Abstract 5604: Antitumor activity of YH42946, a potent tyrosine kinase inhibitor, in NSCLC harboring EGFR exon 20 insertion mutations

Abstract Introduction: Epidermal growth factor receptor (EGFR) mutations are the most common in non-small cell lung cancer (NSCLC) patients, with around 30% carrying these mutations, of which approximately 4-10% are EGFR exon 20 insertion (ex20ins) mutations. The most common EGFR ex20ins mutations in NSCLC are ASV and SVD variants in the kinase domain. Currently, treatment options for this subset of patients are limited. YH42946 is an orally available tyrosine kinase inhibitor (TKI) targeting EGFR ex20ins mutations, and the potential to be a best-in-class drug candidate to address this unmet clinical need. Method: Competitive binding affinity was measured using the KINOMEscan screening platform. The inhibitory activity of YH42946 was evaluated through a cell viability assay in Ba/F3 cell lines expressing EGFR ASV, SVD, GY, and HH mutations. A549 cells were used to assess the cellular activity of EGFR wild-type (WT). To further confirm the mechanism of action, western blot analysis was performed on patient-derived cells (PDCs), including YU-1163 (S768_D770dup, SVD) and DFCI-127 (P772_H773insPNP). Results: Kinome profiling against a panel of various kinases revealed that 100 nM of YH42946 bound strongly to EGFR mutants. In a cell viability assay, YH42946 strongly inhibited cellular activity in Ba/F3 cell lines engineered to express the EGFR mutants ASV, SVD, GY (IC50 < 10 nM), and HH (IC50 < 30 nM). It demonstrated superior activity compared to Mobocertinib (IC50 < 30 nM for ASV and IC50 < 30 nM for SVD), Furmonertinib (IC50 < 100 nM for ASV and IC50 < 100 nM for SVD), and Zipalertinib (IC50 < 100 nM for ASV and IC50 < 100 nM for SVD), and was comparable to Poziotinib (IC50 < 10 nM for ASV and IC50 < 10 nM for SVD). In normal cell lines, YH42946 did not inhibit the activity of normal cell lines, largely sparing EGFR WT activity (IC50 > 1000 nM). In protein expression analysis, YH42946 effectively inhibited the signaling pathways of p-EGFR, p-AKT, p-ERK1/2, and p-S6 in YU-1163 and DFCI-127 PDC cell lines at a low dose level. Conclusion: YH42946 is a potent small-molecule inhibitor that selectively targets EGFR ex20ins while sparing EGFR WT in preclinical models, offering potential therapeutic benefits for NSCLC patients with EGFR ex20ins mutations. Additionally, YH42946 has demonstrated effective inhibition of the EGFR pathway. Given these robust activities against EGFR ex20ins, YH42946 is anticipated to provide a significant therapeutic option for NSCLC patients harboring EGFR ex20ins mutations. Citation Format: Mi Ra Yu, Jii Bum Lee, Kwang Ho Lee, Min Hee Hong, Sun Min Lim, Byoung Chul Cho. Antitumor activity of YH42946, a potent tyrosine kinase inhibitor, in NSCLC harboring EGFR exon 20 insertion mutations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 5604.