A Study to Evaluate the Safety and Tolerability of Pumitamig Alone or In Combination With Ipilimumab in Participants With First-Line Advanced or Unresectable Hepatocellular Carcinoma (HCC) (ROSETTA HCC-206)

Inclusion Criteria * Participants must have a histologically confirmed diagnosis of locally advanced or unresectable Hepatocellular Carcinoma (HCC). * Participants must have an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1. * Participants must have no prior systemic therapy for advanced/ unresectable HCC. * Participants must have measurable disease as per Response Evaluation Criteria in Solid Tumors (RECIST) v1.1. Exclusion Criteria * Participants must not have significant bleeding or coagulation disorders or other obvious bleeding risk evidence. * Participants must not have an organ transplant or autoimmune disease. * Other protocol-defined Inclusion/Exclusion criteria apply.