Probing the KRas Switch II Groove by Fluorine NMR Spectroscopy.

While there has been recent success in the development of KRas G12C inhibitors, unmet needs for selective inhibitors of KRas G12D and the remaining oncogenic KRas proteins remain. Here, we applied trifluoromethyl-containing ligands of KRas proteins as competitive probe ligands to assay the occupancy of the switch II pocket by 19 F NMR spectroscopy. Structure-activity-relationship studies of probe ligands increased the sensitivity of the assay and identified structures that differentially detected each nucleotide state of KRas G12D . These differences in selectivity, combined with the high resolution of 19 F NMR spectroscopy, enabled this method to be expanded to assay both nucleotide states of the protein simultaneously.