Abstract 6943: RV-1521: A broad-spectrum mRNA vaccine targeting KRAS mutations in cancer

Abstract KRAS mutations, particularly G12 and G13 variants, are common in cancers but remain difficult to target therapeutically. While KRAS G12C inhibitors, such as sotorasib and adagrasib, have made significant progress, their mutation-specificity excludes up to 85% of KRAS-mutant cancers, including those with G12D, G12V, and G13D mutations. To address this gap, we developed RV-1521, a broad-spectrum mRNA vaccine targeting multiple KRAS mutations, including G12D and G13D, and evaluated its efficacy in a CT26 colon cancer model in Balb/c mice. RV-1521 induced robust immune responses, with serum IgG titers increasing 3.5-fold (p < 0.01). B cell epitope mapping identified four immunogenic KRAS regions. T cell profiling revealed activation hotspots in peptides P1, P35, and P36, with significant IFN-γ secretion in response to both wild-type and G12D-mutant KRAS epitopes. Flow cytometry analysis showed a 2.7-fold increase in IFN-γ+ CD4+ T cells in splenocytes from vaccinated mice. These results highlight RV-1521's capacity to activate diverse immune mechanisms targeting KRAS-mutant tumor elimination, particularly through CD4+ T cell-mediated responses. As a monotherapy, RV-1521 demonstrated dose-dependent antitumor efficacy, reducing tumor volume by 50% (p < 0.001) and tumor mass by 45%. This was accompanied by a 3-fold increase in CD8+ T cell infiltration and a 2.8-fold increase in granzyme B expression. These findings were consistent with reduced tumor proliferation and enhanced T cell-mediated cytotoxicity. When combined with anti-PD-1 therapy, RV-1521 further amplified its efficacy, achieving a 70% reduction in tumor volume (p < 0.001) and a 2.5-fold increase in tumor IFN-γ levels, while preserving cytotoxic T cell activity and reversing T cell exhaustion. Transcriptomic analysis revealed upregulation of immune pathways, including T cell receptor and Th1/Th2 signaling, alongside downregulation of key oncogenic drivers such as EGR1, FOS, and JUN. Strain-specific analysis revealed stronger immune responses in Balb/c mice compared to C57BL/6 mice, suggesting that genetic background may influence immune activation. Notably, RV-1521 elicited immune responses against both wild-type and mutant KRAS, addressing tumor heterogeneity and minimizing immune escape. The unexpected cytotoxic role of CD4+ T cells further underscores the therapeutic potential of this vaccine. By targeting multiple KRAS mutations, RV-1521 overcomes the limitations of mutation-specific therapies. Its ability to synergize with anti-PD-1 therapy and elicit a robust, multi-faceted antitumor immune response positions it as a promising strategy for treating KRAS-driven cancers. Ongoing studies will evaluate its safety and adaptability across diverse microenvironments and patient populations. Citation Format: Renxiang Chen, Yongsik Bong, Wei Liu, Ezra Chung, David Brown, Evan Lewoczko, Zachary Dorsey, Steven Long, Cun Yu Wang, Dong Shen. RV-1521: A broad-spectrum mRNA vaccine targeting KRAS mutations in cancer [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 6943.