A Study of Biomarker-Driven Therapy in Metastatic Colorectal Cancer (mCRC)

Inclusion Criteria

• ECOG PS of less than or equal to ( ] 325 milligrams per day [mg/day]), clopidogrel (> 75 mg/day), or current or recent (within 10 days prior to the start of study induction treatment) use of therapeutic oral or parenteral anticoagulants or thrombolytic agents for therapeutic purposes (prophylactic uses allowed)
• Active infection requiring intravenous antibiotics at the start of study induction treatment
• Previous or concurrent malignancy, except for adequately treated basal or squamous cell skin cancer, in situ cervical cancer, or other cancer for which the participant has been disease-free for 5 years prior to study entry
• Inadequately controlled hypertension; prior history of hypertensive crisis or hypertensive encephalopathy
• Clinically significant (active) cardiovascular disease, for example cerebrovascular accidents = 450 millisecond assessed within 3 weeks prior to randomization, long QT syndrome or, uncorrectable electrolyte abnormalities (including magnesium) or requirement for medicinal products known to prolong the QT interval
• ECOG PS > 2

Exclusion Criteria for Participants in Cohort 2 (MP):

• History of autoimmune disease including but not limited to myasthenia gravis, myositis, autoimmune hepatitis, systemic lupus erythematosus, rheumatoid arthritis, inflammatory bowel disease, vascular thrombosis associated with antiphospholipid syndrome, Wegener's granulomatosis, Sjögren's syndrome, Guillain-Barré syndrome, multiple sclerosis, vasculitis, or glomerulonephritis
• Prior allogeneic bone marrow transplantation or prior solid organ transplantation
• History of idiopathic pulmonary fibrosis (including pneumonitis), drug-induced pneumonitis, organizing pneumonia, or evidence of active pneumonitis at most recent chest imaging (computed tomography [CT] scan or magnetic resonance imaging [MRI])
• Positive test for human immunodeficiency virus (HIV)
• Active hepatitis B virus (HBV) or hepatitis C virus (HCV) at Screening
• Active tuberculosis
• Severe infection within 4 weeks prior to start of maintenance treatment including, but not limited to, hospitalization for complications of infection, bacteremia, or severe pneumonia; has signs or symptoms of significant infection or has received oral or IV antibiotics within 2 weeks prior to start of maintenance treatment
• Administration of a live, attenuated vaccine within 4 weeks prior to start of maintenance treatment or anticipation that such a live attenuated vaccine will be required during the remainder of the study
• Prior treatment with cluster of differentiation (CD) 137 agonists, anti-cytotoxic T-lymphocyte-associated antigen (CTLA) 4, anti-programmed death-1 (PD-1), or anti-programmed death-ligand 1 (PD-L1) therapeutic antibody or pathway-targeting agents
• Treatment with systemic immunostimulatory agents (including but not limited to interferons or interleukin-2) within 4 weeks or five half-lives of the drug, whichever is longer, prior to start of maintenance treatment
• Treatment with systemic corticosteroids or other systemic immunosuppressive medications within 2 weeks prior to start of maintenance treatment, or anticipated requirement for systemic immunosuppressive medications during the remainder of the study
• If receiving receptor activator of nuclear factor kappa-B ligand (RANKL) inhibitor (for example, denosumab) and unwilling to adopt alternative treatment such as bisphosphonates while receiving atezolizumab

Exclusion Criteria for Participants in Cohort 3 (MP):

• Inability to swallow pills
• Left ventricular ejection fraction (LVEF) less than (<) 50 percent (%) as assessed after completion of induction treatment by either 2-dimensional echocardiogram or multiple-gated acquisition
• Clinically significant cardiovascular disease, including unstable angina, history of or active congestive heart failure of ≥ NYHA Grade 2, history of or ongoing serious cardiac arrhythmia requiring treatment (except for controlled atrial fibrillation