We Claim:
1. An antibody or antigen-binding fragment thereof, which binds:
(i) to a peptide having the amino acid sequence EYPTKNY (SEQ ID NO: 38), and/or
(ii) to claudin 6 (CLDN6), wherein said antibody or antigen-binding fragment thereof binds to CLDN6 by binding at least to an epitope within CLDN6 having the amino acid sequence EYPTKNY (SEQ ID NO: 38), and/or
(iii) to a peptide having the amino acid sequence EYPTKNYV (SEQ ID NO: 29), and/or
(iv) to claudin 6 (CLDN6), wherein said antibody or antigen-binding fragment thereof binds to CLDN6 by binding at least to an epitope within CLDN6 having the amino acid sequence EYPTKNYV (SEQ ID NO: 29), and/or
(v) to a peptide having the amino acid sequence AISRGPSEYPTKNYV (SEQ ID NO: 15), wherein the antibody or antigen-binding fragment thereof does not bind to a peptide having the amino acid sequence TSAPAISRGPSEYPT (SEQ ID NO: 14), and/or
(vi) to claudin 6 (CLDN6), wherein said antibody or antigen-binding fragment thereof binds to CLDN6 by binding at least to an epitope within CLDN6 having the amino acid sequence AISRGPSEYPTKNYV (SEQ ID NO: 15), wherein the antibody or antigen-binding fragment thereof does not bind to a peptide having the amino acid sequence TSAPAISRGPSEYPT (SEQ ID NO: 14).
2. The antibody or antigen-binding fragment thereof of claim 1, wherein said CLDN6 is cell surface membrane-bound CLDN6.
3. The antibody or antigen-binding fragment thereof of claim 1 or 2, wherein said CLDN6 is present on cancer cells.
4. The antibody or antigen-binding fragment thereof of claim 3, wherein said cancer cells are CLDN6 expressing cancer cells.
5. The antibody or antigen-binding fragment thereof of claim 3 or 4, wherein said cancer cells are selected from the group consisting of ovarian, testicular, stomach, breast,

pancreatic, lung, uterine, and urinary bladder cancer cells,
6. The antibody or antigen-binding fragment thereof of claim 3 or 4, wherein said cancer cells are metastatic cancer cells.
7. The antibody of any one of claims 1 to 5 which is a chimeric, human or humanized antibody.
8. The antibody of any one of claims 1 to 7, which is a monoclonal antibody.
9. A monoclonal antibody or antigen-binding fragment thereof which
(i) binds to a peptide having the amino acid sequence AISRGPSEYPTKNYV (SEQ ID NO: 15) and/or
(ii) binds to claudin 6 (CLDN6), wherein said antibody or antigen-binding fragment thereof binds to CLDN6 by binding at least to an epitope within CLDN6 having the amino acid sequence AISRGPSEYPTKNYV (SEQ ID NO: 15).
10. An antibody or antigen-binding fragment thereof, which binds to one or more,
preferably all, of the following peptides:
PAISRGPSEYPTKNY (SEQ ID NO: 22), AISRGPSEYPTKNYV (SEQ ID NO: 15), ISRGPSEYPTKNYV (SEQ ID NO: 23), SRGPSEYPTKNYV (SEQ ID NO: 24), RGPSEYPTKNYV (SEQ ID NO: 25), GPSEYPTKNYV (SEQ ID NO: 26), PSEYPTKNYV (SEQ ID NO: 27), SEYPTKNYV (SEQ ID NO: 28), and EYPTKNYV (SEQ ID NO: 29), wherein the antibody or antigen-binding fragment thereof does not bind to a peptide having the amino acid sequence TSAPAISRGPSEYPT (SEQ ID NO: 14).
11. The antibody or antigen-binding fragment thereof of claim 10, wherein the difference in binding affinity to the peptide to which the antibody or antigen binding fragment binds with the lowest affinity and to the peptide to which the antibody or antigen binding fragment binds with the highest affinity is 50% or less.
12. An antibody selected from the group consisting of:

(i) an antibody produced by or obtainable from a clone deposited under the accession
no. DSM ACC3313 (58-IB), DSM ACC3312 (58-3A) or DSM ACC3311 (58-4B-2),
(ii) an antibody which is a chimerized or humanized form of the antibody under (i),
(iii) an antibody which competes for CLDN6 binding with an antibody under (i),
(iv) an antibody which has the specificity of the antibody under (i),
and
(v) an antibody comprising the antigen binding portion or antigen binding site of the
antibody under (i), or
an antigen-binding fragment of the antibody under any one of (i) to (v).
13. The antibody of claim 12, wherein the antigen binding portion or antigen binding site of the antibody under (i) comprises the variable region of the antibody under (i).
14. A conjugate comprising an antibody or antigen-binding fragment of any one of claims 1 to 13 coupled to at least one detectable label.
15. A hybridoma capable of producing the antibody of any one of claims 1 to 13.
16. A hybridoma deposited under the accession no. DSM ACC3313 (58-1B), DSM ACC3312 (58-3A) or DSM ACC3311 (58-4B).
17. A method for detecting CLDN6 or determining the quantity of CLDN6 in a sample comprising the steps of:
(i) contacting a sample with the antibody or antigen-binding fragment of any one of claims 1 to 13 or the conjugate of claim 14 and
(ii) detecting the formation of a complex or determining the quantity of a complex between the antibody, the antigen-binding fragment or the conjugate and CLDN6.
18. A method for determining whether cells express CLDN6 comprising the steps of:
(i) contacting a cellular sample with the antibody or antigen-binding fragment of any one of claims 1 to 13 or the conjugate of claim 14 and
(ii) detecting the formation of a complex between the antibody, the antigen-binding fragment or the conjugate and CLDN6 expressed by cells in said sample.

19. A method for diagnosis, detection or monitoring of cancer comprising the steps of:
(i) contacting a biological sample with the antibody or antigen-binding fragment of
any one of claims 1 to 13 or the conjugate of claim 14 and
(ii) detecting the formation of a complex and/or determining the quantity of a
complex between the antibody, the antigen-binding fragment or the conjugate and
CLDN6.
20. A method for determining whether a cancer is treatable by a cancer therapy targeting
CLDN6 comprising the steps of:
(i) contacting a sample comprising cancer cells with the antibody or antigen-binding fragment of any one of claims 1 to 13 or the conjugate of claim 14 and (ii) detecting the formation of a complex between the antibody, the antigen-binding fragment or the conjugate and CLDN6.
21. A method for determining the prognosis of a patient having cancer comprising the
steps of:
(i) contacting a sample comprising cancer cells with the antibody or antigen-binding fragment of any one of claims 1 to 13 or the conjugate of claim 14 and (ii) detecting the formation of a complex between the antibody, the antigen-binding fragment or the conjugate and CLDN6.
22. The antibody or antigen-binding fragment of any one of claims 1 to 13, the conjugate of claim 14, the hybridoma of claim 15 or 16, or the method of any one of claims 17 to 21, wherein said CLDN6 comprises the amino acid sequence according to SEQ ID NO: 1 or a variant of said amino acid sequence.
23. A diagnostic test kit which comprises the antibody or antigen-binding fragment of any one of claims 1 to 13 or the conjugate of claim 14.