Inclusion Criteria:

• Males or females aged 30-80 years.
• Participants who are willing and able to give informed consent.
• “Normal” cognition as assessed by MMSE. We will require a value > 24.
• MSA patients fulfill the following criteria:
  • Fulfill Consensus Criteria 3, 4 for possible or probable MSA;
  • UMSARS I (minus question 11) between 5-16 and able to walk unaided;
  • Anticipated survival of at least 3 years in the opinion of the investigator.
• PD patients at Hoehn and Yahr stage 2 to 3
• Healthy controls without evidence of neurologic disease or autonomic dysfunction.
• iRBD patients with sleep-study confirmed RBD by International Classification of Sleep Disorders V3 criteria, with absence of a diagnosis of dementia, PD, MSA, or other overt neurodegenerative disease.

Exclusion Criteria:

• Pregnant or breastfeeding women, and women of childbearing potential who do not practice an acceptable method of birth control.
• Participants with a clinically significant or unstable medical or surgical condition that, in the opinion of the investigator, might preclude safe completion of the study or might affect the results of the study.
• Participants who have taken any investigational products within 60 days prior to baseline.
• Medications that could affect autonomic function are permitted but need to be withdrawn at least four half-lives prior to autonomic evaluations.
• Patients with contraindication for MRI scanning, including those with MRI-incompatible pacemakers.

Note: Other protocol defined Inclusion/Exclusion Criteria may apply.

Eligibility last updated 12/28/23. Questions regarding updates should be directed to the study team contact.