RBM39（一种调节mRNA前体剪接的蛋白质）的分子胶降解剂，该公司的ST-00937分子能够通过重塑DCAF15来泛素化RBM39，目前处于临床前阶段，预计明年进入临床阶段。除ST-00937外，SEED Therapeutics还有近10款在研药物，它们都不依赖于常用的CRBN和VHL（另一种常用的E3泛素连接酶）。 PROTAC的探索之路 异双功能降解剂（heterobifunctional）是一种“哑铃状”分子，具有独特的结构：一端结合目标蛋白（POI），另一端则与E3泛素连接酶相互作用。首批进入临床的蛋白降解剂主要集中在已有上市药物的靶点。 然而，Kymera Therapeutics采取了不同的策略，专注于开发哪些尚未有上市药物的靶点。Kymera Therapeutics的首个进入临床的PROTAC项目靶向IRAK4，这是一个在调节IL-1受体和Toll样受体（TLR）信号通路方面具有重要的作用的蛋白。由于IRAK4的活性既包括酶活性，也包括作为骨架蛋白的功能，因此蛋白降解剂可能比酶活性抑制剂具有更好的效果。Kymera Therapeutics的潜在first-in-class蛋白降解剂KT-474目前处于IIb期试验中，它是首个进入非肿瘤学适应症领域中，进入临床开发阶段的PROTAC分子。 Kymera Therapeutics的下一个临床候选药物KT-621是一种靶向STAT6的PROTAC分子，能够用于特应性皮炎（AD）、哮喘以及慢性阻塞性肺病等疾病。今年10月，Kymera宣布其KT-621的IND已获FDA批准，预计将在不久后在健康志愿者中开展I期试验。 BCL6是一种转录抑制因子，它通过BCL6的BTB结构域招募辅助抑制因子，调节B淋巴细胞的分化，并在生发中心（GCs）的形成中发挥作用。由于BCL6在转录抑制因子复合体中的不受调控的表达和支架作用，使其成为一个理想的PROTAC靶点。 Arvinas公司研发的ARV-393是一种靶向BCL6蛋白的PROTAC药物，目前正在进行临床I期研究。初步研究显示，ARV-393在体内外均能显著降解BCL6，并在多种肿瘤异种移植模型中表现出良好的肿瘤生长抑制（TGI）效果。BMS-986458是由BMS研发的一种BCL6降解剂，目前也处于临床I期，用于治疗非霍奇金淋巴瘤。 结语 从最初偶然发现的沙利度胺，到如今几百条蛋白降解剂管线；从开发已有上市药物的成熟靶点，到探索新一代靶点；从肿瘤领域，到神经退行性疾病、自身免疫性疾病、炎症性疾病等领域……蛋白降解的应用正被不断拓宽，随着更多新靶点的探索和新药物的开发，蛋白降解技术有望在未来实现更多的突破和创新。 参考资料： [1]Brandon Dale et al. Advancing targeted protein degradation for cancer therapy. Nature Reviews Cancer（2021） https://www.nature.com/articles/s41568-021-00365-x [2]Asher Mullard. Protein degraders push into novel target space. Nature Reviews Drug Discovery（2024） https://www.nature.com/articles/d41573-024-00170-9 Copyright © 2024 PHARMCUBE. All Rights Reserved. 欢迎转发分享及合理引用，引用时请在显要位置标明文章来源；如需转载，请给微信公众号后台留言或发送消息，并注明公众号名称及ID。 免责申明：本微信文章中的信息仅供一般参考之用，不可直接作为决策内容，医药魔方不对任何主体因使用本文内容而导致的任何损失承担责任。

NEW YORK, Oct. 26, 2023 (GLOBE NEWSWIRE) -- SEED Therapeutics Inc. (“SEED”), a biotech company focused on harnessing and engineering Molecular Glues for targeted protein degradation (TPD) of disease-causing proteins, announced at its Monday, October 23, 2023 Targeted Protein Degradation (TPD) Think Tank symposium that it had successfully discovered a ST-00937, a new chemical entity (NCE) molecular glue that has already achieved IND Candidate status and will be advanced for the treatment of cancers in SEED’s first IND filing, as early as 2024. SEED is a subsidiary of BeyondSpring, Inc. (NASDAQ: BYSI), a clinical-stage biopharmaceutical company focusing on developing innovative therapies. Dr. James Tonra, SEED President, and Chief Scientific Officer, said, “Preclinical data over the last two to three years has uncovered new and important cancer indications for agents that can inhibit or degrade the RNA splicing factor RBM39, but clinical activity in these new indications is minimal or absent.” According to Dr. Tonra, SEED’s research and development scientists recognized this unmet need, as well as the opportunity to discover yet unrecognized additional indications for an RBM39 targeted molecular glue. “Our seasoned R&D team proceeded to discover and patent application for an oral RBM39 degrader that causes complete tumor regressions in select tumor models without detectable toxicities. SEED’s rapid progress on this program towards clinical testing within a year of project initiation reflects the power and potential of TPD science, as well as SEED’s expertise and determination to lead the way to patient benefits and the first regulatory approval with an RBM39 degrader.” The SEED TPD Think Tank was led by SEED Co-Founders who are at the forefront of TPD thought leadership: Nobel Laureate Dr. Avram Hershko, who uncovered the Ubiquitin Proteasome System almost 50 years ago; SEED Chairman and CEO Dr. Lan Huang, who pioneered the understanding of E3 ligase structure by solving the first E3 ligase structure over 20 years ago; Professor Michele Pagano, Howard Hughes Medical Institute Investigator, TPD biology and cancer expert, and chair of New York University biochemistry and molecular pharmacology departments; and