Molecular dynamics simulations. Molecular modeling was conducted with Maestro (Schrödinger release 2020-2, Schrödinger LLC, New York, NY) with OPLS3e force field, using Desmond MD engine for the simulations. More detailed description on the system preparation and simulations is provided in the SI Appendix. In brief, simulations with noncovalently bound sotorasib and adagrasib in SII-P were based on their published co-crystal structures (PDB ID: 6OIM 56 and 6UT0 ). Engineered residues of the structures were reverse mutated to the native ones, and specific mutations were introduced to obtain the studied systems (Table ). Protein Preparation Wizard 70 prepared systems were solvated in a 15 Å cubic box with TIP3P water with 150 mM K + and Cl -salt (adjusted to a neutral net charge). Prior to the production simulations, the default Desmond relaxation was applied for all systems. The production simulations (4-5 µs) were run in NpT ensemble (p = 1.01325 bar; T = 310 K) with settings as in previous report, resulting generally in 20-25 µs aggregate of simulation data for each system (Table ) The analysis of trajectories were conducted with Schrödinger Maestro tools. Analysis of SII-P volume was conducted with trajectory_binding_site_volumes.py script (Schrödinger LLC) by analyzing every 50th frame (50 ns intervals) of the trajectories using residues 12, 58, 72 and 96 for the site definition. resources. The authors gratefully acknowledge the Functional Genomics Center Zurich (FGCZ) of University of Zurich and ETH Zurich, and in particular Serge Chesnov, for the support on Proteomics analyses.