OBJECTIVE:Omalizumab (Xolair), is a recombinant humanised monoclonal anti-immunoglobulin E (IgE) antibody, for the treatment of allergic asthma. This review describes how the correlation between clinical outcomes and a suitable surrogate marker (free serum IgE) led to the development of an individualised dosing strategy for omalizumab. It also demonstrates how subsequent studies using this dosing strategy were able to achieve low levels of IgE and clinical benefit. DATA SOURCES:Published articles and data on file (Novartis Pharma AG, Genentech). RESULTS:Studies in patients with IgE-mediated diseases of the airways have shown that clinical benefit with omalizumab is observed when free IgE levels in serum are reduced to 50 ng/ml (20.8 IU/ml) or less (target 25 ng/ml (10.4 IU/ml)). The ability of omalizumab to reduce free IgE levels to such levels is dependent on dose, the patient's weight and baseline IgE level. To simplify dosing, and ensure that free IgE reduction is achieved, an individualised tiered dosing table was developed from which patients with asthma, depending on weight and starting IgE level, receive omalizumab 150-375 mg by subcutaneous injection every 2 or 4 weeks. This dosing strategy has proved clinically efficacious for improving disease control in patients with allergic asthma, as shown by significantly lower exacerbation rates and decreased dependence on treatment with inhaled corticosteroids, along with improvements in symptoms, lung function and usage of rescue bronchodilators. CONCLUSIONS:The clinical efficacy of omalizumab has been optimised through the development of an individualised dosing table that emerged from an understanding of the pharmacodynamics of this agent.