Discovery of a Highly Selective BET BD2 Inhibitor from a DNA-Encoded Library Technology Screening Hit

Second-generation bromodomain and extra terminal (BET) inhibitors, which selectively target one of the two bromodomains in the BET proteins, have begun to emerge in the literature. These inhibitors aim to help determine the roles and functions of each domain and assess whether they can demonstrate an improved safety profile in clinical settings compared to pan-BET inhibitors. Herein, we describe the discovery of a novel BET BD2-selective chemotype using a structure-based drug design from a hit identified by DNA-encoded library technologies, showing a structural differentiation from key previously reported greater than 100-fold BD2-selective chemotypes GSK620, GSK046, and ABBV-744. Following a structure-based hypothesis for the selectivity and optimization of the physicochemical properties of the series, we identified 60 (GSK040), an in vitro ready and in vivo capable BET BD2-inhibitor of unprecedented selectivity (5000-fold) against BET BD1, excellent selectivity against other bromodomains, and good physicochemical properties. This novel chemical probe can be added to the toolbox used in the advancement of epigenetics research.第二代溴结构域与额外末端结构域（bromodomain and extra terminal, BET）抑制剂，可选择性靶向BET蛋白两个溴结构域中的其中一个，近年来逐渐见诸学术报道。此类抑制剂旨在阐明单个溴结构域的生理角色与功能，并评估其相较于全BET抑制剂，是否能在临床场景中展现更优的安全性特征。本文基于结构导向药物设计策略，从DNA编码文库技术筛选得到的命中化合物出发，发现了一种新型BET BD2（溴结构域2）选择性化学型，其结构与此前报道的3种关键的、对BD2选择性达100倍以上的BD2选择性化学型GSK620、GSK046及ABBV-744存在显著差异。基于该系列化合物选择性的结构假说，对其理化性质进行优化后，我们得到了化合物60（GSK040）：这是一款可用于体外实验与体内研究的BET BD2抑制剂，对BET BD1（溴结构域1）展现出前所未有的5000倍选择性，对其他溴结构域亦具备优异的选择性，且理化性质良好。这一新型化学探针可被纳入表观遗传学研究工具库，用于推动表观遗传学相关研究的进展。