Monoclonal antibody against human LAG-3, method for preparing the same, and use thereof

1. An isolated antibody or the antigen-binding portion thereof that binds LAG-3, wherein the isolated antibody or the antigen-binding portion thereof comprises:

a CDRH1 comprising the amino acid sequence of SEQ ID NO: 1, a CDRH2 comprising the amino acid sequence of SEQ ID NO: 2, a CDRH3 comprising the amino acid sequence of SEQ ID NO: 3, a CDRL1 comprising the amino acid sequence of SEQ ID NO: 4, a CDRL2 comprising the amino acid sequence of SEQ ID NO: 5, a CDRL3 comprising the amino acid sequence of SEQ ID NO: 6; or

a CDRH1 comprising the amino acid sequence of SEQ ID NO: 7, a CDRH2 comprising the amino acid sequence of SEQ ID NO: 8, a CDRH3 comprising the amino acid sequence of SEQ ID NO: 9, a CDRL1 comprising the amino acid sequence of SEQ ID NO: 10, a CDRL2 comprising the amino acid sequence of SEQ ID NO: 11, a CDRL3 comprising the amino acid sequence of SEQ ID NO: 12.

2. The isolated antibody or the antigen-binding portion thereof of claim 1 , wherein the isolated antibody or the antigen-binding portion thereof comprises:

(a) a CDRH1 consisting of SEQ ID NO: 1;

(b) a CDRH2 consisting of SEQ ID NO: 2;

(c) a CDRH3 consisting of SEQ ID NO: 3;

(d) a CDRL1 consisting of SEQ ID NO: 4;

(e) a CDRL2 consisting of SEQ ID NO: 5; and

(f) a CDRL3 consisting of SEQ ID NO: 6.

3. The isolated antibody or the antigen-binding portion thereof of claim 1 , wherein the isolated antibody or the antigen-binding portion thereof comprises:

(a) a CDRH1 consisting of SEQ ID NO: 7;

(b) a CDRH2 consisting of SEQ ID NO: 8;

(c) a CDRH3 consisting of SEQ ID NO: 9;

(d) a CDRL1 consisting of SEQ ID NO: 10;

(e) a CDRL2 consisting of SEQ ID NO: 11; and

(f) a CDRL3 consisting of SEQ ID NO: 12.

4. The isolated antibody or the antigen-binding portion thereof of claim 1 , wherein the isolated antibody or the antigen-binding portion thereof comprises:

(A) a heavy chain variable region:

(i) comprising the amino acid sequence of SEQ ID NO: 13; or

(ii) comprising an amino acid sequence having same CDRs as those in SEQ ID NO: 13 and framework regions at least 85%, 90%, or 95% identical to those in SEQ ID NO: 13; and

(B) a light chain variable region:

(i) comprising the amino acid sequence of SEQ ID NO: 14;

(ii) comprising an amino acid sequence having same CDRs as those in SEQ ID NO: 14 and framework regions at least 85%, at least 90%, or at least 95% identical to those in SEQ ID NO: 14.

5. The isolated antibody or the antigen-binding portion thereof of claim 1 , wherein the isolated antibody or the antigen-binding portion thereof comprises:

(A) a heavy chain variable region:

(i) comprising the amino acid sequence of SEQ ID NO: 15;

(ii) comprising an amino acid sequence having same CDRs as those in SEQ ID NO: 15 and framework regions at least 85%, at least 90%, or at least 95% identical to those in SEQ ID NO: 15; and

(B) a light chain variable region:

(i) comprising the amino acid sequence of SEQ ID NO: 16;

(ii) comprising an amino acid sequence having same CDRs as those in SEQ ID: 16 and framework regions at least 85%, at least 90%, or at least 95% identical to those in SEQ ID NO: 16.

6. The isolated antibody or the antigen-binding portion thereof of claim 1 , having one or more of the following properties:

(a) binds to human LAG-3 with a K D of 2×10 −10 M or less;

(b) inhibits binding of LAG-3 to major histocompatibility (MHC) class II molecules;

(c) inhibits binding of LAG-3 to fibrinogen-like protein 1 (FGL1) ligand molecules;

(d) inhibits binding of LAG-3 to LSECtin and/or Galectin-3;

(e) binds to human LAG-3 without cross-family reactions; or

(f) has no cross-reactivity to human CD4.

7. The isolated antibody or the antigen-binding portion thereof of claim 1 , wherein the antibody is a fully human monoclonal antibody.

8. An isolated nucleic acid molecule, comprising a nucleic acid sequence encoding the heavy chain variable region and/or the light chain variable region of the isolated antibody as defined in claim 1 .

9. An expression vector comprising the nucleic acid molecule of claim 8 .

10. A host cell comprising the expression vector of claim 9 .

11. A pharmaceutical composition comprising at least one antibody or antigen-binding portion thereof as defined in claim 1 and a pharmaceutically acceptable carrier.

12. A method for preparing an antibody or antigen-binding fragment thereof that binds to LAG-3, the method comprising:

incubating the host cell of claim 10 in conditions suitable for expression the antibody or antigen-binding fragment thereof; and

isolating the antibody or antigen-binding fragment thereof.

13. A method for inhibiting or blocking the binding of LAG-3 to LSECtin and/or Galectin-3, comprising in the presence of LAG-3 contacting LSECtin and/or Galectin-3 with the antibody or antigen-binding portion thereof as defined in claim 1 .

14. A method for inhibiting growth of tumor cells in a subject, comprising administering to the subject the antibody or antigen-binding portion thereof as defined in claim 1 such that growth of the tumor is inhibited in the subject.

15. A method for treating cancers in a subject, comprising administering an effective amount of the antibody or antigen-binding portion thereof as defined in claim 1 to the subject.

16. A kit for treating or diagnosing cancers, comprising a container comprising at least one antibody or antigen-binding portion thereof as defined in claim 1 .

17. A method for detecting LAG 3 in a sample, comprising contacting the sample with the antibody or antigen-binding portion thereof as defined in claim 1 , and detecting presence or absence, or level of association, of the antibody bound in the sample.

18. The isolated antibody or the antigen-binding portion thereof of claim 7 , wherein the antibody is produced by transgenic rat with recombinant immunoglobulin loci.

19. The isolated nucleic acid molecule of claim 8 , comprising a nucleic acid sequence as shown in any of SEQ ID NOs: 17-20.