Inclusion Criteria:

• Signed Informed Consent Form
• 18 to 65 years of age and in general good health
• History of moderate asthma, defined by the need for routine inhaled corticosteroids for at least the last 90 days prior to screening as well as the routine use of additional medication(s) (e.g., short- or long-acting β2-agonists, leukotriene antagonist, or theophylline) to control asthma symptoms
• History of cat dander-induced asthma in the 3 years prior to randomization
• Cat exposure at the time of screening must remain constant throughout the duration of the study (e.g., patients having cat exposure at home must continue to have regular exposure during the study; patients having no cat exposure at home must continue having no exposure at home during the study)
• Positive skin test to cat allergen, defined as a ≥ 5-mm wheal over the saline control wheal
• Baseline FEV1 ≥ 70% predicted after withholding long-acting β2-agonists for > 36 hours and short-acting β2-agonists for > 6 hours
• Eligibility per the study drug dosing table (serum IgE level ≥ 30 to ≤ 700 IU/mL and body weight ≥ 30 to ≤ 150 kg) and ability to be dosed per the dosing table
• Less than 10 pack-years of smoking history
• Demonstrated ≥ 20% fall in FEV1 during up to 1 hour of exposure in the cat environmental exposure chamber and ability to withstand exposure for at least 20 minutes

Exclusion Criteria:

• Unstable asthma (defined as a hospitalization within the prior 6 months or an exacerbation requiring oral corticosteroids within 4 weeks of study entry)
• Life-threatening episode of asthma in the previous year
• History of severe allergic reactions to cat exposure
• Having undergone cat immunotherapy within 6 months prior to screening
• Upper respiratory infection within 2 weeks of study entry
• Active lung disease other than asthma
• Significant medical illness other than asthma, including malignancies, parasitic infections, immune system disorders, and thrombocytopenia
• History of hypersensitivity to the study drug or to drugs with similar chemical structures or to any ingredients, including excipients of the study medication or drugs related to omalizumab (e.g., monoclonal antibodies, polyclonal gamma globulin)
• Documented medical history of anaphylaxis
• Receipt of other investigational drugs within 30 days or 5 half-lives prior to screening, whichever is longer
• Pregnant women and nursing mothers
• Treatment with omalizumab within 12 months prior to screening
• History of drug or alcohol abuse that, in the judgment of the investigator, may put the patient at risk for being unable to participate fully in the study