The assembly of single domain antibodies into bispecific decavalent molecules

Bispecific antibodies present unique opportunities in terms of new applications for engineered antibodies. However, designing ideal bispecific antibodies remains a challenge. Here we describe a novel bispecific antibody model in which five single domain antibodies (sdAbs) are fused via a linker sequence to the N-terminus of the verotoxin B (VTB) subunit, a pentamerization domain, and five sdAbs are fused via a linker sequence to the VTB C-terminus. Fifteen such decavalent bispecific molecules, termed decabodies, were constructed and characterized for the purpose of identifying an optimal decabody design. One of the fifteen molecules existed in a non-aggregated decavalent form. In conjunction with the isolation of sdAbs with the desired specificities from non-immune phage display libraries, the decabody strategy provides a means of generating high avidity bispecific antibody reagents, with good physical properties, relatively quickly.