Omalizumab (Xolair®) is a recombinant DNA-derived humanized IgG1κ monoclonal antibody that binds human immunoglobulin E (IgE) for the treatment of moderate to severe persistent allergic asthma and Chronic Idiopathic Urticaria (CIU). Omalizumab inhibits the binding of IgE to IgE receptor (FcεRI) on the surface of mast cells and basophils thereby limiting the release of mediators of the allergic response from the FcεRI bearing cells.