Method for the production and selection of molecules comprising at least two different entities and uses thereof

1. A method for producing a polypeptide comprising at least two polypeptide domains comprising the step of

cultivating a cell comprising

a) a nucleic acid encoding a soluble S. aureus sortase A with a C-terminal endoplasmic reticulum retention signal,

b) a nucleic acid encoding a first polypeptide domain comprising at its C-terminus a sortase motif followed by an endoplasmic reticulum retention signal, wherein the sortase motif comprises LPXTG (SEQ ID NO: 01, wherein X can be any amino acid residue) and

c) a nucleic acid encoding a second polypeptide domain comprising an oligoglycine G m (m=2, or 3, or 4, or 5) (SEQ ID NO: 53) at its N-terminus,

wherein the cell secretes a sortase A conjugate of the first polypeptide domain and the second polypeptide domain,

thereby producing a polypeptide comprising at least two polypeptide domains.

2. A method for producing a multispecific binder comprising at least two binding entities comprising the step of

cultivating a cell comprising

a) a nucleic acid encoding a soluble S. aureus sortase A with a C-terminal endoplasmic reticulum retention signal,

b) a nucleic acid encoding a first binding entity comprising at its C-terminus a sortase motif followed by an endoplasmic reticulum retention signal, wherein the sortase motif comprises LPXTG (SEQ ID NO: 01, wherein X can be any amino acid residue) and

c) a nucleic acid encoding a second binding entity comprising an oligoglycine G m (m=2, or 3, or 4, or 5) (SEQ ID NO: 53) at its N-terminus,

wherein the cell secretes a sortase A conjugate of the first binding entity and the second binding entity, and wherein the first binding entity specifically binds to a first antigen or target and the second binding entity specifically binds to a second antigen or target,

thereby producing a multispecific binder comprising at least two binding entities.

3. A method for selecting a multispecific binder that specifically binds to two different epitopes or antigens comprising the step of

selecting from a multitude of multispecific binders comprising different combinations of a first binding entity and a second binding entity a multispecific binder that specifically binds to two different epitopes or antigens,

wherein the members of the multitude of multispecific binders are each obtained by a method according to claim 2 .

4. The method according to claim 3 , wherein the multispecific binder is selected based on its binding specificity and/or selectivity and/or affinity and/or effector function and/or in vivo half-life.

5. The method according to claim 2 , wherein the first and second binding entities comprise a cognate pair of an antibody heavy chain variable domain and an antibody light chain variable domain.

6. The method according to claim 2 , wherein the multispecific binder is a bispecific antibody comprising two or four binding entities.

7. The method according to claim 1 , wherein the first polypeptide domain and the second polypeptide domain are selected independently of each other from the group consisting of a full length antibody, a scFv, a scFab, an antibody heavy chain, an antibody light chain, an antibody heavy chain Fc-region fragment, a pair of antibody light chain variable domain and antibody heavy chain variable domain, a VH, a VL, a CH1, a CH2, a CH3,a CH4, a CL, an antibody hinge region, a cytokine, a receptor, a receptor ligand, a detectable label, a tag, and a partner of a binding pair.

8. The method according to claim 1 or 2 , wherein the endoplasmic reticulum retention signal is selected from the group consisting of SEQ ID NO: 02 (KDEL), SEQ ID NO: 03 (HDEL), and SEQ ID NO: 04 (SFIXXXXMP).

9. The method according to claim 1 or 2 , wherein the first polypeptide domain or the first binding entity has within the 20 C-terminal amino acid residues the amino acid sequence LPXTG (SEQ ID NO: 01, wherein X can be any amino acid residue).

10. The method according to claim 1 or 2 , wherein the cell is a mammalian cell or a yeast cell.

11. The method according to claim 10 , wherein the mammalian cell is selected from the group consisting of a HEK cell, a CHO cell, and a BHK cell.

12. A method for producing a bispecific antibody comprising the following steps

(i) determining the cell surface makers present in a cell containing sample and selecting thereof at least a first surface marker and a second surface marker,

(ii) transfecting a cell with

(a) a nucleic acid encoding an antibody Fab fragment, or an antibody scFab, or a scFv antibody comprising within the 20 C-terminal amino acid residues the amino acid sequence LPXTG (SEQ ID NO: 01, wherein X can be any amino acid residue) followed by an endoplasmic reticulum retention signal KDEL (SEQ ID NO: 02), wherein the Fab fragment or scFv antibody specifically binds to the first surface marker or its ligand,

(b) a nucleic acid encoding an one-armed antibody fragment comprising a full length antibody heavy chain, a full length antibody light chain, and an antibody heavy chain Fc-region polypeptide, wherein the full length antibody heavy chain and the full length antibody light chain are cognate antibody chains complementary to each other and the pair of variable domains (VH and VL) thereof forms an antigen binding site that specifically binds to the second surface marker or its ligand, and wherein the full length antibody heavy chain and the antibody heavy chain Fc-region polypeptide are covalently linked to each other via one or more disulfide bonds forming an antibody hinge region, and wherein the antibody heavy chain Fc-region polypeptide has an oligoglycine G m (m=2, or 3, or 4, or 5) (SEQ ID NO: 53) amino acid sequence at its N-terminus, and

(c) a nucleic acid encoding a soluble S. aureus sortase A with a C-terminal endoplasmic reticulum retention signal,

and thereby producing the bispecific antibody.

13. The method according to claim 6 or 12 , wherein the Fc-region comprises a mutation of the naturally occurring amino acid residue at position 329 and at least one further mutation of at least one amino acid residue selected from the group consisting of amino acid residues at position 228, 233, 234, 235, 236, 237, 297, 318, 320, 322 and 331 to a different residue, wherein the residues in the Fc-region are numbered according to the EU index of Kabat.