GDC-6036 was ordered from Chemgood LLC (Henrico, VA, USA) and LY3537982 was obtained from MedChemExpress, (Sollentuna, Sweden). E. coli expression, and purification of SOS cat (564-1048), and full-length KRAS(G12C), KRAS(G12C/H95L), and KRAS(G12C/Y96D) is described elsewhere , and proteins were a kind gift from Leidos Biomedical Research, Inc., Frederick National Laboratory for Cancer Research and from University of Zurich. Eu 3+ -GTP and MT2 quencher were from QRET Technologies (Turku, Finland) . FRET-Probe was designed and produced as described previously . FRET-Probe thermal stability assays were conducted in white 96-well PCR-plates (BioRad, Hercules, USA). Chemical stability and nucleotide exchange assays were performed in white 384-well low volume plates (Corning, USA). All measurements were performed using a Spark 20M from Tecan Life Sciences (Männedorf, Switzerland). Time-resolved luminescence signals from nucleotide exchange assay was monitored using 340/620 nm excitation/emission wavelengths, and 800 µs and 400 µs delay and integration times, respectively.