Abstract A037: Enhanced anti-tumor activity through targeted immunotherapy combined with mutant KRAS inhibition in pancreatic cancer

Abstract

Abstract Constitutively-active KRASG12D has become targetable via clinical-stage KRASG12D-selective small molecule inhibitors. Prior preclinical research has demonstrated that KRASG12D inhibition makes pancreatic ductal adenocarcinoma (PDAC) more amenable to immunotherapy. However, the impact of such inhibition on antigen presentation by tumor cells remains unclear. To elucidate this phenomenon, we employed a multi-omic profiling workflow to investigate alterations in the proteome and peptide MHC ligandome (immunopeptidome) following treatment of HPAC human cancer cells with a RAS(ON) G12D-selective inhibitor RM-044 (representative of investigational agent RMC-9805) and/or IFNɣ in vitro. Multi-omic profiling revealed significant changes in antigen presentation following KRASG12D inhibition. Pairwise comparisons of differentially expressed proteins in treated vs. untreated conditions showed increased expression of proteins associated with interferon signaling and replication stress. Notably, antigen processing and presentation proteins such as HLA-B and -C alpha chains showed some of the highest expression levels. Immunopeptidomic analysis revealed a 2-fold increase in ligand diversity and abundance in treated vs. untreated conditions. Sequence motif enrichment analysis depicted motifs consistent with HPAC’s HLA-B and -C but not -A alleles, aligning with proteomic findings and highlighting how the integration of these two data layers informs the shaping of the immunopeptidomic landscape. Building on these findings, we hypothesized that KRASG12D signaling inhibition in preclinical models could augment immune responses initiated by immunization targeting tumor antigens in vivo. Our hypothesis was that the release of antigens from KRASG12D-induced cell death, coupled with increased MHC-I expression in remaining tumor cells, would enhance interactions with T cells activated by immunization. To test this, we orthotopically inoculated C57Bl/6 mice with a murine PDAC-KRASG12D cell line engineered to express the model self/tumor-associated antigen gp100. Mice were immunized with either empty ionizable lipid nanoparticles (e-iLNPs) or iLNPs packaged with mRNA encoding full-length gp100 (gp100-iLNP). Following a priming and boost series, mice were treated with either KRASG12D inhibitior MRTX1133 or vehicle for two weeks. Remarkably, mice treated with the gp100 mRNA-iLNP immunization followed by KRASG12D inhibition experienced significant tumor regression compared to mice that received KRASG12D inhibition alone. These preclinical findings underscore the dynamic nature by which PDAC antigen presentation can be modulated by KRAS signaling inhibition and IFNɣ. The combination of allele-specific KRAS inhibition with tumor antigen immunization resulted in significant tumor regression in a stringent in vivo PDAC preclinical model, compared to either treatment modality alone. This rationalizes the combination of both approaches for enhanced anti-tumor activity, offering a strategy that is worth exploring clinically for improving outcomes in pancreatic cancer treatment. Citation Format: Amanda Creech, Hailey Lee, Khalid Rashid, Thuc Le, Alykhan Premji, Tony Luu, Ahmad Kassem, Weihang Zhao, Luyi Li, Nanping Wu, Norbert Pardi, James Wohlschlegel, Timothy Donahue, Caius Radu. Enhanced anti-tumor activity through targeted immunotherapy combined with mutant KRAS inhibition in pancreatic cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor Immunology and Immunotherapy; 2024 Oct 18-21; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2024;12(10 Suppl):Abstract nr A037.