RNA interference (RNAi)

RNAi/siRNA based therapeutics specifically target and degrade mRNA using a naturally occurring cellular mechanism that regulates the expression of genes. RNAi/siRNA is a highly promising therapeutic appoach for those diseases where aberrant protein production is a problem.

  1. A small interfering RNA (siRNA) drug is targeted to a specific gene
  2. Within cells, the siRNA duplex unwinds and is incorporated into RISC, a protein-RNA complex
  3. The incorporated strand of the siRNA directs mRNA target recognition.
  4. RISC mediates mRNA degradation, disrupting gene expression.

Animation of the RNA interference process (external links):
 

http://www.nature.com/focus/rnai/animations/index.html

http://www.pbs.org/wgbh/nova/sciencenow/3210/02.html

 

Advantages of RNAi Therapeutics

RNAi-based therapeutics have:

  • Great potential for highly specific and safe targeting of aberrant gene expression underlying diverse diseases and conditions.
  • Potential for faster identification of a lead drug since rational design allows a faster screening process in vitro and more predictable pharmacokinetics in vivo.
  • A special promise for the field of oncology, where a combinatorial treatment stratagem may bypass resistance to traditional drugs and/or increase specificity of action.

Technology : Selected readings

Relevant RNAi publications from company AAG members:

  • Amarzguioui M et al. Rational design and in vitro and in vivo delivery of Dicer substrate siRNAs. Nature Protocols 2006. 2:508-517.
  • Amarzguioui M. RNAi-based therapeutics – promises and challenges. Innovations in Pharmaceutical Technology 2006. April edition (p 30-35).
  • Amarzguioui M et al. Ex vivo and in vivo delivery of anti-Tissue Factor siRNA inhibits mouse pulmonary metastasis of B16 melanoma cells. Clin Cancer Research 2006. 12:4055-4061.
  • Holen T, et al. Tolerated wobble mutations in siRNAs decrease specificity, but can enhance activity in vivo. Nucleic Acids Res. 2005. 33(15):4704-10.
  • Wang, X et al. Down-regulation of Tissue Factor by RNA interference in human melanoma LOX-L cells reduce pulmonary metastasis in nude mice. In J. Cancer 2004. 112:994-1002.
  • Snøve, O & Holen, T. Many commonly used siRNAs risk off-target activity. Biochem Biophys Res Commun. 2004. 319(1):256-263.
  • Amarzguioui M & Prydz H. An algorithm for selection of functional siRNA sequences. Biochem Biophys Res Commun. 2004. 316:1050-1058.
  • Amarzguioui M, Holen T, et al. Tolerance for mismatches and chemical modifications in an siRNA. Nucleic Acids Res. 2003. 31:589-595.
  • Holen T, Amarzguioui M, et al. Positional effects of short interfering RNAs targeting the human coagulation trigger Tissue factor. Nucleic Acids Res. 2003. 30:1757-1766.

Recommended readings from other scientists:

Design considerations

  • Jackson AL, et al (2006). Position-specific chemical modification of siRNAs reduces "off-target" transcript silencing. RNA, 2006. 12(7):1197-1205.
  • Elbashir, S.M., et al., Duplexes of 21-nucleotide RNAs mediate RNA interference in cultured mammalian cells. Nature, 2001. 411(6836): p. 494-8.
  • Schwarz, D.S. et al. Asymmetry in the assembly of the RNAi enzyme complex. Cell 115, 199-208 (2003)
  • Reynolds, A. et al. Rational siRNA design for RNA interference. Nat Biotechnol 22, 326-330 (2004)
  • Kim, D.H. et al. Synthetic dsRNA Dicer substrates enhance RNAi potency and efficacy. Nat Biotechnol 23, 222-226 (2005) Rose, S.D., et al., Functional polarity is introduced by Dicer processing of short substrate RNAs. Nucleic Acids Res, 2005. 33(13): p. 4140-56.
  • Huesken, D. et al. Design of a genome-wide siRNA library using an artificial neural network. Nat Biotechnol 23, 995-1001 (2005).

In vivo applications

  • Song E, et al.Antibody mediated in vivo delivery of small interfering RNAs via cell-surface receptors. Nature Biotechnology. Nat Biotechnol. 2005. 23(6):709-717
  • Zimmermann, TS et al. RNAi-mediated gene silencing in non-human primates. Nature, 2006. 441(7089):111-114.
  • Geisbert, TW et al. Postexposure protection of guinea pigs against a lethal ebola virus challenge is conferred by RNA interference.
  • Soutschek, J., et al., Therapeutic silencing of an endogenous gene by systemic administration of modified siRNAs. Nature, 2004. 432(7014): p. 173-8.
  • Morrissey, D.V., et al., Potent and persistent in vivo anti-HBV activity of chemically modified siRNAs. Nat Biotechnol, 2005. 23(8): p. 1002-7.
  • Hu-Lieskovan, S., et al., Sequence-specific knockdown of EWS-FLI1 by targeted, nonviral delivery of small interfering RNA inhibits tumor growth in a murine model of metastatic Ewing's sarcoma. Cancer Res, 2005. 65(19): p. 8984-92.
  • Judge, A.D., et al., Design of Noninflammatory Synthetic siRNA Mediating Potent Gene Silencing in Vivo. Mol Ther, 2006. 13(3): p. 494-505.