Basophil Histamine Release Decreases during Omalizumab Therapy in Allergic Asthmatics

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Abstract
Omalizumab is an established add-on therapy efficacious in allergic diseases with additional anti-inflammatory activity in the treatment of asthma. The evaluation of responders to anti-IgE treatment is critical to maximize benefit/risk/cost ratio. The aim of the study was to monitor the efficacy of anti-IgE treatment by ex vivo basophil histamine release. Seventeen patients with allergic asthma were enrolled and received omalizumab at a dose of > or =0.016 mg/kg/IgE every 4 weeks. Histamine release from basophils was evaluated fluorometrically after dose-dependent allergen challenge at baseline and after 16 weeks of treatment. Maximal histamine release and cellular sensitivity to the allergen were calculated. Clinical measurements consisted of body plethysmography, skin prick test, beta2-agonist usage, serum free IgE levels, peripheral eosinophils and investigator ratings of global evaluation of treatment effectiveness. Maximal histamine release and cellular sensitivity to the allergen were significantly decreased in the omalizumab group compared to placebo. These changes were accompanied by significant changes in the clinical markers airway resistance, beta-agonist usage, skin prick test wheal area and investigator ratings of global evaluation of treatment effectiveness. Omalizumab therapy decreases basophil histamine release and cellular sensitivity with high effectivity of 95.8% (median). The decline of ex vivo basophil responses does not always parallel individual clinical improvement. Basophil-based stimulation tests should be further evaluated before being regarded as useful parameters monitoring omalizumab therapy.