Discovery and engineering of novel anti-IgE disruptive inhibitors

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Project Summary The majority of allergic reactions are caused by anti-allergen IgE antibodies, which sensitize allergic effector cells such as mast cells and basophils. In contrast to IgG antibodies, IgE binds with subnanomolar affinity to the high affinity IgE receptor (FceRI) and persists in a receptor-bound form on allergic effector cells for months even in the presence of high affinity anti-IgE antibody inhibitors, such as omalizumab. We have shown that both antibodies and Designed Ankyrin Repeat Proteins (DARPins) are able to kinetically accelerate the dissociation of IgE from FceRI through two mechanisms: a facilitated dissociation mechanism that allows receptor-adjacent inhibitors to promote receptor dissociation and an allosteric mechanism that restricts IgE to a conformation incompatible with receptor binding. We have developed a yeast display approach to selecting anti-IgE inhibitors capable of disrupting receptor complexes and demonstrated our ability to select more potent anti-IgE variants of omalizumab. In addition, we have demonstrated pathways to engineering more potent bivalent disruptive inhibitors consisting of a disruptive anti-IgE domain and a non-competitive IgE anchoring domain. Here we propose to apply these approaches to interrogate an anti-IgE immune library, to isolate more potent disruptive inhibitors, to explore the mechanistic diversity of disruptive inhibitors and to develop ultrapotent bivalent anti-IgE inhibitors compatible with future clinical development.