This study will help determine the safety and effectiveness of BIIB122, compared to placebo (an inactive substance), in people with early-stage Parkinson's disease. The use of BIIB122 in this study is investigational. "Investigational" means that the study drug is currently being tested and is not approved by the U.S. Food and Drug Administration (FDA) or any other health authorities around the world for treating people with PD. The study is expected to last a minimum of 1 year to a maximum of 3 years. You may or may not receive direct medical benefit from participating in this study. Your condition may get better, worse, or stay the same. The information obtained from this study, however, could help other patients with your disease in the future.

This study aims to study the natural progression of P-SYN quantification by conducting skin biopsies in patients with Parkinson's Disease (PD) and REM sleep behavior disorder (RBD). Participation will be over an 18-month period and will include skin biopsies and clinical examinations every six months. Subjects will be male or female between the ages of 50-100 and have a diagnosis of PD or RBD.

This is an observational study to further characterize and quantify disease severity
and impact (including change over time) in individuals with either segmental, multifocal, or generalized dystonia. Subjects will be aged 12-65 years old and clinically diagnosed with isolated (or primary) dystonia. Participation will include 2 visits over 120 days in which subjects will be asked to answer questions about their dystonia and related symptoms.

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.