Background: Serum albumin binding is an established mechanism to extend the serum half-life of antibody fragments and peptides. The cysteine rich knob domains, isolated from bovine antibody ultralong CDRH3, are the smallest single chain antibody fragments described to date and versatile tools for protein engineering.
Methods: Here, we used phage display of bovine immune material to derive knob domains against human and rodent serum albumins. These were used to engineer bispecific Fab fragments, by using the framework III loop as a site for knob domain insertion.
Results: By this route, neutralisation of the canonical antigen (TNFα) was retained but extended pharmacokinetics in-vivo were achieved through albumin binding. Structural characterisation revealed correct folding of the knob domain and identified broadly common but non-cross-reactive epitopes. Additionally, we show that these albumin binding knob domains can be chemically synthesised to achieve dual IL-17A neutralisation and albumin binding in a single chemical entity.
Conclusions: This study enables antibody and chemical engineering from bovine immune material, via an accessible discovery platform.
Competing Interests: This work was funded by UCB Biopharma UK. The funder had a role in data collection and analysis, decision to publish and preparation of the manuscript. All authors except KH, RJP and JE are past or present UCB employees and may hold shares and/or stock options. AM, AL and AS-T are inventors on patent applications relating to knob domain peptides and RA is an inventor on a patent relating to framework III insertions. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
(Copyright © 2023 Adams, Joyce, Kuravskiy, Harrison, Ahdash, Balmforth, Chia, Marceddu, Coates, Snowden, Goursaud, Ménochet, Elsen, Payne, Lawson, Scott-Tucker and Macpherson.)