A Rapidly Excretable, ROS-Scavenging Ionizable Lipid Decouples mRNA Delivery Potency from Toxicity

The broader clinical application of mRNA therapeutics remains constrained by dose-limiting toxicities, vector-associated immunogenicity, and prolonged tissue retention of lipid nanoparticles (LNPs) in vivo. Here, we report a class of ionizable lipids incorporating a sulfur-bearing hexyl 2-hydroxyethyl sulfide (HHES) motif that decouples mRNA delivery potency from these safety liabilities through dual functionality: the sulfur moiety acts as an intrinsic reactive oxygen species scavenger to suppress oxidative stress, while undergoing oxidative conversion into hydrophilic metabolites to promote rapid systemic clearance. HHES-based LNPs demonstrated a 3.3-fold shorter hepatic half-life and 29-fold lower total hepatic exposure than MC3, while maintaining robust protein expression including functional monoclonal antibody production in vivo. Repeated dosing in non-human primates confirmed negligible systemic, hepatic, or hematological toxicity. Leveraging this safety profile, subretinal HHES LNP delivery achieved up to 57% genome editing efficiency in retinal pigment epithelium, suppressing choroidal neovascularization by [~]65% in a wet age-related macular degeneration model without structural damage or microglial activation. This dual-function design provides a generalizable framework for safe, transient, non-accumulative mRNA nanomedicines.