SERUM HALF-LIFE EXTENSION USING IGBD

1 . A complex comprising

(i) an immunoglobulin (Ig) binding moiety and

(ii) a pharmaceutically active moiety,

wherein the Ig binding moiety specifically binds to the constant domain 1 of the heavy chain (CH1) of an Ig molecule.

2 . The complex of claim 1 , wherein the Ig binding moiety specifically binds to the surface-exposed region of the C H 1 domain of an Ig molecule.

3 . The complex of claim 1 , wherein the Ig binding moiety specifically binds to the Fc portion of the Ig molecule.

4 . The complex of claim 1 , wherein the Ig molecule is an IgG molecule, preferably an IgG1, IgG2, or IgG4 molecule.

5 . The complex of claim 1 , wherein the Ig binding moiety specifically binds to an epitope formed by amino acid positions 122-127 and/or 207-214 of an Ig molecule according to EU index.

6 . The complex of claim 1 , wherein the Ig binding moiety comprises an immunoglobulin binding domain (IgBD), preferably a streptococcus -derived IgBD.

7 . The complex of claim 1 , wherein the Ig binding moiety comprises a C H 1 binding-IgBD of streptococcal protein G.

8 . The complex of claim 1 , wherein the Ig binding moiety comprises an amino acid sequence according to SEQ ID NO: 1 or variants thereof.

9 . The complex of claim 1 , wherein the pharmaceutically active moiety comprises a biological and/or chemical pharmaceutical.

10 . The complex of claim 9 , wherein the biological is a pharmaceutically active polypeptide, preferably an antigen-binding molecule.

11 . The complex of claim 10 , wherein the antigen-binding molecule is selected from the group consisting of an antibody fragment, a Fab fragment, a Fab′ fragment, a F(ab′) 2 fragment, a heavy chain antibody, a single-domain antibody (sdAb), a single-chain variable fragment (scFv), a di-scFv, a bispecific T-cell engager (BITEs), a diabody, a single-chain diabody, a DART, a triple body, an alternative scaffold protein, and a fusion protein thereof.

12 . The complex of claim 10 , wherein said antigen-binding molecule further comprises a radioactive moiety, a cytotoxic drug, a chelating moiety, a photosensitizer, or an imaging reagent.

13 . The complex of claim 11 , wherein said antigen binding molecule is a fusion protein, which further comprises a proapoptotic protein, an immuno-(co)stimulatory protein, immuno-suppressive protein, a cytokine, a chemokine, a toxin, a growth factor or an enzyme, preferably an RNase, a prodrug-converting enzmye, or a kinase.

14 . The complex of claim 1 , wherein the Ig binding moiety and the pharmaceutically active moiety are connected via covalent or non-covalent bond(s).

15 . The complex of claim 1 , wherein the Ig binding moiety and the pharmaceutically active moiety are connected directly or indirectly via one or more linkers.

16 . The complex of claim 14 , wherein the one or more linkers comprise peptide linkers, preferably flexible peptide linkers.

17 . The complex of claim 16 , wherein the one or more peptide linker comprise one or more cleavage sites, preferably one or more endopeptidase cleavage sites.

18 . A nucleic acid molecule comprising a sequence encoding the complex of claim 1 .

19 . A vector comprising the nucleic acid of claim 18 .

20 . A cell comprising the complex of claim 1 , the nucleic acid of claim 18 and/or the vector of claim 19 .

21 . A pharmaceutical composition comprising the complex of claim 1 , the nucleic acid of claim 18 and/or the vector of claim 19 .

22 . The pharmaceutical composition of claim 21 , which further comprises a pharmaceutically acceptable carrier and/or excipient and optionally one or more additional active substances.

23 . A method of extending the serum half-life of an agent comprising combining that agent with the complex of claim 1 .

24 . A method of treating a subject by administration of a medicament comprising the complex of claim 1 to a subject in need thereof.