One of the gene therapy based approach involves gene delivery of neurturin and gilial cell-derived neurotrophic factor (GDNF) to the putamen in patients with advanced Parkinson’s disease. GDNF protects dopamine neurons "in vitro" and animal models of parkinsonism; neurturin is a structural and functional analogue of GDNF that protected dopamine neuron in animal model of the disease. Despite open-label trials showing benefits of continuous infusion of GDNF, the results were not confirmed in double-blind studies. This may be due to the distribution factor; the trophic factor was not distributed sufficiently throughout the target place.