Multiarm-Assisted Design\nof Dendron-like Degradable\nIonizable Lipids Facilitates Systemic mRNA Delivery to the Spleen

Lipid nanoparticles (LNPs) have emerged as pivotal vehicles\nfor\nmessenger RNA (mRNA) delivery to hepatocytes upon systemic administration\nand to antigen-presenting cells following intramuscular injection.\nHowever, achieving systemic mRNA delivery to non-hepatocytes remains\nchallenging without the incorporation of targeting ligands such as\nantibodies, peptides, or small molecules. Inspired by comb-like polymeric\narchitecture, here we utilized a multiarm-assisted design to construct\na library of 270 dendron-like degradable ionizable lipids by altering\nthe structures of amine heads and multiarmed tails for optimal mRNA\ndelivery. Following in vitro high-throughput screening, a series of\ntop-dendron-like LNPs with high transfection efficacy were identified.\nThese dendron-like ionizable lipids facilitated greater mRNA delivery\nto the spleen in vivo compared to ionizable lipid analogs lacking\ndendron-like structure. Proteomic analysis of corona-LNP pellets showed\nenhancement of key protein clusters, suggesting potential endogenous\ntargeting to the spleen. A lead dendron-like LNP formulation, 18–2–9b2,\nwas further used to encapsulate Cre mRNA and demonstrated excellent\ngenome modification in splenic macrophages, outperforming a spleen-tropic\nMC3/18PA LNP in the Ai14 mice model. Moreover, 18–2–9b2\nLNP encapsulating therapeutic BTB domain and CNC homologue 1 (BACH1)\nmRNA exhibited proficient BACH1 expression and subsequent Spic downregulation\nin splenic red pulp macrophages (RPM) in a Spic-GFP transgene model\nupon intravenous administration. These results underscore the potential\nof dendron-like LNPs to facilitatem RNA delivery to splenic macrophages,\npotentially opening avenues for a range of mRNA-LNP therapeutic applications,\nincluding regenerative medicine, protein replacement, and gene editing\ntherapies.