RMC-4998 is a tri-complex inhibitor that selectively targets the GTP-bound state of mutant KRASG12C, with high potency for KRASG12C-CYPA tri-complex formation with an IC50 of 28 nM. It strongly inhibits ERK signaling with an IC50 of 1–10 nM and attenuates AKT/MTOR and RAL pathways, leading to potent suppression of KRASG12C-driven tumor growth and can used in cancer research.