Fast and facile synthesis of amidine-incorporated degradable lipids for versatile mRNA delivery in vivo

Lipid nanoparticles (LNPs) are widely used for mRNA delivery, with cationic lipids greatly affecting biodistribution, cellular uptake, endosomal escape and transfection efficiency. However, the laborious synthesis of cationic lipids limits the discovery of efficacious candidates and slows down scale-up manufacturing. Here we develop a one-pot, tandem multi-component reaction based on the rationally designed amine–thiol–acrylate conjugation, which enables fast (1 h) and facile room-temperature synthesis of amidine-incorporated degradable (AID) lipids. Structure–activity relationship analysis of a combinatorial library of 100 chemically diverse AID-lipids leads to the identification of a tail-like amine–ring-alkyl aniline that generally affords efficacious lipids. Experimental and theoretical studies show that the embedded bulky benzene ring can enhance endosomal escape and mRNA delivery by enabling the lipid to adopt a more conical shape. The lead AID-lipid can not only mediate local delivery of mRNA vaccines and systemic delivery of mRNA therapeutics, but can also alter the tropism of liver-tropic LNPs to selectively deliver gene editors to the lung and mRNA vaccines to the spleen. A class of cationic—amidine-based degradable—lipids can now be readily synthesized through a tandem multi-component amine–thiol–acrylate conjugation reaction. Mechanistic studies provided key insights, from which the observed lead lipid enabled mRNA delivery to multiple organs, highlighting the potential for developing mRNA vaccines and therapeutics to treat various diseases.