1. Histologically confirmed diagnosis of HCC
2. Barcelona Clinic Liver Cancer (BCLC) Stage B or C disease not amenable to or progressing after loco-regional therapy and not amenable to a curative treatment approach
3. No prior systemic therapy for HCC (with the exception of HCC participants enrolled in the safety run-in substudy [Japan only])
4. Measurable disease
5. Child-Pugh score A
6. Easter Cooperative Oncology Group (ECOG) Performance Status ≤ 1
7. Adequate organ function

Key Ex

1. Known fibrolamellar HCC, sarcomatoid HCC, or mixed cholangiocarcinoma and HCC histology
2. Tumor thrombus involving main trunk of portal vein or inferior vena cava
3. Loco-regional therapy to the liver within 28 days before randomization
4. Clinical evidence of portal hypertension with bleeding esophageal or gastric varices at Screening, or within 6 months before randomization
5. Bleeding or thrombotic disorder or any prescribed anticoagulant requiring therapeutic international normalized ratio monitoring (eg, warfarin or similar agents) at Screening, or within 6 months before randomization/enrollment
6. Presence at Screening of active immune deficiency or autoimmune disease and/or prior history of any immune deficiency or autoimmune disease that may relapse
7. Participant with any condition requiring systemic treatment with either corticosteroids (> 10 mg daily of prednisone or equivalent) or other immunosuppressive medication within 14 days before randomization
8. History of interstitial lung disease or non-infectious pneumonitis, unless induced by radiation therapy
9. QT interval corrected for heart rate (QTc) (corrected by Fridericia's method) > 450 msec at Screening

NOTE: Other protocol defined Inclusion/Exclusion criteria may apply.