Furthermore, a recent clinical study showed that weekly intravenous infusions of N-acetyl-cysteine (NAC), the prodrug to L-cysteine, a GSH precursor (50 mg/kg), in combination with oral doses (500 mg twice per day) for 3 months significantly increased DAT binding (DaTscan) in the caudate and putamen of patients with PD, along with significantly improved PD symptoms [212]. The gene discussed is SLC6A3; the disease is Parkinson disease.