Mutationally activated KRAS comprises the major oncogenic driver in the top three causes of cancer deaths in the US: lung (LAC), colorectal (CRC), and pancreatic ductal adenocarcinoma (PDAC). In 2021, a milestone in anti-KRAS drug discovery was achieved, with the first clinically effective direct inhibitor of KRAS approved, for the treatment of KRASG12C mutant lung cancer. However, as with essentially all targeted anti-cancer therapies, both de novo resistance and treatment-associated acquired resistance have recently been reported. As anticipated, mutations that reactivate RAS and RAS effector signaling through the RAF-MEK-ERK mitogen- activated protein kinase signaling network (e.g., activating mutations in BRAF, MEK1) were identified in LAC and CRC patients treated with KRASG12C selective inhibitors (G12Ci), and combinations that concurrently target these resistance mechanisms are now under clinical evaluation. However, no genetic mechanisms were identified in up to 50% of patients who relapsed on G12Ci treatment. To address possible ERK MAPK-independent resistance mechanisms, my studies have identified and validated the downstream target of the Hippo tumor suppressor pathway, the YAP1 transcriptional coactivator and oncoprotein, as a driver of resistance to G12Ci- mediated growth suppression. Consistent with previous studies that established the ability of YAP1 activation to overcome addiction to mutant KRAS, my preliminary analyses demonstrated that ectopic overexpression of wild- type or activated YAP1 drives resistance to G12Ci treatment in KRASG12C mutant LAC, CRC and PDAC cell lines. This finding establishes the rationale and foundation for my research goal: to determine the mechanistic basis for YAP1-mediated resistance to G12Ci treatment. I hypothesize that identification of YAP1-driven resistance mechanisms will establish combinations of pharmacologic inhibitors that can enhance the long-term anti-tumor efficacy of G12Ci and other KRAS-targeted therapies. I have developed three aims to address the mechanisms by which YAP1 drives resistance. First, I will determine the role of the TEAD transcription factors in YAP1-driven KRAS-independence. These studies may validate the clinical application of TEAD inhibitors for the treatment of KRAS-mutant PDAC and other cancers. Second, I will identify YAP1- regulated genes that sustain KRAS-independent growth, in support of a model where YAP1 overcomes KRAS- addiction by restoring expression of key KRAS-regulated genes. Finally, I will identify KRAS-regulated metabolic processes that are both sustained by YAP1 activation and important for PDAC growth. Taken together, my studies may validate an important driver of resistance to all KRAS-targeted therapies and define therapeutic approaches to overcome YAP1-driven drug resistance. These studies will require my application of a diverse spectrum of experimental approaches, advance my understanding of key steps in anti-cancer drug development, and foste...