Omalizumab in the Treatment of Urticaria

Omalizumab is a humanized mouse monoclonal IgG1 antibody directed against the third heavy chain domain of IgE. It has been approved for moderate to severe asthma since 2003, for adults and adolescents with chronic spontaneous urticaria unresponsive to antihistamines since 2014. The evidence base for its efficacy and safety in chronic urticaria is strong. Its introduction has changed the outlook for patients with chronic spontaneous urticaria not responding to older medications including up-dosed H1 antihistamines with complete disease control being achieved in over 40% and partial control in the majority of patients when administered subcutaneously at the approved dose of 300 mg every 4 weeks. Shortening or lengthening the interval between doses may be appropriate for a few patients with a consistent pattern of symptomatic relapse before or after 4 weeks. Increasing the dose to 450 or 600 mg may benefit poor responders. Lengthening the interval between doses in completely controlled patients can be used to assess whether patients are ready to stop treatment. Clinical experience has shown that treatment with omalizumab is not disease modifying but can be maintained until natural remission occurs. Stopping and restarting treatment does not lead to lack of efficacy. Patients with normal or high baseline total IgE (indicative of autoallergic urticaria) tend to be fast and complete responders. Delayed responses may be seen in patients with evidence of functional autoantibodies (Type IIb autoimmune urticaria). Angioedema burdened days are reduced. There is increasing clinical evidence that chronic urticaria patients with inducible urticarias may also respond to omalizumab. Apart from a very low risk of anaphylaxis, omalizumab is safe and well tolerated. It has been used off label in children. There is no evidence to date of harm in pregnancy (FDA category B). Self-administration by patients or trained care-givers from the fourth dose onwards was approved by the European Commission in 2018.