Abstract Current small molecule inhibitors of KRAS(G12C) bind irreversibly in the switch-II pocket, exploiting the strong nucleophilicity of the acquired cysteine as well as the preponderance of the GDP-bound form of this mutant. Nevertheless, many oncogenic KRAS mutants lack these two features, and it remains unknown whether targeting the switch-II pocket is a practical therapeutic approach for KRAS mutants beyond G12C. Here we use NMR spectroscopy and a novel cellular KRAS engagement assay to address this question by examining a collection of SII-P ligands from the literature and from our own laboratory. We show that the switch-II pockets of many GTP hydrolysis-deficient KRAS hotspot (G12, G13, Q61) mutants are accessible using non-covalent ligands, and that this accessibility is not necessarily coupled to the GDP state of KRAS. The results we describe here emphasize the switch-II pocket as a privileged drug binding site on KRAS and unveil new therapeutic opportunities in RAS-driven cancer.

KRAS is vulnerable to reversible switch-II pocket engagement in cells