Development of a generic, automated, microfluidic human IgG-FcRn affinity assay in-solution for antibody engineering

Robust IgG Fc-FcRn binding and affinity assays are increasingly important to support antibody therapeutic engineering targeted to the Fc region of IgGs to extend serum half-life. Measuring the affinity of this interaction can be challenging due to the acidic pH required and the relatively low K_D values. In this study, a proof-of-principle automated microfluidic assay was developed to measure in-solution affinity of IgG-FcRn interactions. This approach allowed determination of in-solution FcRn-IgG affinity of the reactants in their native state by measuring free FcRn from a dilution series of FcRn (fixed concentration) with the IgG therapeutic. The microfluidic format, with low volume, shorter assay time and rapid fluid handling, was suitable to determine these relatively low affinity interactions and for use in antibody engineering screening or development.

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