Targeted Lipid Nanoparticles Loaded With siRNA Can Specifically Manipulate Gut-homing Leukocytes in IBD

Altering gene expression in vivo using nucleic acids prompted much interest since the recent approval of the first RNAi-based drug by the FDA for the treatment of liver diseases. Applying RNAi-based therapeutics in non-hepatic tissues relies on a suitable, non-immunogenic delivery vehicle. Lipid nanoparticles (LNPs) are currently the most advanced non-viral, nucleic acid delivery system in vivo. Most LNP formulations, however, still naturally accumulate in the liver and kidney. Therefore, there is an urgent need for the development of targeting moieties that can be included in the LNP formulation to reach specific cells in other tissues. Here we demonstrate the successful delivery of siRNA to defined subsets of leukocytes using a specific targeting strategy. We used experimental colitis as a model to display the specificity of the targeted LNPs. During colitis, inflammatory cells home to the gut by using the homing receptor α₄β₇ integrin. Like for many integrins, the functionality of α₄β₇ integrin depends on its conformational state. To target a specific conformation, we generated a recombinant protein based on two domains of the integrin ligand MAdCAM-1. This protein binds α₄β₇ integrin exclusively in the open conformation. We were able to conjugate this targeting protein to the surface of the LNPs using a linker. The MAdCAM-targeted LNPs facilitated specific gene silencing in two distinct models of experimental colitis. Gene knockdown was absent in healthy mice, indicating that our targeting system is inflammation dependent as it relies on the presence of α₄β₇ integrin specifically configured in the open conformation.