Allergen skin tests and free IgE levels during reduction and cessation of omalizumab therapy.

BACKGROUND: The recombinant humanized anti-IgE antibody omalizumab rapidly reduces serum free IgE concentrations and alleviates allergic airway disease. It is not known whether stopping or reducing the dose of omalizumab maintains adequate suppression of free IgE levels and IgE-mediated mast cell activation.

OBJECTIVE: To determine the effects of omalizumab on serum free IgE and immediate allergen skin test reactivity during initial therapy followed by treatment reduction and cessation.

METHODS: Forty patients with perennial allergic rhinitis were randomized to receive 0.015 or 0.030 mg/kg/IU/mL open-label intravenous omalizumab every 2 weeks for 28 weeks, followed by 0.0015 or 0.0050 mg/kg/IU/mL every 2 weeks for 18 weeks. Serum free IgE levels were measured and titrated dust mite allergen skin tests conducted throughout.

RESULTS: At day 98, serum free IgE concentrations were decreased by 96% to 99%, and wheal-and-flare reactions to skin tests were markedly suppressed. After reduced omalizumab doses (day 322), serum free IgE and allergen skin test reactivity increased significantly. On complete discontinuation of therapy (day 378), serum free IgE levels and skin test reactivity returned to baseline levels. Patients with lower initial levels of IgE had significantly less suppression of skin test reactivity.

CONCLUSION: Omalizumab reduced serum free IgE and immediate skin test reactivity to allergen during initial, high-dose administration. These effects were not fully maintained during dose reduction and returned to baseline after cessation of chronic treatment.