In this context, different types of the antiparkinsonian agents are under preclinical research, including neurotrophic factors, natural antioxidants, MAO inhibitors, COMT inhibitors, dopamine agonists, and anti-inflammatory agents, among others, with PLGA being the polymer most frequently used for the development of micro- and nano-systems for PD, as it is approved by the FDA and the EMA for use in humans due to its properties of biocompatibility and biodegradability, suitable mechanical properties, and biodegradation kinetics, as well as ease of processing. Here, COMT is linked to Parkinson disease.