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

Inclusion Criteria:

1. 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
2. Disease that is not amenable to curative surgical and/or locoregional therapies
3. No prior systemic treatment for locally advanced or metastatic and/or unresectable HCC
4. Measurable disease according to RECIST v1.1
5. ECOG Performance Status of 0 or 1 within 7 days prior to randomization
6. Child-Pugh Class A within 7 days prior to randomization
7. Adequate hematologic and end-organ function
8. 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
9. 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:

1. 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
2. Prior treatment with CD137 agonists or immune checkpoint blockade therapies
3. Treatment with investigational therapy within 28 days prior to initiation of study treatment
4. 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
5. Treatment with systemic immunostimulatory agents
6. Treatment with systemic immunosuppressive medication
7. Untreated or incompletely treated esophageal and/or gastric varices with bleeding or that are at high risk for bleeding
8. A prior bleeding event due to esophageal and/or gastric varices within 6 months prior to initiation of study treatment
9. Active or history of autoimmune disease or immune deficiency
10. 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
11. 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
12. 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
13. Co-infection with hepatitis B virus (HBV) and hepatitis C virus (HCV)
14. Acute Epstein-Barr virus (EBV) infection or known or suspected chronic active EBV infection
15. Symptomatic, untreated, or actively progressing central nervous system (CNS) metastases.