Combination of ionizable lipids with oleic acid and vitamin E scaffolds for RNA cancer vaccine delivery

RNA vaccines based on lipid nanoparticles (LNPs) encapsulating in vitro transcribed mRNA (IVT-mRNA) are a successful but evolving vaccine modality. It has been increasingly recognized that LNPs, which are mainly composed of ionizable lipids, have two roles in the action of RNA vaccines: delivering mRNA into the cytoplasm by overcoming the endosomal membrane and stimulating the innate immune system as an adjuvant. In this study, we report the development of LNPs with enhanced capability to induce cellular immunity by using a combination of ionizable lipids: one containing an oleic scaffold with high transfection activity (ssPalmO-Phe; SS-OP) and the other containing a vitamin E scaffold with high adjuvant activity (ssPalmE; SS-EC), referred to as LNP_OP/EC. The formulation's efficacy was evaluated in tumor-bearing mice, focusing on immune responses and tumor suppression. The results showed that the inclusion of vitamin E moieties in LNP_OP/EC significantly enhanced cellular immune responses and suppressed tumor growth in an E.G7-OVA tumor-bearing mouse model. Additionally, it demonstrated robust activation of reactive CD8⁺ T cells specifically recognizing the neoantigens mCdt1, mScarb2, and mZfp106, which are expressed in YTN16 murine gastric cells. Suppression of YTN16 tumors was also observed using LNP_OP/EC. The study suggests that LNP_OP/EC is a viable platform for RNA-based cancer vaccines, offering a potent combination of gene expression and immune stimulation.