Structure-guided design of ionizable lipids with distinct amine headgroups for muscle-selective mRNA delivery and enhanced antitumor immunotherapy.

The development of messenger RNA (mRNA)-based cancer immunotherapies has gained significant attention due to their potential to activate robust immune responses against tumors. However, a major challenge remains in developing an efficient delivery system that targets mRNA to specific tissues while minimizing off-target accumulation in the liver. Ionizable lipid nanoparticles (LNPs) are a promising platform for mRNA vaccine delivery, but achieving tissue-selective delivery is essential for maximizing both safety and efficacy. In this study, we synthesized a series of ionizable lipids with varying amine head groups and hydrophobic tail lengths using a Michael addition reaction and incorporated them into LNPs. Through systematic screening of physicochemical properties and in vitro mRNA expression profiles, spermine was identified as the optimal amine head group. Further optimization of hydrophobic tail chain length led to the identification of 114-LNP as the most effective formulation. Compared with SM-102-based LNP (SM102-LNP), 114-LNP offers distinct advantages for muscle-selective mRNA delivery, achieving efficient expression in muscle tissue while markedly reducing off-target accumulation in organs such as the liver, thereby minimizing the risk of off-target toxicity. When loaded with ovalbumin (OVA) mRNA, 114-LNP enhanced antigen presentation and dendritic cell maturation, leading to robust anti-tumor immune responses and significant inhibition of tumor growth in E.G7-OVA tumor-bearing mice. Overall, this study demonstrates that rational molecular design and systematic screening of ionizable lipids can yield LNPs with improved tissue-selective mRNA delivery and therapeutic performance, highlighting 114-LNP as a safe and effective platform for mRNA-based cancer immunotherapy.