4A3-SCC-PH is a groundbreaking linker-degradable ionizable lipid (LDIL) that features a glutathione (GSH)-responsive cone-shaped molecular structure. This unique architecture enables superior endosomal escape and rapid mRNA release, making it highly effective for mRNA delivery. In vivo studies have highlighted its exceptional performance, showing a 176-fold increase in mRNA delivery efficiency to the liver compared to DLin-MC3-DMA, a widely used benchmark lipid. Both 4A3-SCC-PH and its structural analog, 4A3-SCC-10, also demonstrated significantly enhanced mRNA delivery efficacy compared to their non-disulfide-containing parent compounds and disulfide-containing controls with modified lipid tails.