Study of Atezolizumab as Monotherapy and in Combination With Platinum-Based Chemotherapy in Participants With Untreated Locally Advanced or Metastatic Urothelial Carcinoma

Inclusion Criteria

• Considered to be eligible to receive platinum-based chemotherapy, in the investigator's judgment
• Eastern Cooperative Oncology Group (ECOG) performance status of less than or equal to ( ) 12 months between the last treatment administration and the date of recurrence is required in order to be considered treatment naive in the metastatic setting
• Prior local intravesical chemotherapy or immunotherapy is allowed if completed at least 4 weeks prior to the initiation of study treatment
• Measurable disease, as defined by RECIST v1.1
• Adequate hematologic and end-organ function
• For women of childbearing potential: agreement to remain abstinent (refrain from heterosexual intercourse) or use contraceptive methods that result in a failure rate of /=4 weeks since completion of radiotherapy or surgical resection and >/=2 weeks since discontinuation of corticosteroids
• Prior treatment with CD137 agonists, anti-CTLA-4, anti-programmed death-1 (PD-1), or anti-PD-L1 therapeutic antibody or pathway-targeting agents
• Treatment with systemic corticosteroids or other systemic immunosuppressive medications (including but not limited to prednisone, dexamethasone, cyclophosphamide, azathioprine, methotrexate, thalidomide, and anti-tumor necrosis factor [TNF] agents) within 2 weeks prior to Cycle 1, Day 1 or anticipated requirement for systemic immunosuppressive medications during the study
• Leptomeningeal disease
• Uncontrolled pleural effusion, pericardial effusion, or ascites requiring recurrent drainage procedures (once monthly or more frequently)
• Uncontrolled tumour-related pain or hypercalcemia
• Significant cardiovascular disease including known left ventricular ejection fraction (LVEF) <40%
• Severe infections within 4 weeks before randomization or therapeutic oral or IV antibiotics within 2 weeks before randomization
• Major surgical procedure within 4 weeks prior to randomization or anticipation of need for a major surgical procedure during the course of the study other than for diagnosis
• Malignancies other than urothelial carcinoma within 5 years prior to Cycle 1, Day 1
• Life expectancy of <12 weeks
• Pregnant or lactating, or intending to become pregnant during the study
• Serum albumin <25 gram per liter (g/L)
• History of severe allergic, anaphylactic, or other hypersensitivity reactions to chimeric or humanized antibodies or fusion proteins
• Known hypersensitivity or allergy to biopharmaceuticals produced in Chinese hamster ovary cells or any component of the atezolizumab formulation
• History of autoimmune disease
• Participants with prior allogeneic stem cell or solid organ transplantation
• History of idiopathic pulmonary fibrosis (including pneumonitis), drug-induced pneumonitis, organizing pneumonia (i.e., bronchiolitis obliterans, cryptogenic organizing pneumonia), or evidence of active pneumonitis on screening chest CT scan
• Positive test for human immunodeficiency virus (HIV)
• Active hepatitis B or hepatitis C
• Active tuberculosis
• Administration of a live, attenuated vaccine within 4 weeks before Cycle 1, Day 1