The main goals of this study are to evaluate the safety and efficacy of casdozokitug in combination with toripalimab plus bevacizumab and to define a recommended dose for casdozokitug in combination with toripalimab plus bevacizumab.

Key Inclusion Criteria:

• Unresectable locally advanced or metastatic HCC with diagnosis confirmed by histology/cytology or clinically by American Association for the Study of Liver Diseases criteria in cirrhotic participants.
• Disease that is not amenable to curative surgical and/or locoregional therapies or progressive disease (PD) after surgical and/or locoregional therapies.
• ≥ 1 measurable lesion (per RECIST v1.1) that is untreated.

Exclusion Criteria:

• Has received prior systemic therapy for HCC.
• Has previously received an anti-IL-27 antibody (Ab) or anti-IL-27-targeted therapy.
• Has known fibrolamellar HCC histology, sarcomatoid HCC, or mixed cholangiocarcinoma and HCC.
• Has moderate or severe ascites.
• Has uncontrolled pleural effusion, pericardial effusion, or ascites requiring recurrent drainage procedures (once monthly or more frequently).

Additional protocol-defined inclusion/exclusion criteria apply.