Abstract 5561: Ankyrin repeat domain 1 confers resistance to tepotinib in MET-altered cancers

Purpose: The mesenchymal epithelial transition factor receptor (MET) is a promising therapeutic target in various cancers, including non-small cell lung cancer (NSCLC). In NSCLC, activation of the MET pathway occurs through diverse mechanisms, influencing cancer cell survival, growth, and invasiveness. These tumors exhibit oncogene addiction to MET and show remarkable responses to MET-Tyrosine Kinase Inhibitors (TKIs). However, the long-term effectiveness of MET-TKIs is usually limited due to acquired drug resistance. The mechanisms underlying primary and acquired resistance to MET-TKIs in NSCLC remain poorly understood. In this study, we investigated the mechanisms to tepotinib in MET-amplified and MET exon 14 skipping cancer cell lines. Experimental Design: Two MET-amplified lung cancer cell lines, EBC-1 and H1993, and one MET exon 14 skipping gastric cancer cell line, Hs746T, were used to establish models of acquired resistance to MET-TKI tepotinib. Resistance mechanisms were explored through functional analyses, comprehensive gene expression analysis using RNA sequencing, and the alterations hypothesized to confer resistance were validated. Results: Multiple mechanisms contributing to tepotinib resistance were identified. In EBC1 and Hs746T derived resistant cells, Ankyrin Repeat Domain 1 (ANKRD1) was highly expressed, and suppression of ANKRD1 using shRNA impaired resistance to tepotinib. Additionally, activation of the MAPK pathway was observed in EBC1 derived resistant cells, and inhibition of this pathway with MEK inhibitors had a synergistic effect with tepotinib. All 3 resistant cell lines used in this study showed epithelial-mesenchymal transition (EMT), which may further contribute to the resistance. Conclusions: In this study, we revealed the different mechanisms of acquired resistance to MET-TKI tepotinib with potential therapeutic application. Citation Format: Ryunosuke Fujii, Tomoaki Higashihara, Ken Suzawa, Kousei Ishimura, Kazuya Hisamatsu, Ryota Fujiwara, Atsushi Matsuoka, Ryo Yoshichika, Naohiro Hayashi, Yuma Fukumoto, Kazuhiro Okada, Fumiaki Mukohara, Mao Yoshikawa, Kazuhiko Shien, Shinichi Toyooka. Ankyrin repeat domain 1 confers resistance to tepotinib in MET-altered cancers [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 5561.