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