biostudies-literatureDe CKEuropean Research CouncilDeutsche ForschungsgemeinschaftJapan Agency for Medical Research and DevelopmentJapan Society for the Promotion of Science28595-28600https://www.ebi.ac.uk/biostudies/studies/S-EPMC12356529biostudies-literatureUnknown147(32)Lipid nanoparticles (LNPs) are a powerful delivery platform for nucleic acid therapeutics such as mRNA vaccines and gene therapies. Central to their success are ionizable lipids, which facilitate the cellular uptake and endosomal escape of nucleic acids. However, achieving a high delivery efficiency often comes with the drawback of increased cytotoxicity. Here, we report a chemical, biological, and toxicological investigation into the three stereoisomers of ALC315, a mixture of which constitutes one of the most successful marketed ionizable lipids for LNPs. We demonstrate that the individual stereoisomers of ALC315 can be accessed by either the asymmetric chemical synthesis or chromatography of an intermediate. An LNP formulation based on a single stereoisomer of ALC315 enhances mRNA transJournal of the American Chemical SocietyThe Overlooked Stereoisomers of the Ionizable Lipid ALC315.PMC1235652923K0658422H04989JP24gm1810006h694228EXC 2033 - 390677874223fa627002h24H00037JP24ek0410124h101055472Arase HDehn SHinrichs HJin HTanaka STsuda MTsuji NDe CKList BZhu CfalseThe Overlooked Stereoisomers of the Ionizable Lipid ALC315.Lipid nanoparticles (LNPs) are a powerful delivery platform for nucleic acid therapeutics such as mRNA vaccines and gene therapies. Central to their success are ionizable lipids, which facilitate the cellular uptake and endosomal escape of nucleic acids. However, achieving a high delivery efficiency often comes with the drawback of increased cytotoxicity. Here, we report a chemical, biological, and toxicological investigation into the three stereoisomers of ALC315, a mixture of which constitutes one of the most successful marketed ionizable lipids for LNPs. We demonstrate that the individual stereoisomers of ALC315 can be accessed by either the asymmetric chemical synthesis or chromatography of an intermediate. An LNP formulation based on a single stereoisomer of ALC315 enhances mRNA trans2025-01-01T00:00:00Z2025 Aug2026-05-01T18:43:50.37Z2026-04-07T17:09:25.221ZS-EPMC123565294074569910.1021/jacs.5c08345