Optimizing drug inhibition of IgE-mediated anaphylaxis in mice

Background: Administering allergens in increasing doses can temporarily suppress IgE-mediated allergy and anaphylaxis by desensitizing mast cells and basophils; however, allergen administration during desensitization therapy can itself induce allergic responses. Several small molecule drugs and nutraceuticals have been used clinically and experimentally to suppress these allergic responses. Objectives: This study sought to optimize drug inhibition of IgE-mediated anaphylaxis. Methods: Several agents were tested individually and in combination for ability to suppress IgE-mediated anaphylaxis in conventional mice, Fc epsilon RI alpha-humanized mice, and reconstituted immunodeficient mice that have human mast cells and basophils. Hypothermia was the readout for anaphylaxis; therapeutic efficacy was measured by degree of inhibition of hypothermia. Serum mouse mast cell protease 1 level was used to measure extent of mast cell degranulation. Results: Histamine receptor 1 (HR1) antagonists, beta-adrenergic agonists, and a spleen tyrosine kinase (Syk) inhibitor were best at individually inhibiting IgE-mediated anaphylaxis. A Bruton's tyrosine kinase (BTK) inhibitor, administered alone, only inhibited hypothermia when Fc epsilon RI signaling was suboptimal. Combinations of these agents could completely or nearly completely inhibit IgE-mediated hypothermia in these models. Both Syk and BTK inhibition decreased mast cell degranulation, but only Syk inhibition also blocked desensitization. Many other agents that are used clinically and experimentally had little or no beneficial effect. Conclusions: Combinations of an HR1 antagonist, a beta-adrenergic agonist, and a Syk or a BTK inhibitor protect best against IgE-mediated anaphylaxis, while an HR1 antagonist plus a beta-adrenergic agonist +/- a BTK antagonist is optimal for inhibiting IgE-mediated anaphylaxis without suppressing desensitization.