He was a key investigator in the US-Venezuela Collaborative Huntington Disease Project, which identified the gene responsible for this fatal hereditary disorder. Dr Shoulson has served as principal investigator of the National Institutes of Health-sponsored trials “Deprenyl and Tocopherol Antioxidative Therapy of Parkinsonism” (DATATOP), the “Prospective Huntington At Risk Observational Study” (PHAROS), and in the leadership of more than 35 other multi-center clinical research studies. He played an instrumental role in the development of 10 new drugs for neurological disorders, including seven for Parkinson disease (selegiline, lazabemide, pramipexole, entacapone, clozapine, rasagiline, rotigitine), two for Huntington disease (tetrabenazine, dutetetrabenazine) and one for attention deficit disorder (Concerta). He was formerly a health policy fellow in the US Senate, a member of the National Institute of Neurological Disorders and Stroke Council, and president of the American Society for Experimental NeuroTherapeutics (ASENT). He is currently principal investigator of the FDA-Georgetown University Collaborating Center of Excellence in Regulatory Science and Innovation (CERSI – FD004319), associate editor of JAMA Neurology and an active elected member of the Institute of Medicine of the National Academy of Sciences. He has authored more than 310 scientific reports.