Safety and Pharmacology Study of Atezolizumab Alone and in Combination With Bacille Calmette-Guérin (BCG) in High-Risk Non-Muscle-Invasive Bladder Cancer (NMIBC) Participants

Inclusion Criteria:

   - Histologically confirmed non-muscle-invasive transitional cell carcinoma (TCC) of the
   bladder with carcinoma in-situ (CIS)

   - High-risk NMIBC defined by the following:

BCG-unresponsive NMIBC:

Persistence of high-grade CIS at 6 months following an adequate course of BCG; or
Stage/grade progression at 3 months after induction BCG; or Recurrence of high-grade CIS
after achieving a disease-free state (i.e., CR) following induction of an adequate course
of BCG that occurs less than (<) 6 months after the last exposure to BCG

BCG-relapsing NMIBC:

Recurrence of high-grade CIS after achieving a disease-free state following induction of an
adequate course of BCG that occurs greater than or equal to (>/=) 6 months after the last
exposure to BCG

Very high-risk (VHR) BCG-naïve NMIBC:

VHR NMIBC, defined as having at least 1 of the following: Multiple and/or large (greater
than [>] 3 centimeters [cm]) T1, (HG/G3) tumors; T1, (HG/G3) tumor with concurrent CIS; T1,
G3 with CIS in prostatic urethra; Micropapillary variant of non-muscle invasive urothelial
carcinoma

   - For BCG-unresponsive and BCG-relapsing NMIBC, participants must have received an
   adequate course of BCG

   - Resection of all pTa/pT1 papillary disease

   - No prior radiation to bladder or pelvic region

   - Eastern Cooperative Oncology Group (ECOG) performance status of less than or equal to
   (
   - Life expectancy >/=12 weeks

   - Adequate hematologic and end-organ function

   - Creatinine clearance >/=30 milliliters per minute (mL/min) (calculated using the
   Cockcroft-Gault formula)

   - For women of childbearing potential: agreement to remain abstinent (refrain from
   heterosexual intercourse) or use contraceptive methods that result in a failure rate
   of <1% per year during the treatment period and for at least 5 months after the last
   dose of study drug. Women must refrain from donating eggs during this same period.

   - For men receiving BCG: Agreement to remain abstinent (refrain from sexual intercourse)
   or use a condom

   - Tumor tissue biopsy within 60 days prior to study entry or availability of an archival
   specimen obtained within 60 days of study screening

Exclusion Criteria:

   - Evidence of locally advanced, metastatic, muscle-invasive, and/or extravesical bladder
   cancer

   - Any malignancy within 5 years prior to Cycle 1, Day 1

   - History of autoimmune disease, idiopathic pulmonary fibrosis, organizing pneumonia
   (e.g., bronchiolitis obliterans), drug-induced pneumonitis, idiopathic pneumonitis, or
   active pneumonitis

   - Signs or symptoms of infection within 2 weeks prior to the first dose of study
   treatment

   - Treatment with therapeutic oral or IV antibiotics within 2 weeks prior to the first
   dose of study treatment

   - Treatment with any approved anti-cancer therapy within 3 weeks prior to the first dose
   of study treatment

   - Treatment with any other investigational agent or participation in another clinical
   trial with therapeutic intent within 4 weeks prior to the first dose of study
   treatment

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

   - Prior allogeneic stem cell or solid organ transplantation

   - Positive test for human immunodeficiency virus (HIV)

   - Active hepatitis B or C and/or tuberculosis

   - Severe infections within 28 days prior to the first dose of study treatment

   - Significant cardiovascular disease

   - Major surgical procedure other than for diagnosis within 4 weeks prior to the first
   dose of study treatment, or anticipation of need for a major surgical procedure during
   the course of the study

   - Administration of a live/attenuated vaccine within 4 weeks prior to the first dose of
   study treatment, within 5 months following the administration of the last dose of
   study drug, or anticipation that such a live/attenuated vaccine will be required
   during the study

   - History of prior significant toxicity or intolerance to BCG requiring discontinuation
   of treatment

   - History of prior systemic BCG infection

   - History of immunosuppression, or conditions associated with congenital or acquired
   immune deficiency

   - Concurrent febrile illness, urinary tract infection, or gross hematuria

   - Prior treatment with cluster of differentiation 137 (CD137) agonists or immune
   checkpoint blockade therapies

   - Treatment with systemic immunostimulatory agents within 6 weeks or five half-lives of
   the drug, whichever is shorter, prior to the first dose of study treatment

   - Treatment with systemic immunosuppressive medications within 2 weeks prior to the
   first dose of study treatment, or anticipated requirement for systemic
   immunosuppressive medications during the trial