Schematic diagrams of DNL modules and structures. (A) The design for CH1-DDD2-Fab module. (B) The design for CH3-AD2-IgG modules. (C) The structure of CH1-DDD2-Fab as a dimer. (D) The structure of CH3-AD2-IgG as a monomer. (E) The structure of a bispecific hexavalent construct generated by DNL from reacting CH1-DDD2-Fab with CH3-AD2-IgG. (F) The interaction of the DDD2 and AD2 peptides. The variable domains for the heavy and light chains (VH + VL) are shown in green or orange. The constant domains of the heavy and light chains (CH + CL), the hinge (Hg), the 14-amino-acid residue (L14), and 9-amino-acid residue peptide linkers (L9) are shown in gray. The DDD2 and AD2 peptides are shown in blue and pink, respectively.