Molecular Therapy
Volume 13, Issue 3, March 2006, Pages 494-505
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Article
Design of Noninflammatory Synthetic siRNA Mediating Potent Gene Silencing in Vivo

https://doi.org/10.1016/j.ymthe.2005.11.002Get rights and content
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Abstract

Targeted silencing of disease-associated genes by synthetic short interfering RNA (siRNA) holds considerable promise as a novel therapeutic strategy. However, unmodified siRNA can be potent triggers of the innate immune response, particularly when associated with delivery vehicles that facilitate intracellular uptake. This represents a significant barrier to the therapeutic development of siRNA due to toxicity and off-target gene effects associated with this inflammatory response. Here we show that immune stimulation by synthetic siRNA can be completely abrogated by selective incorporation of 2′-O-methyl (2′OMe) uridine or guanosine nucleosides into one strand of the siRNA duplex. These noninflammatory siRNA, containing less than 20% modified nucleotides, can be readily generated without disrupting their gene-silencing activity. We show that, coupled with an effective systemic delivery vehicle, 2′OMe-modified siRNA targeting apolipoprotein B (apoB) can mediate potent silencing of its target mRNA, causing significant decreases in serum apoB and cholesterol. This is achieved at therapeutically viable siRNA doses without cytokine induction, toxicity, or off-target effects associated with the use of unmodified siRNA. This approach to siRNA design and delivery should prove widely applicable and represents an important step in advancing synthetic siRNA into a broad range of therapeutic areas.

Abbreviations

apoB
apolipoprotein B
TLR
Toll-like receptor
ssRNA
single-stranded RNA
dsRNA
double-stranded RNA
siRNA
short interfering RNA
IFN-α
interferon-α
IL-6
interleukin-6
TNF-α
tumor necrosis factor-α
RNAi
RNA interference
β-gal
β-galactosidase
PBMC
peripheral blood mononuclear cells

Keywords

RNA interference
nucleic acid therapeutics
synthetic siRNA
chemical Modification
inflammatory response
apolipoprotein B
interferons
liposomes

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