This study focuses on people who may have metabolic dysfunction-associated steatohepatitis (MASH), also called nonalcoholic steatohepatitis, that will be confirmed by a biopsy. The purpose of the study is to learn about the safety and effectiveness of an experimental drug called pegozafermin in patients with MASH when compared to a placebo (inactive substance) in assessing response to novel therapy in terms of improving inflammation and scar tissue in the liver (called fibrosis). Pegozafermin is a hormone made from protein that naturally occurs in the body and works on the metabolism of fats and glucose (sugar). Study procedures include blood draws, urine collection, liver biopsy, electrocardiograms, imaging, and scans. Another goal of the study is to learn the impact of pegozafermin on measures of organ function (such as blood cell counts, blood sugar, cholesterol and other blood fats, proteins, hormones, and bone production).