Large and low-PEG lipid nanoparticles enable efficient dendritic cell targeting for potent mRNA Cancer vaccines.

Efficient delivery of messenger RNA (mRNA) to dendritic cells (DCs) remains a major challenge limiting the efficacy of mRNA cancer vaccines. Here, we report a large-sized lipid nanoparticle (LLNP) platform specifically engineered for enhanced DC targeting. By reducing PEG-lipid content to 0.3% and proportionally increasing the concentrations of structural lipids and mRNA sixfold relative to the Moderna classic formulation, we generated LLNPs with enlarged size and optimized surface properties that favor DC uptake. Following intravenous administration, LLNPs achieved markedly enhanced mRNA expression in DCs, with ∼82% of GFP+ cells identified as DCs and ∼ 44% of CD11c+ DCs expressing GFP. LLNPs also promoted DC maturation and antigen presentation. LLNP-mediated delivery of HPV16 E6E7 mRNA elicited robust effector and memory cytotoxic T lymphocyte responses, enabling effective tumor regression at doses as low as 1 μg. Both conventional type 1 dendritic cells (cDC1) and conventional type 2 dendritic cells contributed to antigen presentation, with cDC1 playing the predominant role. Compared with BioNTech's RNA-lipoplex delivery platform, LLNPs demonstrated superior DC transfection, T cell activation, and antitumor efficacy. Collectively, these findings establish LLNPs as a robust and versatile platform for next-generation mRNA cancer vaccines with enhanced therapeutic potential.