Abstract 412: Drug combination screen identifies pemigatinib, an FGFR inhibitor, as a mechanism to overcome KRASG12C inhibitor resistance in lung cancer

Background: Lung cancer is one of the most common tumors, accounting for approximately 1.8 million deaths worldwide in 2020. KRAS is a frequently mutated oncogene, with mutations reported in roughly 20-25% of non-small cell lung cancer cases. Specifically, KRAS mutations at amino acid 12, resulting in a glycine to cysteine (G12C) substitution, occur in approximately 13% and 3% of lung and colon cancers, respectively, and less frequently in other solid tumors. Recently, the development of covalent KRASG12C inhibitors has shown meaningful anticancer activity in patients. However, many patients with KRASG12C do not respond and/or develop resistance to single-agent treatment. Here we investigate combination therapies that may overcome resistance and broaden patient response to KRASG12C inhibitors. Methods: In vitro preclinical KRASG12C models including lung and colon cancer cell lines were treated with a panel of small molecule and covalent KRASG12C inhibitors. The activity of single-agent versus combination treatments was measured in cell viability assays, and screen hits were validated by in vitro mechanism of action studies. Results: A curated set of 152 compounds was used in combination with screen monitoring cell-viability assays across 12 KRAS mutant lung and colon cancer cell lines. Compounds tested included kinase inhibitors targeting oncogenic signaling pathways, epigenetics modifiers, regulators of apoptosis, chemotherapeutics, and other anticancer agents. The screen identified synergy between covalent KRASG12C and several other inhibitors including those for FGFR, EGFR, and SHP2. Notably, pemigatinib, a potent and selective FGFR1-3 inhibitor, had a significantly high Bliss synergy score. Selectivity and siRNA knockdown experiments were performed to identify the specific FGFR isoform involved in synergistic anticancer activity. Inhibition of FGFR1 activity was shown to be essential, whereas an FGFR2-3 specific inhibitor demonstrated only modest activity in combination with KRASG12C inhibitors. Additionally, FGFR1 knockdown combined with KRASG12C inhibition resulted in increased drug sensitivity; in contrast, knockdown of other FGFR family members did not demonstrate similar increase in sensitivity to KRASG12C inhibition. Conclusions: Cell-viability combination screening identified strong synergy between KRASG12C covalent inhibitors and the FGFR1-3 inhibitor pemigatinib in KRASG12C cancer cell lines. The synergistic effect of pemigatinib and KRASG12C inhibition was notably strongest in mesenchymal cancer cell lines. This effect was further validated in in vitro selectivity and siRNA studies. Together, our results support pemigatinib as a promising agent for combination therapy with KRAS inhibitors in lung cancer. Citation Format: Angela Abdollahi, Margaret Favata, Darlise DiMatteo, Sean Schuette, Erika Boarder, Mark Rupar, Ricardo Macarron, Aidan Gilmartin, Hui Wang, Alejandro Amador-Arjona. Drug combination screen identifies pemigatinib, an FGFR inhibitor, as a mechanism to overcome KRASG12C inhibitor resistance in lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 412.