Compositions and methods for treating IgE-mediated disorders

#The present disclosure relates to immunoglobulin compositions that bind IgE and FcγRIIb with high affinity, said compositions being capable of inhibiting cells that express membrane-anchored IgE. Such compositions are useful for treating IgE-mediated disorders, including allergies and asthma.

#Allergic diseases and conditions, such as asthma, allergic rhinitis, atopic dermatitis, and food allergy, have become increasingly prevalent over the past few decades and now affect 10-40% of the population in industrialized countries. Allergic diseases profoundly affect the quality of life, and can result in serious complications, including death, as may occur in serious cases of asthma and anaphylaxis. Allergies are prevalent, and are the largest cause of time lost from work and school and their impact on personal lives as well as their direct and indirect costs to the medical systems and economy are enormous. For example, allergic rhinitis (hay fever) affects 22% or more of the population of the USA, whereas allergic asthma is thought to affect at least 20 million residents of the USA. The economic impact of allergic diseases in the United States, including health care costs and lost productivity, has been estimated to amount to $6.4 billion in the early nineties alone.

#Most allergic diseases are caused by immunoglobulin E (IgE)-mediated hypersensitivity reactions. IgE is a class of antibody normally present in the serum at minute concentrations. It is produced by IgE-secreting plasma cells that express the antibody on their surface at a certain stage of their maturation. Allergic patients produce elevated levels of IgE with binding specificity for ordinarily innocuous antigens to which they are sensitive. These IgE molecules circulate in the blood and bind to IgE-specific receptors on the surface of basophils in the circulation and mast cells along mucosal linings and underneath the skin. Binding of antigen or allergen to IgE on mast cells, basophils, and other cell types, crosslink the IgE molecules, and aggregate the underlying receptors, thus triggering the cells to release vasoactive and neuronal stimulatory mediators such as histamines, leukotrienes, prostaglandins, bradykinin, and platelet-activating factor. The rapid reaction of the immune system to antigen caused by antibody immune complexes has led to the term immediate or antibody-mediated hypersensitivity reaction, in contrast to delayed or cell-mediated hypersensitivity reactions that are mediated by T cells. IgE-mediated immune reactions are specifically referred to as type hypersensitivity reactions.

#FIG. 1. Illustration of the novel mechanistic approach for inhibiting IgE+ FcγRIIb+ B cells. Under appropriate stimuli, naive B cells can differentiate into IgE+ B cells. Engagement of antigen with the IgE B cell receptor activates these cells, which can then differentiate into plasma cells that release circulating IgE. Binding of circulating IgE binds to FcεR's, for example on mast cells, basophils, and eosinophils, activates these cells. Release of histamine, prostaglandins, and other chemical mediators ultimately results in the clinical symptoms of allergy and asthma. Omalizumab, having a native IgG1 Fc region; is capable of blocking binding of IgE to FcεR. Anti-IgE antibodies with high affinity for FcγRIIb, referred to as Anti-IgE-IIbE in the figure, are capable of not only blocking binding of IgE to FcεR, but also of inhibiting activation of IgE+ B cells by mIgE FcεRIIb coengagement.

#FIG. 2. Biacore surface plasmon resonance sensorgrams showing binding of Fc variant anti-CD19 antibodies to human FcγRIIb.

#FIG. 3. Affinities of Fc variant antibodies for human FcγRs as determined by Biacore. The graph shows the log(KA) for binding of variant and WT IgG1 antibodies to human FcγRI (I), H131 FcγRIIa (H IIa), FcγRIIb (IIb), and V158 FcγRIIIa (V IIIa). Binding of G236D/S267E and S267E/L328F to V158 FcγRIIIa was not detectable. Binding of G236R/L328R (Fc-KO) to all receptors tested was not detectable.

#Described herein are coengagement molecules that mimic the inhibitory effects of coengagement of membrane-anchored IgE with FcγRIIb on B cells. For example, described herein are variant anti-IgE antibodies engineered such that the Fc domain binds to FcγRIIb with up to ˜430-fold greater affinity. Relative to native IgG1, the FcγRIIb binding-enhanced (IIbE) variants strongly inhibit BCR-induced calcium mobilization and viability in primary human IgE+ B cells. The use of a single molecule, such as an antibody to suppress B cell functions by coengagement of cognate IgE BCR and FcγRIIb may represent a novel approach in the treatment of IgE-mediated diseases. Nonlimiting examples of IgE-mediated diseases include allergic responses and asthma and are described in more detail below.

#Coengagement molecules according to the disclosure may take on a variety of configurations as outlined in more detail below. In one embodiment the coengagement molecule includes an immunoglobulin that binds IgE and FcγRIIb with high affinity. In this embodiment the immunoglobulin preferably coengages membrane-anchored IgE and FcγRIIb on a cell's surface and binds with a Kd of less than about 100 nM. In another embodiment, the coengagement molecule is a bispecific molecule having a first target specific region and a second target specific region, wherein the first target specific region binds IgE and the second target specific region binds FcγRIIb with a Kd of less than about 100 nM, although in some embodiments it may bind FcγRIIb with a Kd of less than about 10 nM or a Kd of less than about 1 nM and in some embodiments may bind with a Kd less than 100 pM. In a preferred embodiment the coengagement molecule is a bispecific antibody and the first and second target specific regions are Fv regions, wherein the first Fv region binds IgE, and the second Fv region binds FcγRIIb with a Kd of less than about 100 nM. In another embodiment, coengagement molecule is an Fc fusion comprising an Fc region, wherein said Fc region binds FcγRIIb with a Kd of less than about 100 nM. In this embodiment, the Fc fusion partner of the immunoglobulin binds IgE.

#Described herein are several definitions. Such definitions are meant to encompass grammatical equivalents.