Anti-cd276 antibody, antibody-drug conjugate, and use thereof

An isolated antibody or an antigen-binding portion thereof, comprising:

• two heavy chains each comprising:
• (a) a hinge region comprising an amino acid sequence of:
• —(X1)—C—(X2)—CPPCP—, wherein X1 is a polypeptide segment having 0-7 amino acid residues each independently selected from any amino acid residue that is not a cysteine residue, and X2 is a polypeptide segment having 2-7 amino acid residues each independently selected from any amino acid residue that is not a cysteine residue;
• (b) a human CH1 domain located upstream of and connected to the hinge region, the CH1 domain comprising a cysteine at the position of 142 according to the IMGT numbering scheme;
• wherein the antibody specifically binds to human B7-H3 protein.

An antibody-drug conjugate (ADC) or a pharmaceutically acceptable salt thereof, comprising:

• (A) an isolated antibody, or an antigen-binding portion thereof, comprising:
• (a1) a heavy chain hinge region comprising the amino acid sequence set forth in SEQ ID NO:11;
• and
• (a2) a heavy chain variable domain comprising a CDR1 region, a CDR2 region, and a CDR3 region comprising the amino acid sequences of SEQ ID NO:6, SEQ ID NO:7, and SEQ ID NO:8, respectively, and
• (a3) a light chain variable domain comprising a CDR1 region, a CDR2 region, and a CDR3 region comprising the amino acid sequences of SEQ ID NO:9, WAS, and SEQ ID NO:10, respectively;
• (B) a cytotoxic drug, wherein the isolated antibody or an antigen-binding portion thereof is conjugated to the cytotoxic drug by a chemical linker.