Tetrahedral antibodies

An octahedral antibody comprising a first, second, third, fourth, fifth and sixth domain, wherein:

• a) each of the first, second and third domains are selected from the group consisting of a Fab domain and an Fc domain,
• b) each of the first, second and third domains comprise:
• i) a first polypeptide chain comprising a first N-terminus of the domain, and
• ii) a second polypeptide chain comprising a second N-terminus of the domain,
• c) the first N-terminus of the first domain, the first N-terminus of the second domain and the first N-terminus of the third domain are joined to each other by a non-peptidyl linkage wherein the non-peptidyl linkage is:
• i) a branched covalent linkage, or
• ii) a non-covalent linkage between
• (1) a first trimerizing polypeptide attached by a peptide bond or via a peptide linker to the first N-terminus of the first domain,
• (2) a second trimerizing polypeptide attached by a peptide bond or via a peptide linker to the first N-terminus of the second domain, and
• (3) a third trimerizing polypeptide attached by a peptide bond or via a peptide linker to the first N-terminus of the third domain,
• wherein the first, second, and third trimerizing polypeptides are not immunoglobulin polypeptides,
• d) the fourth domain is attached at its C-terminus by a peptide bond or via a peptide linker to:
• i) the second N-terminus of the first domain, or
• ii) the N-terminus terminus of the first trimerizing polypeptide,
• e) the fifth domain is attached at its C-terminus by a peptide bond or via a peptide linker to:
• i) the second N-terminus of the second domain, or
• ii) the N-terminus of the second trimerizing polypeptide, and
• f) the sixth domain is attached at its C-terminus by a peptide bond or via a peptide linker to:
• i) the second N-terminus of the third domain, or
• ii) the N-terminus of the third trimerizing polypeptide.