Multicenter, open-label, phase 1 study of Cu(II)ATSM administered orally to patients with early idiopathic Parkinson's disease. The study will be conducted in two phases. In the first phase, dose cohorts of six patients each will receive escalating daily doses of Cu(II)ATSM to establish the recommended phase 2 dose (RP2D). The starting dose will be 12 mg/day, which has been shown to be well tolerated in an ongoing phase 1 pharmacokinetic and dose-finding study of Cu(II)ATSM in patients with ALS (ClinicalTrials.gov identifier NCT02870634). In the second phase of the study, an expansion cohort of 20 patients will be treated at the RP2D to confirm tolerability and assess preliminary evidence of efficacy.