Identification of metabolically stable 5′-phosphate analogs that support single-stranded siRNA activity |
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Authors: | Thazha P Prakash Walt F Lima Heather M Murray Wenyu Li Garth A Kinberger Alfred E Chappell Hans Gaus Punit P Seth Balkrishen Bhat Stanley T Crooke Eric E Swayze |
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Institution: | Isis Pharmaceuticals Inc., 2855 Gazelle Ct, Carlsbad, CA 92010, USA |
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Abstract: | The ss-siRNA activity in vivo requires a metabolically stable 5′-phosphate analog. In this report we used crystal structure of the 5′-phosphate binding pocket of Ago-2 bound with guide strand to design and synthesize ss-siRNAs containing various 5′-phosphate analogs. Our results indicate that the electronic and spatial orientation of the 5′-phosphate analog was critical for ss-siRNA activity. Chemically modified ss-siRNA targeting human apoC III mRNA demonstrated good potency for inhibiting ApoC III mRNA and protein in transgenic mice. Moreover, ApoC III ss-siRNAs were able to reduce the triglyceride and LDL cholesterol in transgenic mice demonstrating pharmacological effect of ss-siRNA. Our study provides guidance to develop surrogate phosphate analog for ss-siRNA and demonstrates that ss-siRNA provides an alternative strategy for therapeutic gene silencing. |
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