This study investigates the long-term safety and effects of an investigational medication for non-motor symptoms in patients with Parkinson's Disease. The investigational medication is similar to tetrahydrocannabinol (THC), the active component of cannabis, but is designed to have fewer side effects and less euphoria. It works by partially activating certain receptors in the body that THC normally affects.

Participants will first go through a phase where their dose of the investigational medication is adjusted to find the best amount for them. After this, they will take a stable dose for six months. During this time, they will have regular visits every three months as part of their usual outpatient care, and they will receive phone calls every other day to monitor their condition. The study will include a final visit to wrap up participation and ensure safety.

• Who can participate: Participants must have completed the previous phase of the study as responders within the last two months and must not have had any serious or moderate adverse events related to the drug. They must be in good health and able to take oral medication.
• Study details: Participants will take part in a dose adjustment phase to find the optimal amount of the investigational medication, followed by a six-month period on a stable dose. A placebo is not used in this study phase.
• Study Timelines and Visits: The study will last 6 months. The study requires 3 visits.