A Study of Amivantamab Monotherapy in Participants With Previously Treated Advanced Hepatocellular Carcinoma

Inclusion Criteria: Participant must have histologically or cytologically confirmed diagnosis of hepatocellular carcinoma (HCC) (fibrolamellar and mixed hepatocellular / cholangiocarcinoma subtypes are not eligible) based on pathology report, who have barcelona clinic liver cancer (BCLC) Stage C disease or BCLC Stage B disease not amenable to locoregional therapy or refractory to locoregional therapy, and not amenable to a curative treatment approach Participant must have measurable disease according to response criteria in solid tumors (RECIST) Version 1.1. Selected target lesions must meet 1 of 2 criteria: 1) not previously treated with local therapy or 2) within the field of prior local therapy but with documented subsequent progression as per RECIST v1.1 Participant must have Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1 Participant must have adequate organ and bone marrow function A female participant must agree not to donate eggs (ova, oocytes) or freeze for future use for the purposes of assisted reproduction during the study and for a period of 6 months after receiving the last dose of study treatment. Female participants should consider preservation of eggs prior to study treatment as anti-cancer treatments may impair fertility Exclusion Criteria: Participants with prior liver transplant, history of hepatic encephalopathy, portal vein invasion at the main portal branch (Vp4), inferior vena cava, or cardiac involvement of HCC based on imaging, or any current moderate or severe ascites as measured by physical examination that requires active paracentesis for control due to the underlying HCC Participant has known allergies, hypersensitivity, or intolerance to excipients of amivantamab Participant has received a live or live attenuated vaccine within 3 months before Cycle 1 Day 1. The seasonal influenza vaccine and non-live vaccines against Coronavirus disease 19 (COVID-19) are not exclusionary Other clinically active liver disease of infectious origin Participant has a history of clinically significant cardiovascular disease including, but not limited to: a. diagnosis of deep vein thrombosis or pulmonary embolism within 4 weeks prior to the first dose of study treatment or any of the following within 6 months prior to the first dose of study treatment: myocardial infarction, unstable angina, stroke, transient ischemic attack, coronary/peripheral artery bypass graft, or any acute coronary syndrome. Clinically non-significant thrombosis, such as nonobstructive catheter-associated clots, are not exclusionary; b. prolonged corrected QT interval using Fridericia's formula (QTcF) greater than (>)480 millisecond (msec) or clinically significant cardiac arrhythmia or electrophysiologic disease (example, placement of implantable cardioverter defibrillator or atrial fibrillation with uncontrolled rate); c. uncontrolled (persistent) hypertension: systolic blood pressure >160 mm Hg; diastolic blood pressure >100 millimeter of mercury (mm Hg), or congestive heart failure (CHF) defined as New York Heart Association (NYHA) class III/IV or hospitalization for CHF (any NYHA class) within 6 months of study enrollment; d. pericarditis/clinically significant pericardial effusion; e. myocarditis