iL-19 is an aminoethoxy-functionalized ionizable lipid with a triamine scaffold, two ester linkages and four doubly branched hydrophobic tails. It was identified as the overall lead for circular RNA delivery in a 2026 JACS study. With circRNA encoding firefly luciferase, iL-19 LNPs produced approximately 28-fold higher expression than the SM-102 benchmark in C2C12 cells and approximately 2.5-fold higher expression after intramuscular administration in BALB/c mice under the reported conditions. The reported circRNA formulation uses iL-19, DSPC, cholesterol and DMG-PEG2000 at 50:10:38.5:1.5 mol%. It supports preclinical investigation of circular RNA delivery to muscle; comprehensive safety and immunogenicity evaluation remains outstanding.
