Abstract A116: Combined KRAS and AXL inhibition synergizes in PDAC

Abstract Background: Targeted therapies have so far failed in eliciting sustained responses in advanced PDAC. Given the ubiquity of KRAS mutations in PDAC, KRAS-targeted therapies hold great promise to improve treatment outcomes, however, emerging evidence indicate that only a subset of patients respond, and that acquired resistance is common. Resistance and lack of response has been associated with reactivation of MAPK signaling, in some cases through compensatory activation of receptor tyrosine kinases. Here, we set out to identify treatments that synergize with KRAS inhibition to suppress MAPK reactivation. Materials and Methods: We used our CRISPRa-competent PPKS (P53 (F/F), Kras (LSL-G12D/+), R26 (LSL-SAM) ) model of adenocarcinoma to identify candidate drivers of resistance to KRAS inhibition. Candidate drivers were evaluated using pharmacologic inhibition in a panel of mouse model-derived and human cell lines, and patient-derived organoids. Promising combinations were investigated further using transcriptomic analysis and western blotting for MAPK-signaling members. We generated subcutaneous syngeneic tumors in C57BL/6 mice and treated with KRAS and AXL inhibitor alone, or in combination. Tumor sizes were assessed with caliper and weighed at endpoint. Tumors were subjected to transcriptomic analysis and IHC staining for tumor and immune markers. Results: Using in vivo CRISPRa screening, we identified a set of genes as potential drivers of resistance to KRAS inhibition, including AXL receptor tyrosine kinase. In vitro, we identified increased levels of phosphorylated AXL in response to KRAS inhibition, indicating a potential role of AXL signaling in MAPK reactivation. We found that combined pharmacological inhibition of KRAS (allele-specific and KRAS (MULTI) ) and AXL resulted in significant synergistic effects across a large panel of mouse model-derived KRAS-G12D mutant pancreatic and lung cancer cell lines, as well as in a smaller set of PDAC and NSCLC cell lines, and patient-derived organoids. Combined treatment resulted in significantly reduced phospho-ERK, DUSP6 and MYC protein levels at 24 hours, and we found that combined treatment significantly extended suppression of DUSP6 and MYC transcription, consistent with a synergistic effect on MAPK-signaling. Transcriptomic analysis of a panel of treated cell lines revealed a profound effect of combined inhibition on gene expression and confirmed enhanced suppression of the KRAS and ERK-regulated transcriptome, including significantly lower MAPK pathway activity scores. Finally, we performed syngeneic transplantation experiments. These experiments showed that combined treatment significantly inhibited tumor growth beyond the effect of KRAS inhibition alone. IHC staining and transcriptomic analysis revealed significant recruitment immune cell lineages in KRAS inhibitor and combination treated mice, with an enhanced effect in the combination cohort. Together, these results highlight the potential of exploring combined KRAS and AXL inhibition in patients with KRAS mutant PDAC and NSCLC. Citation Format: Fredrik I. Thege, Annaliese Kramer, Amber Hoskins, Ashwath Seetharaman, Sonja Woermann, Anirban Maitra. Combined KRAS and AXL inhibition synergizes in PDAC 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 A116.