The purpose of this study is to measure improvements in liver fibrosis and inflammation with GSK4532990 compared with placebo in participants with NASH and advanced fibrosis on biopsy (F3 or F4). The study duration will be up to 76 weeks including the screening period. The treatment duration will be up to 52 weeks.

Inclusion Criteria:

• Body Mass Index (BMI) ≥25 kilogram per meter square (kg/m^2) (all ethnic origins) except for Asian participants who qualify for the study with BMI ≥23 kg/m2 at Screening.
• In the opinion of the investigator, there are features of metabolic syndrome and NAFLD is the most likely cause of liver disease. Metabolic syndrome may include type 2 diabetes mellitus (T2DM), obesity, dyslipidemia and hypertension.
• A liver biopsy at baseline showing NAFLD Activity Score (NAS) >=4 with at least 1 point each in steatosis, inflammation and ballooning and either Fibrosis 3 or Fibrosis 4 using NASH CRN Scoring System.
• Able and willing to comply with all study assessments, including a liver biopsy at Week 52.

Exclusion Criteria:

• Current alcohol consumption ≥14 standard drinks (24 units, 196 g ethanol) per week for females or ≥21 standard drinks (37 units, 294g ethanol) per week for males.
• Weight reduction surgery or procedures (including gastric banding and intragastric balloon insertion) within 2 years of Screening 1 and/or planned during the study.
• History of cancer within previous 2 years from Screening 1, except basal or squamous cell carcinoma of the skin or in situ cervical carcinoma or any other type of cancer which has been treated medically or surgically with curative outcome.

IPD for this study will be made available via the Clinical Study Data Request site.

IPD will be made available within 6 months of publishing the results of the primary endpoints, a key secondary endpoints and safety data of the study.

Access is provided after a research proposal is submitted and has received approval from the Independent Review Panel and after a Data Sharing Agreement is in place. Access is provided for an initial period of 12 months but an extension can be granted, when justified, for up to another 12 months.