Overview

The purpose of this study is to evaluate the safety, tolerability and pharmacokinetics of NNC0581-0001 in participants with hepatic steatosis and suspected steatohepatitis (increased liver fat and suspected inflammation). NNC0581-0001 will be given in 2 different dose levels as injection under the skin (once per month for 3 months). Participants will either get NNC0581-001 or Placebo (dummy treatment). Which treatment participants get is decided by chance. NNC0581-0001 is a new medicine which cannot be prescribed by doctors. The study will last about 58 weeks.

Eligibility

Inclusion Criteria:

• Considered eligible based on the medical history, physical examination, and the results of vital signs, electrocardiogram and clinical laboratory tests performed during the screening visit, as judged by the investigator.
• Male or female (of non-childbearing potential) aged 18-64 years (both inclusive) at the time of signing the informed consent.
• Body mass index (BMI) 25.0 to 39.9 kilogram per square meter (kg/m^2) (both inclusive) at screening.
• Liver fat content measured by magnetic resonance imaging - estimated proton density fat fraction (MRI-PDFF) greater than or equal to (>=) 10 percent and liver stiffness greater than 8 kilopascal (kPa) as measured by FibroScan® (vibration-controlled transient elastography [VCTE™]).

Additional inclusion criteria for participants in the open-label liver biopsy cohort apply:

• Alanine aminotransferase (ALT) in men greater than (>) 30 units per liter (U/L), women > 19 U/L
• Liverstiffness, measured by FibroScan® (VCTE) > 8 kPa and less than (<) 12 kPa
• Informed consent obtained at screening for a liver biopsy to be performed at baseline and post-treatment.

Note: Participants with confirmed metabolic dysfunction-associated steatohepatitis (MASH), based on a prior liver biopsy, can be included in the open-label cohort.

Exclusion Criteria:

• Any disorder, which in the investigator's opinion might jeopardise participant's safety or compliance with the protocol.
• Any laboratory safety parameter, at screening, outside the extended laboratory ranges, and considered clinically significant per the principal investigator (see laboratory provided reference ranges for specific values). Of note, re-screening or re-sampling is NOT allowed if the individual has failed one of the exclusion criteria related to the following laboratory parameters:
• ALT >= 3 × upper limit of normal (ULN)
• Aspartate aminotransferase (AST) >= 3 × ULN
• Bilirubin > 1.5 × ULN
• Estimated glomerular filtration rate (eGFR) < 60 milliliter per minute per 1.73 square meters (mL/min/1.73 m^2) at screening.