Modified siRNA molecules and uses thereof

• US 7,915,399 B2
• Filed: 06/08/2007
• Issued: 03/29/2011
• Est. Priority Date: 06/09/2006
• Status: Active Grant

• Current Assignee: Arbutus Biopharma Corporation
• Original Assignee: Protiva Biotherapeutics Inc (Arbutus Biopharma Corporation)
• Inventors: Judge, Adam, MacLachlan, Ian
• Primary Examiner(s): WHITEMAN, BRIAN A
• Application Number:
  US11/760,627
• Publication Number:
  US 20080249046A1
• Time in Patent Office: 1,390 Days
• Field of Search: 536/24.5
• US Class Current: 536/24.5
• CPC Class Codes: A61P 43/00 Drugs for specific purposes, not provided for in groups A61P1/00-A61P41/00
• CPC Class Codes: C12N 15/111 General methods applicable to biologically active non-coding nucleic acids
• CPC Class Codes: C12N 2310/14 interfering N.A.
• CPC Class Codes: C12N 2310/321 2'-O-R Modification
• CPC Class Codes: C12N 2310/322 2'-R Modification
• CPC Class Codes: C12N 2310/3521 Methyl
• CPC Class Codes: C12N 2320/53 reducing unwanted side-effects

Abstract

The present invention provides chemically modified siRNA molecules and methods of using such siRNA molecules to silence target gene expression. Advantageously, the modified siRNA of the present invention is less immunostimulatory than its corresponding unmodified siRNA sequence and retains full RNAi activity against the target sequence. The present invention also provides nucleic acid-lipid particles comprising a modified siRNA, a cationic lipid, and a non-cationic lipid, which can further comprise a conjugated lipid that inhibits aggregation of particles. Methods for identifying and/or modifying an siRNA having immunostimulatory properties are also provided.

Claims

1. A method for generating a chemically modified double-stranded short interfering nucleic acid (siNA) molecule that directs cleavage of a target RNA via RNA interference and has reduced immunostimulatory properties compared to a corresponding siNA molecule having unmodified nucleotides, said method comprising:

(a) introducing 2′

-O-methyl (2′

OMe) nucleotides in one or more of the nucleotide positions of the siNA molecule, wherein

(i) each strand of said siNA molecule is about 18 to about 38 nucleotides in length;

(ii) one strand of said siNA molecule comprises a nucleotide sequence having sufficient complementarity to said target RNA for the siNA molecule to direct cleavage of the target RNA via RNA interference;

(iii) said siNA molecule does not comprise phosphorothioate backbone modifications; and

(iv) said 2′

OMe nucleotides are not 2′

OMe-cytosine nucleotides; and

(b) assaying the siNA molecule of step (a) under conditions suitable for isolating an siNA molecule having reduced immunostimulatory properties compared to a corresponding siNA molecule having unmodified nucleotides wherein said reduced immunostimulatory properties comprise an abrogated or reduced induction of inflammatory or pro-inflammatory cytokines and/or an abrogated or reduced induction of Toll Like Receptors (TLRs) in response to the siNA being introduced in a cell, tissue, or organism.

2. The method of claim 1, wherein said reduced immunostimulatory properties comprise an abrogated or reduced induction of inflammatory or proinflammatory cytokines in response to the siNA being introduced in a cell, tissue, or organism.

3. The method of claim 2, wherein said cytokine comprises interleukin-6 (IL-6) or tumor necrosis alpha (TNF-α

).

4. The method of claim 1, wherein said reduced immunostimulatory properties comprise an abrogated or reduced induction of Toll Like Receptors (TLRs) in response to the siNA being introduced in a cell, tissue, or organism.

5. The method of claim 4, wherein said Toll Like Receptor comprises TLR3, TLR7, TLR8 or TLR9.

6. The method of claim 1, wherein said 2′

OMe nucleotides are 2′

OMe-guanosine nucleotides, 2′

OMe-uridine nucleotides, or combinations thereof.

7. The method of claim 1, wherein less than about 20% of the nucleotides in said siNA molecule comprise 2′

OMe nucleotides.

8. The method of claim 1, wherein each strand of said siNA molecule is about 19 to about 25 nucleotides in length.

9. The method of claim 1, wherein said siNA molecule comprises 3′

overhangs.

10. The method of claim 1, wherein said siNA molecule is chemically synthesized.

11. The method of claim 1, wherein said siNA molecule is assayed by contacting said siNA molecule with a mammalian responder cell.