Multicomponent Thiolactone-Based Ionizable Lipid Screening Platform for an Efficient and Tunable mRNA Delivery to the Lungs

ABSTRACT Ionizable lipids are an essential component of lipid nanoparticles (LNPs) for an efficient mRNA delivery. However, optimizing their chemical structures for high protein expression, efficient endosomal escape, and selective organ targeting remains challenging due to complex structure-activity relationships and multistep synthesis. In this study, we introduce a rapid, high-throughput platform for screening ionizable lipids using a two-step, scalable synthesis involving a one-pot 3-component click-like reaction. This method, herein known as the STAAR approach, standing for Sequential Thiolactone Amine Acrylate Reaction, allowed for the combinatorial synthesis and in vivo screening of 91 novel lipids, followed by a structure-activity study. This led to the development of CP-LC-0729, an ionizable lipid that significantly surpasses the benchmark in protein expression while showing no in vivo toxicity. Additionally, the STAAR lipid platform was further validated by incorporating a one-step strategy to yield a permanently cationic lipid which was tested following a fifth-lipid formulation strategy. The in vivo results showed a highly selective lung delivery with a 32-fold increase in protein expression, outperforming current endogenous targeting strategies. All these findings underscore the potential of lipid CP-LC-0729 and the STAAR lipid platform in advancing the efficiency and specificity of mRNA delivery systems, while also advancing the development of new ionizable lipids.