The design, synthesis and biological evaluation of PROTACs for CREBBP and p300

本项目涉及组蛋白乙酰转移酶CREB结合蛋白(CREBBP)及其密切相关的p300蛋白的蛋白水解靶向嵌合体(PROTAC)的设计、合成和生物学评价。这两种蛋白质都广泛表达，并作为转录共激活因子与多种蛋白质相互作用。因此，CREBBP和p300参与了重要的生物学过程，如增殖、细胞周期和细胞分化。许多人类癌症类型的特征是CREBBP基因的突变，并引起了人们对CREBBP/p300调控作为癌症药物治疗的重要选择的兴趣。然而，到目前为止，还没有对CREBBP或p300具有选择性并允许研究CREBBP或p300生物学功能的基本方面的小分子配体。PROTAC是结合目标蛋白和E3连接酶的嵌合分子。因此，目标蛋白将被泛素化，被蛋白酶体识别，并被降解。在项目开始时，我们将设计和合成一种能降解CREBBP和p300的PROTAC，并在体外研究其对一系列人类癌细胞的生物学作用。Conway教授团队之前的研究发现了一种选择性的高亲和力CREBBP/p300溴域抑制剂，它被认为是目的蛋白的结合基序，并形成了PROTAC设计的基础。作为E3连接酶，我们选择了Cereblon、von Hippel-Lindau(VHL)和MDM2，因为文献中已经为它们建立了沙利度胺、VH032和Nutlin等配体。目的蛋白和E3连接酶的配体由连接体连接，连接体的链长将在构效关系的第一步进行研究，以确保CREBBP和p300的最佳降解。此外，应开发PROTAC以选择性地降解CREBBP或P300。为了实现这一点，我们将根据CREBBP/p300配体的链长和连接点对连接子进行优化，并选择不同的E3配体。最后，我们将验证这样的假设，即这些选择性PROTAC导致癌细胞株中不同的表型，并且CREBBP和p300不是多余的。由此产生的PROTAC将提供工具化合物，以深入了解CREBBP和/或p300的功能，这是传统小分子抑制剂由于缺乏选择性而无法实现的。此外，这些化合物使我们能够更深入地了解它们参与多种癌症类型的发病机制，并为开发新的癌症临床候选药物提供了途径。

This project deals with the design, synthesis and biological evaluation of proteolysis-targeting chimeras (PROTACs) for the histone acetyltransferases CREB binding protein (CREBBP) and the closely related p300. Both proteins are ubiquitously expressed and function as transcriptional coactivators that interact with a multitude of proteins. Thus, CREBBP and p300 are involved in essential biological processes such as proliferation, cell cycle, and cell differentiation. Many human cancer types are characterised by mutations in the CREBBP gene and arouse interest in CREBBP/p300 modulation as an important option in cancer pharmacotherapy. So far, there is no small molecule ligand, that is selective for CREBBP or p300 and would allow to investigate fundamental aspects of the biological function of CREBBP or p300, however.PROTACs are chimeric molecules that bind both the target protein and an E3 ligase. Consequently, the target protein will be ubiquitinated, recognised by the proteasome, and degraded. At the outset of the project, we will design and synthesise a PROTAC to degrade CREBBP and p300 and we will study its biological effects on a series of human cancer cell lines in vitro. Previous studies in the group of Prof. Conway identified a selective high affinity CREBBP/p300 bromodomain inhibitor, which is supposed to act as a binding motif for the protein of interest and forms the basis of the PROTAC design. As E3 ligase, we selected cereblon, von Hippel-Lindau (VHL), and MDM2 because ligands such as thalidomide, VH032, and nutlin have been established for them in the literature. The ligands for the protein of interest and the E3 ligase are connected by a linker, whose chain length will be investigated in the first step of structure-activity relationship to ensure optimised degradation of CREBBP and p300. Moreover, PROTACs shall be developed to selectively degrade either CREBBP or p300. To achieve this, we will optimise the linker in terms of chain length and attachment point of the CREBBP/p300 ligand, and choose different E3 ligase ligands. Finally, we will check the hypotheses that these selective PROTACs cause a different phenotype in cancer cell lines and that CREBBP and p300 are not redundant. The resulting PROTACs would provide tool compounds to obtain insights into CREBBP and/or p300 function, what has not been achieved by conventional small molecule inhibitors due to lack of selectivity. Furthermore, these compounds enable us to gain a deeper understanding of their involvement in the pathogenesis of numerous cancer types and offer access to the development of novel clinical candidates for cancer.