From Bench to Bedside and Back: Improving the Safety of GalNAc-siRNA Conjugates Using GNA-Destabilized Seed-Pairing

Preclinical mechanistic studies have pointed towards RNAi-mediated off-target effects as a major driver of hepatotoxicity for GalNAc-siRNA conjugates. Here we demonstrate that a single glycol nucleic acid (GNA) modification can substantially reduce siRNA seed-mediated binding to off-target transcripts while maintaining on-target activity. In siRNAs with established off-target effects leading to hepatotoxicity, these Enhanced Stabilization Chemistry plus (ESC+) designs exhibit a substantially improved therapeutic window in rat. We utilized this strategy to improve the safety of ALN-HBV, which exhibited dose-dependent, transient, and asymptomatic alanine aminotransferase elevations in healthy volunteers. Overall design: The increased specificity of GNA-containing GalNAc-siRNAs is demonstrated in vitro and in vivo using measures of differential expression derived from RNA-seq data.