Allosteric Costimulatory Blockade

蛋白质-蛋白质相互作用（PPI）是所有蛋白质功能的最终决定因素，很少能被小分子调节，因为相应的蛋白质界面没有足够的结合口袋。最近，一种有趣的替代方案已经被认可为组成型多聚蛋白，如重要的TNF超家族（TNFSF）中的蛋白，通过变构机制扭曲其中一个结合伙伴。由于我们最近发现了CD40¿CD154共刺激相互作用的第一个小分子抑制剂，它是该家族的一员，我们建议利用这种机制可能带来的优势，并且(1)确认变构、三聚体扭曲机制干扰CD40¿CD154共刺激蛋白相互作用的可行性，CD40¿CD154共刺激蛋白相互作用是TNFSF的一员，在免疫应答的激活中起重要作用；(2)利用这些信息设计适合治疗应用的改进的小分子抑制剂，并确认最有希望的抑制剂的免疫抑制活性，(3)研究是否可以在TNF超家族的其他成员（特别是OX40¿OX40L， BAFF- r¿BAFF, RANK¿RANKL, 4- 1bb¿4- 1BBL）中发现类似的机制，以及是否可以用来识别特定的抑制剂。TNFSF共刺激相互作用在有效免疫反应的发展中起着关键作用，但直到最近，它们和大多数其他ppi一样，被认为是“不可药物”的。现在已经有人提出，这种对CD40 - CD154和其他TNFSF家族成员的抑制可能是通过一种独特的变构机制发生的，即干扰分子不是插在受体-配体界面之间，而是插在三聚体配体（或受体）的单体单元之间。这可以允许更有效的结合，使这些相互作用特别容易被小分子靶向。虽然通常用于高通量筛选的“类药物”化学文库现在被认为不太适合抑制PPI，但我们抑制剂的化学空间可以快速探索这种组成型同源三聚体细胞因子的新机制，并可以为涉及TNF超家族相互作用的许多疾病领域带来新的药理工具和新的创新药物。对CD40 - CD154和TNF超家族的其他受体-配体对的小分子抑制的详细机制理解的发展，可以导致开发新的、临床可行的方法，解决T、B和APC细胞中共刺激分子功能失调引起的治疗需求，如自身免疫性疾病和移植排斥。因此，提出的工作应该导致阐明一个有趣的新机制，可以使小分子共刺激阻断成为可能，并为涉及TNF超家族相互作用的许多疾病领域提供新的药理工具和新的创新药物。由于我们在小分子药理学、药物化学、分子生物学、细胞移植和免疫生物学方面的专业知识的独特结合，我们相信我们的团队在这些方面取得了相当大的进展。

Protein-protein interactions (PPI), which are the ultimate determinants of the function of all proteins, can rarely be modulated by small molecules because the corresponding protein interfaces do not have adequate binding pockets. Recently, an intriguing alternative has been recognized for constitutively multimeric proteins such as those in the important TNF superfamily (TNFSF) via an allosteric mechanism that distorts one of the binding partners. Since we have recently identified the first small-molecule inhibitors of the CD40¿CD154 costimulatory interaction, which is a member of this family, we propose to exploit the possible advantages that can be derived from such a mechanism and (1) confirm the feasibility of an allosteric, trimer-distorting mechanism in interfering with the CD40¿CD154 costimulatory proteinprotein interaction, a member of the TNFSF that plays an important role in the activation of immune responses, (2) use this information and design improved small-molecule inhibitors suitable for therapeutic applications and to confirm the immunosuppressive activity of the most promising inhibitors, and (3) investigate whether similar mechanism can be found for other members of the TNF superfamily (in particular, OX40¿OX40L, BAFF-R¿BAFF, RANK¿RANKL, 4-1BB¿4- 1BBL) and whether it can be used to identify specific inhibitors. TNFSF costimulatory interactions play key roles in the development of effective immune responses, but until relatively recently, they, just as most other PPIs, were considered ¿undruggable¿. It has now been suggested that such inhibitions for CD40¿CD154 and other members of the TNFSF family might occur via a unique allosteric mechanism whereby the disruptor molecule intercalates not between the receptorligand interface, but between monomeric units of the trimeric ligand (or receptor). This can allow more efficient binding making these interactions particularly targetable by small molecule. Whereas ¿drug-like¿ chemical libraries commonly used for high-throughput screening are now recognized to not be well-suited for PPI inhibition, the chemical space of our inhibitors can allow quick exploration of this novel mechanism for constitutively homotrimeric cytokines, and can lead to novel pharmacological tools and new innovative drugs for the many disease areas where TNF superfamily interactions are involved. Development of a detailed mechanistic understanding of the small-molecule inhibition of CD40¿CD154 and possibly other receptor-ligand pairs of the TNF superfamily can lead to the development of novel, clinically feasible approaches addressing therapeutic needs arising from dysregulated functions of costimulatory molecules in T-, B-, and APC cells such as autoimmune diseases and transplant rejection. Accordingly, the proposed work should lead to the elucidation of an intriguing new mechanism that can make possible small-molecule costimulatory blockade as well as to novel pharmacological tools and new innovative drugs for a number of disease areas where TNF superfamily interactions are involved. Because of its unique combination of expertise in small molecule pharmacology, medicinal chemistry, molecular biology, cell transplant, and immunobiology, we believe that our team is very well positioned to achieve considerable progress along these lines.