Abstract 4311: Exploiting the spontaneous intrahepatic cholangiocarcinoma mouse models to uncover MRTX1133's dual role in directly inhibiting KRASG12D-driven tumor progression and modulating the immune landscape

Abstract Purpose: Mutations in the KRAS gene, particularly the G12D variant, are prevalent in intrahepatic cholangiocarcinoma (iCCA) and correlate with unfavorable patient outcomes. Currently, there is an urgent need for targeted therapeutic strategies against KRASG12D iCCA. This study aims to investigate the impact and mechanisms of KRASG12D mutation on iCCA progression and to conduct a preclinical evaluation of MRTX1133, a non-covalent inhibitor of KRASG12D. Methods: We developed spontaneous tumorigenesis mouse models of iCCA harboring KRASG12D mutation (YAPS127A+AKT+KRASWT/G12D model and AKT+NICD+KRASWT/G12D model) using hydrodynamic tail vein injection, aiming to study the oncogenic role and mechanisms of KRASG12D in iCCA. The impact of MRTX1133 on KRASG12D iCCA was investigated using human iCCA cell lines, patient-derived organoids (PDOs), cell line xenografts, patient-derived xenografts (PDXs), and spontaneous tumorigenesis mice. Single-cell RNA sequencing (scRNA-seq) and multiplex immunofluorescence were utilized to assess changes in the tumor microenvironment following KRASG12D mutation and MRTX1133 treatment. Results: The KRASG12D mutation significantly increased oncogenicity in several iCCA mouse models, characterized by increased tumor proliferation, reduced survival, and robust activation of downstream ERK pathway, along with elevated Ki67 expression. MRTX1133 demonstrated potent antitumor activity against human KRASG12D iCCA cell lines, PDOs, and in vivo models, including PDX and iCCA spontaneous tumorigenesis mice, exhibiting inhibited tumor proliferation, suppressed ERK and AKT pathway activation, and extended mouse survival. The scRNA-seq analysis revealed a reduction in CD8+ T cells and an increase in M2-type macrophages in the tumor microenvironment of KRASG12D iCCA mice, while these alterations were reversed by MRTX1133 treatment, as validated by multiplexed immunofluorescence. Notably, MRTX1133 showed a more pronounced antitumor effect in immunocompetent C57 mice compared to immunodeficient NSG mice (68% tumor volume reduction versus 36%), suggesting that immune system engagement enhances the efficacy of MRTX1133. The in vivo studies combining MRTX1133 with immune checkpoint blockade (ICB) are underway to determine their potential synergistic effects. Conclusion: This study is the first to validate the oncogenic role and therapeutic vulnerability of the KRASG12D mutation in iCCA. It also suggests the potential benefits of combining KRASG12D inhibitor MRTX1133 with ICB immunotherapy with synergistic effects. Citation Format: Xiuxian Li, Guanhua Wu, Zhixiao Song, Jiahao Xue, Honghua Zhang, Chao Liu. Exploiting the spontaneous intrahepatic cholangiocarcinoma mouse models to uncover MRTX1133's dual role in directly inhibiting KRASG12D-driven tumor progression and modulating the immune landscape [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 4311.