ACAT-IN-4 hydrochloride is primarily utilized in research settings to study the inhibition of acyl-CoA:cholesterol acyltransferase (ACAT), an enzyme involved in cholesterol esterification. By blocking this enzyme, it helps researchers investigate the mechanisms of cholesterol metabolism and its role in conditions like atherosclerosis and hypercholesterolemia. This compound is particularly valuable in preclinical studies aimed at developing therapeutic strategies for managing cholesterol-related disorders. It is also used in cellular and biochemical assays to explore lipid metabolism pathways and evaluate potential drug candidates targeting ACAT activity.