Background: Non-small cell lung cancer (NSCLC) patients with activating EGFR mutations initially respond to first-generation EGFR inhibitors; however, the efficacy of these drugs is limited by acquired resistance driven by the EGFR^T790Mmutation. The discovery of third-generation EGFR inhibitors overcoming EGFR^T790Mand their new resistance mechanisms have attracted much attention.Methods: We examined the antitumor activities and potential resistance mechanism of a novel EGFR third-generation inhibitor in vitro and in vivo using ELISA, SRB assay, immunoblotting, flow cytometric analysis, kinase array, qRT-PCR and tumor xenograft models. The clinical effect on a patient was evaluated by computed tomography scan.Results: We identified compound ASK120067 as a novel inhibitor of EGFR^T790M, with selectivity over EGFR^WT. ASK120067 exhibited potent anti-proliferation activity in tumor cells harboring EGFR^T790M(NCI-H1975) and sensitizing mutations (PC-9 and HCC827) while showed moderate or weak inhibition in cells expressing EGFR^WT. Oral administration of ASK120067 induced tumor regression in NSCLC xenograft models and in a PDX model harboring EGFR^T790M. The treatment of one patient with advanced EGFR T790M-positive NSCLC was described as proof of principle. Moreover, we found that hyperphosphorylation of Ack1 and the subsequent activation of antiapoptotic signaling via the AKT pathway contributed to ASK120067 resistance. Concomitant targeting of EGFR and Ack1 effectively overrode the acquired resistance of ASK120067 both in vitro and in vivo.Conclusions: Our results idenfity ASK120067 as a promising third-generation EGFR inhibitor and reveal for the first time that Ack1 activation as a novel resistance mechanism to EGFR inhibitors that guide to potential combination strategy.

Single-cell proteomics offers unparalleled insights into cellular diversity and molecular mechanisms, enabling a deeper understanding of complex biological processes at the individual cell level. Here, we develop an integrated sample processing on an active-matrix digital microfluidic chip for single-cell proteomics (AM-DMF-SCP). Employing the AM-DMF-SCP approach and data-independent acquisition (DIA), we identify an average of 2258 protein groups in single HeLa cells within 15 min of the liquid chromatography gradient. We performed comparative analyses of three tumor cell lines: HeLa, A549, and HepG2, and machine learning was utilized to identify the unique features of these cell lines. Applying the AM-DMF-SCP to characterize the proteomes of a third-generation EGFR inhibitor, ASK120067-resistant cells (67R) and their parental NCI-H1975 cells, we observed a potential correlation between elevated VIM expression and 67R resistance, which is consistent with the findings from bulk sample analyses. These results suggest that AM-DMF-SCP is an automated, robust, and sensitive platform for single-cell proteomics and demonstrate the potential for providing valuable insights into cellular mechanisms.

Third-generation EGFR tyrosine kinase inhibitors (TKIs), exemplified by osimertinib, have demonstrated promising clinical efficacy in the treatment of non-small cell lung cancer (NSCLC). Our previous work has identified ASK120067 as a novel third-generation EGFR TKI with remarkable antitumor effects that has undergone New Drug Application (NDA) submission in China. Despite substantial progress, acquired resistance to EGFR-TKIs remains a significant challenge, impeding the long-term effectiveness of therapeutic approaches. In this study, we conducted a comprehensive investigation utilizing high-throughput proteomics analysis on established TKI-resistant tumor models, and found a notable upregulation of branched-chain amino acid transaminase 1 (BCAT1) expression in both osimertinib- and ASK120067-resistant tumors compared with the parental TKI-sensitive NSCLC tumors. Genetic depletion or pharmacological inhibition of BCAT1 impaired the growth of resistant cells and partially re-sensitized tumor cells to EGFR TKIs. Mechanistically, upregulated BCAT1 in resistant cells reprogrammed branched-chain amino acid (BCAA) metabolism and promoted alpha ketoglutarate (α-KG)-dependent demethylation of lysine 27 on histone H3 (H3K27) and subsequent transcriptional derepression of glycolysis-related genes, thereby enhancing glycolysis and promoting tumor progression. Moreover, we identified WQQ-345 as a novel BCAT1 inhibitor exhibiting antitumor activity both in vitro and in vivo against TKI-resistant lung cancer with high BCAT1 expression. In summary, our study highlighted the crucial role of BCAT1 in mediating resistance to third-generation EGFR-TKIs through epigenetic activation of glycolysis in NSCLC, thereby supporting BCAT1 as a promising therapeutic target for the treatment of TKI-resistant NSCLC.

With the wide clinical use of the third‐generation epidermal growth factor receptor (EGFR) inhibitor osimertinib for the treatment of EGFR‐mutated non–small cell lung cancer (NSCLC), acquired resistance caused by EGFR C797S tertiary mutation has become a concern. 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 antitumor activity both in vitro and in vivo. In cell‐free assay, LS‐106 potently inhibited the kinase activities of EGFR^{19del/T790M/C797S} and EGFR^{L858R/T790M/C797S} with IC₅₀ values of 2.4 nmol/L and 3.1 nmol/L, respectively, which was more potent than osimertinib. Meanwhile, LS‐106 exhibited comparable kinase inhibitory effect to osimertinib on EGFR^L858R/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 EGFR^{19del/T790M/C797S} or EGFR^{L858R/T790M/C797S}, and thus inhibited the proliferation of these cells. We also constructed tumor cells harboring EGFR^{19del/T790M/C797S} (named PC‐9‐OR cells) using the CRISPR/Cas9 system and found that LS‐106 markedly suppressed the activation of EGFR^{19del/T790M/C797S} and the proliferation of PC‐9‐OR cells. Moreover, cells harboring EGFR^{19del/T790M/C797S} underwent remarkable apoptosis upon LS‐106 treatment. In vivo experiments further demonstrated that oral administration of LS‐106 caused significant tumor regression in a PC‐9‐OR xenograft model, with a tumor growth inhibition rate (TGI) of 83.5% and 136.6% at 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 antitumor effects in C797S–triple‐mutant tumor models.