Antibodies for epidermal growth factor receptor 3 (HER3)

1. An isolated monoclonal antibody or antigen binding fragment thereof that recognizes a conformational epitope of a HER3 receptor, wherein the conformational epitope comprises amino acid residues 265-277, and 315 within domain 2 and amino acid residues 571, 582-584, 596-597, 600-602, and 609-615 within domain 4 of the HER3 receptor of SEQ ID NO: 1, and wherein the antibody or fragment thereof blocks both ligand-dependent and ligand-independent signal transduction.

2. The isolated monoclonal antibody or antigen binding fragment thereof of claim 1 , wherein the antibody or fragment thereof binds to the inactive state of the HER3 receptor.

3. The isolated monoclonal antibody or antigen binding fragment thereof of claim 1 , wherein the antibody or fragment thereof stabilizes the HER3 receptor in the inactive state.

4. The isolated monoclonal antibody or antigen binding fragment thereof of claim 1 , which when the antibody or antigen binding fragment thereof is bound to the HER3 receptor allows a HER3 ligand to concurrently bind to a ligand binding site on the HER3 receptor.

5. The isolated monoclonal antibody or antigen binding fragment thereof of claim 4 , wherein the HER3 ligand is selected from the group consisting of neuregulin 1 (NRG), neuregulin 2, betacellulin, heparin-binding epidermal growth factor, and epiregulin.

6. The isolated monoclonal antibody or antigen binding fragment thereof of claim 1 , wherein the VH of the antibody or fragment thereof binds the following HER3 receptor residues: Asn266, Lys267, Leu268, Thr269, Gln271, Glu273, Pro274, Asn275, Pro276, His277, Asn315, Asp571, Pro583, His584, Ala596, and Lys597 of SEQ ID NO: 1.

7. The isolated monoclonal antibody or antigen binding fragment thereof of claim 1 , wherein the VL of the antibody or fragment thereof binds the following HER3 receptor residues: Tyr265, Lys267, Leu268, Phe270, Gly582, Pro583, Lys597, Ile600, Lys602, Glu609, Arg611, Pro612, Cys613, His614, and Glu615 of SEQ ID NO: 1.

8. An isolated monoclonal antibody or antigen binding fragment thereof that recognizes a conformational epitope of a HER3 receptor, wherein the conformational epitope comprises amino acid residues 265-277, and 315 within domain 2 and amino acid residues 571, 582-584, 596-597, 600-602, and 609-615 within domain 4 of the HER3 receptor of SEQ ID NO:1, wherein binding of the antibody or fragment thereof to the HER3 receptor in the absence of a HER3 ligand reduces ligand-independent formation of a HER2-HER3 protein complex in a cell which expresses HER2 and HER3.

9. The isolated monoclonal antibody or antigen binding fragment thereof of claim 8 , wherein the antibody or fragment thereof stabilizes the HER3 receptor in an inactive state such that the HER3 receptor fails to dimerize with the HER2 receptor to form a HER2-HER3 protein complex.

10. The isolated monoclonal antibody or antigen binding fragment thereof of claim 9 , wherein the failure to form a HER2-HER3 protein complex prevents activation of signal transduction.

11. An isolated monoclonal antibody or antigen binding fragment thereof that recognizes a conformational epitope of a HER3 receptor, wherein the conformational epitope comprises amino acid residues 265-277, and 315 within domain 2 and amino acid residues 571, 582-584, 596-597, 600-602, and 609-615 within domain 4 of the HER3 receptor of SEQ ID NO:1, wherein binding of the antibody or fragment thereof to the HER3 receptor in the presence of a HER3 ligand reduces ligand-dependent formation of a HER2-HER3 protein complex in a cell which expresses HER2 and HER3.

12. The isolated monoclonal antibody or antigen binding fragment thereof of claim 11 , wherein the antibody or fragment thereof stabilizes the HER3 receptor in an inactive state such that the HER3 receptor fails to dimerize with the HER2 receptor in the presence of a HER3 ligand to form a HER2-HER3 protein complex.

13. The isolated monoclonal antibody or antigen binding fragment thereof of claim 11 , wherein the failure to form a HER2-HER3 protein complex prevents activation of signal transduction.

