AY 9944 is primarily used in biochemical research to study cholesterol biosynthesis. It acts as an inhibitor of the enzyme 7-dehydrocholesterol reductase, which is crucial in the final steps of cholesterol synthesis. By inhibiting this enzyme, AY 9944 is utilized to investigate the effects of cholesterol depletion in cellular and animal models. This has significant implications for understanding diseases related to cholesterol metabolism, such as Smith-Lemli-Opitz syndrome, a genetic disorder characterized by defective cholesterol synthesis. Additionally, AY 9944 is employed in pharmacological studies to explore potential therapeutic interventions targeting cholesterol pathways, aiding in the development of treatments for hypercholesterolemia and related cardiovascular conditions.