Neurturin (NTN) is a neurotrophic factor with known potential to protect and restore the function of dopaminergic substantia nigra neurons whose degeneration has been most closely linked to the major motor deficits in Parkinson's disease (PD). CERE-120, an adeno-associated virus serotype 2 (AAV2)-based gene delivery vector encoding human NTN, is being developed as a potential therapeutic for PD. In a series of preclinical studies reported herein, CERE-120 delivery to the striatum produced a dose-related neuroprotection of nigrostriatal neurons in the rat 6-hydroxydopamine (6-OHDA) lesion model. Long-lasting efficacy of CERE-120 was evidenced by substantia nigra cell protection, preserved fiber innervation of the striatum, and behavioral recovery for at least 6 months. In addition, striatal infusion of CERE-120 was found to have a safety and tolerability profile devoid of side effects or toxicological responses, for at least 12 months post-treatment, even at dose multiples 125 times that of the lowest efficacious dose tested. These results support the ongoing CERE-120 clinical program in PD patients.