Research Study on Whether Semaglutide Works in People With Non-alcoholic Steatohepatitis (NASH)

Semaglutide is a medicine studied in patients with NASH. Semaglutide is a well-known medicine, which is already used by doctors to treat type 2 diabetes in many countries. Participants will either get semaglutide or a dummy medicine - which treatment participants get is decided by chance. Participants will need to inject themselves with medicine under the skin. Participants will need to do this once a week. The study will last for about 5 years. Participants will have up to 21 clinic visits and 9 phone calls with the clinical staff during the study. Some of the clinic visits may be spread over more than one day. Participants with other chronic liver diseases cannot take part in this study. Women cannot take part in the study if they are pregnant, breast-feeding or plan to become pregnant during the study period.

Inclusion Criteria: * Age above or equal to 18 years at the time of signing informed consent. * Histological evidence of NASH based on a central pathologist evaluation of the baseline liver biopsy. The baseline liver biopsy can be a historical biopsy obtained within 180 days prior to the screening visit (V1). * Histological evidence of fibrosis stage 2 or stage 3 according to the NASH CRN (Clinical Research Network) classification based on a central pathologist evaluation of the baseline liver biopsy. * A histological NAS (Non-alcoholic fatty liver disease Activity Score) above or equal to 4 with a score of 1 or more in steatosis, lobular inflammation and hepatocyte ballooning based on a central pathologist evaluation of the baseline liver biopsy. Exclusion Criteria: * Documented causes of chronic liver disease other than non-alcoholic fatty liver disease (NAFLD) * Positive HBsAg, positive anti-HIV, positive HCV RNA at screening (V2A) or any known presence of HCV RNA or HBsAg within 2 years of screening (V2A). * Presence or history of ascites, variceal bleeding, hepatic encephalopathy, spontaneous bacterial peritonitis or liver transplantation at randomisation. * Known or suspected excessive consumption of alcohol (greater than 20 g/day for women or greater than 30 g/day for men) or alcohol dependence (assessed by the Alcohol Use Disorders Identification Test (AUDIT questionnaire)). * Treatment with vitamin E (at doses greater than or equal to 800 IU/day) or pioglitazone or medications approved for treatment of NASH which has not been at a stable dose in the period from 90 days prior to the screening visit (V2A). In addition, for subjects with historical liver biopsies taken more than 90 days prior to screening, treatment should be at a stable dose from time of biopsy until screening. * Treatment with GLP-1 RAs in the period from 90 days prior to the screening visit (V2A). In addition, for subjects with historical liver biopsies taken more than 90 days prior to screening, any treatment with GLP-1 RAs from time of biopsy until screening (V2A). * Treatment with glucose-lowering agent(s) (other than GLP-1 RAs), lipid-lowering medication or weight loss medication not stable in the opinion of the investigator in the period from 90 days prior to the screening visit (V2A). In addition, for subjects with historical liver biopsies taken more than 90 days prior to screening, treatment should be at a stable dose in the opinion of the investigator from time of biopsy until screening.