LS-106, a novel EGFR inhibitor targeting C797S, exhibits anti-tumor activities both in vitro and in vivo.

With the widely clinical use of third-generation EGFR inhibitor osimertinib for the treatment of EGFR-mutated NSCLC, acquired resistance caused by EGFR C797S tertiary mutation has become a concerned problem. Therefore, fourth-generation EGFR inhibitors that could overcome this mutation have gained increasing attention in recent years. Here, we identified LS-106 as a novel EGFR inhibitor against C797S mutation and evaluated its anti-tumor activity both in vitro and in vivo. In cell-free assay, LS-106 potently inhibited the kinase activities of EGFR19del/T790M/C797S and EGFRL858R/T790M/C797S with IC50 values of 2.4 nM and 3.1 nM, respectively, which was more potent than osimertinib. Meanwhile, LS-106 exhibited comparable kinase inhibitory effect to osimertinib on EGFRL858R/T790M and wild-type EGFR. Results from cellular experiments demonstrated that LS-106 potently blocked the phosphorylation of EGFR C797S triple mutations in the constructed BaF3 cells that highly expressed EGFR19del/T790M/C797S or EGFRL858R/T790M/C797S , and thus inhibited the proliferation of these cells. We also constructed tumor cells harboring EGFR19del/T790M/C797S (named PC-9-OR cells) using CRISPR/Cas9 system, and found that LS-106 markedly suppressed the activation of EGFR19del/T790M/C797S and the proliferation of PC-9-OR cells. Moreover, cells harboring EGFR19del/T790M/C797S underwent remarkable apoptosis upon the treatment of LS-106. In vivo experiments further demonstrated that oral administration of LS-106 caused significant tumor regression in PC-9-OR xenograft model, with tumor growth inhibition rate (TGI) of 83.5% and 136.6% at the doses of 30 and 60 mg/kg, respectively. Taken together, we identified LS-106 as a novel fourth-generation EGFR inhibitor against C797S mutation and confirmed its preclinical anti-tumor effects in C797S triple mutant tumor models.