Abstract
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 RNAs (siRNAs) targeting luciferase by examining siRNA concentration in plasma and liver, the temporal RNA-induced silencing complex binding profiles, mRNA reduction, and protein inhibition measured by noninvasive bioluminescent imaging. A dose-dependent and time-related decrease in bioluminescence was detected over 25 days after a single treatment of a lipid nanoparticle-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 Sjögren syndrome antigen B (Ssb) mRNA, 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.
Footnotes
↵ The online version of this article (available at http://molpharm.aspetjournals.org) contains supplemental material.
This work was supported by Merck and Co., Inc.
Article, publication date, and citation information can be found at http://molpharm.aspetjournals.org.
doi:10.1124/mol.110.070409.
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ABBREVIATIONS:
- RNAi
- RNA interference
- siRNA
- small interfering RNA
- PK
- pharmacokinetic
- PD
- pharmacodynamic
- RISC
- RNA-induced silencing complex
- RSV
- respiratory syncytial virus
- LNP
- lipid nanoparticle
- CMV
- cytomegalovirus
- AUC
- area under the curve
- RT-PCR
- reverse transcription-polymerase chain reaction
- qPCR
- quantitative PCR
- GAPDH
- glyceraldehyde 3-phosphate dehydrogenase
- UC3
- scrambled universal control
- PBS
- phosphate-buffered saline
- Ago2
- Argonaute2
- Luc
- Luciferase
- Ssb
- Sjögren syndrome antigen B
- MGBNFQ
- minor groove binder nonfluorescent quencher.
- Received December 7, 2010.
- Accepted March 21, 2011.
- Copyright © 2011 The American Society for Pharmacology and Experimental Therapeutics
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