Discovery of ARS-1620 analogs as KRas G12C inhibitors with high in vivo antitumor activity

KRas is the most frequently mutated protein of the three Ras isoforms in various cancer types. KRas mutations (i.e. G12C) are present in approximately 30% of human cancers. Based on our previously reported KRas G12C inhibitor LLK-10, we designed a series of quinazoline analogues with a trifluoromethacrylic acid warhead as covalent inhibitor of KRas G12C. The pharmacological activities of these compounds were assessed against a panel of KRas G12C mutated cancer cells (i.e. H358 and H23). Among them, K20 showed that highest antiproliferative potency with an average IC50 of 1.16 μM, clearly better than that of the lead LLK-10 (average IC50 = 2.32 μM), and comparable to that of ARS-1620 (average IC50 = 1.32 μM, a known KRas G12C inhibitor). K20 also exhibited better selectivity index (SI = 5 ∼ 23) than LLK-10 (SI = 1.5-3) for inhibiting the growth of KRas G12C mutated cancer cells (i.e. H358 and H23) over other KRas (e.g. G13D, G12S, G12D, G12V) mutated cancer cells. Utilizing a KRAS-GTP pull-down assay, it was demonstrated that K20 decreased the active form of KRAS (KRAS-GTP) in NCI-H358 cells. In addition, K20 reduced the level of phosphorylated Erk and caused cancer cell apoptosis. Further, K20 could inhibit the formation of H358 or H23 tumor colonies. Moreover, K20 displayed significant tumor-suppressing effects in NCI-H358 xenograft-bearing nude mice with a TGI (tumor growth inhibition) of 41%, comparable to that of ARS-1620 (47%). Lastly, K20 exhibited benign toxicity profiles without causing bone marrow suppression and any other apparent toxicity to major organs of mice. Collectively, these results indicate that K20 is a KRas G12C inhibitor deserving further investigation.