CDNF and Parkinson disease: Delivery of CDNF protein or gene therapy with viral vector protects and restores dopaminergic (DAergic) function in rat, mouse and monkey models of Parkinson’s disease (PD) (Lindholm et al., 2007; Airavaara et al., 2011; Voutilainen et al., 2011; Bäck et al., 2013; Ren et al., 2013; Garea-Rodríguez et al., 2016).