A Study Evaluating Atezolizumab and Bevacizumab, With or Without Tiragolumab, in Participants With Untreated Locally Advanced or Metastatic Hepatocellular Carcinoma (HCC) (IMbrave152)

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 participants * Disease that is not amenable to curative surgical and/or locoregional therapies * No prior systemic treatment for locally advanced or metastatic and/or unresectable HCC-measurable disease according to RECIST v1.1 * Eastern cooperative oncology group (ECOG) performance status of 0 or 1 within 7 days prior to randomization * Child-pugh Class A within 7 days prior to randomization * Adequate hematologic and end-organ function * Female participants of childbearing potential must be willing to avoid pregnancy within 5 months after the final dose of atezolizumab, within 6 months after the final dose of bevacizumab, and within 90 days after the final dose of tiragolumab/placebo * Male participants with a female partner of childbearing potential or pregnant female partner must remain abstinent or use a condom during the treatment period and for 6 months after the final dose of bevacizumab and for 90 days after the final dose of tiragolumab/placebo to avoid exposing the embryo. Exclusion Criteria: * Pregnancy or breastfeeding within 5 months after the final dose of atezolizumab, within 6 months after the final dose of bevacizumab, and within 90 days after the final dose of tiragolumab/placebo * Prior treatment with cluster of differentiation 137 (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 * 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 * 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 * History of malignancy other than HCC within 5 years prior to screening, with the exception of malignancies with a negligible risk of metastasis or death * Mixed histology or other subtypes/variants of HCC, including, but not limited to, known liver adenocarcinoma, fibrolamellar HCC, sarcomatoid HCC, other rare HCC variant, or mixed cholangiocarcinoma and HCC * Co-infection with hepatitis B virus (HBV) and hepatitis C virus (HCV) * Acute epstein-barr virus (EBV) infection or known or suspected chronic active EBV infection * Symptomatic, untreated, or actively progressing central nervous system (CNS) metastases.