For oligonucleotide therapeutics, chemical modifications of the sugar-phosphate backbone are frequently used to confer drug-like properties. Because 2′-deoxy-2′-fluoro (2′-F) nucleotides are not known to occur naturally, their safety profile was assessed when used in revusiran and ALN-TTRSC02, two short interfering RNAs (siRNAs), of the same sequence but different chemical modification pattern and metabolic stability, conjugated to an N-acetylgalactosamine (GalNAc) ligand for targeted delivery to hepatocytes. Exposure to 2′-F-monomer metabolites was low and transient in rats and humans. In vitro, 2′-F-nucleoside 5′-triphosphates were neither inhibitors nor preferred substrates for human polymerases, and no obligate or non-obligate chain termination was observed. Modest effects on cell viability and mitochondrial DNA were observed in vitro in a subset of cell types at high concentrations of 2′-F-nucleosides, typically not attained in vivo. No apparent functional impact on mitochondria and no significant accumulation of 2′-F-monomers were observed after weekly administration of two GalNAc–siRNA conjugates in rats for ∼2 years. Taken together, the results support the conclusion that 2′-F nucleotides can be safely applied for the design of metabolically stabilized therapeutic GalNAc–siRNAs with favorable potency and prolonged duration of activity allowing for low dose and infrequent dosing.
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Date of publication: 01 March 2019; Nucleic Acids Research
Author information: Maja M Janas (1), Ivan Zlatev (1), Ju Liu (1), Yongfeng Jiang (1), Scott A Barros (1), Jessica E Sutherland (1), Wendell P Davis (1), Jingxuan Liu (1), Christopher R Brown (1), Xiumin Liu (1), Mark K Schlegel (1), Lauren Blair (1), Xuemei Zhang (1), Biplab Das (1), Chris Tran (1), Krishna Aluri (1), Jing Li (1), Saket Agarwal (1), Ramesh Indrakanti (1), Klaus Charisse (1), Jayaprakash Nair (1), Shigeo Matsuda (1), Kallanthottathil G Rajeev (1), Tracy Zimmerman (1), Laura Sepp-Lorenzino (1), Yuanxin Xu (1), Akin Akinc (1), Kevin Fitzgerald (1), Akshay K Vaishnaw (1), Peter F Smith (1), Muthiah Manoharan (1), Vasant Jadhav (1), Jing-Tao Wu (1), & Martin A Maier (1)
(1) Alnylam Pharmaceuticals, Inc., Cambridge, MA 02142, USA