A mutation in the gene GCH1, which encodes the enzyme GTP cyclohydrolase I, disrupts the production of BH4, decreasing dopamine levels (hypodopaminergia).
Prosavin uses Oxford BioMedica's Lentivector delivery system to transfer three genes, aromatic amino acid dopa decarboxylase, tyrosine hydroxylase and GTP-cyclohydrolase 1, to the striatum in the brain, reprogramming transduced cells to secrete dopamine.