Lipid encapsulated interfering RNA

1. A nucleic acid-lipid particle, said nucleic acid-lipid particle comprising:

a chemically synthesized siRNA;

a cationic lipid;

a non-cationic lipid; and

a conjugated lipid that inhibits aggregation of particles, wherein the conjugated lipid that inhibits aggregation of particles comprises a polyethyleneglycol-dialkyloxypropyl (PEG-DAA) conjugate having the following structure:

wherein:

R 1 and R 2 are independently selected and are alkyl groups having from about 10 to about 22 carbon atoms;

PEG is a polyethyleneglycol, wherein the terminal hydroxyl group is substituted with a methyl group; and

L is a carbamate linker moiety; and

wherein said siRNA is fully encapsulated in said nucleic acid-lipid particle.

2. The nucleic acid-lipid particle in accordance with claim 1 , wherein said siRNA component of said nucleic acid-lipid particle is resistant in aqueous solution to degradation by a nuclease.

3. The nucleic acid-lipid particle in accordance with claim 1 , wherein said particle has a median diameter of less than about 150 nm.

4. The nucleic acid-lipid particle in accordance with claim 1 , wherein said siRNA comprises about 15 to about 60 nucleotides.

5. The nucleic acid-lipid particle in accordance with claim 1 , wherein said cationic lipid is a member selected from the group consisting of N,N-dioleyl-N,N-dimethylammonium chloride (DODAC), N,N-distearyl-N,N-dimethylammonium bromide (DDAB), N-(1-(2,3-dioleoyloxy)propyl)-N,N,N-trimethylammonium chloride (DOTAP), N-(1-(2,3-dioleyloxy)propyl)-N,N,N-trimethylammonium chloride (DOTMA), N,N-dimethyl-2,3-dioleyloxypropylamine (DODMA), and combinations thereof.

6. The nucleic acid-lipid particle in accordance with claim 1 , wherein said non-cationic lipid is a member selected from the group consisting of dipalmitoylphosphatidylcholine (DPPC), dioleoylphosphatidylethanolamine (DOPE), palmitoyloleoylphosphatidylcholine (POPC), egg phosphatidylcholine (EPC), distearoylphosphatidylcholine (DSPC), cholesterol, and combinations thereof.

7. The nucleic acid-lipid particle in accordance with claim 1 , wherein said cationic lipid comprises from about 2% to about 60% of the total lipid present in said particle.

8. The nucleic acid-lipid particle in accordance with claim 1 , wherein said cationic lipid comprises from about 5% to about 45% of the total lipid present in said particle.

9. The nucleic acid-lipid particle in accordance with claim 1 , wherein said cationic lipid comprises from about 40% to about 50% of the total lipid present in said particle.

10. The nucleic acid-lipid particle in accordance with claim 1 , wherein said non-cationic lipid comprises from about 5% to about 90% of the total lipid present in said particle.

11. The nucleic acid-lipid particle in accordance with claim 1 , wherein said non-cationic lipid comprises from about 20% to about 85% of the total lipid present in said particle.

12. The nucleic acid-lipid particle in accordance with claim 1 , wherein said conjugated lipid that inhibits aggregation of particles comprises from about 0.5% to about 50% of the total lipid present in said particle.

13. The nucleic acid-lipid particle in accordance with claim 1 , wherein said conjugated lipid that inhibits aggregation of particles comprises from about 0.5% to about 25% of the total lipid present in said particle.

14. The nucleic acid-lipid particle in accordance with claim 1 , wherein said conjugated lipid that inhibits aggregation of particles comprises from about 1% to about 20% of the total lipid present in said particle.

15. The nucleic acid-lipid particle in accordance with claim 1 , wherein said conjugated lipid that inhibits aggregation of particles comprises from about 3% to about 15% of the total lipid present in said particle.

16. The nucleic acid-lipid particle in accordance with claim 1 , wherein said conjugated lipid that inhibits aggregation of particles comprises from about 4% to about 10% of the total lipid present in said particle.

17. The nucleic acid-lipid particle in accordance with claim 1 , wherein said non-cationic lipid comprises dipalmitoylphosphatidylcholine (DPPC).

18. The nucleic acid-lipid particle in accordance with claim 1 , wherein said nucleic acid-lipid particle further comprises cholesterol.

19. The nucleic acid-lipid particle in accordance with claim 18 , wherein the cholesterol comprises from about 10% to about 60% of the total lipid present in said particle.

20. The nucleic acid-lipid particle in accordance with claim 18 , wherein the cholesterol comprises from about 20% to about 45% of the total lipid present in said particle.

21. The nucleic acid-lipid particle in accordance with claim 1 , wherein said particle has an siRNA:lipid ratio (mg:mg) of from about 0.01 to about 0.08.

22. The nucleic acid-lipid particle in accordance with claim 1 , wherein said particle has an siRNA:lipid ratio (mg:mg) of about 0.04.

23. The nucleic acid-lipid particle in accordance with claim 1 , wherein said particle has a median diameter of less than about 100 nm.

24. The nucleic acid-lipid particle in accordance with claim 1 , wherein said non-cationic lipid comprises a phospholipid and cholesterol, and wherein R 1 and R 2 are both myristyl (C14).

