Omalizumab for urticaria

Author: Anoma Ranaweera B.V. Sc; PhD (Clinical Biochemistry, University of Liverpool, UK), 2013.

Introduction

Omalizumab is a humanised monoclonal antibody that binds to circulating immunoglobulin E (IgE) and reduces the release of inflammatory mediators from mast cells and basophils.

It is currently licensed as add-on therapy for patients with severe, persistent allergic asthma. It is given by subcutaneous injection once every 4 weeks.

Omalizumab has also been reported to be highly effective in treating severe chronic spontaneous urticaria in teenagers and adults.

The trade name of omalizumab is Xolair™.

What is chronic spontaneous urticaria?

Chronic spontaneous urticaria (also called chronic idiopathic urticaria) is defined as hives or wheals that last for at least 6 weeks, with or without angioedema. Urticaria is often extremely itchy, interfering with sleep, daily activities, social interactions, school and work life.

Symptoms may resolve after a few months; however in about 50% of cases symptoms persist for 3-5 years, and in 20% of cases symptoms can persist for more than 10 years.

Urticaria most often results from the effect of histamine on H1-receptors located on the endothelial cells lining blood vessels. Histamine causes the cells to separate, so that tissue fluid leaks out, forming a wheal. Histamine also affects sensory nerves, resulting in neurogenic flare (red skin) and pruritus (itch).

Chronic urticaria may be refractory to antihistamines and associated with a pronounced cellular infiltrate.

What is the role of omalizumab in treatment of urticaria?

Omalizumab is intended to be used as second-line therapy for the treatment of chronic spontaneous urticaria that is refractory to oral antihistamines. Many patients also fail to respond to a variety of other systemic therapies including systemic steroids and immunomodulating drugs.

Omalizumab is currently in phase III clinical trials in chronic spontaneous urticaria.

How does omalizumab work in urticaria?

The immunoglobulin "E" (IgE) triggers an allergic reaction (e.g. asthma) in response to an allergen (e.g. cat dander). Although chronic spontaneous urticaria is not due to allergy, it occurs through a similar pathway.

Omalizumab has been designed to recognise and attach to a specific structure on circulating human IgE. This prevents IgE binding to high affinity receptors (FcεRI) on the surface of mast cells and basophils, thus reducing receptor expression and the release of inflammatory mediators.

What is the available clinical evidence for the effect of omalizumab?

Results of at least 2 published randomised controlled trials support the efficacy of omalizumab in chronic spontaneous urticaria.

ASTERIA II

Mean Change from baseline in the weekly itch-severity score
GroupMean ChangeP-Value
Omalizumab 300 mg -9.8 < 0.001
Omalizumab 150 mg -8.1 = 0.001
Omalizumab 75 mg -5.9 = 0.46
Placebo -5.1 Not reported

ClinicalTrials.gov number NCT01264939

Omalizumab in chronic urticaria with IgE against thyroperoxidase

Disadvantages of omalizumab

So far, there is no evidence that omalizumab is disease modifying. When patients stopped the study drug, their symptoms recurred. At the end of 16 weeks off treatment, symptoms of urticaria were similar to patients treated with placebo.

What is the risk associated with omalizumab use?

Omalizumab in inducible-urticaria

Inducible or physical urticaria, such as solar urticaria or cold urticaria, does not always respond well to antihistamines. To date, no randomised placebo-controlled trial of omalizumab has been performed in inducible urticarias.

Future directions

IgE autoantibodies are also detected in a large number of patients with atopic dermatitis and bullous pemphigoid. In case reports, omalizumab treatment has been reported to be effective in some patients with these conditions. It has also been reported effective in chronic recurrent angioedema. Randomised controlled trials are warranted.

New Zealand approved datasheets are the official source of information for these prescription medicines, including approved uses and risk information. Check the individual New Zealand datasheet on the Medsafe website.

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