Exploring Clearance Pathways for GalNAc–siRNAs: Insights into Intracellular Kinetics and Therapeutic Implications

Small interfering RNA (siRNA) represents a transformative therapeutic class that enables precise gene silencing through RNA interference (RNAi). N-acetyl galactosamine (GalNAc)-conjugated siRNAs have achieved remarkable clinical success with six FDA-approved therapeutics targeting liver diseases. Following subcutaneous administration, GalNAc-siRNAs rapidly accumulate in hepatocytes via asialoglycoprotein receptor (ASGPR)-mediated endocytosis and are sequestered within endolysosomal compartments, creating an intracellular depot that sustains therapeutic effects for weeks to months. While RNAi-mediated degradation and nuclease metabolism contribute to siRNA clearance, the detection of full-length, active siRNA in circulation long after dosing suggests alternative clearance mechanisms exist. This review examines the pharmacokinetic properties and intracellular trafficking of GalNAc-siRNA, with particular focus on underexplored clearance pathways from hepatocytes. We discuss potential mechanisms including endosomal recycling, efflux via exosomes and lysosomal exocytosis that may facilitate siRNA redistribution from tissues to circulation. Understanding these clearance mechanisms could enable correlation of plasma and tissue drug concentrations, reduce preclinical animal use, inform clinical dosing strategies and guide the design of next-generation siRNA therapeutics with optimized tissue residence time and enhanced therapeutic durability.