Abstract 1933: Dissecting acquired resistance to KRASG12D inhibition in a mouse model of pancreatic ductal adenocarcinoma

Abstract KRAS is a major oncogenic driver in pancreatic ductal adenocarcinoma (PDAC) and is mutationally activated in approximately 90% of cases, with the glycine-to-aspartic acid substitution at position 12 (p.G12D) being the most prevalent alteration. Mutations in this oncogene have been associated with more aggressive disease and poorer outcomes and have remained “undruggable” for more than three decades. However, the recent development of mutant-specific small molecule inhibitors of KRAS has given hope for the treatment of this highly lethal and treatment-refractory malignancy. Here we evaluated the genomic and transcriptional mechanisms of resistance to MRTX1133, a first-in-class inhibitor of KRASG12D, in an autochthonous mouse model of PDAC. We leveraged single-nucleus RNA sequencing and whole-exome sequencing on 17 tumors from KPC mouse specimens (LSL-KrasG12D/+; LSL-Trp53R172H/+; p48-Cre) that were treated with either MRTX1133 or the vehicle, including 6 samples from mice that developed acquired resistance to KRASG12D inhibition. Our analysis has uncovered that resistance is multifaceted and characterized by both emergent genomic and transcriptional features. Genetically, resistant tumors harbored clonal and subclonal amplifications in the HIPPO pathway, cell cycle regulators, and ABC transporters. Transcriptionally, we employed non-negative matrix factorization and identified recurrent gene expression programs in resistant and vehicle samples. Using this approach, we uncovered the existence of an intermediate phenotype between classical and mesenchymal cell states that is enriched in tumors with evolved resistance to MRTX1133. In summary, our study provides a high-resolution genomic and transcriptional landscape of resistance to KRAS targeting in a preclinical in vivo model of PDAC, highlighting the complexity of treatment resistance and identifying various pathways and effectors that may serve as potential new targets for combination therapy. Citation Format: Julien Dilly, Laleh Abbassi, Connor J. Hennessey, Giselle A. Uribe, Brendan Parent, Annan Yang, Kevin S. Kapner, Ziyue Li, Kyle E. Evans, Shatavisha Dasgupta, Megan T. Hoffman, Li Qiang, Felix P. Hambitzer, Seema Chugh, Alex K. Shalek, Stephanie K. Dougan, Brian M. Wolpin, Jonathan A. Nowak, Srivatsan Raghavan, Peter S. Winter, Andrew J. Aguirre. Dissecting acquired resistance to KRASG12D inhibition in a mouse model of pancreatic ductal adenocarcinoma [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(6_Suppl):Abstract nr 1933.