A Study of UBT251 in Participants With Metabolic Dysfunction-Associated Steatohepatitis (MASH)

Inclusion Criteria: Age 18-75 years (inclusive) at screening; sex unrestricted. Subjects with centrally confirmed MASH (metabolic dysfunction-associated steatohepatitis) based on liver histopathology must meet all the following criteria: 1. NAS (Appendix 1) ≥ 4 （with at least 1 point each for lobular inflammation and ballooning degeneration）; 2. CRN fibrosis stage (see Appendix 2) of F2 or F3 (a liver biopsy obtained ≤ 6 months before screening is acceptable if it meets the above criteria). 3.Magnetic Resonance Imaging-Proton Density Fat Fraction (MRI-PDFF) ≥ 8 % at screening (MRI-PDFF results obtained within 2 months prior to screening at the trial site are acceptable). 4.Subjects must have \<5% body weight fluctuation during the 6 weeks prior to randomization (based on self-reported data), calculated as: \[(Highest weight - Lowest weight) / Highest weight\] × 100%. For subjects using historical liver biopsy, documented weight change from biopsy to randomization must also be \< 5 %. 5.At least one cardiometabolic risk factor at screening: 1. Body mass index (BMI) ≥ 24.0 kg/m², or waist circumference ≥90 cm for males or ≥85 cm for females; 2. Blood pressure ≥ 130/85 mmHg, or on antihypertensive therapy; 3. Fasting triglycerides ≥ 1.70 mmol/L and \< 5.6 mmol/L, or on lipid-lowering therapy; 4. Fasting HDL-C ≤ 1.0 mmol/L for males or ≤ 1.3 mmol/L for females; or on lipid-lowering therapy; 5. Fasting glucose ≥ 6.1 mmol/L or glycated hemoglobin (HbA1c) ≥ 5.7 %, or documented history of type 2 diabetes mellitus (T2DM), or Homeostatic Model Assessment of Insulin Resistance index ≥ 2.5. 6.Subjects with type 2 diabetes mellitus (T2DM) must meet glycated hemoglobin (HbA1c) ≤ 9.0 % at screening (local result obtained ≤ 2 weeks before randomization accepted), and stable glycemic control regimen for at least 3 months prior to screening: subjects must be on diet and exercise control alone, or in combination with stable-dose glucose-lowering medications, with the following requirements:: 1. Diet and exercise alone; 2. Stable-dose use of metformin, sulfonylureas, sodium-glucose cotransporter-2 (SGLT2) inhibitors, or insulin, stable insulin dose defined as ≤35% variation in total daily insulin dose; 7. Subjects (including partners) must have no pregnancy plans from screening through 6 months post-trial and must practice contraception during the study, with no plans to donate sperm/oocytes for 6 months after trial completion. 8\. Subjects must provide informed consent prior to trial participation and voluntarily sign the written informed consent form. 9.Voluntarily comply with all trial follow-up requirements, demonstrate good protocol adherence, and be willing and able to undergo protocol-specified liver biopsies. Exclusion Criteria: 1. Known hypersensitivity to the investigational product or any of its excipients, or allergy to other GLP-1 receptor agonists, or clinically significant history of multiple/severe drug allergies, or current allergic diseases or hypersensitivity diathesis; 2. Previous use of any of the following drugs or treatments: 1\) Use of GLP-1 receptor agonists (GLP-1R), or GLP-1R/GCGR agonists, or GLP-1R/GIPR/GCGR agonists within 3 months prior to screening; 2) Cumulative use for ≥4 weeks within 3 months prior to screening, use within 1 month prior to screening, or planned use during the trial of vitamin E (dose \>400 IU/day), thiazolidinediones, polyunsaturated fatty acids, or ursodeoxycholic acid; 3) Cumulative use for ≥4 weeks within 3 months prior to screening, use within 1 month prior to screening, or planned use during the trial of drugs associated with liver injury, hepatic steatosis, or steatohepatitis: including amiodarone, methotrexate, systemic glucocorticoids (dose \>5 mg/day prednisone equivalent), estrogens (dose exceeding hormone replacement therapy or contraceptive use), tetracyclines, tamoxifen, anabolic steroids, valproate, or restricted drugs, or any drug deemed likely to interfere with efficacy or safety evaluations; 4) Unstable doses of statins, fibrates, or PCSK9 inhibitors within 1 month prior to screening; 3.History or evidence of any of the following diseases: 1. Chronic liver disease other than MASH (e.g., autoimmune liver disease, primary biliary cholangitis, primary sclerosing cholangitis, chronic liver disease-related ascites, esophageal varices, hepatic encephalopathy, etc.). 2. Diagnosis of type 1 diabetes or other specific types of diabetes, except resolved gestational diabetes; 3. Acute pancreatitis or chronic pancreatitis within 1 year prior to screening, history of pancreatic surgery; or symptomatic gallbladder disease within 1 year prior to screening (e.g., choledocholithiasis, multiple gallstones, etc., except those who underwent cholecystectomy or stone removal); 4. Personal or family history (first-degree relatives-parents, children, or siblings) of medullary thyroid carcinoma (MTC) or multiple endocrine neoplasia type 2 (MEN2); 5. History of severe psychiatric disorders, including but not limited to depression, suicidal tendencies or attempts, schizophrenia, bipolar disorder, etc.; 6. Clinically significant active cardiovascular/cerebrovascular disease within 6 months prior to screening, defined as: ① Myocardial infarction (MI) or unstable angina; ② Cardiac-related surgery (including coronary artery bypass grafting, percutaneous coronary intervention); ③Congestive heart failure (New York Heart Association \[NYHA\] Class III-IV) (see Appendix 3); ④ Cerebrovascular accident (except old lacunar infarction), including but not limited to stroke/transient ischemic attack; ⑤ Other cardiovascular or cerebrovascular diseases deemed unsuitable for trial participation by the investigator; 7. Retinal diseases requiring urgent treatment at screening (including but not limited to retinal vascular disorders, retinal inflammation, retinal detachment, retinal degeneration, etc.), as assessed by the investigator; 8. History of severe hypoglycemic