Dose Exploration Study of GSK4532990 in. Participants With NASH or Suspected NASH

The purpose of this study is to understand how the drug GSK4532990 is processed in the body (pharmacokinetics) and how it works in the liver (pharmacodynamics) as well as to ensure it is safe and well-tolerated. The total study duration for each participant will be approximately 24-36 weeks.

Inclusion Criteria: * Participant must be 18 to 75 years of age. * Participant must be capable of giving signed informed consent which includes compliance with the requirements and restrictions listed for the study. * Participants who have proven diagnosis of NASH or suspected NASH based on defined study criteria. * Participants must meet predefined stable use requirements of concomitant medications based on study criteria. Exclusion Criteria: Individuals who meet any of the following exclusion criteria will not be eligible to participate in the study: * Cirrhosis or current unstable liver or biliary disease. * Other causes of liver disease including, but not limited to, alcohol-related liver disease, autoimmune disorders. * Known weight loss of ≥5% within 3 months prior to Screening. * Weight reduction surgery or procedures within 2 years of Screening. * Any contraindication to undergoing liver biopsy. * Any contraindication to undergoing Magnetic Resonance Imaging or FibroScan®.