Abstract
Bispecific antibodies have become important formats for therapeutic discovery. They allow for potential synergy by simultaneously engaging two separate targets and enable new functions that are not possible to achieve by using a combination of two monospecific antibodies. Antagonistic antibodies dominate drug discovery today, but only a limited number of agonistic antibodies (i.e. those that activate receptor signaling) have been described. For receptors formed by two components, engaging both of these components simultaneously may be required for agonistic signaling. As such, bispecific antibodies may be particularly useful in activating multicomponent receptor complexes. Here, we describe a biparatopic (i.e. targeting two different epitopes on the same target) format that can activate the endocrine fibroblast growth factor (FGF) 21 receptor (FGFR) complex containing β-Klotho and FGFR1c. This format was constructed by grafting two different antigen-specific VH domains onto the VH and VL positions of an IgG, yielding a tetravalent binder with two potential geometries, a close and a distant, between the two paratopes. Our results revealed that the biparatopic molecule provides activities that are not observed with each paratope alone. Our approach could help address the challenges with heterogeneity inherent in other bispecific formats and could provide the means to adjust intramolecular distances of the antibody domains to drive optimal activity in a bispecific format. In conclusion, this format is versatile, is easy to construct and produce, and opens a new avenue for agonistic antibody discovery and development.
Highlights
Bispecific antibodies have become important formats for therapeutic discovery
In contrast to results obtained with -Klotho, no detectable interaction was observed between either VH only (VHO) and FGFR1c (Fig. 1C)
To better understand if the two VHOs bind to distinct regions on -Klotho, we performed cross-competition studies. -Klotho extracellular domain (ECD) was immobilized onto a biosensor and presented to the two VHOs in consecutive association steps (Fig. 1D)
Summary
Bispecific antibodies have become important formats for therapeutic discovery. They allow for potential synergy by simultaneously engaging two separate targets and enable new functions that are not possible to achieve by using a combination of two monospecific antibodies. We describe a biparatopic (i.e. targeting two different epitopes on the same target) format that can activate the endocrine fibroblast growth factor (FGF) 21 receptor (FGFR) complex containing -Klotho and FGFR1c This format was constructed by grafting two different antigen-specific VH domains onto the VH and VL positions of an IgG, yielding a tetravalent binder with two potential geometries, a close and a distant, between the two paratopes. We demonstrate that our tetravalent, biparatopic format binds two distinct epitopes on -Klotho, eliminates product heterogeneity due to multiple chains, and can activate the -Klotho/FGFR1c complex with superior activity than each paratope alone This approach offers the potential to address the heterogeneity concerns with other bispecific formats as well as a novel way to adjust intramolecular distances of the antibody domains to drive optimal activity in a bispecific format
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