Inclusion Criteria:

• Have a documented history of asthma as well as evidence of ≥ 12% reversibility of FEV1. Evidence of ≥ 12% reversibility of FEV1 may be obtained by any one of the following measures: 1) Documentation of ≥ 12% reversibility of FEV1 after albuterol administration at any time during the preceding 24 months; 2) Documentation of ≥ 12% improvement in FEV1 with two separate measurements obtained within a 4-week period surrounding an asthma exacerbation during the preceding 24 months; 3) Demonstration of ≥ 12%reversibility of FEV1 after albuterol administration at the time of screening
• Have screening FEV1 ≥ 80% predicted normal value
• Have a positive skin test (diameter of wheal ≥ 3 mm vs. control) or in vitro RAST(R) or ImmunoCap(R) to one relevant perennial aeroallergen such as cat or house dust mites documented within the previous year
• Be receiving at least an inhaled corticosteroid dosage of fluticasone dry powder inhaler (DPI) ≥ 200 ug/day or equivalent ex-valve dose during the 12 weeks prior to the screening visit
• Have had at least one asthma exacerbation requiring treatment with at least one course of oral or intravenous corticosteroids or a doubling of the dose of inhaled corticosteroids for at least 3 days in the 12 months prior to screening despite being on a minimum of fluticasone DPI ≥ 200 ug/day or equivalent ex-valve dose
• During the 4-week run-in period prior to randomization, demonstrate evidence of inadequate asthma symptom control despite inhaled corticosteroids with or without other controller asthma medications (e.g., LABA, LTRA, immunotherapy). Inadequate asthma symptom control is defined as at least one of the following reported on the subject diary card during the 4-week run-in period: Daytime asthma symptoms as a score of ≥ 1 (scale of 0-4) on at least 20 of 28 days (missing data to be treated as a day with no symptoms) and a mean symptom score of ≥ 1.5 (mean will be calculated based on only data supplied; missing values will not be considered) or Nighttime awakening because of asthma symptoms (more than 4 times during the 4-week run-in period)
• Meet the study drug-dosing table eligibility criteria (serum baseline IgE level ≥ 30 to ≤ 1300 IU/mL and body weight ≥ 20 to ≤ 150 kg)
• If a female of childbearing potential, use an effective method of contraception (in the opinion of the investigator) to prevent pregnancy and agree to continue to practice an acceptable method of contraception for the duration of their participation in the study

Exclusion Criteria:

• Have received chronic systemic corticosteroids (oral or intravenous) within 3 months or have received a burst of oral corticosteroids within the last 2 weeks prior to screening
• Have received Xolair therapy at any time within 12 months prior to screening
• Are pregnant or lactating
• Have a known hypersensitivity to any ingredients of Xolair, including excipients (sucrose, histidine, polysorbate 20)
• Have a lifetime history of smoking > 10-pack years
• Have active lung disease other than asthma (e.g., chronic bronchitis, emphysema, cystic fibrosis, chronic obstructive pulmonary disease)
• Have a history of upper respiratory infection or lower respiratory infection within the 30 days prior to randomization
• Have a diagnosis of aspirin or nonsteroidal anti-inflammatory drug-induced asthma
• Have taken immunosuppressants or other investigational drugs within the 30 days prior to screening
• Have a significant medical illness other than asthma