Hyperglycosylated binding polypeptides

1. An isolated binding polypeptide comprising a CH1 domain, wherein the CH1 domain comprises an asparagine residue at amino acid position 114, according to Kabat numbering, wherein the side chain of said asparagine residue is linked to a glycan.

2. The binding polypeptide of claim 1 , wherein the CH1 domain further comprises: any amino acid residue except proline at position 115, according to Kabat numbering; and a serine or threonine residue at position 116, according to Kabat numbering.

3. The binding polypeptide of claim 1 , wherein the CH1 domain is an IgG1 CH1 domain, or a variant thereof.

4. The binding polypeptide of claim 3 , wherein the CH1 domain is a human IgG1 CH1 domain, or a variant thereof.

5. The binding polypeptide of claim 1 , wherein the side chain of the asparagine residue is linked to a glycan though a β-glycosylamide linkage.

6. The binding polypeptide of claim 5 , wherein the glycan is a biantennary glycan.

7. The binding polypeptide of claim 5 , wherein the glycan is a naturally occurring mammalian glycoform.

8. The binding polypeptide of claim 5 , wherein the glycan comprises a reactive aldehyde group.

9. The binding polypeptide of claim 5 , wherein the glycan comprises an oxidized saccharide residue comprising a reactive aldehyde group.

10. The binding polypeptide of claim 9 , wherein the oxidized saccharide residue is a terminal sialic acid or galactose.

11. The binding polypeptide of claim 5 , wherein the glycan is linked to an effector moiety.

12. The binding polypeptide of claim 11 , wherein the effector moiety is a cytotoxin or a detection agent.

13. The binding polypeptide of claim 12 , wherein the cytotoxin is selected from the group consisting of:

wherein R 1 is any alkyl, aryl, alkoxy, or aryloxy moiety and R 2 and R 3 may are any alkyl or aryl moiety.

14. The binding polypeptide of claim 11 , wherein the effector moiety is linked through an oxime or hydrazone linkage to saccharide residue of the glycan.

15. The binding polypeptide of claim 14 , wherein the saccharide is a terminal sialic acid or galactose residue of the glycan.

16. The binding polypeptide of claim 11 , wherein the effector moiety comprises a pH-sensitive linker, disulfide linker, enzyme-sensitive linker or other cleavable linker moiety.

17. An isolated binding polypeptide comprising a CH1 domain, wherein the CH1 domain comprises a free asparagine residue at amino acid position 114, according to Kabat numbering.

18. An isolated binding polypeptide comprising a CH1 domain, wherein the CH1 domain comprises a modified asparagine residue at amino acid position 114, according to Kabat numbering, wherein the side chain of said asparagine residue is linked to a glycan, and wherein said glycan is linked to an effector moiety.

19. The binding polypeptide of claim 11 , wherein the effector moiety is linked through a side chain of the modified asparagine residue to a saccharide residue of a glycan.

20. The binding polypeptide of claim 19 , wherein the saccharide is a terminal sialic acid or galactose residue of the glycan.

21. The binding polypeptide of claim 19 , wherein the effector moiety is linked through an oxime or hydrazone linkage to a saccharide residue of the glycan.

22. The binding polypeptide of claim 19 , wherein the saccharide is a terminal sialic acid or galactose residue of the glycan.

23. The binding polypeptide of claim 1 which is an antibody, or an antigen-binding fragment thereof.

24. The binding polypeptide of claim 23 wherein the antibody, or an antigen-binding fragment thereof is linked to a drug effector moiety to form an antibody drug conjugate (ADC).

25. A composition comprising the binding polypeptide of claim 1 and a pharmaceutically acceptable carrier or excipient.