FEBRUARY 2007 QUIZ OF THE MONTH . . . There has been considerable interest in the use of omalizumab (Omal), a monoclonal anti-IgE antibody, in the treatment of persistent asthma . Which of the statements below about Omal are true or false? 1. Omal treatment results in a significant decrease in the serum total IgE levels. 2. Omal treatment is followed by decreased expression of the high affinity IgE receptor (Fc epsilon RI) on basophils and mast cells. 3. Omal therapy is indicated for the treatment of severe, uncontrolled asthma. 4. Omal therapy is as effective in asthmatics with normal serum IgE levels as in those with moderately elevated serum IgE levels. 5. Omal therapy is contraindicated in asthmatics receiving allergy immunotherapy. Discussion Injected Omal, a monoclonal anti-IgE antibody marketed as Xolair in the USA , complexes to circulating IgE, reducing the serum levels of free (unbound) IgE but not a decrease in total IgE levels. The degree of expression of the Fc epsilon RI on basophils and mast cells of an individual appears to be related to the serum levels of free IgE in that person. Therefore, likely because of the reduction in serum free IgE levels during Omal therapy, there is a subsequent reduced expression of the Fc epsilon RI on basophils and mast cells. Omal therapy is approved for asthmatics with moderately elevated serum IgE levels at baseline but not when the serum IgE levels are within normal limits. Because of the need for repeated injections and the sizable costs involved, Omal therapy has generally been limited to those with more severe asthma unresponsive to treatment with inhaled corticosteroids and possibly inhaled long acting beta agonists. Omal treatment is not contra-indicated in those receiving allergy immunotherapy. Indeed, clinical trials have shown a reduced frequency of systemic allergic reactions during “rush” allergy immunotherapy in individuals also receiving Omal treatment. References N Engl J Med. 2006;354:2689-95 Can Respir J. 2006;13 Suppl B:1B-9B Think you have the answers? Click here to find out if you're right! Please tell us what you think of this site. © Copyright 1997-2007 American Academy of Allergy, Asthma & Immunology All rights reserved