Fra-2 controls the response to the KRAS inhibitor MRTX-1133 in pancreatic ductal adenocarcinoma

: KRAS mutations are a hallmark of pancreatic ductal adenocarcinoma (PDAC), driving tumor initiation and progression in the vast majority of cases, with KRASG12D being the most prevalent variant. Recent advances have led to the development of mutation-specific KRAS inhibitors (KRASi), yet their clinical impact is hindered by the rapid onset of drug resistance. In this study, we identify Fos-related antigen-2 (Fra-2), a stress-responsive transcription factor of the AP-1 family, as a key mediator of adaptive resistance to the KRASG12D selective inhibitor MRTX-1133. Using a combination of established PDAC cell lines, xenograft models, and patient-derived organoids, we demonstrate that Fra-2 expression is consistently upregulated following MRTX-1133 treatment. Functional assays reveal that Fra-2 overexpression promotes resistance by reprogramming the transcriptional landscape, directly enhancing mTOR expression and signaling. Consistently, FRA2 and MTOR levels strongly correlate in PDAC patient samples. Collectively, these findings uncover a mechanistic interplay between Fra-2 and the mTOR pathway in MRTX-1133-resistant PDAC, highlighting that targeting Fra-2 may represent a valuable approach to enhance the efficacy of KRASi.