A Clinical Study Investigating the Efficacy, Tolerability, and Safety of Continuous Subcutaneous ND0612 Infusion Given as Adjunct Treatment to Oral Levodopa in Patients With Parkinson's Disease With Motor Fluctuations

Key Inclusion Criteria: 1. Male and female PD subjects of any race aged 30-80 years 2. PD diagnosis consistent with the UK Brain Bank Criteria. 3. Modified Hoehn \& Yahr scale in "ON" state ≤3 4. Subjects must experience motor fluctuations and experience an average of at least 2 hours daily in the "OFF" state 5. Taking at least 4 doses/day of IR LD/DDI (or at least 3 doses/day of Rytary) and taking, or having taken therapeutic doses of at least 2 other classes of anti-PD medications. 6. Subjects must be on stable doses of all their anti-PD medications for at least 28 days before Baseline (Day 1). 7. Subject and/or study partner must demonstrate ability to keep accurate diary entries of PD symptoms ("ON-OFF" diaries) with at least 75% concordance with the study rater by the end of the diary training session at the end of the screening period. 8. Mini Mental State Examination (MMSE) score \>26. 9. Female subjects must be surgically sterile (hysterectomy, bilateral oophorectomy, or tubal ligation), postmenopausal (defined as cessation of menses for at least 1 year), or willing to practice a highly effective method of contraception. Key Exclusion Criteria: 1. Atypical or secondary parkinsonism. 2. Psychosis or hallucinations in past 6 months. 3. Subjects with a clinically significant or unstable medical, surgical, psychiatric condition or laboratory abnormalities which, in the opinion of the Investigator or the EAC, represents a safety risk, makes the subject unsuitable for study entry or potentially unable to complete all aspects of the study. 4. Clinically significant ECG abnormalities. 5. Renal or liver dysfunction that may alter drug metabolism including Screening visit serum levels of creatinine \>1.3 mg/dL, aspartate aminotransferase (AST) or alanine aminotransferase (ALT) \>2x upper limit of normal (ULN), total bilirubin \>2.5 mg/dL. 6. Positive serum serology for Hepatitits B Virus (HBV), Hepatitits C Virus (HCV) or Human Immunodeficiency Virus (HIV) at the Screening visit 7. Any malignancy in the 5 years prior to randomization excluding basal cell carcinoma of the skin or cervical carcinoma in situ that have been successfully treated 8. Use of prohibited medications as per protocol 9. Subjects who have previously undergone treatment for PD with a neurosurgical intervention (e.g., pallidotomy, thalamotomy, transplantation, deep brain stimulation procedures), Duodopa/Duopa, or continuous dopaminergic or apomorphine infusion.