Tribodies: Fab–scFv Fusion Proteins as a Platform to Create Multifunctional Pharmaceuticals
Tribodies are multifunctional recombinant antibody derivatives, which utilize the natural in vivo heterodimerization of the heavy chain (Fd fragment) and light chain (L) of a Fab fragment, to form a scaffold, upon which additional functions can be incorporated, such as additional binders – e.g., scFv binding domains.
Each chain can be extended preferably at the C terminus with an additional scFv binder. The chains are coproduced in mammalian cells, where the host-cell BiP chaperone drives the formation of the heavy chain–light chain heterodimer (Fd:L) – this reaction does not appear to be inhibited by the chain extensions, and leads to a very specific heterodimerization, using molecules abundantly present in serum (non-immunogenic)
These heterodimers are stable, with each of the binders retaining their specific affinities, with the bivalent tribody having higher affinity, and higher activation of T-cell proliferation and cytotoxicity in vivo.
This design allows easy engineering of multispecificity in a single molecule, e.g., bispecific antibodies bivalent for the target and monovalent for effector activation (e.g., for T-cell activation), or trispecific antibodies pur sang.
KeywordsBispecific Antibody Bivalent Binding scFv Molecule Antibody Derivative Monovalent Binding
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