Abstract LB290: Identifying novel mechanisms of resistance to KRAS-inhibitors in NSCLC

Abstract Mutations in the KRAS oncogene are commonly associated with pancreatic, colorectal, and lung malignancies. A frequently observed mutation involves the substitution of glycine at position 12 (e.g., G12C, G12D, G12V), which locks the protein in its active conformation, driving uncontrolled cell growth. KRAS was considered "undruggable" for decades due to its lack of accessible binding sites. Recent breakthroughs, however, have led to the development of covalent inhibitors such as Sotorasib (AMG510) and Adagrasib (MRTX849), which specifically target the KRAS G12C mutation and have received FDA approval following successful clinical trials. Research efforts are now focused on discovering inhibitors for other KRAS mutations, including the noncovalent KRAS-G12D inhibitor MRTX1133 and the pan-KRAS inhibitor BI3706674, offering new hope for KRAS-driven cancers. While these inhibitors have shown early success, resistance to treatment frequently arises, and the mechanisms behind this resistance remain unclear. To address this critical challenge, we are leveraging pre-clinical syngeneic mouse models and KRAS mutant allele-specific cell lines to investigate the molecular pathways responsible for resistance to allele-specific KRAS inhibitors. By generating a panel of acquired resistant cell lines from both murine syngeneic and human NSCLC models, we have begun to uncover the molecular drivers of resistance. Proteomic profiling using RPPA analysis has identified significant changes in protein expression, with the YAP/TEAD1 and the PDK1 pathways consistently upregulated in cells resistant to MRTX849 (G12Ci), MRTX1133 (G12Di) and the pan-RAS inhibitor BI3706674. Notably, resistant cells regained sensitivity to KRAS inhibitors when treated in combination with a TEAD inhibitor or PDK1 inhibitor in vitro. In vivo tumors from syngeneic mice implanted with resistant or sensitive cells and treated with KRAS inhibitors over 3-4 weeks exhibited increased nuclear localization of YAP1 and elevated expression of PDK1 in the drug-resistant tumors. Using genetic knockout and over-expression models, we could establish that both PDK1 and YAP1 are necessary and sufficient to impart resistance to MRTX1133 (G12Di). When we administered a combination treatment of MRTX1133 with a TEADi to mice bearing MRTX1133-resistant tumors, we also observed a partial reversal of MRTX1133 resistance. Currently, we are performing in vitro and in vivo studies to understand the role of PDK1 signaling in MRT1133 resistance. We are also trying to understand the molecular crosstalk between the PDK1 and YAP1/TEAD signaling pathways to functionally induce or maintain resistance to MRTX1133. Achieving the objectives of this research project will be instrumental in addressing the critical challenge of overcoming resistance to KRAS inhibitors and enhancing their effectiveness in clinical applications. Citation Format: Samrat Kundu. Identifying novel mechanisms of resistance to KRAS-inhibitors in NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_2):Abstract nr LB290.