The opportunity to harness the RNA interference (RNAi) pathway to silence disease-causing genes holds great promise for the development of therapeutics directed against targets that are otherwise not addressable with current medicines1,2. Although there are numerous examples of in vivo silencing of target genes after local delivery of small interfering RNAs (siRNAs)3,4,5, there remain only a few reports of RNAi-mediated silencing in response to systemic delivery of siRNA6,7,8, and there are no reports of systemic efficacy in non-rodent species. Here we show that siRNAs, when delivered systemically in a liposomal formulation, can silence the disease target apolipoprotein B (ApoB) in non-human primates. APOB-specific siRNAs were encapsulated in stable nucleic acid lipid particles (SNALP) and administered by intravenous injection to cynomolgus monkeys at doses of 1 or 2.5 mg kg-1. A single siRNA injection resulted in dose-dependent silencing of APOB messenger RNA expression in the liver 48 h after administration, with maximal silencing of >90%. This silencing effect occurred as a result of APOB mRNA cleavage at precisely the site predicted for the RNAi mechanism. Significant reductions in ApoB protein, serum cholesterol and low-density lipoprotein levels were observed as early as 24 h after treatment and lasted for 11 days at the highest siRNA dose, thus demonstrating an immediate, potent and lasting biological effect of siRNA treatment. Our findings show clinically relevant RNAi-mediated gene silencing in non-human primates, supporting RNAi therapeutics as a potential new class of drugs.

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We are grateful to P. Sharp, J. Maraganore and N. Mahanthappa for their assistance and support in this study. We would also like to thank W. J. Schneider, J. Frohlich, M. Hayden and J. E. Vance for discussions. We acknowledge the technical assistance of C. Woppmann and A. Wetzel, and thank V. Kesavan and G. Wang for preparation of the cholesterol-conjugated siRNA used in this study. Finally, we thank S. Young for providing anti-ApoB antibodies. This work was supported by grants from the National Science and Engineering Research Council of Canada (to A.J.W. and M.N.F.). Author Contributions This work represents the outcome of a collaboration between scientists at Alnylam Pharmaceuticals and Protiva Biotherapeutics Inc.

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  1. Alnylam Pharmaceuticals Inc., 300 Third Street, Cambridge, Massachusetts 02142, USA

    • Tracy S. Zimmermann
    • , Akin Akinc
    • , David Bumcrot
    • , Jens Harborth
    • , Lubomir V. Nechev
    • , Timothy Racie
    • , Sumi Shanmugam
    • , Ivanka Toudjarska
    • , William Zedalis
    • , Victor Koteliansky
    •  & Muthiah Manoharan
  2. Protiva Biotherapeutics Inc., 100-3480 Gilmore Way, Burnaby, British Columbia V5G 4YI, Canada

    • Amy C. H. Lee
    • , Matthew N. Fedoruk
    • , James A. Heyes
    • , Lloyd B. Jeffs
    • , Adam D. Judge
    • , Kieu Lam
    • , Kevin McClintock
    • , Lorne R. Palmer
    • , Vandana Sood
    • , Amanda J. Wheat
    • , Ed Yaworski
    •  & Ian MacLachlan
  3. Alnylam Europe AG, Fritz-Hornschuch-Str. 9, 95326 Kulmbach, Germany

    • Birgit Bramlage
    • , Matthias John
    • , Ingo Röhl
    • , Stephan Seiffert
    • , Jürgen Soutschek
    •  & Hans-Peter Vornlocher


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Competing interests

The authors of this paper are employees of either Alnylam Pharmaceuticals or Protiva Biotherapeutics Inc., and therefore declare competing financial interests.

Corresponding authors

Correspondence to Tracy S. Zimmermann or Ian MacLachlan.

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    Supplementary Methods

    This file contains details of experimental methods used in this study.

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