Omalizumab: a review of its use in patients with chronic spontaneous urticaria.

Omalizumab (Xolair(®)) is a humanized, recombinant, IgG, anti-IgE monoclonal antibody that binds to the Fc region of free IgE and prevents it from binding to its high-affinity receptor (FcεR1) on mast cells and basophils. This reduction in free IgE leads to a reduction in mast cell/basophil degranulation and the release of histamine, and to the down-regulation of FcεR1 receptors on these cells. Omalizumab does not bind to cell-bound IgE or to IgG. In well-controlled clinical trials in patients with chronic spontaneous urticaria and persistent symptoms despite background treatment with antihistamines, add-on therapy with subcutaneous omalizumab 300 mg every 4 weeks for 12 or 24 weeks significantly reduced the severity of itching, and the number and size of hives, and increased patients' health-related quality of life and the proportion of days free from angioedema compared with placebo. Subcutaneous omalizumab was generally well tolerated; the incidence and severity of adverse events in omalizumab recipients were similar to those in placebo recipients, and most adverse events were of mild or moderate severity. The only adverse events occurring more frequently with omalizumab than with placebo during treatment in a safety study were headache and upper respiratory tract infection. Thus, omalizumab is an effective and well-tolerated add-on therapy in patients with chronic spontaneous urticaria who are symptomatic despite background therapy with H1 antihistamines.