A Study of the Efficacy and Safety of Omalizumab Through 48 Weeks in Participants With Chronic Idiopathic Urticaria

Inclusion Criteria:

- Diagnosis of CIU refractory to H1 antihistamines at baseline

- Presence of itch and hives for at least 8 consecutive weeks at any time prior to
enrollment despite current use of H1 antihistamine treatment (up to four times the
approved dose) during this time period

- UAS7 score (range 0-42) ≥ 16 and itch component of UAS7 (range 0-21) ≥ 8 during 7 days
prior to baseline

- Participants must have been on a non-sedating H1 antihistamine treatment (up to four
times the approved dose) for CIU for at least 3 consecutive days immediately prior to
screening visit with continued current use on the day of the initial screening visit

- CIU diagnosis for ≥ 6 months

- Willing and able to complete a daily symptom eDiary for the duration of the study

Exclusion Criteria:

- Treatment with an investigational agent within 30 days of the initial screening visit

- Body weight less than 20 kilograms

- Clearly defined underlying etiology for chronic urticarias other than CIU

- Evidence of a parasitic infection

- Atopic dermatitis, bullous pemphigoid, dermatitis herpetiformis, senile pruritus or
other skin disease associated with itch

- Previous treatment with omalizumab within 1 year prior to the initial screening visit

- Participants may not have taken during treatment period or have been taking within 30
days before the initial screening visit any of the following medications or
treatments:

regular (daily/every other day during 5 or more consecutive days) systemic corticosteroids,
hydroxychloroquine, methotrexate, mycophenolate, cyclosporine, cyclophosphamide,
intravenous immunoglobulin G or plasmapheresis

- Regular (daily/every other day) oral doxepin use within 14 days prior to the initial
screening visit

- Pregnant or lactating women, or women intending to become pregnant during the study