Abstract 4651: A macrocyclic kinase inhibitor overcomes the compound mutations that cause the resistance to all approved EGFR inhibitors in EGFR-positive lung cancer

Abstract EGFR mutant cancers account for 20-30 % of non-small cell lung cancers and show marked sensitivity to EGFR tyrosine kinase inhibitors (TKIs). However, the tumor almost inevitably relapses due to acquired resistance. To date, several EGFR-TKIs have been approved, and the third-generation EGFR-TKI, osimertinib, has been widely used both as first-line therapy and for patients with the EGFR-T790M mutation after 1st or 2nd generation EGFR-TKI therapy. However, the EGFR-T790M+C797S compound mutation confers resistance to all approved EGFR-TKIs. In our previous study, we experimentally demonstrated that brigatinib with anti-EGFR antibody was effective against osimertinib-resistant EGFR-C797S and EGFR-T790M+C797S mutants, and is currently undergoing clinical studies. However, the tumor would relapse because of the acquisition of additional resistance mutations. Here, we first demonstrated the binding mode of brigatinib to the EGFR-T790M/C797S mutant by crystal structure analysis and predicted brigatinib-resistant mutations through a cell-based assay, including N-ethyl-N-nitrosourea (ENU) mutagenesis. We found that clinically reported L718 and G796 compound mutations appeared, consistent with their proximity to the binding site of brigatinib, and brigatinib-resistant quadruple mutants, such as EGFR-activating mutation/T790M/C797S/L718M, were resistant to all clinically available EGFR-TKIs. BI-4020, a fourth-generation macrocyclic EGFR inhibitor plus anti-EGFR antibody, overcomes the quadruple and major EGFR-activating mutants in vitro and in vivo, but not the minor mutants such as L747P. Microsecond molecular dynamics simulations revealed the binding mode and affinity between BI-4020 and the EGFR mutants. This study identified potential therapeutic strategies using new-generation macrocyclic EGFR inhibitor to overcome the emerging resistance mutants. Citation Format: Ryohei Katayama, Ken Uchibori, Makoto Nishio, Naoya Fujita. A macrocyclic kinase inhibitor overcomes the compound mutations that cause the resistance to all approved EGFR inhibitors in EGFR-positive lung cancer abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 4651.