High-Throughput Kinetic Characterization of Irreversible Covalent Inhibitors of KRAS G12C by Intact Protein MS and Targeted MRM.

With recent advances and success in several drugs designed to treat acute and chronic diseases, targeted covalent inhibitors show a resurgence in drug discovery. As covalent inhibition is time-dependent, the preferred quantitative potency metric of irreversible inhibitors is the second-order rate constant k inact / K i , rather than IC 50 . Here, we present the development of a mass spectrometry-based platform for rapid kinetic analysis of irreversible covalent inhibitors. Using a simple liquid handling robot for automated sample preparation and a solid-phase extraction-based RapidFire-MS system for rapid MS analysis, kinetic characterization of covalent inhibitors was performed in high throughput both by intact protein analysis and targeted multiple reaction monitoring (MRM). In addition, a bimolecular reaction model was applied to extract k inact / K i in data fitting, providing tremendous flexibility in the experimental design to characterize covalent inhibitors with various properties. Using KRAS G12C inhibitors as a test case, the platform was demonstrated to be effective for studying covalent inhibitors with a wide range of k inact / K i values from single digit to 3 × 10 5 M -1 s -1 .