Structure-Guided Conformational Restriction Leading to High-Affinity, Selective, and Cell-Active Tetrahydroisoquinoline-Based Noncovalent Keap1-Nrf2 Inhibitors

Inhibition of the protein–protein interaction between Kelch-like ECH-associated protein 1 (Keap1) and nuclear factor erythroid 2-related factor 2 (Nrf2) has been recognized as an attractive approach for treating oxidative stress-related diseases. Here, we present a new series of noncovalent Keap1-Nrf2 inhibitors developed by a conformational restriction strategy of our fluorenone-based compounds previously identified by fragment-based drug discovery. The design was guided by X-ray cocrystal structures, and the subsequent optimization process aimed at improving affinity, cellular activity, and metabolic stability. From the noncyclic compound 7 (Ki = 2.9 μM), a new series of tetrahydroisoquinoline-based Keap1 inhibitors with up to 223-fold improvement in binding affinity (57, Ki = 13 nM), better metabolic stability, and enhanced cellular activity was obtained. In addition, the compounds showed selectivity for the Keap1 Kelch domain across a panel of 15 homologous proteins. We thereby demonstrate the utility of cyclic rigidification in the design of potent and more drug-like Keap1-Nrf2 inhibitors.

抑制Kelch样ECH相关蛋白1（Kelch-like ECH-associated protein 1，Keap1）与核因子红细胞2相关因子2（nuclear factor erythroid 2-related factor 2，Nrf2）之间的蛋白相互作用，已被视为治疗氧化应激相关疾病的极具潜力的策略。本研究通过构象限制策略，对我们此前基于片段药物发现所筛选得到的芴酮类化合物进行改造，得到了一系列全新的非共价Keap1-Nrf2抑制剂。该设计以X射线共晶结构为指导，后续优化工作旨在提升化合物的结合亲和力、细胞活性与代谢稳定性。以非环化合物7（抑制常数Ki=2.9 μM）为起始，我们获得了一系列基于四氢异喹啉的Keap1抑制剂，其结合亲和力最高提升达223倍（化合物57，Ki=13 nM），同时具备更优的代谢稳定性与更强的细胞活性。此外，在包含15种同源蛋白的测试组中，这类化合物对Keap1 Kelch结构域展现出优异的选择性。本研究由此证实了环状刚性化策略在设计强效且更具成药性的Keap1-Nrf2抑制剂中的应用价值。