Targeted Delivery of RNAi Therapeutics With Endogenous and Exogenous Ligand-Based Mechanisms

TLDR

Lipid nanoparticles are highly efficient carriers of siRNAs to hepatocytes, yet the precise mechanism of this delivery remains unclear. The study aimed to develop an exogenous GalNAc‑cluster ligand that targets the ASGPR on hepatocytes as an alternative to endogenous apoE‑mediated delivery. The authors examined apoE’s role using recombinant protein and wild‑type versus apoE‑knockout mice, assessed receptor dependence with LDLR‑deficient mice, and engineered the GalNAc ligand to bind ASGPR. They found that apoE serves as an endogenous targeting ligand for ionizable LNPs but not for cationic LNPs, and that both apoE‑based and GalNAc‑based strategies effectively deliver iLNPs to the liver.

Abstract

Lipid nanoparticles (LNPs) have proven to be highly efficient carriers of short-interfering RNAs (siRNAs) to hepatocytes in vivo; however, the precise mechanism by which this efficient delivery occurs has yet to be elucidated. We found that apolipoprotein E (apoE), which plays a major role in the clearance and hepatocellular uptake of physiological lipoproteins, also acts as an endogenous targeting ligand for ionizable LNPs (iLNPs), but not cationic LNPs (cLNPs). The role of apoE was investigated using both in vitro studies employing recombinant apoE and in vivo studies in wild-type and apoE(-/-) mice. Receptor dependence was explored in vitro and in vivo using low-density lipoprotein receptor (LDLR(-/-))-deficient mice. As an alternative to endogenous apoE-based targeting, we developed a targeting approach using an exogenous ligand containing a multivalent N-acetylgalactosamine (GalNAc)-cluster, which binds with high affinity to the asialoglycoprotein receptor (ASGPR) expressed on hepatocytes. Both apoE-based endogenous and GalNAc-based exogenous targeting appear to be highly effective strategies for the delivery of iLNPs to liver.