20 Aug, 2020 Nonclinical Research on Pharmacodynamic Durability of GalNAc-siRNA Conjugates Published in “Nucleic Acids Research”
We published nonclinical research describing the durability of gene silencing by GalNAc-conjugated siRNAs. The article, titled, “Investigating the Pharmacodynamic Durability of GalNAc-siRNA Conjugates,” was selected as a Breakthrough Paper by Nucleic Acids Research.
One hallmark of trivalent N-acetylgalactosamine (GalNAc)-conjugated siRNAs is the remarkable durability of silencing that can persist for months in preclinical species and humans. Here, we investigated the underlying biology supporting this extended duration of pharmacological activity. We found that siRNA accumulation and stability in acidic intracellular compartments is critical for long-term activity. We show that functional siRNA can be liberated from these compartments and loaded into newly generated Argonaute 2 protein complexes weeks after dosing, enabling continuous RNAi activity over time. Identical siRNAs delivered in lipid nanoparticles or as GalNAc conjugates were dose-adjusted to achieve similar knockdown, but only GalNAc–siRNAs supported an extended duration of activity, illustrating the importance of receptor-mediated siRNA trafficking in the process. Taken together, we provide several lines of evidence that acidic intracellular compartments serve as a long-term depot for GalNAc–siRNA conjugates and are the major contributor to the extended duration of activity observed in vivo.