Nuclease resistant double-stranded ribonucleic acid

1. A double-stranded ribonucleic acid (dsRNA) having increased stability in a biological sample, wherein the dsRNA comprises:

(I) a nucleotide overhang having the nucleotide sequence 5′-GCNN-3′, wherein N is A, G, C, U, dT, dU or absent; and

(II) at least one of

(a) 2′-modified uridines in all occurrences of the sequence motif 5′-uridine-adenine-3′ (5′-ua-3′), or

(b) 2′-modified uridines in all occurrences of the sequence motif 5′-uridine-guanine-3′ (5′-ug-3′), or

(c) 2′-modified 5′-most uridines in all occurrences of the sequence motif 5′-uridine-uridine-3′ (5′ -uu-3′), or

(d) 2′-modified uridines in all occurrences of the sequence motif 5′-uridine-cytidine-3′ (5′ -uc-3′), or

(e) 2′-modified cytidines in all occurrences of the sequence motif 5′-cytidine-adenine-3′ (5′-ca-3′), or

(f) 2′-modified cytidines in all occurrences of the sequence motif 5′-cytidine-uridine-3′ (5′-cu-3′), or

(g) 2′-modified 5′-most cytidines in all occurrences of the sequence motif 5′-cytidine-cytidine-3′ (5′-cc-3′).

2. The dsRNA of claim 1 , wherein the first paired nucleotide on the 5′-end of the 5′-GCNN-3′ overhang is cytidine (C).

3. The dsRNA of claim 1 , wherein the unpaired nucleotides comprise at least one phosphorothioate dinucleotide linkage.

4. The dsRNA of claim 1 , wherein nucleotide overhang is at the 3′-end of the antisense RNA strand of the dsRNA.

5. The dsRNA of claim 1 , wherein the antisense RNA strand of the dsRNA comprises a nucleotide sequence 18-30 nucleotides in length which is complementary to the sense strand.

6. The dsRNA of claim 1 , wherein the antisense and sense RNA strands of the dsRNA are connected by a chemical linker.

7. A method of preparing a pharmaceutical composition, comprising formulating the dsRNA of claim 1 , in a pharmaceutically acceptable carrier.

8. A pharmaceutical composition for inhibiting the expression of a target gene in a mammal, comprising:

(A) at least one dsRNA of claim 1 ; and

(B) a pharmaceutical acceptable carrier.

9. The pharmaceutical composition of claim 8 , wherein the pharmaceutically acceptable carrier is an aqueous solution.

10. The pharmaceutical composition of claim 8 , wherein the pharmaceutically acceptable carrier is physiological saline.

11. The dsRNA of claim 1 , wherein the dsRNA comprises at least two different features of the features (a) through (g).

12. The dsRNA of claim 1 , wherein the dsRNA comprises at least three different features of the features (a) through (g).

13. The dsRNA of claim 1 , wherein the dsRNA comprises at least four different features of the features (a) through (g).

14. The dsRNA of claim 13 , wherein the four different features dsRNA comprises at least four different features of the features (a), (b), (c) and (e).

15. The dsRNA of claim 1 , wherein the dsRNA comprises at least five different features of the features (a) through (g).

16. The dsRNA of claim 1 , wherein the dsRNA comprises at least two occurrences of at least one of the sequence motifs of (a) through (g).

17. The dsRNA of claim 1 , wherein the dsRNA comprises at least three occurrences of at least one of the sequence motifs of (a) through (g).

18. The dsRNA of claim 1 , further comprising at least one dinucleotide selected from group of 5′-uu-3′, 5′-ua-3′, 5′-ug-3′, 5′-uc-3′, 5′-cu-3′, 5′-ca-3′, 5′-cg-3′, 5′-cc-3′, wherein no nucleotide is a 2′-O-modified nucleotide.

19. The dsRNA of claim 1 , wherein the 2′-modified nucleotide is a 2′-deoxy nucleotide, a 2′-O-methyl nucleotide, a 2′-deoxyfluoro nucleotide, a 2′-O- methoxyethyl (2′-MOE)) nucleotide, a 2′-O-methylacetamido (2′-NMA), a 2′-O- dimethyl-amino-ethoxy-ethyl nucleotide, a 2′-O-dimethylaminopropyl (2′-O-AP) nucleotide, 2′-ara-F nucleotide, or a locked nucleic acid nucleotide, extended nucleic acid nucleotide, a hexose nucleic acid, or cyclohexose nucleic acid.