Delivery of neurturin by AAV2 (CERE-120)-mediated gene transfer provides structural and functional neuroprotection and neurorestoration in MPTP-treated monkeys

Objective: We tested the hypothesis that gene delivery of the trophic factor neurturin could preserve motor function and protect nigrostriatal circuitry in hemiparkinsonian monkeys. Methods: An adeno-associated virus-based vector encoding human neurturin (AAV2-NTN; also called CERE-120) was injected into the striatum and substantia nigra of monkeys 4 days after a unilateral intracarotid injection of N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) tendered them hemiparkinsonian. Control hemiparkinsonian monkeys received either AAV2 encoding green fluorescent protein or formulation buffer. Results: Although stable deficits were seen in all control monkeys, AAV2-NTN significantly improved MPTP-induced motor impairments by 80 to 90% starting at approximately month 4 and lasting until the end of the experiment (month 10). AAV2-NTN significantly preserved nigral neurons, significantly preserved striatal dopaminergic innervation, and activated phospho-extracellular signal-regulated kinase, consistent with a mechanism involving a trophic factor-initiated molecular cascade. Histological analyses of numerous brain regions, including the cerebellum, showed normal cytoarchitecture and no aberrant pathology. Interpretation: These data demonstrate that AAV2-NTN (CERE-120) can preserve function and anatomy in degenerating nigrostriatal neurons and are supportive of ongoing clinical tests in Parkinson's disease patients.