In search of clinically relevant parameters to monitor successful omalizumab therapy in allergic asthma.

Background: Omalizumab is approved as add-on therapy for the treatment of severe uncontrolled allergic asthma. Increase in quality of life and decrease of exacerbations and hospital admission, as well as immunmodulatory effects have been described with omalizumab therapy. However, to date there are few parameters to monitor success and to evaluate the individual advantage of this therapy for the patient. Furthermore, no reliable parameter to predict response to treatment exists so far. The aim of this study was to define an easily applicable parameter for response to treatment with omalizumab.

Method: 43 patients with allergic asthma were treated with omalizumab at a dose of at least 0,016 mg/kg/IgE every 4 weeks. Before, and 12 weeks after initiation of therapy, bodyplethysmography including airway resistance was performed. Efficacy of treatment was judged by the attending physician on the basis of a five point chart. Furthermore, a differential blood count was performed before, and 12 weeks after initiation of treatment. Total and specific IgE against all relevant antigens were determined before start of therapy.

Results: Airway resistance in patients with response to treatment with omalizumab (responders) was significantly decreased in comparison to patients without clinical benefit (non-responder). The number of eosinophil granulocytes in the peripheral blood was decreased in both groups without significant difference. Response to therapy was associated with younger age and lower levels of specific IgE against the allergen with the highest sIgE-level (seasonal and perennial), but not with the sIgE level of the perennial allergens in general.

Conclusion: Measurement of airway resistance might be an additional parameter for monitoring response to therapy with omalizumab. High specific IgE levels, for both perennial and concomitant seasonal allergens as well as increasing age, seem to predict less favorable treatment outcomes.