Advanced siRNA Designs Further Improve In Vivo Performance of GalNAc-siRNA Conjugates

• Published in: Molecular therapy Vol. 26; no. 3; pp. 708 - 717
• Main Authors: Foster, Donald J., Brown, Christopher R., Shaikh, Sarfraz, Trapp, Casey, Schlegel, Mark K., Qian, Kun, Sehgal, Alfica, Rajeev, Kallanthottathil G., Jadhav, Vasant, Manoharan, Muthiah, Kuchimanchi, Satya, Maier, Martin A., Milstein, Stuart
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 07.03.2018; Elsevier Limited; American Society of Gene & Cell Therapy
• Subjects: Acetylgalactosamine - chemistry; Animals; Argonaute Proteins - genetics; Chemistry; Datasets; Design; Experiments; GalNAc conjugates; Gene Expression Regulation; Gene Silencing; Genes; Hepatocytes - metabolism; Ligands; Liver; Liver - metabolism; Male; Metabolism; Mice; Mice, Transgenic; N-Acetylgalactosamine; Original; RNA Interference; RNA, Messenger - genetics; RNA, Small Interfering - administration & dosage; RNA, Small Interfering - chemistry; RNA, Small Interfering - genetics; RNA-mediated interference; RNAi; siRNA; GalNAc conjugates; RNAi; siRNA
• ISSN: 1525-0016; 1525-0024
• DOI: 10.1016/j.ymthe.2017.12.021

Significant progress has been made in the advancement of RNAi therapeutics by combining a synthetic triantennary N-acetylgalactosamine ligand targeting the asialoglycoprotein receptor with chemically modified small interfering RNA (siRNA) designs, including the recently described Enhanced Stabilization Chemistry. This strategy has demonstrated robust RNAi-mediated gene silencing in liver after subcutaneous administration across species, including human. Here we demonstrate that substantial efficacy improvements can be achieved through further refinement of siRNA chemistry, optimizing the positioning of 2′-deoxy-2′-fluoro and 2′-O-methyl ribosugar modifications across both strands of the double-stranded siRNA duplex to enhance stability without compromising intrinsic RNAi activity. To achieve this, we employed an iterative screening approach across multiple siRNAs to arrive at advanced designs with low 2′-deoxy-2′-fluoro content that yield significantly improved potency and duration in preclinical species, including non-human primate. Liver exposure data indicate that the improvement in potency is predominantly due to increased metabolic stability of the siRNA conjugates. Foster et al. use an iterative screening strategy to optimize the chemical modification patterns on siRNAs, improving stability and activity. The authors present data demonstrating that the improvements translate across species from mouse to non-human primate, enhancing the potential of this class of therapeutics.