ML221 is a selective antagonist of the orphan G protein-coupled receptor GPR3. It is primarily used in biomedical research to study GPR3 signaling pathways and their roles in diseases such as Alzheimer's, where it inhibits amyloid-beta production. Researchers utilize ML221 in cellular assays, animal models, and pharmacological studies to explore neurodegeneration, pain modulation, and other GPCR-mediated processes. This compound aids in identifying therapeutic targets and developing novel treatments for neurological disorders.