Abstract 5521: Integrative analysis of acquired drug resistance to KRAS(G12D) inhibitors

Abstract KRAS is the most frequently mutated oncogene in cancer and, until recently, targeted therapies against mutant KRAS haven’t been successful. However, new breakthroughs in pharmacological design have led to the FDA-approval of two KRAS G12C inhibitors and one inhibitor specific to target the KRAS glycine to aspartic acid in codon 12 (G12D) mutation has shown strong responses in vitro and has entered phase I in clinical trials, MRTX1133. KRAS(G12D) is the most common KRAS mutation, being found in 37% of pancreatic ductal adenocarcinomas (PDACs), as well as in 12.5% of colorectal cancer and 4.9% of lung adenocarcinoma (LUAD) patients. MRTX1133, a selective non-covalent inhibitor of the KRAS(G12D) mutation, has demonstrated promising preclinical efficacy and has entered phase 1 clinical trials; however, the acquired drug resistance is expected to emerge. We have generated an acquired resistant model to KRASG12D inhibitors by drug escalation of MRTX1133. Our results show that although the IC50 for parental AsPC-1 cells is 0.2nM, drug resistant AsPC-1M-R cells can grow normally at 10 µM. Expression of KRAS, NRAS but more significantly HRAS are increased in the drug-resistant phenotype, likely to bypass inhibition of KRAS(G12D). Oncogenic KRAS(G12D) signaling isn’t essential in AsPC-1M-R cells as determined by a persistent RAS-GTP activity after MRTX1133 treatment due to the emergence of a secondary mutation in KRAS. In fact, tumor proliferation and survival in the resistant phenotype is sustained by increased receptor tyrosine kinase (RTK) phosphorylation. Evaluation of RTK activity demonstrated that resistant tumor cells activated several RTK such as the ErbB and Eph families and MET, predominantly. Dual inhibition with SHP2, SOS or ErbB in combination with MRTX113 didn’t exhibit a synergistic effect. Novel therapeutic approaches such as RAS(ON) inhibitors like RMC-6236 or specific KRAS(G12D) PROTAC degraders can significantly inhibit cell proliferation in vitro not only in MRTX1133 acquired resistance but also in adagrasib resistance models. To determine the underlying mechanisms of acquired drug resistance to MRTX1133, RNAseq analysis was performed. Complex transcriptomic reorganization shows the upregulation of CD24 -a potential cancer stem cell related gene- and the epithelial to mesenchymal signature highlight the difficulty to target drug resistant cells. These findings emphasize the necessity to design combinatorial treatments to prevent and delay the acquisition of drug resistance in KRAS-driven cancers. Citation Format: Ines Pulido Endrino, Laura Gunder, Malek Massad, Julian Carretero, Takeshi Shimamura. Integrative analysis of acquired drug resistance to KRAS(G12D) inhibitors [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 5521.