Safety and Tolerability of Atezolizumab (ATZ) in Combination With Radium-223 Dichloride (R-223-D) in Metastatic Castrate-Resistant Prostate Cancer (CRPC) Progressed Following Treatment With an Androgen Pathway Inhibitor

Inclusion Criteria:

- Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1

- Life expectancy greater than or equal to (>/=) 12 weeks

- Histologically confirmed, castrate-resistant adenocarcinoma of the prostate

- Measurable disease according to RECIST v1.1

- Multiple bone metastases within 12 weeks prior to study drug

- Participants receiving bisphosphonate or denosumab therapy must have been on a stable
dose for at least 4 weeks

- Visceral metastasis and/or lymphadenopathy

- Tumors that are amenable to serial biopsy

- Disease progression according to Prostate Cancer Working Group 2 (PCWG2) criteria
during or following treatment with at least one second generation androgen pathway
inhibitor (for example, enzalutamide, abiraterone) for metastatic prostate cancer

- Adequate hematologic and end-organ function

- One prior taxane-containing regimen for mCRPC, or refusal or ineligibility of a
taxane-containing regimen

Exclusion Criteria:

- History of small-cell or neuroendocrine prostate carcinoma

- Treatment with approved anti-cancer therapy (with the exception of abiraterone) within
3 weeks of study drug. Abiraterone must not be administered within 2 weeks prior to
initiation of study treatment

- Participation in another clinical trial/investigation within 28 days prior to study
drug

- Brain metastases or active leptomeningeal disease (with the exception of participants
with treated epidural disease and no other epidural progression)

- Uncontrolled tumor-related pain

- Uncontrolled hypercalcemia

- Significant cardiovascular disease

- History of autoimmune disease except controlled/treated hypothyroidism, type 1
diabetes mellitus, or certain skin disorders

- Prior allogeneic stem cell or solid organ transplant

- History of pulmonary fibrosis/inflammation, including active tuberculosis

- Human immunodeficiency virus (HIV) or hepatitis B or C

- Prior treatment with cluster of differentiation (CD) 137 agonist, anti-programmed
death (PD) 1, or anti-programmed death ligand (PD-L) 1 therapeutic antibody or
pathway-targeting agents

- Immunostimulants within 4 weeks or immunosuppressants within 14 days prior to study
drug

- Prior radium-223 dichloride or hemibody external radiotherapy

- Systemic strontium-89, samarium-153, rhenium-186, or rhenium-188 for bone metastases
within 24 weeks prior to initiation of study treatment

- Spinal compression or structurally unstable bone lesions suggesting impending
pathologic fractures based on clinical findings and/or magnetic resonance imaging
(MRI)

- Bone marrow dysplasia

- Unmanageable fecal incontinence