Omalizumab

Omalizumab is a humanized monoclonal antibody that binds to immunoglobulin E (IgE). By binding circulating IgE, omalizumab blocks IgE interaction with the high-affinity IgE receptor (FcεRI) on mast cells and basophils, leading to downregulation of FcεRI expression and a reduction in mediator release during allergic reactions.

It is approved for the treatment of moderate-to-severe persistent allergic asthma in patients aged 6 years and older with sensitivity to perennial allergens and who are inadequately controlled with inhaled corticosteroids, and for chronic idiopathic urticaria in adults and adolescents aged 12 years and older who remain symptomatic despite H1 antihistamines. Dosing and administration are individualized based on body weight and baseline serum IgE levels, using a subcutaneous injection given every two to four weeks. The medication is supplied in prefilled syringes or pens and is intended for outpatient use under medical supervision.

Pharmacokinetically, omalizumab has a long half-life, with onset of clinical effect occurring over weeks to months as IgE levels decline and FcεRI receptor expression decreases. The safety profile includes common adverse effects such as injection site reactions, headaches, and upper respiratory tract infections. A minority of patients may experience hypersensitivity or anaphylaxis, which necessitates appropriate monitoring after injections and patient education about signs of a severe reaction.

Regulatory status varies by country, but omalizumab is marketed under the brand name Xolair and was first approved by the U.S. FDA in 2003 for asthma, with later approvals expanding to CSU in 2014. Its use requires prescription and ongoing clinical evaluation to assess efficacy and safety.