Inclusion Criteria:  Men or women at least 30 and no more 75 years of age Diagnosis of PD consistent with UK Brain Bank Criteria or MDS Research Criteria for the Diagnosis of PD, with bradykinesia and a clear motor response to levodopa Stable doses of all PD medications for at least 4 weeks prior to Screening Carbidopa/levodopa dose of at least 400 mg daily, distributed over a minimum of 4 dosing intervals during waking hours Participants must have history of motor fluctuations with reliable early-morning OFF episodes and a history of a good response to levodopa, in the judgement of the investigator  If of reproductive potential, willing and able to use a highly effective form of birth control during the study and for 30 days following last dose of study drug. Examples of highly effective forms of birth control are:  Surgical sterility (via vasectomy, hysterectomy, or bilateral tubal ligation) or postmenopausal status in females Sexual partner who is sterile or of the same sex Double-barrier method (any combination of physical and chemical methods) Intrauterine device in females not containing hormones. Able and willing to comply with study drug administration, scheduled visits, treatment plan, laboratory tests, and other study-related procedures to complete the study Investigational Review Board/Ethics Committee-approved consent form signed and date by the participant Assessed as an appropriate and suitable candidate by the Enrollment Authorization Committee (EAC)  Exclusion Criteria:  Diagnosis of secondary or atypical parkinsonism Severe or disabling fluctuations or dyskinesias that would, in the opinion of the investigator, interfere with completion of the study Clinically significant cognitive impairment Clinically significant hallucinations or delusions Clinically significant orthostatic hypotension Currently active major depression as determined by BDI-II score of >19 Previous surgical procedure for PD (Duopa, DBS, etc.) History of small bowel or gastric surgery History of clinically significant GI abnormality (inflammatory bowel disease, significant motility disorder or emesis of any cause, etc.) Use of long-acting levodopa formulations (Sinemet CR, ER, Rytary, etc.) Routine use of proton pump inhibitors or H2 blockers Routine use of medications that may influence gastric motility (opiates, TCA antidepressants, anticholinergics, etc.) Other clinically significant medical, surgical, psychiatric, or laboratory abnormality that, in the judgment of the investigator, is likely to interfere with study compliance or assessment of safety or efficacy Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) levels greater than 2.5 times the upper limit of normal (ULN) Significant renal impairment as determined by creatinine clearance (CrCL) less than or equal to 50 mL/min  Participant has an ECG or clinical evidence of potentially unstable heart disease, including the following:  QTcF > 470 msec females; > 450 msec males Complete right or left bundle branch block Ischemia or myocardial infarct within 1 year prior to the Screening Visit Clinically significant atrial or ventricular dysrhythmia; the heart must be in predominantly normal sinus rhythm Second- or third-degree AV block Heart failure of NYHA classification III or greater Serious cardiomyopathy or cardiac structural abnormality Symptomatic coronary artery or ischemic cardiac disease Any other cardiac condition that the Investigator feels may predispose the participant to ischemia or arrhythmia. Current (or within past 12 months) diagnosis or history of substance abuse, including alcohol (excluding nicotine or caffeine) by Diagnostic and Statistical Manual of Mental Disorders 5 criteria, or positive urine drug screen for tetrahydrocannabinol or any drugs that may affect participant safety or interfere with efficacy assessments Medical or recreational use of marijuana or CBD within 3 months of the Screening Visit Active suicidal ideation within 1 year prior to Screening Visit as determined by a positive response to Question 4 or 5 on the C-SSRS Currently lactating or pregnant, or planning to become pregnant during the study Current participation in another investigational clinical study and/or receipt of any investigational drug within 90 days prior to screening Prior randomization into this study Diabetes requiring insulin treatment