Biodegradable lipid nanoparticles for genome editing in the brain via intrathecal administration.

Messenger RNA (mRNA)-based nonviral delivery of gene editors offers transformative potential for therapeutic genome editing in neurological diseases, but efficient and safe delivery to the brain remains a formidable challenge due to the restrictive blood-brain barrier. Intrathecal administration provides a clinically validated route to bypass this barrier, yet the design principles for biodegradable lipid nanoparticles (LNPs) optimized for central nervous system (CNS) delivery remain poorly defined. Here, we synthesized a 200-member combinatorial library of structurally diverse, biodegradable ionizable lipids using the Passerini three-component reaction. High-throughput in vivo screening identified P3B, a lead lipid incorporating degradable linkages and optimized ionizable head groups, which enables potent and well-tolerated intrathecal mRNA delivery. In Ai9 reporter mice, P3B-LNPs encapsulating Cas9 mRNA/sgRNA induced robust and widespread tdTomato expression in neurons and astrocytes across multiple brain regions, achieving substantially higher editing efficiency than the clinical benchmark DLin-MC3-DMA (MC3). In LumA reporter mice, P3B-LNPs mediated efficient adenine base editing, restoring luciferase expression throughout the brain with 14.8% on-target correction and minimal off-target activity. Compared with MC3, P3B-LNPs exhibited enhanced tolerability, with attenuated inflammatory responses and a safety profile supportive of repeated dosing. These findings establish P3B-LNPs as a potent, safe, and biodegradable platform for genome editing in the brain and underscore the power of combinatorial lipid chemistry and high-throughput in vivo screening to accelerate the development of next-generation LNPs for CNS-targeted mRNA therapeutics.