A Study of Atezolizumab in Participants With Locally Advanced or Metastatic Urothelial Bladder Cancer (Cohort 1)

Inclusion Criteria

• Histologically or cytologically documented locally advanced or metastatic transitional cell carcinoma of the urothelium (including renal pelvis, ureters, urinary bladder, urethra)
• Representative tumor specimens as specified by the protocol
• Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1
• Life expectancy greater than or equal to (>=) 12 weeks
• Measurable disease, as defined by RECIST v1.1
• Adequate hematologic and end organ function

Cohort 1-Specific Inclusion Criteria

• No prior chemotherapy for inoperable locally advanced or metastatic or recurrent urothelial carcinoma
• Ineligible for cisplatin-based chemotherapy due to one of the following: Impaired renal function, a hearing loss of 25 decibels (dB) at two contiguous frequencies, Grade 2 or greater peripheral neuropathy, or ECOG performance score of 2

Exclusion Criteria

• Any approved anti-cancer therapy within 3 weeks prior to initiation of study treatment
• Treatment with any other investigational agent or participation in another clinical trial with therapeutic intent within 28 days prior to enrollment
• Active or untreated central nervous system (CNS) metastases as determined by computed tomography (CT) or magnetic resonance imaging (MRI) evaluation during screening and prior radiographic assessments
• Leptomeningeal disease
• Uncontrolled tumor-related pain
• Uncontrolled pleural effusion, pericardial effusion, or ascites requiring recurrent drainage procedures (once monthly or more frequently)
• Uncontrolled hypercalcemia (greater than [>] 1.5 millimoles per liter [mmol/L] ionized calcium or Ca > 12 milligrams per deciliter [mg/dL] or corrected serum calcium > upper limits of normal [ULN]) or symptomatic hypercalcemia requiring continued use of bisphosphonate therapy or denosumab
• Malignancies other than urothelial bladder cancer within 5 years prior to Cycle 1, Day 1, with the exception of those with a negligible risk of metastasis or death treated with expected curative outcome or incidental prostate cancer
• Pregnant and lactating women
• History of autoimmune disease
• History of idiopathic pulmonary fibrosis, organizing pneumonia, drug-induced pneumonitis, idiopathic pneumonitis, or evidence of active pneumonitis on screening chest CT scan
• Serum albumin less than (<) 2.5 grams per deciliter (g/dL)
• Positive test for human immunodeficiency virus (HIV) and/or active hepatitis B or hepatitis C or tuberculosis
• Severe infections within 4 weeks prior to Cycle 1, Day 1
• Significant cardiovascular disease
• Major surgical procedure other than for diagnosis within 28 days prior to Cycle 1, Day 1
• Prior allogeneic stem cell or solid organ transplant
• Administration of a live, attenuated vaccine within 4 weeks before Cycle 1, Day 1
• Any other diseases, metabolic dysfunction, physical examination finding, or clinical laboratory finding giving reasonable suspicion of a disease or condition that contraindicates the use of an investigational drug or that may affect the interpretation of the results or render the patient at high risk from treatment complications
• Prior treatment with CD137 agonists or immune checkpoint blockade therapies, including anti-cytotoxic T lymphocyte-associated antigen 4 (anti-CTLA-4), anti-programmed death-1 receptor (anti-PD-1), and anti-programmed death-ligand 1 (anti-PD-L1) therapeutic antibodies