Thursday, April 18, 2013

Omalizumab for the Treatment of Chronic Idiopathic Urticaria

By: Carol Smith, MD
Chronic Idiopathic Urticaria (CIU) was described in a 1995 article in the NEJM as itchy hives that last for at least 6 weeks, with or without angioedema, and that have no apparent external trigger. This definition still holds true today, and we know that these patients can have a prolonged course lasting years, that plays havoc on their emotional and physical quality of life. H1 antihistamines have been the mainstay of treatment, but a majority of patients don’t respond even at quadruple the licensed dose. As we’ve come to understand more of this complex disease, new treatment options are emerging.
We typically like to rule out underlying conditions that can trigger chronic hives, such as allergy, chronic infection, autoimmune disorders such as hypothyroidism, and treat these accordingly. Also, recently linked to CIU, is an autoantibody directed against the high affinity IgE Fc receptor (FceR1), which stimulates mast cells and basophils to produce histamine.
For the patients not responding to high dose antihistamines or treatment of underlying diseases, more aggressive therapies are an option. High dose or prolonged course of oral steroids may be efficacious, but the side effects can be dire. Steroid-sparing immunosuppressant therapies frequently used include cyclosporine, methotrexate, tacrolimus, dapsone, with variable results and their own potential side effects.
A new treatment option is being studied, and was recently reported in the March 2013 NEJM. Omalizumab is a recombinant monoclonal anti-IgE antibody currently approved as an add-on therapy for moderate-to-severe asthma.  It binds free IgE antibody and reduces the high-affinity IgE Fc receptor, both of which are essential for the activation of mast cells and basophils.  The summary of this phase 3 multi-center, randomized, double-blind study found that omalizumab administered at three doses of 150 mg or 300 mg at 4-week intervals significantly reduced symptoms, as compared to placebo, in patients who were unresponsive to H1 antihistamines.
More studies are underway, but I am cautiously optimistic for the potential use of omalizumab as a safer option for the treatment of recalcitrant chronic idiopathic urticaria.

Carol Smith, M.D. _ Birmingham Allergy and Asthma


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