Abstract 5691: Preclinical evaluation of RMC-7977, a multi-selective RAS(ON) inhibitor, as a therapeutic strategy for KRAS-mutant cholangiocarcinoma

Abstract Background: Cholangiocarcinoma (CCA), comprises approx. 3% of all gastrointestinal tumors, and is characterized by highly dismal prognosis. Therapies predominantly rely on chemotherapy, and treatment advancements have been stagnant over the past decades, underscoring the critical need for innovative therapies. Mutant KRAS is among the most prevalent oncogenes in CCA, highlighting a potential role for KRAS inhibitors as therapeutic avenues. Here, we present preclinical data on RMC-7977, a RAS (ON) inhibitor as a potential therapeutic strategy for CCA with KRAS mutations. Materials and Methods: Human and murine KRAS mutated cell lines were utilized to determine the effect of RMC-7977 both in vitro and in vivo. H69 immortalized cholangiocytes were virally infected with KRAS mutant isoforms (4B, G12, G13, Q61). RNA-seq and Western blot was conducted to analyze the molecular changes and potential resistance mechanisms. The tumor immune microenvironment was assessed via multiplex flow cytometry. Combinatorial pharmacological treatments were conducted in vitro and in vivo to study resistance mechanisms overcome. Both human and murine cell lines resistant to the RAS(ON) inhibitor were generated. Subsequently RNA seq and WES were performed to identify possible transcriptomic changes and acquired mutations in resistant cells. Results: RMC-7977 elicited antiproliferative effects in mouse and human CCA cell lines with different KRAS mutations (G12D/G12V/G13C) and H69 expressing various KRAS mutations in vitro. In vivo experiments with human xenografts or mouse allografts revealed heterogeneous antitumor responses ranging from tumor regressions to growth delay. In vitro mouse cell line/CD8+ co-culture experiments, showed RMC-7977 capacity to increase CD8 cytotoxicity. Tumor immune phenotyping of immunocompetent mice showed a notable increase in NK, CD8, and CD4 infiltration, and a reduction of PMN-MDSCs, indicative of a less immunosuppressive microenvironment. RNA-seq and Western blot analysis revealed increased activity of the SHP2, FGFR, and JAK/STAT pathways. Further in vitro testing confirmed the synergistic effects when we combined RMC-7977 plus SHP2 (in parental and resistant models) but also combinatorial benefit in xenograft models in vivo. Addition of the standard of care (Gem/Cis/PD1) to the RAS(ON) inhibitor resulted in significant tumor regression and enhanced anti-tumor activity compared to single treatments. Identification of potential resistant mechanisms related to transcriptomic changes, acquired mutations and CNV in resistant models is currently ongoing. Conclusion: In summary, our preclinical findings support the clinical testing of a RAS(ON) multi-selective inhibitor, either alone or in combination with other in-pathway or out-of-pathway partners, as a potential therapeutic strategy for CCA treatment. Citation Format: Rodrigo Entrialgo-Cadierno, Iker Feliu, Ines Lopez, Yaiza Senent, Shruthi Narayanan, Nicole Nasholm, Ruben Pio, Jingjing Jiang, Silvestre Vicent. Preclinical evaluation of RMC-7977, a multi-selective RAS(ON) inhibitor, as a therapeutic strategy for KRAS-mutant cholangiocarcinoma [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 5691.