Lipid 17 is a novel, highly potent ionizable lipid designed for mRNA delivery within lipid nanoparticles (LNPs) developed by AstraZeneca . Its structure features a secondary amine head group attached to a cyclic ether moiety (specifically, the 2-oxaspiro[3.3]heptan-6-amine head group). It possesses an asymmetric tail architecture: one tail is derived from heptadecan-9-ol (a branched C17 secondary alcohol), while the other tail is a modified nonyl chain (C9) with a key ethyl branch at the 3-position. The linker connecting the head group to the tails has a length equivalent to n=3 (three methylene units) as defined in the study. This specific combination of the secondary amine cyclic ether head group, asymmetric tails, and the ethyl branch at the 3-position of the nonyl chain proved critical for its exceptional performance. When formulated into LNPs and administered intravenously in mice, Lipid 17 demonstrated a remarkable 6-fold increase in functional protein (eGFP) expression in the liver compared to the benchmark lipid MC3, with high statistical significance (P < 0.0001). This makes Lipid 17 one of the most active lipids identified in the study and a promising candidate for liver-targeted mRNA therapeutics.
