Lipid nanoparticles (LNPs) carrying mRNA have emerged as potent tools for gene therapies targeting cancer, infectious diseases, and immune disorders. Despite the growing interest in mRNA-LNPs, their therapeutic potential is hindered by mRNA entrapment within endosomes, and the precise mechanism of LNP-mediated mRNA delivery remains poorly understood. To address these challenges, we investigated LNP-mediated mRNA delivery using a library of small molecules targeting endosomal trafficking. Our findings reveal that inhibiting endocytic recycling significantly enhances mRNA expression both in cells and in live mice. Notably, a particularly effective small molecule, endosidine 5 (ES5), disrupts recycling endosomes via Annexin A6, facilitating mRNA release and expression in the cytoplasm. These results underscore the potential of targeting endosomal trafficking with small molecules to enhance the efficacy of mRNA-LNPs.
Over the past two decades, mRNA-LNPs have demonstrated remarkable performance in therapeutic development, notably during the COVID-19 pandemic. Through LNP-mediated delivery, mRNAs encoding therapeutic proteins can be efficiently expressed in targeted cells and tissues, offering promise for treating a spectrum of human diseases, including viral infections, cancer, immune disorders, and neurological conditions. Moreover, recent advancements have leveraged mRNA-LNPs for genome editing, enabling the development of potent immunotherapies by reprogramming T cells.
The efficacy of mRNA therapeutics hinges on effective delivery and translation of mRNAs in target cells. Early efforts were impeded by mRNA degradation and limited protein expression. The discovery of pseudouridine, which enables mRNA escape from the innate immune system, marked a significant breakthrough, substantially enhancing the efficacy of mRNA-LNPs. Further improvements, such as self-replicating and circular mRNAs, hold promise for enhancing therapeutic outcomes. However, the inefficient delivery of mRNA remains a major hurdle, necessitating high doses for treatment. Understanding how LNPs facilitate mRNA entry into cells is crucial for improving delivery efficiency. While LNPs were initially designed for siRNA delivery, the exact mechanism of LNP-mediated mRNA delivery remains elusive. Current understanding suggests LNPs promote siRNA entry by escaping late endosomes; however, recent studies challenge this model, proposing early endosomal release for mRNA. To address these gaps, we investigated small molecules targeting different stages of endosomal trafficking to enhance mRNA-LNP delivery. Our study underscores the significance of targeting the endosomal recycling pathway for advancing mRNA-LNP research and therapeutic applications.
