Fc binding fragments comprising a pd-l1 antigen-binding site

An antibody molecule, or fragment thereof, which binds to programmed death-ligand 1 (PD-L1), comprising a PD-L1 antigen-binding site located in a CH3 domain of the antibody molecule, or fragment thereof, wherein the PD-L1 binding site comprises:

• (i) a first sequence located in the AB structural loop at positions 14 to 18 of the CH3 domain, wherein the antibody molecule, or fragment thereof, comprises an amino acid deletion at position 14, 15 or 16 of the CH3 domain, and wherein the first sequence consists of:
• (a) amino acid sequence SGYW (SEQ ID NO:
• 23), or
• (b) a variant of SEQ ID NO:
• 23, wherein
• the serine (S) is substituted with amino acid A, E, F, G, H, I, L, P, R, T, V, or Y, and/or
• the glycine (G) is substituted with amino acid A, D, E, F, H, K, L, N, P, R, T, V, or Y;
• (ii) a second sequence located in the CD structural loop at positions 45.1 to 78 of the CH3 domain, wherein the second sequence consists of:
• (a) amino acid sequence EPQYWA (SEQ ID NO:
• 11), or
• (b) a variant of SEQ ID NO:
• 11, wherein
• the glutamic acid (E) is substituted with amino acid A, G, H, I, L, N, Q, R, S, or W, and/or
• the proline (P) is substituted with amino acid A, D, E, G, H, N, Q, W, or Y, and/or
• the glutamine (Q) is substituted with amino acid H, or N, and/or
• the tyrosine (Y) is substituted with amino acid A, D, H, T, or V, and/or
• the alanine (A) is substituted with amino acid D, E, G, L, R, S, or W;
• and
• (iii) a third sequence located in the EF structural loop at positions 92 to 100 of the CH3 domain, wherein the third sequence consists of:
• (a) amino acid sequence SNWRWQMDD (SEQ ID NO:
• 19), or
• (b) a variant of SEQ ID NO:
• 19, wherein
• the serine (S) at position 92 is substituted with amino acid A, or G, and/or
• the asparagine (N) at position 93 is substituted with amino acid A, E, F, G, H, I, K, L, Q, R, S, T, or Y, and/or
• the glutamine (Q) at position 97 is substituted with amino acid A, D, E, F, G, H, K, L, N, R, S, or V, and/or
• the methionine (M) at position 98 is substituted with amino acid F, I, L, V, W, or Y, and/or
• the aspartic acid (D) at position 99 is substituted with amino acid A, I, L, R, S, T, V, W, Y, or G, and/or
• the aspartic acid (D) at position 100 is substituted with amino acid A, E, F, I, K, L, N, R, V, W, or Y;
• and
• wherein the amino acid at position 101 of the CH3 domain is valine (V), alanine (A) or is absent;
• wherein the amino acid residue numbering is according to the ImMunoGeneTics (IMGT) numbering scheme;
• and
• wherein the antibody molecule, or antigen-binding fragment thereof, is not an antibody molecule, or antigen-binding fragment thereof, which comprises a CDR-based antigen-binding site which binds Inducible T-cell COStimulator (ICOS) and a PD-L1 binding site comprising a first sequence located in the AB structural loop at positions 14 to 18 of the CH3 domain, wherein the antibody molecule, or antigen-binding fragment thereof, comprises an amino acid deletion at position 14, 15 or 16 of the CH3 domain, and wherein the first sequence consists of the sequence set forth in SEQ ID NO:
• 23, a second sequence located in the CD structural loop at positions 45.1 to 78 of the CH3 domain, wherein the second sequence consists of the sequence set forth in SEQ ID NO:
• 11, and a third sequence located in the EF structural loop at positions 92 to 100 of the CH3 domain, wherein the third sequence consists of the sequence set forth in SEQ ID NO:
• 31.