25. The nucleic acid-lipid particle in accordance with claim 1 , wherein said siRNA is about 15 to about 30 base pairs in length.

26. The nucleic acid-lipid particle in accordance with claim 1 , wherein said siRNA is about 19 to about 25 base pairs in length.

27. The nucleic acid-lipid particle in accordance with claim 1 , wherein said siRNA comprises 3′ overhangs.

28. The nucleic acid-lipid particle in accordance with claim 1 , wherein said siRNA comprises 2′-O-methyl ribonucleotides.

29. A pharmaceutical composition comprising a nucleic acid-lipid particle in accordance with claim 1 and a pharmaceutically acceptable carrier.

30. The nucleic acid-lipid particle in accordance with claim 1 , wherein R 1 and R 2 are selected from the group consisting of lauryl (C12), myristyl (C14), palmityl (C16), stearyl (C18), and icosyl (C20).

31. The nucleic acid-lipid particle in accordance with claim 1 , wherein R 1 and R 2 are the same.

32. The nucleic acid-lipid particle in accordance with claim 31 , wherein R 1 and R 2 are both myristyl (C14).

33. The nucleic acid-lipid particle in accordance with claim 31 , wherein R 1 and R 2 are both stearyl (C18).

34. The nucleic acid-lipid particle in accordance with claim 1 , wherein said alkyl groups are saturated.

35. The nucleic acid-lipid particle in accordance with claim 1 , wherein said alkyl groups are unsaturated.

36. The nucleic acid-lipid particle in accordance with claim 1 , wherein said PEG has an average molecular weight of from about 550 daltons to about 8,500 daltons.

37. The nucleic acid-lipid particle in accordance with claim 1 , wherein said PEG has an average molecular weight of from about 1,000 daltons to about 5,000 daltons.

38. The nucleic acid-lipid particle in accordance with claim 1 , wherein said PEG has an average molecular weight of from about 1,000 daltons to about 3,000 daltons.

39. The nucleic acid-lipid particle in accordance with claim 1 , wherein said PEG has an average molecular weight of about 2,000 daltons.

40. A method of introducing an siRNA into a cell, said method comprising contacting said cell with a nucleic acid-lipid particle in accordance with claim 1 .

41. The method in accordance with claim 40 , wherein the presence of said nucleic acid-lipid particle in said cell is detectable at least 24 hours after administration of said particle.

42. The method in accordance with claim 40 , wherein the presence of said nucleic acid-lipid particle in said cell is detectable at least 48 hours after administration of said particle.

43. The method in accordance with claim 40 , wherein said cell is in a mammal.

44. The method in accordance with claim 43 , wherein more than 10% of said particles are present in the plasma of said mammal 24 hours after administration.

45. The method in accordance with claim 43 , wherein the presence of said siRNA at a site distal to the site of administration is detectable for at least 48 hours after administration of said particle.

46. The method in accordance with claim 43 , wherein the presence of said siRNA at a site distal to the site of administration is detectable for at least 24 hours after administration of said particle.

47. The method in accordance with claim 43 , wherein the mammal is a human.

48. A method for silencing the expression of a target sequence, said method comprising administering to a mammalian subject a therapeutically effective amount of a nucleic acid-lipid particle in accordance with claim 1 .

49. The method in accordance with claim 48 , wherein said administration is intravenous.

50. The method in accordance with claim 48 , wherein said mammalian subject is a human.

51. The method in accordance with claim 50 , wherein said human has a disease or disorder associated with expression or overexpression of a gene comprising a target sequence for said siRNA.

52. The method in accordance with claim 51 , wherein said gene is selected from the group consisting of a gene associated with viral infection and survival, a gene associated with a metabolic disease or disorder, and a gene associated with tumorigenesis and cell transformation.

53. A method for the in vivo delivery of an siRNA, said method comprising administering to a mammalian subject a nucleic acid-lipid particle in accordance with claim 1 .

54. The method in accordance with claim 53 , wherein said administration is intravenous.

55. The method in accordance with claim 53 , wherein said mammalian subject is a human.

56. The method in accordance with claim 55 , wherein said human has a disease or disorder associated with expression or overexpression of a gene comprising a target sequence for said siRNA.

57. The method in accordance with claim 56 , wherein said gene is selected from the group consisting of a gene associated with viral infection and survival, a gene associated with a metabolic disease or disorder, and a gene associated with tumorigenesis and cell transformation.

58. A method for the in vivo delivery of an siRNA to a liver cell, said method comprising administering to a mammalian subject a nucleic acid-lipid particle in accordance with claim 1 .

59. The method in accordance with claim 58 , wherein said administration is intravenous.

60. The method in accordance with claim 58 , wherein said mammalian subject is a human.

61. The method in accordance with claim 60 , wherein said human has a disease or disorder associated with expression or overexpression of a gene comprising a target sequence for said siRNA.

62. The method in accordance with claim 61 , wherein said gene is associated with a metabolic disease or disorder.

63. The method in accordance with claim 62 , wherein said metabolic disease or disorder is a dyslipidemia.