One of the most investigated A2AR antagonists is istradefylline (former KW-6002; Nourianz®, Kyowa Kirin Inc., Bedminster, NJ, USA), which was approved by the U.S. Food and Drug Administration (FDA) in April 2019 for adjunctive treatment in patients with PD [34,35]. Here, ADORA2A is linked to Parkinson disease.