This study will test if bemdaneprocel (the "study drug") is safe and effective in improving symptoms in participants with Parkinson's Disease. The symptoms of PD are due to a loss of cells that make a specific chemical in your brain called dopamine. The study drug is a cell therapy that contains live brain cells that produce dopamine. This study will last 5 to 8 years, and depending on randomization group between 23-32 study visits.