Omalizumab therapy in atopic dermatitis: depletion of IgE does not improve the clinical course - a randomized, placebo-controlled and double blind pilot study

Background: Our understanding of the pathogenic role of IgE in atopic dermatitis is incomplete. We asked whether blocking free IgE would alter the course of the disease. Patients and Methods: We administered either omalizumab, a humanized monoclonal mouse antibody against IgE, or placebo subcutaneously for 16 weeks to 20 atopic dermatitis patients and measured immunological and clinical disease parameters. Results: Omalizumab (I) reduced free serum IgE, (II) lowered surface IgE and Fc epsilon RI expression on different peripheral blood mononuclear cells, (III) reduced the saturation of Fc epsilon RI with IgE, (IV) increased the number of free Fc epsilon RI and (V) lowered the number of IgE+, but not of Fc epsilon RI+ cells in skin. The in vivo relevance of these results is evidenced by the increase in the threshold allergen concentration required to give a type I hypersensitivity reaction in the titrated skin test. While not significantly altering the clinical disease parameters, omalizumab treatment led to an improvement of the atopy patch test results in single patients, i.e. an eczematous reaction upon epicutaneous allergen challenge. Conclusions: The interference with immediate and delayed type skin tests may imply that a therapeutic benefit of omalizumab treatment, if present at all, would be seen in patients with acute rather than chronic forms of the disease.