title: Design of noninflammatory synthetic siRNA mediating potent gene silencing in vivo.
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.
authors.affiliation: Protiva Biotherapeutics, 100-3480 Gilmore Way, Burnaby, BC, Canada V5G 4Y1.
authors.forename: Adam D
authors.initials: AD
authors.lastname: Judge
authors.forename: Gurneet
authors.initials: G
authors.lastname: Bola
authors.forename: Amy C H
authors.initials: AC
authors.lastname: Lee
authors.forename: Ian
authors.initials: I
authors.lastname: MacLachlan
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D019175:DNA Methylation; D020868:Gene Silencing / Q000276:immunology; D006801:Humans; D007166:Immunosuppressive Agents / Q000008:administration & dosage / Q000138:chemical synthesis*; D018836:Inflammation Mediators / Q000008:administration & dosage / Q000138:chemical synthesis* / Q000502:physiology; D007963:Leukocytes, Mononuclear / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D008813:Mice, Inbred ICR; D008969:Molecular Sequence Data; D034622:RNA Interference / Q000276:immunology; D034741:RNA, Small Interfering / Q000008:administration & dosage* / Q000138:chemical synthesis* / Q000502:physiology
chemical_list: D007166:Immunosuppressive Agents; D018836:Inflammation Mediators; D034741:RNA, Small Interfering