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

INTERVENTION: Tiragolumab: Tiragolumab will be administered by intravenous (IV) infusion at a fixed dose of 600 mg on Day 1 of each 21‐day cycle. Atezolizumab: Atezolizumab will be administered by IV infusion at a fixed dose of 1200 mg on Day 1 of each 21‐day cycle. Bevacizumab: Bevacizumab will be administered by IV infusion at a dose of 15 mg/kg on Day 1 of each 21‐day cycle. CONDITION: Carcinoma, Hepatocellular PRIMARY OUTCOME: efficacy; Observation and examination, RECIST v1.1 SECONDARY OUTCOME: safety, efficacy, phamacokinetics,other; Observation and examination, RECIST v1.1 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 ‐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 ‐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 to av