Targeted Delivery of mRNA with Polymer–Lipid Nanoparticles for In Vivo Base Editing

Messenger RNA (mRNA) encoding base editors, along with single guide RNAs (sgRNAs), have emerged as a promising therapeutic approach for various disorders. However, there is still insufficient exploration in achieving targeted and efficient delivery of mRNA and sgRNA to multiple organs while ensuring high biocompatibility and stability in vivo. To address this challenge, we synthesized a library of 108 poly(β-amino) esters (PBAEs) by incorporating 100% hydrophobic side chains and end-caps with varying amines. These PBAEs were further formulated with other excipients, including helper lipids, cholesterol, and PEGylated lipids, to form polymer–lipid nanoparticles (PLNPs). Structure–function analysis revealed that eLog P of PBAEs could serve as a predictive parameter for determining the liver or lung tropism of PLNPs. The biocompatibility of PBAEs end-capped with monoamines was significantly higher compared to those end-capped with diamines. Leveraging these findings, we expanded the PBAE library and identified a leading PBAE (7C8C8) with mRNA delivery efficiency outperforming current FDA-approved ionizable lipids (ALC-0315, SM-102, and Dlin-MC3-DMA). The LD50 of the empty PLNPs (7C8C8) was determined to be 403.8 ± 49.46 mg/kg, indicating a significantly high safety profile. Additionally, PLNPs (7C8C8) demonstrated sustained transfection activity for at least 2 months when stored at −20 °C after freezing or at 4 °C following lyophilization. Subsequently, in vivo base editing using PLNPs (7C8C8) achieved an impressive editing efficiency of approximately 70% along with a significant reduction in protein levels exceeding 90%. Notably, synergistic effects were observed through simultaneous disruption of proprotein convertase subtilisin/kexin type 9 and angiopoietin-like protein 3 genes, resulting in a sustained low-density lipoprotein cholesterol reduction of over 60% for several months. These compelling findings provide strong support for the further development of PLNPs as promising platforms for mRNA-based therapies.