A Study of Buntanetap in Participants With PD

This study will examine the long-term safety of buntanetap in participants with PD. This will be a 36-month open-label safety study. This study will be conducted with two cohorts. Cohort 1 will enroll via invitation only for PD participants who have previously participated in buntanetap clinical trials. Cohort 2 will be for PD participants who are receiving deep brain stimulation (DBS) treatment. Qualified participants will receive buntanetap 30mg QD after a screening period of up to 42 days.

Inclusion Criteria: 1. Diagnosis of idiopathic PD according to MDS Clinical Diagnostic Criteria for Parkinson's Disease (Postuma et al., 2015) and a. Cohort 1: Participated in a prior PD clinical trial with buntanetap. i. A legally authorized representative is required for any participant whose MMSE \ 2.0X ULN). 8. Any clinically significant abnormal laboratory values. Participants with liver function tests (aspartate aminotransferase \[AST\] or alanine aminotransferase \[ALT\]) greater than twice ULN will be excluded. 9. Is at imminent risk of self-harm, based on clinical interview and responses on the C-SSRS, or of harm to others in the opinion of the investigators. Participants must be excluded if they report suicidal ideation with intent, with or without a plan or method (e.g., positive response to Items 4 or 5 in assessment of suicidal ideation on C-SSRS) in the past 2 months, or suicidal behavior in the past 6 months. 10. Cancer or has had a malignant tumor within the past year, except participants who underwent potentially curative therapy with no evidence of recurrence (participants with stable untreated cancer are not excluded). 11. Alcohol / Substance use disorder, moderate to severe, in the last 5 years according to the most current version of the DSM. 12. Participation in another clinical trial with an investigational agent and have taken at least one dose of study medication, unless unblinded on placebo, within 4 weeks prior to the start of screening, or five half-lives of the investigational drug, whichever is greater. The end of a previous investigational trial is the date the last dose of an investigational agent was taken. 13. A learning disability or developmental delay. 14. Participants whom the site PI deems to be otherwise ineligible. 15. A known allergy to the investigational drug or any of its components. Inactive ingredients of the investigational medicinal product: * Silicified microcrystalline cellulose * Dibasic calcium phosphate dihydrate * Mannitol * Stearic acid * Hypromellose (capsule shells structure) * Titanium dioxide (opacifier of the capsule shells) 16. Is currently pregnant, breast-feeding, and/or lactating. 17. Uncontrolled hypertension (systolic \>160mmHg and/or diastolic \>95mmHg) or hypotension (systolic \