A Study to Evaluate the Effectiveness of Two Doses of AP-472 as Adjunctive Therapy to Levodopa in Parkinson's Disease (PD) Participants With Motor Fluctuations

Prior treatment

• Have previously received, or plan to receive during the study, advanced Parkinson's therapies such as continuous levodopa or dopamine delivery systems, or Parkinson's disease-related brain surgery.
• Are currently taking medications that block dopamine, except for low-dose quetiapine (up to 50 mg per day) used for insomnia.
• Routinely use on-demand "rescue" Parkinson's medications more than three times per week.

Other illness

• Have a form of parkinsonism that is not typical Parkinson's disease, such as secondary or atypical parkinsonism.
• Have a history of only certain types of dyskinesias (such as OFF-state, diphasic, myoclonic, or dystonic dyskinesias) without typical peak-dose dyskinesias.

Other

• Participants cannot take part in the study if any of the following apply:
• Have dyskinesias (involuntary movements) that are severe enough, in the study doctor's opinion, to interfere with participation.

• Participants must meet all of the following criteria to take part in the study:
• Be a man or woman between 30 and 80 years of age at the time of screening.
• Have a diagnosis of Parkinson's disease, confirmed using standard medical criteria, including slowness of movement and symptoms that affect one side of the body more than the other.
• Have mild to moderate Parkinson's disease, defined as stage 3 or lower on the Hoehn and Yahr scale when medications are working ("ON" state).
• Experience an average of at least 3 hours of OFF time per day, based on home symptom diaries, with at least 2.5 hours of OFF time each day during the baseline period.
• Have a Montreal Cognitive Assessment (MoCA) score of 24 or higher at screening.
• Be able to walk independently, with or without the use of a walking aid.
• Be able to swallow oral medication.
• Have been on a stable Parkinson's medication regimen for at least 4 weeks before screening. Medications known as MAO-B inhibitors must have been stable for at least 12 weeks.
• Be taking levodopa at least four times daily (immediate- or controlled-release formulations) or three times daily (extended-release formulations such as Rytary or Crexont).