Spotlight on omalizumab in allergic asthma

Omalizumab (Xolair) is a humanized monoclonal antibody used in the treatment of adolescent and adult patients with moderate to severe allergic asthma inadequately controlled with inhaled corticosteroids (ICS). It selectively binds to circulating immunoglobulin E (IgE) and, thereby, prevents binding of IgE to mast cells and other effector cells. Without surface-bound IgE, these cells are unable to recognize allergens, thus preventing cellular activation by antigens and the subsequent allergic/asthmatic symptoms. Omalizumab decreases free serum IgE levels in a dose-dependent manner, reduces IgE receptor density on effector cells, and significantly improves airway inflammation parameters. Omalizumab is slowly absorbed after subcutaneous administration, and mean elimination half-life is 26 days, thus allowing infrequent administration of the drug. Omalizumab dosage is determined by bodyweight and pretreatment serum total IgE levels. Patients treated with subcutaneous omalizumab in clinical trials received a dosage that was approximately equal to 0.016 mg/kg/IgE (IU/mL) per 4 weeks. Thus, patients received 150 or 300 mg every 4 weeks, or 225, 300, or 375 mg every 2 weeks. In adults and adolescents (> or = 12 years of age) with moderate to severe allergic asthma, subcutaneous administration of omalizumab as add-on therapy with ICS improved the number of asthma exacerbations, rescue medication use, asthma symptom scores, and quality-of-life (QOL) scores compared with placebo during 28- and 32-week double-blind trials. In addition, concomitant ICS use was significantly decreased in patients receiving omalizumab, and in the two largest double-blind trials approximately 40% of omalizumab recipients completely withdrew from ICS therapy while maintaining effective asthma control. In general, results of extension studies showed that the beneficial effects of omalizumab were maintained over a total period of 52 weeks. Omalizumab was well tolerated as add-on therapy with ICS during treatment for up to 52 weeks. Common adverse events in clinical trials included injection site reaction, viral infection, upper respiratory tract infection, sinusitis, headache, and pharyngitis, although the incidence of adverse events with omalizumab was similar to that with placebo. In conclusion, omalizumab, as add-on therapy with ICS, is an effective and well tolerated agent for the treatment of moderate to severe allergic asthma in adolescents and adults. In addition to its symptomatic and QOL benefits, omalizumab therapy allows ICS dosage reduction or discontinuation of ICS in many patients. Comparisons of omalizumab with other asthma therapies have yet to be conducted; however, clinical efficacy and tolerability data indicate that omalizumab is a valuable option in the treatment of allergic asthma.