Design,Synthesis And Bioevaluation Of Novel Small Molecule KRas G12C Inhibitors Based On 7-Phenyl-4-Piperazine-Quinazoline Scaffold

Ras is the most frequently mutated oncogene in human carcinogenesis.Ras proteins are an important member of the GTPases family,which play important roles in transducing extracellular signals,proliferation,apoptosis and differentiation.There are three mutant isoforms in the Ras protein family,KRas,HRas and NRas.Among them,KRas is the most frequently mutated isoform in the Ras family,with most of the mutations occur at codon 12.In the past few decades,small molecule inhibitors that directly target KRas have all failed,due to the extremely high binding affinity of GTP to KRas and the high concentrations of intracellular GTP.In recent years,great progress has been made in the development of covalent inhibitors of KRas mutants such as KRas G12C.KRas G12C is a common KRas mutation where the 12-position glycine is mutated to cysteine,thus can covalently bind to small molecules.Therefore,the development of covalent inhibitors targeting the cysteine moiety at the allosteric site appears promising.Based on our previously reported KRas G12C inhibitor LLK-10,we designed a series of novel quinazoline analogues with a trifluoromethacrylic acid warhead as covalent inhibitors 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,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 novel KRas G12C inhibitor deserving further investigation.