Carbonate-Bearing Ionizable Lipids for mRNA Delivery to Splenic NK Cells

mRNA immunotherapies targeting natural killer (NK) cells hold substantial potential for treating cancer and viral diseases. However, achieving functional delivery of mRNA to splenic NK cell subsets remains a formidable challenge. Herein, we rationally design a library of 161 carbonate-bearing ionizable lipids (CAILs) and formulate lipid nanoparticles (LNPs) for functional mRNA delivery to the spleen and NK cells following intravenous administration. Unlike traditional LNPs that primarily target the liver, CAIL-based four-component LNPs predominantly deliver mRNA to the spleen. Notably, the removal of cholesterol from CAIL LNPs further enhances the spleen-targeting specificity and efficacy, significantly surpassing those of previous spleen-targeted LNPs. As a result, the optimized CAIL LNPs achieve robust mRNA translation in splenic NK cells, inducing encouraging transfection of 21% of splenic NK cells in an Ai9 mouse model. The lipid structural design and LNP formulation optimization pave the way to address the challenge of efficient mRNA delivery to NK cells, presenting opportunities for the development of NK cell-based mRNA therapies.