Fusion Peptide‐Incorporated Lipid Nanoparticles Boost Endosomal Escape and Enhance Cytosolic mRNA Delivery

The endosomal escape capability of current mRNA-loaded lipid nanoparticles (mRNA-LNPs) is generally low, which restricts their overall delivery efficiency. To address this limitation, we adopted a strategy inspired by the viral infection mechanism, utilizing fusion peptides to enhance the intracellular release of mRNA. Nine viral-derived and artificial fusion peptides were co-encapsulated within mRNA-LNPs respectively, termed FP-LNPs, and systematically assessed their efficacy in improving mRNA delivery. Notably, the HA2 fusion peptide from the influenza virus demonstrated a marked enhancement in mRNA delivery efficiency both in vitro and in vivo. Under acidic conditions of endosomes, HA2 collaborates with ionizable cationic lipids to facilitate endosomal membrane rupture, thereby promoting the release of mRNA into the cytoplasm and enhancing protein expression. Moreover, the incorporation of fusion peptides into various types of mRNA-LNP formulations significantly improved their in vivo delivery efficiency of mRNA, resulting in improved gene editing outcomes in the liver and lungs. Furthermore, in a Hereditary Tyrosinemia Type 1 (HT-1) mouse model, HA2-LNP significantly boosted FAH protein expression in the liver and more effectively prevented body weight loss and reduced liver fibrosis. Overall, this approach offers a promising strategy for enhancing endosomal escape and boosting the delivery efficiency of mRNA, underscoring its enhanced therapeutic potential.