A Study to Evaluate AMG 133 in Participants With Varying Degrees of Hepatic Impairment or Normal Hepatic Function

Inclusion Criteria: 1. Adults 18 to 75 years of age, male or female. 2. Body mass index ≥ 22 kg/m\^2 at screening. 3. For participants with normal hepatic function: * In good health with no clinically significant findings from medical history, physical exam, electrocardiogram (ECG), vital signs, or laboratory tests. * Systolic blood pressure (BP) 90-150 mmHg and diastolic BP 50-100 mmHg; pulse 40-110 bpm. * Stable body weight (\< 5 kg change) and no recent dietary modifications within 3 months. 4. For participants with hepatic impairment: * Documented Child-Pugh Class A (mild), B (moderate), or C (severe) hepatic impairment. * Clinically stable chronic liver disease (e.g., cirrhosis, hepatitis B, alcoholic liver disease, or stable hepatitis C). * Systolic BP ≤ 170 mmHg and diastolic BP ≤ 100 mmHg. 5. Willing to use reliable contraception (if of childbearing potential) or practice abstinence through 16 weeks after dosing. Exclusion Criteria: 1. Any unstable medical condition (e.g., recent hospitalization or major surgery). 2. History of acute or chronic pancreatitis within 1 year or lipase/amylase \> 2× ULN at screening. 3. Endocrine disorder that can cause obesity (e.g., Cushing's syndrome). 4. Significant cardiac conditions (e.g., clinically meaningful arrhythmias, 2nd/3rd-degree AV block, QT Interval Corrected Using Fridericia's Formula (QTcF) \>450 msec men / \>470 msec women for normal hepatic group; \> 490 msec men / \> 500 msec women for hepatic impairment). 5. Estimated glomerular filtration rate \< 60 mL/min/1.73 m\^2 (normal/mild) or \< 50 mL/min/1.73 m\^2 (moderate/severe impairment). 6. Personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia type 2. 7. Uncontrolled thyroid disease or clinically significant gastroparesis. 8. Prior bariatric surgery within 6 months. 9. Poor venous access. 10. Positive Human Immunodeficiency Virus (HIV) test. 11. Hypersensitivity to AMG 133 or its components. 12. Current use of GLP-1 or GIP receptor agents within 3 months. 13. Pregnancy or lactation, or unwillingness to follow contraception requirements. 14. History of substance or alcohol abuse within 1 year or current alcohol intake \> 21 units/week (men) or \> 14 units/week (women). 15. Positive test for hepatitis B surface antigen or active hepatitis C (with unstable disease). 16. Diabetes mellitus not meeting glycemic cutoffs (hemoglobin A1C ≥ 6.5 % for normal hepatic group or \> 11 % for hepatic impairment group). 17. Active malignancy (within 18 months for hepatic impairment group; within 5 years for normal hepatic group). 18. Hepatic encephalopathy Grade ≥ 3 (uncontrolled) or severe uncontrolled ascites. 19. Organ transplant recipients or those on immunosuppressants. 20. Participation in another clinical trial within 30 days or 5 drug half-lives (whichever is longer).