COMT and Parkinson disease: In the 1970s, Madopar®, which is still the gold standard to treat PD, came to the market, apomorphine, a dopamine receptor agonist, was known to be a potential agent; more dopamine agonists were discovered, monoamine oxidase (MAO)-B-inhibitors had their clinical breakthrough and clinical catechol-O-methyltransferase (COMT)-inhibitors studies were initiated.