Enhanced Intramuscular mRNA Activity of Peptide-Lipid Nanoparticles with Hydrophobized Head Groups.

A library of xenopeptide-based ionizable lipids (XP-ILs) was evaluated in mRNA lipid nanoparticles (LNPs) to investigate the impact of modifications within the polar oligoamine headgroup. Modifications included hydrophobic or bulky side chains or a reduced number of protonatable amines. The resulting XP-ILs were characterized by their key physicochemical properties (logD, logP, HLB, CMC), which were correlated with LNP transfection efficiency and cytotoxicity. The inverse relationship between computational logP and experimental logD5.5 is consistent with the HLB, indicating a lower tendency for water-in-oil micelle formation in carriers with larger hydrophobic headgroups. Four-tailed oleic acid (OleA)4-XP-ILs strongly benefited from a cyclohexyl substituent in the polar ionizable headgroup. Hydrophobization of already highly effective bundle-shaped lipoamino fatty acid (LAF)4-XP-ILs moderately improved efficiency. Notably, intramuscular LNP administration resulted in enhanced in vivo mRNA activity of hydrophobized carriers over previous lead compounds, LAF4-XP (2-fold) and OleA4-XP (12-fold).