Abstract RAS inhibitors (RASi) have the potential to change the clinical landscape for pancreatic ductal adenocarcinoma (PDAC) and improve patient survival. Nevertheless, clinical resistance is likely to reduce the long-term benefits of RASi, and combinations that can bypass or overcome resistance will be needed. Here, we studied the dynamics of resistance to the RAS multi (ON) inhibitor RMC-6236 (daraxonrasib). Prior to frank drug resistance, PDAC cells persist in a drug tolerant state characterized by reduced proliferation; however, only a fraction of the drug-tolerant persister cells contributes to resistance. To identify and study the relevant, resistance-contributing cells, we developed a highly multiplexed, lentiviral DNA barcode system that is compatible with single-cell technologies, enabling paired lineage tracing and phenotypic profiling throughout RASi treatment. Our lineage tracing studies suggest that drug persistence and resistance are fueled by a subset of cells that are primed to survive RASi treatment. Ongoing work is directed at defining and tracking the cell states associated with each stage of resistance emergence. Citation Format: Jayne C. McDevitt, Connor J. Hennessey, Robert Vander Velde, Sydney M. Shaffer, Ben Z. Stanger. Clonal dynamics and molecular mechanisms mediating resistance to RAS inhibition abstract. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research—Emerging Science Driving Transformative Solutions; Boston, MA; 2025 Sep 28-Oct 1; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2025;85 (18Suppl₃): Abstract nr B082.
McDevitt et al. (Sun,) studied this question.