A Study of Lebrikizumab (RO5490255) in Participants With Severe Oral Corticosteroids (OCS) Dependent Asthma

Inclusion Criteria: * Severe asthma despite intensive follow-up by an asthma specialist for \>/=6 months prior to Visit 1 * Baseline forced expiratory volume in 1 second (FEV1) \>/=40% of predicted prior to randomization * Receiving high doses of inhaled glucocorticosteroids at a total daily dose of \>/=1500 micrograms (mcg) beclomethasone dipropionate or equivalent and long-acting beta-adrenoceptor agonist (LABA), with or without an additional controller, for at least 3 months prior to Visit 1 * Chronic treatment with maintenance OCS for \>/=6 months prior to Visit 1 * Assessment to ensure diagnosis of refractory asthma and OCS dependence on minimal effective or maximum tolerated dose prior to Visit 1 with compliance Exclusion Criteria: * History of a severe allergic reaction or anaphylactic reaction to a biologic agent or known hypersensitivity to any component of the lebrikizumab injection * Asthma exacerbation within 28 days prior to Visit 1 or during screening (prior to Visit 3) * For adults: Active tuberculosis requiring treatment within the 12 months prior to Visit 1 * For adolescents: History of active tuberculosis requiring treatment * Evidence of acute or chronic hepatitis or known liver cirrhosis * Known current malignancy or current evaluation for a potential malignancy * History of interstitial lung disease, chronic obstructive pulmonary disease, or other clinically significant lung disease other than asthma * Infection requiring hospital admission or requiring treatment with intravenous (IV) or intramuscular (IM) antibiotics within 4 weeks prior to Visit 1 or during screening * Upper or lower respiratory tract infection within 4 weeks prior to Visit 1 or during screening * Active parasitic infection or Listeria monocytogenes infection within 6 months prior to Visit 1 or during screening * Current smoker or former smoker with a smoking history of more than 15 pack-years * Current use of an immunomodulatory/ immunosuppressive therapy or past use within 3 months or 5 drug half-lives (whichever is longer) prior to Visit 1 * Use of a licensed or investigational monoclonal antibody other than anti-interleukin (IL)-13 or anti-IL-4/IL-13, including but not limited to, omalizumab, anti-IL-5, or anti-IL-17, within 6 months or 5 drug half-lives (whichever is longer) prior to Visit 1 * Receipt of a live attenuated vaccine within the 4 weeks prior to Visit 1 during screening or anticipation of receipt of a live attenuated vaccine throughout the study