Omalizumab for difficult-to-treat dermatological conditions: clinical and immunological features from a retrospective real-life experience.

Background: Omalizumab, a therapeutic monoclonal antibody specific for human IgE, has thus far been used as add-on therapy for moderate-to-severe allergic asthma in adults and children.

Objective: The objective of this study was to test omalizumab efficacy in other conditions in which the IgE-mast cell axis is supposed to play a role.

Methods: Nine patients with dermatological manifestations possibly related to activation of the IgE-mast cell axis (six chronic spontaneous urticaria and three atopic dermatitis patients) were administered off-label omalizumab because of refractoriness to standard therapy. All patients were subjected to strict clinical, laboratoristic, and imaging follow-up to monitor for possible adverse effects. In addition, to further assess the role of omalizumab on T cells, mast cells, and eosinophils, T-cell immune polarisation as well as eosinophil cationic protein and tryptase serum levels were determined before and during omalizumab administration.

Results: Therapy was effective in seven out of nine patients (six complete responses, one partial response, and two no responses). Interestingly, omalizumab appeared to induce lymphocyte polarisation toward a type 2 immune response and to be able to quench eosinophil-mediated inflammation, particularly in atopic dermatitis patients. Tryptase serum levels were generally low and remained unchanged during omalizumab treatment. Despite treatment spanning over several years in most of the patients, no adverse effects nor new ensuing medical conditions have thus far been observed (median follow-up: 42 months).

Conclusions: Off-label omalizumab was safe and effective in our patients. The novel immunologic features recorded in our patients add further complexity to the mechanism of action of omalizumab.