Optimization of α-Fluoro, β-Heteroaryl Acrylamide Warheads for KRAS ^G12C Active-State Inhibition

We provide herein a detailed investigation of the warhead reactivity and pharmaceutical properties of a novel α-fluoro, β-heteroaryl acrylamide class of covalent warhead in the context of KRAS^G12C active-state inhibition. Unlike traditional unsubstituted acrylamide warheads, which undergo conjugate addition with cysteine at the β-position, these acrylamides react at the α-position in a vinylogous nucleophilic aromatic substitution (S_NAr) transformation. Systematic examination of pyridine warhead substitutions and bioisosteric replacements elucidated a dependence of these warheads' reactivity on heterocycle basicity in addition to electrophilicity. In vitro characterization revealed the effects of heterocycle identity on cellular potency, free fraction, permeability, and efflux ratio. These lessons informed in vivo studies, culminating in the discovery of a lead molecule that showed low clearance across species and robust efficacy in a mouse xenograft model.