A platform for the early selection of non-competitive antibody-fragments from yeast surface display libraries.

In this work, we report the development of a platform for the early selection of non-competitive antibody-fragments against cell surface receptors that do not compete for binding of their natural ligand. For the isolation of such subtype of blocking antibody-fragments, we applied special fluorescence-activated cell sorting strategies for antibody fragments isolation from yeast surface display libraries. Given that most of the monoclonal antibodies approved on the market are blocking ligand-receptor interactions often leading to resistance and/or side effects, targeting allosteric sites represents a promising mechanism of action to open new avenues for treatment. To directly identify these antibody-fragments during library screening, we employed immune libraries targeting the epidermal growth factor receptor as proof of concept. Incorporating a labeled orthosteric ligand during library sorting enables the early selection of non-competitive binders and introduces an additional criterion to refine the selection of candidates exhibiting noteworthy properties. Furthermore, after sequencing, more candidates were identified compared to classical sorting based solely on target binding. Hence, this platform can significantly improve the drug discovery process by the early selection of more candidates with desired properties.