Professor Ning Zheng, Howard Hughes Medical Institute Investigator, TPD structural biologist, and Professor of Pharmacology at the University of Washington. According to Dr. Huang, “The SEED TPD Think Tank shared key TPD developments across academia and industry. But importantly, our SEED Co-Founders, our invited TPD field thought leaders who also presented, and our domestic and foreign attendees engaged in an interactive session that encouraged and challenged scientists, researchers, and developers to extend the boundaries and prospects for TPD through new thinking on TPD molecular mechanism, structural basis, protein proximity in live cells, rational degrader design, and the use of AI-based modeling and computation to speed up discovery efforts.” Invited presenters shared their latest research and insights on translating TPD science to overcoming the hurdles to target “undruggable” disease-causing proteins: Prof. Chittaranjan Das, Purdue University, E3 Ligase Structure Prof. Gaurav Bhardwaj, University of Washington, Computational Design Prof. Lan Huang, University of California Irvine, Proteomics/Proximity Prof. Luca Busino, University of Pennsylvania, TPD Cancer Biology Dr. Jesus Izaguirre, AtomMap, AI Drug Design According to Dr. Huang, “The full impact of TPD on human disease can only be realized with continued scientific advancements on the selection of right E3 ligase for most, if not all disease-causing protein.” Dr. Huang concluded: “At SEED, we thrive on our ability to leverage the scientific leadership of our distinguished Co-Founders. Their research, insight, and conviction allow SEED to focus and accelerate basic research into a fast-expanding TPD drug pipeline, enabled by our unique ability to identify the right E3. This symposium provided a valuable exchange on new directions, opportunities, and challenges on TPD drug development. Together, we are building an exciting ecosystem of best minds in TPD field that will continue to benefit from open collaborations and synergies between academic and industry, as we continue to translate high science into medicine for patients with significant unmet medical needs.” The first “TPD Think Tank” symposium was held at SEED Therapeutics’ laboratory in King of Prussia, PA. About SEED Therapeutics SEED Therapeutics is an innovative biotech company focusing on harnessing and engineering “molecular glues” and targeted protein degradation (TPD) to attack previously undruggable targets. Backed by a comprehensive intellectual property portfolio, SEED Therapeutics' mission is to positively impact human health by creating novel protein degradation therapeutics to treat various severe diseases that currently have limited treatment options for patients and their families. Through ongoing collaborations with world-leading academic experts in the field, SEED Therapeutics is developing a growing pipeline of novel drug candidates on a path to potential clinical and commercial success. SEED has an initial R&D collaboration and investment from Eli Lilly and Company. Learn more by visiting . About BeyondSpring BeyondSpring (NASDAQ: BYSI) is a global clinical-stage biopharmaceutical company focusing on developing innovative therapies to improve clinical outcomes for patients with high unmet medical needs. The Company is advancing its first-in-class lead asset, Plinabulin, as a direct anti-cancer agent in various cancer indications and to prevent chemotherapy-induced neutropenia. Its pipeline also includes three preclinical immuno-oncology assets. Additionally, BeyondSpring’s subsidiary, SEED Therapeutics, leverages a proprietary targeted protein degradation (TPD) drug discovery platform and has an initial R&D collaboration with Eli Lilly and Company. Learn more by visiting . Investor Contact: IR@beyondspringpharma.com Media Contact: PR@beyondspringpharma.com