A Phase II, open-label, multi-cohort, multicenter study in patients with unresectable HEPATOCELLULAR CARCINOMA and CHILDPUGH B7 and B8 Cirrhosis

General Inclusion Criteria: - Locally advanced or metastatic and/or unresectable HCC with diagnosis confirmed by histology/cytology or clinically by American Association for the Study of Liver Diseases (AASLD) criteria in cirrhotic patients - Disease that is not amenable to curative surgical and/or locoregional therapies - No prior systemic treatment (including systemic investigational agents) for locally advanced or metastatic and/or unresectable HCC - Measurable disease (at least one untreated target lesion) according to RECIST v1.1 - ECOG Performance Status of 0-2 within 7 days prior to initiation of study treatment - Child-Pugh B7 or B8 cirrhosis at screening and within 7 days prior to study treatment - Adequate hematologic and end-organ function - Life expectancy of at least 12 weeks - Female participants of childbearing potential must be willing to avoid pregnancy and egg donation General Exclusion Criteria: - Pregnancy or breastfeeding - Prior treatment with CD137 agonists or immune checkpoint blockade therapies - Treatment with investigational therapy within 28 days prior to initiation of study treatment - Treatment with locoregional therapy to liver within 28 days prior to initiation of study treatment, or non-recovery from side effects of any such procedure - Treatment with systemic immunostimulatory agents - Treatment with systemic immunosuppressive medication - Treatment with a live, attenuated vaccine within 4 weeks prior to initiation of study treatment - Inadequately controlled hypertension - Active or history of autoimmune disease or immune deficiency - History of idiopathic pulmonary fibrosis, organizing pneumonia, drug-induced pneumonitis, or idiopathic pneumonitis, or evidence of active pneumonitis on screening chest computed tomography (CT) scan - Patients who have a known concurrent malignancy that is progressing or requires active treatment, who have not completely recovered from treatment, or who have a significant malignancy history that, in the opinion of the investigator, should preclude participation. - Known fibrolamellar HCC, sarcomatoid HCC, other rare HCC variant, or mixed cholangiocarcinoma and HCC - Symptomatic, untreated, or actively progressing central nervous system (CNS) metastases - Prior allogeneic stem cell or solid organ transplantation - Listed for liver transplantation - Co-infection with hepatitis B virus (HBV) and hepatitis C virus (HCV) - Untreated or incompletely treated esophageal and/or gastric varices with bleeding or that are at high risk for bleeding - A prior bleeding event due to esophageal and/or gastric varices within 6 months prior to initiation of study treatment - Grade ≥3 hemorrhage or bleeding event within 6 months prior to initiation of study treatment - History of hepatic encephalopathy requiring hospitalization or treatment escalation within 6 months prior to study treatment, or any continued symptoms of encephalopathy despite medical management - History, planned, or recommended placement of transjugular intrahepatic portosystemic shunt (TIPS) - History of ascites requiring therapeutic paracentesis over the last 3 months - History of spontaneous bacterial peritonitis within last 12 months