This study is for people with Parkinson's disease (PD) who have motor fluctuations, meaning their movement abilities change during the day. The study examines how effective two doses of the medication AP-472 are when added to levodopa, a common PD treatment, compared to a placebo (a harmless pill with no active drug). The study lasts about 12 weeks and includes a screening period and an 8-week treatment period. During the treatment, participants will be randomly assigned to take either one of the two doses of AP-472 or a placebo. Neither the participants nor the doctors will know who gets which treatment, making it a "blind" study.

• The study will last around 12 weeks, including a screening and treatment period.
• Participants need to be between 30 and 80 years old and have a confirmed diagnosis of Parkinson's disease.
• Participants must have been on stable Parkinson's medications for at least 4 weeks before screening.