KRAS inhibitor-9, a potent KRAS inhibitor (Kd=92 μM), blocks the formation of GTP-KRAS and downstream activation of KRAS. KRAS inhibitor-9 binds to KRAS G12D, KRAS G12C and KRAS Q61H protein with a moderate binding affinity. KRAS inhibitor-9 causes G2/M cell cycle arrest and induces apoptosis. KRAS inhibitor-9 selectively inhibits the proliferation of NSCLC cells with KRAS mutation but not normal lung cells.