Figure 1.
Schematic composition of bispecific antibody derivatives. The domain compositions of various bispecific antibody formats (upper panels), as well as the composition of the mRNAs (lower panels) that encode the individual building blocks for these molecules, are shown. A: IgG-derived molecules containing Fc regions. Heterdimerization of different H-chains may be forced by knobs-into-holes technologies, including in common LC (light chain), CrossMab, IgG-dsF, IgG-scFab and Fv2-Fc approaches. Knobs/holes are indicated as complementary black/white circles in the CH3 encoding regions. The dual acting Fab (DAF) which contains evolved Fvs that bind with dual specificity, as well as the DVD (dual variable domain) formats do not require H-chain heterodimerization and hence contain unmodified H-chains. B: Bispecifics without Fc regions. These are generally smaller than Fc-containing entities and are composed of individual scFvs or Fabs of different binding specificities which are fused to each other via linker peptides. Fusion of VH-CH1 and/or L chains to scFvs generate bi- or trivalent Fab-Fv or Fab-Fv2 entities. Fusions of scFvs of different specificities generate rather small scFv-scFv molecules (such as BiTEs). Diabodies, dual-affinity retargeting molecules (DARTs), and TandAbs are generated by modulating the length of the linker peptides to force correct pairing of VH and VL domains (which are not scFvs in a strict sense). These molecules can be additionally stabilized by interchain disulfide bonds (e.g. in DART). Variable regions of different specificities are indicated by different colors (red, blue and green), invariable constant (CH1 and CL) regions are colored grey, and linker peptides that are introduced to connect added entities are colored orange colour. Bispecifics that contain scFvs modules have them frequently additionally stabilized by interchain disulfide bonds between VH and VL. Stars indicate the location of a disulfide bridge. BiTE=Bispecific T-cell engagers; CH1, CH2, CH3=constant region heavy chain domains; CL=constant region light chain; DAF=dual-acting Fab; ds=disulfide; Fab=fragment, antigen binding; Fc=fragment, contant region; Fv=fragment, variable region; HAS=human serum albumin; IgG=immunogobulin G; TandAb=tandem antibody; VH=variable region heavy chain; VL=variable region light chain.