PT  - JOURNAL ARTICLE
AU  - Jie Wei
AU  - Jeffrey Jones
AU  - Jing Kang
AU  - Ananda Card
AU  - Michael Krimm
AU  - Paula Hancock
AU  - Yi Pei
AU  - Brandon Ason
AU  - Elmer Payson
AU  - Natalya Dubinina
AU  - Mark Cancilla
AU  - Mark Stroh
AU  - Julja Burchard
AU  - Alan Sachs
AU  - Jerome Hochman
AU  - William Michael Flanagan
AU  - Nelly Kuklin
TI  - RISC bound siRNA is a determinant of RNAi mediated gene silencing in mice
AID  - 10.1124/mol.110.070409
DP  - 2011 Jan 01
TA  - Molecular Pharmacology
PG  - mol.110.070409
4099  - http://molpharm.aspetjournals.org/content/early/2011/03/22/mol.110.070409.short
4100  - http://molpharm.aspetjournals.org/content/early/2011/03/22/mol.110.070409.full
AB  - Deeper knowledge of pharmacokinetic and pharmacodynamic (PK/PD) concepts for RNA therapeutics is important to streamline the drug development process and for rigorous selection of best performing drug candidates. Here we characterized the PK/PD relationship for small interfering ribonucleic acids (siRNAs) targeting luciferase by examining siRNA concentration in plasma and liver, the temporal RISC (RNA-induced silencing complex) binding profiles, mRNA reduction, and protein inhibition measured by non-invasive bioluminescent imaging. A dose-dependent and time-related decrease in bioluminescence was detected over 25 days following a single treatment of a lipid nanoparticle (LNP) formulated siRNA targeting luciferase messenger RNA. A direct relationship was observed between the degree of in vivo mRNA and protein reduction and the Argonaute2 (Ago2) bound siRNA fraction but not with the total amount of siRNA found in the liver, suggesting that the Ago2-siRNA complex is the key determinant of target inhibition. These observations were confirmed for an additional siRNA that targets endogenously expressed Sjogren syndrome antigen B (Ssb), indicating that our observations are not limited to a transgenic mouse system. Our data provide detailed information of the temporal regulation of siRNA liver delivery, Ago2 loading, mRNA reduction, and protein inhibition that are essential for the rapid and cost-effective clinical development of siRNAs therapeutics..