Half‐Life Extension of the IgG‐Degrading Enzyme (IdeS) Using Fc‐Fusion Technology

Imlifidase (IdeS) is a bacterial protease that hydrolyzes human IgG in their hinge region, decreasing their half-life and abrogating their Fc-mediated properties. It is now successfully used in therapy to prevent graft rejection during kidney transplants and is being clinically evaluated in several IgG-mediated autoimmune diseases. IdeS short half-life however limits its clinical use, particularly in the case of chronic diseases that would request repeated administrations. Here, we developed IdeS-Fc fusion proteins as a divalent homodimer (IdeS-Fc^div) or a monovalent heterodimer (IdeS-Fc^monov), in order to extend the IgG-depleting action of IdeS over time. Both IdeS-Fc efficiently separated monoclonal and polyclonal human IgG into F(ab')₂ and Fc fragments, although with slower kinetics than their native counterpart. IdeS-Fc^monov exhibited a seven-fold half-life extension in vivo as compared with IdeS, and a significantly better residual cleavage of human IgG at later time points after injection. Our results provide proof of concept for the use of an IdeS with extended IgG-hydrolyzing functions in vivo that could rapidly translate to the clinic.