The newly discovered cerebral dopamine neurotrophic factor (CDNF) gained attention because it restored function and promoted survival of midbrain dopaminergic (DA) neurons in 6-hydroxydopamine (6-OHDA) and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) models of PD in rodents when delivered intracranially either as a recombinant protein or with adeno-associated viral serotype 2 (AAV2) vector as treatment regimens in rodent models of PD [1–6]. The gene discussed is CDNF; the disease is Parkinson disease.