KRAS inhibitor-12 (compound 6-1) is a potent KRAS G12C inhibitor with an IC 50 of 0.537 µM. KRAS inhibitor-12 shows p-ERK inhibition activities with IC 50 s of 1.3, 3.7 µM in MIA PaCA-2, A549 cells, respectively. KRAS inhibitor-12 has the potential for the research of pancreatic, colorectal, and lung cancers.