Intracellular formation of peptide conjugates

1. A method of forming a peptide conjugate comprising a covalent linkage between a modifying group and a glycosylated or non-glycosylated peptide, wherein said modifying group is conjugated to the peptide via a glycosyl linking group interposed between and covalently linked to both said peptide and said modifying group, said method comprising:

a. contacting a cell with a modified sugar comprising a sialic acid moiety covalently functionalized with at least one modifying group, wherein said at least one modifying group is a water-soluble polymer;

b. incubating said cell under conditions in which said cell internalizes said modified sugar;

c. after step b, intracellularly contacting said modified sugar with a glycosylated or non-glycosylated peptide and a glycosyltransferase for which said modified sugar is a substrate, thereby forming said peptide conjugate.

2. The method of claim 1 , further comprising, after step b and before step c, intracellularly contacting said modified sugar with a nucleotide and a nucleotidyl transferase, thereby forming a modified nucleotide sugar, wherein

said modified sugar in step c is said modified nucleotide sugar.

3. The method of claim 1 , further comprising isolating said peptide conjugate.

4. The method of claim 1 , wherein said modified sugar is a modified nucleotide sugar.

5. The method of claim 1 , wherein said modified sugar is a modified activated sugar.

6. The method of claim 1 , wherein said glycosyl linking group is an intact glycosyl linking group.

7. The method of claim 1 , wherein said modified sugar is a precursor modified sugar that is intracellularly converted to an intermediate modified sugar by cellular enzymes after step b and before step c.

8. The method of claim 7 , wherein said intermediate modified sugar is a phosphorylated modified sugar, wherein said phosphorylated modified sugar is formed by intracellularly contacting said modified sugar with a kinase for which said modified sugar is a substrate, thereby forming a phosphorylated modified nucleotide sugar.

9. The method of claim 1 , wherein said water-soluble polymer comprises poly(ethylene glycol).

10. The method of claim 9 , wherein said poly(ethylene glycol) has a molecular weight distribution that is essentially homodisperse.

11. The method of claim 1 , wherein said modified sugar has the formula

wherein,

W, X, Y, Z, and A are members independently selected from a bond, substituted or unsubstituted alkylene, substituted or unsubstituted heteroalkylene, substituted or unsubstituted cycloalkylene, substituted or unsubstituted heterocycloalkylene, substituted or unsubstituted arylene, substituted or unsubstituted heteroarylene, —O—, —N(R 7 )—, —S—, and —CH 2 —, wherein,

R 7 is a member independently selected from hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted aryl, and substituted or unsubstituted heteroaryl; and

R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are members independently selected from —OH, —NH 2 , —SH, hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, and a water-soluble polymer, wherein at least one or R 1 , R 2 , R 3 , R 4 , R 5 and R 6 is said water-soluble polymer.

12. The method of claim 2 , wherein said modified nucleotide sugar has the formula

wherein,

W, X, Y, Z, and A are members independently selected from a bond, substituted or unsubstituted alkylene, substituted or unsubstituted heteroalkylene, substituted or unsubstituted cycloalkylene, substituted or unsubstituted heterocycloalkylene, substituted or unsubstituted arylene, substituted or unsubstituted heteroarylene, —O—, —N(R 7 )—, —S—, and —CH 2 —, wherein,

R 7 is a member independently selected from hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted aryl, and substituted or unsubstituted heteroaryl; and

R 1 , R 2 , R 3 , R 4 , and R 5 are independently selected from —OH, —NH 2 , —SH, hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, and a water-soluble polymer, wherein at least one or R 1 , R 2 , R 3 , R 4 , and R 5 is said water-soluble polymer.

13. The method of claim 1 , wherein said peptide is selected from the group consisting of granulocyte colony stimulating factor, interferon-alpha, interferon-beta, Factor VIIa, Factor IX, follicle stimulating hormone, erythropoietin, granulocyte macrophage colony stimulating factor, interferon-gamma, alpha-1-protease inhibitor, glucocerebrosidase, tissue plasminogen activator protein, interleukin-2, Factor VIII, chimeric tumor necrosis factor receptor, urokinase, chimeric anti-glycoprotein IIb/IIIa antibody, chimeric anti-HER2 antibody, chimeric anti-respiratory syncytial virus antibody, chimeric anti-CD20 antibody, DNase, chimeric anti-tumor necrosis factor antibody, human insulin, hepatitis B sAg, interferon-omega, alpha-galactosidase A, alpha-iduronidase, anti-thrombin III, human chorionic gonadotropin, and human growth hormone.

14. The method according to claim 2 , said modified nucleotide sugar having a formula which is a member selected from:

wherein

R is said water-soluble polymer.

15. The method according to claim 1 wherein said water-soluble polymer is a poly(alkylene oxide) selected from linear poly(alkylene oxide) and branched poly(alkylene oxide).

16. The method according to claim 14 wherein said water-soluble polymer is a poly(alkylene oxide) selected from linear poly(alkylene oxide) and branched poly(alkylene oxide).

17. The method according to claim 1 wherein said modified sugar has the formula: