A Study to Evaluate the Efficacy, Response Duration and Safety of Xolair (Omalizumab) in Patients With Chronic Idiopathic Urticaria (CIU)/Chronic Spontaneous Urticaria (CSU) Who Remain Symptomatic Despite Antihistamine Treatment (H1)

Inclusion Criteria:

• Diagnosis of CIU/CSU refractory to H1 antihistamines at the time of randomization

Exclusion Criteria:

• Treatment with an investigational agent within 30 days prior to screening
• Weight less than 20 kg (44 lbs)
• Clearly defined underlying etiology for chronic urticarias other than CIU
• Evidence of parasitic infection
• Atopic dermatitis, bullous pemphigoid, dermatitis herpetiformis, senile pruritus or other skin disease associated with itch
• Previous treatment with omalizumab within a year prior to screening
• Routine doses of the following medications within 30 days prior to screening: systemic or cutaneous (topical) corticosteroids (prescription or over the counter), hydroxychloroquine, methotrexate, cyclosporine, or cyclophosphamide
• IV immunoglobulin G (IVIG), or plasmapheresis within 30 days prior to screening
• Regular (daily/every other day) doxepin (oral) use within 6 weeks prior to screening
• Any H2 antihistamine use within 7 days prior to screening
• Any LTRA (montelukast or zafirlukast) within 7 days prior to screening
• Any H1 antihistamines at greater than approved doses within 3 days prior to screening
• Patients with current malignancy, history of malignancy, or currently under work-up for suspected malignancy except non-melanoma skin cancer that has been treated or excised and is considered resolved
• Hypersensitivity to omalizumab or any component of the formulation
• History of anaphylactic shock
• Presence of clinically significant cardiovascular, neurological, psychiatric, metabolic or other pathological conditions that could interfere with the interpretation of the study results and or compromise the safety of the patients
• Evidence of current drug or alcohol abuse
• Nursing women or women of childbearing potential, unless they meet the following definition of post-menopausal: 12 months of natural amenorrhea or 6 months of spontaneous amenorrhea with serum FSH levels >40 mIU/mL or 6 weeks post surgical bilateral oophorectomy (with or without hysterectomy) or hysterectomy or are using one or more of the following acceptable methods of contraception: surgical sterilization, hormonal contraception, and double-barrier methods