Lipid-peptide nanocomplexes for mRNA delivery in vitro and in vivo

Despite recent advances in the field of mRNA therapy, the lack of safe and efficacious delivery vehicles with pharmaceutically developable properties remains a major limitation. Here, we describe the systematic optimi-sation of lipid-peptide nanocomplexes for the delivery of mRNA in two murine cancer cell types, B16-F10 melanoma and CT26 colon carcinoma as well as NCI-H358 human lung bronchoalveolar cells. Different com-binations of lipids and peptides were screened from an original lipid-peptide nanocomplex formulation for improved luciferase mRNA transfection in vitro by a multi-factorial screening approach. This led to the identi-fication of key structural elements within the nanocomplex associated with substantial improvements in mRNA transfection efficiency included alkyl tail length of the cationic lipid, the fusogenic phospholipid, 1,2-dioleoyl-sn- glycero-3-phosphoethanolamine (DOPE), and cholesterol. The peptide component (K16GACYGLPHKFCG) was further improved by the inclusion of a linker, RVRR, that is cleavable by the endosomal enzymes cathepsin B and furin, and a hydrophobic motif (X-S-X) between the mRNA packaging (K16) and receptor targeting domains (CYGLPHKFCG). Nanocomplex transfections of a murine B16-F10 melanoma tumour supported the inclusion of cholesterol for optimal transfection in vivo as well as in vitro. In vitro transfections were also performed with mRNA encoding interleukin-15 as a potential immunotherapy agent and again, the optimised formulation with the key structural elements demonstrated significantly higher expression than the original formulation. Physi-cochemical characterisation of the nanocomplexes over time indicated that the optimal formulation retained biophysical properties such as size, charge and mRNA complexation efficiency for 14 days upon storage at 4 C without the need for additional stabilising agents. In summary, we have developed an efficacious lipid-peptide nanocomplex with promising pharmaceutical development properties for the delivery of therapeutic mRNA.

Automated summary

Despite recent advances in mRNA therapy, the lack of safe and effective delivery vehicles remains a major challenge. In this study, lipid-peptide nanocomplexes were systematically optimized for mRNA delivery. The optimized formulation showed improved transfection efficiency in vitro and in vivo, and retained stable physicochemical properties for a prolonged period of time. This lipid-peptide nanocomplex provides a promising platform for the delivery of therapeutic mRNA.