A Study Evaluating Efruxifermin in Subjects With Non-invasively Diagnosed Nonalcoholic Steatohepatitis (NASH)/Metabolic Dysfunction-Associated Steatohepatitis (MASH) and Nonalcoholic Fatty Liver Disease (NAFLD)/Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD)

Inclusion Criteria: Main Study Only: * Males and non-pregnant, non-lactating females between 18 - 80 (between 19-80 in the Republic of Korea) years of age inclusive, on the day of signing informed consent * Previous history or presence of 2 out of 4 components of metabolic syndrome (obesity, dyslipidemia, elevated blood pressure, elevated fasting glucose) or type 2 diabetes * Suspected or confirmed diagnosis of NASH/MASH or NAFLD/MASLD or non-invasively diagnosed NASH/MASH or NAFLD/MASLD Open-Label Rollover * Prior participation in a previous Akero Phase 2 study Exclusion Criteria: * Other causes of liver disease based on medical history and/or liver histology and/or central laboratory results, including but not limited to: alcoholic liver disease, autoimmune disorders (e.g., primary biliary cholangitis \[PBC\], primary sclerosing cholangitis \[PSC\], autoimmune hepatitis), drug induced hepatotoxicity, Wilson disease, clinically significant iron overload, or alpha-1-antitrypsin deficiency * Type 1 or unstable Type 2 diabetes A reduced list of inclusion and exclusion criteria apply to participants in the open-label rollover extension. Other inclusion and exclusion criteria may apply.