Liu and colleagues, in 2014, evaluated the limitation imposed by P-gp to the BBB crossing of the new drug candidate for PD treatment, FLZ (N-2-(4- hydroxy-phenyl)-ethyl]-2-(2,5-dimethoxy-phenyl)-3-(3-methoxy-4-hydroxy-phenyl)-acrylamide) [180]. Here, PGP is linked to Parkinson disease.