CD3 binding domains
The invention relates to a humanized CD3 binding site, which comprises (a) a variable heavy chain domain (VH) as depicted in SEQ ID NO:8 and a variable light chain domain (VL) as depicted in SEQ ID NO:3; or (b) a variable heavy chain domain (VH) as depicted in SEQ ID NO:9 and a variable light chain domain (VL) as depicted in SEQ ID NO:4, or c) a variable heavy chain domain (VH) as depicted in SEQ ID NO:7 and a variable light chain domain (VL) as depicted in SEQ ID NO:2; or (d) a variable heavy chain domain (VH) as depicted in SEQ ID NO:6 and a variable light chain domain (VL) as depicted in SEQ ID NO:1. The CD3 binding sites have an increased stability, while the binding affinity has been retained due to mutations at positions VH111 and VL49.
1. An antigen binding protein comprising at least one CD3 binding site, wherein the CD3 binding site comprises:
(a) a variable heavy chain domain (VH) as depicted in SEQ ID NO:8 and a variable light chain domain (VL) as depicted in SEQ ID NO:3; or
(b) a variable heavy chain domain (VH) as depicted in SEQ ID NO:9 and a variable light chain domain (VL) as depicted in SEQ ID NO:4; or
(c) a variable heavy chain domain (VH) as depicted in SEQ ID NO:7 and a variable light chain domain (VL) as depicted in SEQ ID NO:2; or
(d) a variable heavy chain domain (VH) as depicted in SEQ ID NO:6 and a variable light chain domain (VL) as depicted in SEQ ID NO:1.
2. The antigen binding protein according to claim 1 , wherein the protein comprises at least one further functional domain.
3. The antigen binding protein according to claim 2 , wherein the at least one further functional domain is a further antigen binding site.
4. The antigen binding protein according to claim 3 , wherein the further antigen binding site is specific for a tumor cell.
5. The antigen binding protein according to claim 1 , wherein the antigen binding protein is multivalent.
6. The antigen binding protein according to claim 5 , wherein the antigen binding protein is multispecific.
7. The antigen binding protein according to claim 6 , wherein the antigen binding protein is multimeric.
8. The antigen binding protein according to claim 6 , wherein the antigen binding protein is dimeric, comprising a first polypeptide and a second polypeptide, each polypeptide having at least four variable chain domains linked one after another, wherein the antigen binding protein comprises at least one CD3 binding site according to claim 1 and at least one further antigen binding site specific to a second antigen.
9. The antigen binding protein according to claim 8 , wherein each polypeptides has at least four variable domains fused with one another by peptide linkers L1, L2 and L3 in the order of:
(i) VL (CD3)-L1-VH (2nd antigen)-L2-VL (2nd antigen)-L3-VH(CD3);
(ii) VH (CD3)-L1-VL (2nd antigen)-L2-VH (2nd antigen)-L3-VL (CD3);
(iii) VL (2nd antigen)-L1-VH(CD3)-L2-VL (CD3)-L3-VH (2nd antigen); or
(iv) VH (2nd antigen)-L1-VL (CD3)-L2-VH(CD3)-L3-VL (2nd antigen).
10. The antigen binding protein according to claim 9 , wherein linkers L1, L2 and L3 consist of about 12 or less amino acid residues.
11. A pharmaceutical composition comprising (i) the antigen binding protein according to claim 1 , and (ii) a pharmaceutically acceptable carrier.