Repurposing of the RIPK1-Selective Benzo[1,4]oxazepin-4-one Scaffold for the Development of a Type III LIMK1/2 Inhibitor

Benzoxazepinones have been extensively studied as exclusively selective RIP kinase 1 inhibitors. This scaffold binds to an allosteric pocket created by an αC-out/DFG-out conformation. This inactive conformation results in a large expansion of the kinase back pocket, a conformation that has also been reported for LIM kinases. Scaffold hopping is common in the design of orthosteric kinase inhibitors but has not been explored in the design of allosteric inhibitors, mainly due to the typically exclusive selectivity of type III inhibitors. Here, we hypothesized that the shared structural properties of LIMKs and RIPKs could lead to novel type III LIMK inhibitors using the benzoxazepinone scaffold. We report the discovery of a novel LIMK1/2 inhibitor that relies on this scaffold-based approach. The discovered compound 10 showed low nanomolar potency on LIMK1/2 and exceptional selectivity, as confirmed by a comprehensive selectivity panel with residual RIPK activity as the only off-target. The study provides one of the few examples for scaffold hopping for allosteric inhibitors, which are usually associated with exclusive target selectivity.苯并氧氮杂卓酮（Benzoxazepinones）作为具有完全选择性的RIP激酶1（RIPK1）抑制剂已被广泛研究。该药效母核（scaffold）可结合于由αC-out/DFG-out构象所形成的变构口袋。这种非活性构象会导致激酶后口袋大幅扩张，而LIM激酶（LIMKs）也存在该类构象。 母核骨架跃迁（scaffold hopping）在正构激酶抑制剂的设计中极为常见，但在变构抑制剂的研发中尚未得到探索，这主要是因为III型激酶抑制剂通常具有极高的靶点专一性。本研究假设，LIMKs与RIPKs共有的结构特性，可借助苯并氧氮杂卓酮母核骨架开发出新型III型LIMK抑制剂。 本文报道了一款依托该母核骨架策略开发的新型LIMK1/2抑制剂。所发现的化合物10对LIMK1/2展现出低纳摩尔级的抑制活性，且选择性优异；经全面选择性筛选测试组验证，其唯一的脱靶效应为RIPK活性残留。本研究为变构抑制剂的母核骨架跃迁提供了为数不多的范例之一，而这类抑制剂通常被认为具有严格的靶点排他选择性。