Omalizumab is an anti-immunoglobulin E (anti-IgE) monoclonal antibody approved in the United States since 2003 for treatment of moderate-to-severe allergic asthma in adults and adolescents (aged ≥12 years) inadequately controlled with inhaled corticosteroids (ICSs). Current treatment guidelines recommend considering the addition of omalizumab if allergic asthma symptoms are not adequately controlled with high-dose ICS + long-acting beta-agonist (LABA) therapy. This study was designed to review the clinical efficacy and safety of omalizumab as established in previously published pivotal clinical trials used to support registration in the United States, i.e., primarily including patients receiving only concomitant ICS therapy, as well as results from the recently completed additional study, which specifically enrolled patients who were poorly controlled despite high-dose ICS + LABA therapy ± additional controllers (including oral corticosteroids [OCSs]). Summary of published omalizumab pivotal trials and associated extension trials, plus key results from the additional study, were used. Pediatric data (i.e., <12 years) were outside the scope of this article. Treatment with omalizumab significantly reduced asthma exacerbations versus placebo when added to ICS therapy during both steroid-stable and steroid-reduction phases of two pivotal trials. In the additional study, omalizumab significantly reduced asthma exacerbation rates versus placebo when added to high-dose ICS + LABA therapy with or without other controller medications. Results from the additional clinical study further support current asthma guideline recommendations to consider omalizumab in steps 5 or 6 for persistent allergic asthma patients whose symptoms are not adequately controlled despite high-dose ICS + LABA therapy ± additional controllers (including OCS).