Since the dopamine replacement strategy is the most perspective strategy to treat PD [64], a lentiviral multicistronic construct encoding genes of three proteins essential for dopamine biosynthesis, namely tyrosine hydroxylase (TH), aromatic amino acid dopa decarboxylase (AADC) and GTP cyclohydrolase 1 (CH1) linked through IRES has been proposed for restoring dopamine synthesis. The gene discussed is TH; the disease is Parkinson disease.