ADORA2A and Parkinson disease: Nevertheless, its high affinity (Ki = 3.9–4.9 nM for human A2AR) [8,14], unique target selectivity [15] and high in vivo stability [16,17] position tozadenant as a promising lead structure for the development of positron emission tomography (PET) probes, which could be used to visualize and quantify cerebral A2ARs in patients with PD or other neurological diseases [9,18].