Overview

The primary objective of this trial is to evaluate the dose-dependent and comparative effects of ECC4703 (low and high dose), ECC0509 (low and high dose), and their combination on hepatic fat reduction as assessed by change in magnetic resonance imaging proton density fat fraction (MRI-PDFF) at Week 12.

Eligibility

Inclusion Criteria:

1. Adults ≥18 years of age who can provide written informed consent and comply with study procedures.
2. Presumed MASH based on recent liver biopsy (NAFLD activity score \[NAS\] ≥4, fibrosis F1-F3) or non-invasive criteria consistent with liver fibrosis (metabolic syndrome plus FibroScan® liver stiffness 7-14 kPa).
3. Evidence of hepatic steatosis confirmed by FibroScan® CAP \>280 dB/m and MRI-PDFF \>8% at screening.
4. BMI \>25 kg/m\^2 to \<50 kg/m\^2 (non-Asian); BMI ≥23.0 to \<50.0 kg/m\^2 (Asian).
5. ALT \>1.5×upper limit of normal (ULN).
6. Estimated glomerular filtration rate (eGFR) ≥60 mL/min/1.73m\^2 (Chronic Kidney Disease Epidemiology Collaboration, \[CKD-EPI\]).
7. Stable body weight (no \>5% change) for at least 6 months prior to screening.
8. Willing to comply with contraception requirements (as applicable to males and females of childbearing potential).
9. In the opinion of the investigator, able to participate safely and complete required MRI/biomarker assessments.

Exclusion Criteria:

Liver-related:

1. Chronic liver disease other than metabolic dysfunction-associated steatotic liver disease (MASLD)/MASH, including alcoholic liver disease, autoimmune hepatitis, cholestatic disease, genetic liver diseases, or drug-induced liver injury.
2. Evidence of cirrhosis or hepatic decompensation, including prior ascites, varices, encephalopathy, or laboratory/imaging findings consistent with cirrhosis.
3. ALT or AST \>5×ULN or ALP \>2×ULN at screening.
4. Clinically significant thyroid or adrenal dysfunction, including uncontrolled hypothyroidism, hyperthyroidism, or adrenal disorders.
5. Type 1 diabetes, HbA1c \>9.5%, or unstable type 2 diabetes requiring medication changes within 3 months.
6. Use of medications that affect liver fat or fibrosis (e.g., Glucagon-Like Peptide-1 Receptor Agonists (GLP-1 RAs) not on a stable dose, pioglitazone, obeticholic acid, high-dose vitamin E, hepatotoxic drugs) within protocol-specified washout periods.
7. Significant alcohol use within 1 year prior to screening.
8. Recent cardiovascular events, including myocardial infraction (MI), stroke, unstable angina, heart failure (New York heart association \[NYHA III-IV\]), or uncontrolled arrhythmia.
9. Current or recent serious psychiatric illness, including psychosis, active suicidal ideation, or suicide attempt within 5 years.
10. Pregnancy, breastfeeding, or conditions that increase risk or interfere with study procedures, including MRI contraindications or other investigator-determined safety concerns.