14. The isolated monoclonal antibody or antigen binding fragment thereof of claim 11 , wherein the ligand is selected from the group consisting of neuregulin 1 (NRG), neuregulin 2, betacellulin, heparin-binding epidermal growth factor, and epiregulin.

15. The isolated monoclonal antibody or antigen binding fragment thereof of claim 11 , wherein the antibody or fragment thereof inhibits phosphorylation of HER3 as assessed by a HER3 ligand-independent phosphorylation assay.

16. The isolated monoclonal antibody or antigen binding fragment thereof of claim 15 , wherein the HER3 ligand-independent phosphorylation assay uses HER2 amplified cells, wherein the HER2 amplified cells are SK-Br-3 cells.

17. An isolated monoclonal antibody or antigen binding fragment thereof that recognizes a conformational epitope of a HER3 receptor, wherein the conformational epitope comprises amino acid residues 265-277, and 315 within domain 2 and amino acid residues 571, 582-584, 596-597, 600-602, and 609-615 within domain 4 of the HER3 receptor of SEQ ID NO:1, and wherein the antibody or fragment thereof inhibits phosphorylation of HER3 as assessed by HER3 ligand-dependent phosphorylation assay.

18. The isolated monoclonal antibody or antigen binding fragment thereof of claim 17 , wherein the HER3 ligand-dependent phosphorylation assay uses stimulated MCF7 cells in the presence of neuregulin (NRG).

19. An isolated anti-HER3 monoclonal antibody or antigen binding fragment thereof, binds to the same conformational epitope as an anti-HER3 antibody comprising a VH of SEQ ID NO: 141 and VL of SEQ ID NO: 140.

20. An isolated monoclonal antibody or antigen binding fragment thereof to HER3 receptor, comprising a heavy chain variable region CDR1 of SEQ ID NO: 128; CDR2 of SEQ ID NO: 129; CDR3 of SEQ ID NO: 130; and a light chain variable region CDR1 of SEQ ID NO: 131; CDR2 of SEQ ID NO: 132; and CDR3 of SEQ ID NO: 133.

21. The isolated antigen binding fragment of claim 1 , wherein the fragment is selected from the group consisting of Fab, F(ab 2 )′, and scFV.

22. A pharmaceutical composition comprising a monoclonal antibody or antigen binding fragment thereof of any one of claims 1 - 5 , 6 , 8 - 18 , 19 , 20 , and 21 and a pharmaceutically acceptable carrier.

23. The pharmaceutical composition of claim 22 , further comprising an additional therapeutic agent.

24. The pharmaceutical composition of claim 23 , wherein the additional therapeutic agent is a HER2 inhibitor.

25. The pharmaceutical composition of claim 23 , wherein the additional therapeutic agent is a HER2 inhibitor selected from the group consisting of Pertuzumab, Trastuzumab, MM-111, neratinib, lapatinib or lapatinib ditosylate.

26. The pharmaceutical composition of claim 23 , wherein the additional therapeutic agent is an mTOR inhibitor selected from the group consisting of Temsirolimus, ridaforolimus and everolimus.

27. The pharmaceutical composition of claim 23 , wherein the additional therapeutic agent is a PI3 kinase inhibitor selected from the group consisting of GDC 0941, BEZ235, BMK120 and BYL719.

28. A method of treating a breast or pancreatic cancer comprising selecting a human subject having an HER3 receptor expressing breast or pancreatic cancer, administering to the subject an effective amount of a composition comprising an antibody or antigen binding fragment thereof of any one of 1 - 5 , 6 , 7 , 8 - 18 , 19 , 20 and 21 and a pharmaceutically acceptable carrier.

29. The method of claim 28 , wherein the cancer is breast cancer.

30. The method of claim 28 , wherein the cancer is pancreatic cancer.

31. The isolated monoclonal antibody or antigen binding fragment thereof of any one of claims 1 - 5 , 6 , 7 , 8 - 18 , 19 , 20 and 21 , wherein the antibody or antigen binding fragment thereof is a recombinant antibody or antigen binding fragment.