The pharmacological mechanisms of omalizumab in patients with very high IgE levels—Clues from studies on atopic dermatitis

Seventeen case series investigating the effects of omalizumab on patients with atopic dermatitis included patients whose pretreatment serum IgE was above 700 IU/ml, the upper inclusion limit specified in the product label. In all, 107 patients received omalizumab at doses of ≤375 mg every 2 weeks, which is recommended for patients with IgE <700 IU/ml. Among them, 87 improved in clinical symptoms and some did so after the first dose. Among these 87 patients, 35 and 12 had pretreatment serum IgE in the range 700–7000 IU/ml and 7000–121,000 IU/ml, respectively. These results not only suggest the pathogenic roles of IgE and the potential utility of omalizumab in atopic dermatitis, but also raise questions concerning the pharmacological mechanisms of omalizumab in patients with very high IgE levels. If omalizumab at regular doses is proven to treat patients with ultra high IgE (e.g. above 7000 IU/ml) effectively, it probably achieves this without neutralizing most of the IgE produced in the patients and downregulating the high-affinity IgE-Fc receptors on basophils and mast cells. Herein, we propose that a potential main pharmacological mechanism of omalizumab in patients with ultra high IgE is the ability of the rapidly accumulated IgE:omalizumab complexes to trap allergens.