Fig. 3

The figure shows various common bispecific antibody (bsAb) formats. The Fc-modified IgG format leverages KIH technology to facilitate the heterodimerization of two distinct heavy chains. To enhance the pairing of homologous heavy and light chains, DuetMab introduces an alternative disulfide bond, replacing the natural bond at one CH1-CL interface. The Duobody format includes specific Fc region mutations, significantly reducing Fc-mediated cytotoxicity. Appended IgG structures integrate an IgG with a single-chain variable fragment (scFv), either through light chain (LC) or heavy chain (HC) connections. Constructs such as scFv-Fc and Fab-scFv-Fc also rely on the KIH method for their assembly. The DART-Fc structure incorporates two distinct antigen-binding domains, stabilized into a diabetes-like mimic. TriFabs are IgG-derived bsAbs with two standard Fab arms linked to a third Fab-sized unit via flexible peptide linkers. CrossMab, on the other hand, achieves connectivity using domain crossovers involving a shared light chain. Tandem scFv (taFv) represents the most compact bsAb design, closely related to Triplebody constructs. The diabetic (db) format employs a short linker to join VH and VL domains of an scFv, forming a noncovalent heterodimer. Dual-Affinity Re-Targeting (DART) molecules pair two Fv segments to generate distinct antigen-binding regions. Tandem single-domain antibodies (dAb/VHH) are derived from the binding regions of heavy-chain-only antibodies. Lastly, the Fab-scFv "bibody" format links an scFv to the Fab's C-terminus, while the Fab-scFv "tribody" format adds a second scFv segment for enhanced functionality