Homodimeric antibodies for use in treating cancers and methods of use

A method to treat cancer in a human subject, comprising administering to the subject a therapeutically effective amount of an immunotherapeutic, wherein:

• the cancer comprises cells that express human sperm protein 17 (Sp17);
• the immunotherapeutic comprises a homodimeric antibody that comprises two immunoglobulin G (IgG) antibodies that are covalently crosslinked;
• each IgG antibody comprises two antigen-binding sites that each specifically bind Sp17 such that the homodimeric antibody comprises exactly four antigen-binding sites that each specifically bind Sp17;
• and
• each IgG antibody comprises a heavy chain variable region comprising the amino acid sequence set forth in SEQ ID NO:
• 3 and a light chain variable region comprising the amino acid sequence set forth in SEQ ID NO:
• 4.

An immunotherapeutic comprising a homodimeric antibody and either a radioisotope or a labile pharmaceutical agent, wherein:

• the homodimeric antibody comprises two immunoglobulin G (IgG) antibodies that are covalently crosslinked;
• each IgG antibody comprises two antigen-binding sites that each specifically bind a cancer-associated antigen such that the homodimeric immunoconjugate comprises exactly four antigen-binding sites that each specifically bind the cancer-associated antigen, and
• each antigen-binding site binds Sp17 and comprises:
• a first variable domain that comprises a VH CDR1 region comprising the amino acid sequence set forth in SEQ ID NO:
• 5, a VH CDR2 region comprising the amino acid sequence set forth in SEQ ID NO:
• 6, and a VH CDR3 region comprising the amino acid sequence set forth in SEQ ID NO:
• 7;
• and
• a second variable domain that comprises a VL CDR1 region comprising the amino acid sequence set forth in SEQ ID NO:
• 8, a VL CDR2 region comprising the amino acid sequence set forth in SEQ ID NO:
• 9, and a VL CDR3 region comprising the amino acid sequence set forth in SEQ ID NO:
• 10.