Discovery of novel Quinazoline-based KRAS G12C inhibitors as potential anticancer agents

A series of novel quinazoline analogs were designed and synthesized based on ARS-1620 and LLK-10 (a KRAS inhibitor reported by us recently) as KRAS G12C inhibitors with a 5-nitrofuran-2-carboxylic acid warhead. Most of the newly synthesized compounds exhibited antiproliferative activities similar to or better than ARS-1620 and LLK-10. Among them, compound KS-19 showed the highest activity (IC₅₀ = 460 ∼ 870 nM) and reasonable selectivity (3 to 27-fold) for inhibiting the proliferation of KRAS G12C-mutated cells (NCI-H358 and NCI-H23) over other KRAS mutant (e.g. G13D, G12D, G12S, G12V, WT) cancer cells. ITC, KRAS-GTP pull-down assay and western blot analysis demonstrated that KS-19 could bind to KRAS G12C protein with high affinity (K_D = 97 nM), thus decreasing the active form of KRAS G12C (KRAS G12C-GTP) and phosphorylated Erk, and leading to NCI-H358 tumor cell apoptosis. In addition, KS-19 was able to suppress the formation of NCI-H358 and NCI-H23 tumor colonies in a dose-dependent manner. Moreover, in vivo efficacy studies indicated that KS-19 (40 mg/kg) was effective in suppressing tumor growth in nude mice bearing NCI-H358 tumor xenografts with a TGI (tumor growth inhibition) of 47 %, comparable to that of ARS-1620 (50 %). Lastly, KS-19 possessed a benign toxicity profile without causing bone marrow suppression and any obvious morphological abnormalities in major organs of mice. Collectively, these results suggest that KS-19 represents a novel inhibitor of KRAS G12C worthy of further investigation as a potential anticancer agent.