Abstract 4482: Development of a stable and efficient therapeutic mRNA cancer vaccine utilizing RNA-plex technology

Abstract Background: Therapeutic mRNA vaccine is a promising approach for cancer immunotherapy. However, one of its major challenges is the inherent instability of mRNAs, as it is highly sensitive to ambient environments. Consequently, current mRNA vaccines require production, shipping, and storage at ultra-low temperatures, limiting their global application and increasing costs. Thus, enhancing mRNA stability is essential to develop stable mRNA-based therapeutic vaccines. Methods: In this study, we developed a novel mRNA stabilization technology termed "RNA-plex", which prevents mRNA from hydrolytic degradation using polymeric macromolecules known as “carrier-base”, composed of a poly-glutamic/aspartic acid backbone conjugated with nucleobases. Results: We demonstrated that unprotected (naked) mRNA was completely degraded after incubation at 95°C in only 5 minutes, while mRNA complexed with carrier-base remained intact, showing resistance to hydrolytic degradation at high temperatures. Additionally, RNA-plex stabilized mRNA in water at room temperature (RT) for over two weeks and at 4°C for more than two months, whereas naked mRNA degraded within 3 days at RT and within one month at 4°C. Moreover, the protective effect of carrier-base is independent of RNA sequence and structure, effectively safeguarding various linear mRNAs, circular RNAs, and single guide RNAs, and being compatible to commonly used RNA delivery systems. In addition to mRNA protection, RNA-plex effectively boosts mRNA translation in 293T cells and antigen presentation in dendritic cells, making it a potent tool for enhancing cellular responses. We prepared mRNA vaccines by encapsulating either naked OVA mRNA or OVA RNA-plex within in vivo-jetRNA (jetRNA), a liposomal in vivo mRNA transfection reagent, and tested its effectiveness in cancer immunotherapy in an ovalbumin (OVA) engineered B16 melanoma model (B16-OVA). The jetRNA-RNA-plex formulation demonstrated robust efficacy in inhibiting melanoma growth compared to the formulation containing naked mRNA only (p<0.01). Conclusion: Our findings demonstrate that the RNA-plex technology effectively stabilizes mRNA, offering impressive potential for long-term storage in ambient environment. Moreover, RNA-plex enhances mRNA translation and significantly improves anti-cancer efficacy in cancer vaccines by eliciting a robust anti-tumor immune response. These promising results suggest that RNA-plex holds substantial potential for advancing mRNA-based therapeutics for cancers. Citation Format: Yongbin Liu, Dongfang Yu, Lingyi Huang, Junhua Mai. Development of a stable and efficient therapeutic mRNA cancer vaccine utilizing RNA-plex technology [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 4482.