The purpose of this study is to demonstrate that young plasma infusions can be performed safely in patients with Parkinson's Disease (PD). Secondary outcomes will include behavioral and laboratory data that will support the next study that will inquire whether young plasma infusions improve or slow the progression of cognitive, mood and/or motor impairment and rate markers of the disease.

Parkinson's disease (PD) is a neurodegenerative disease that affects over 1.6 million people in the United States and whose incidence increases with age, affecting over 1% of people over the age of 65. The neuropathological processes involved in PD are widespread throughout the brain, and are reflected in a constellation of motor, cognitive, mood and other non-motor symptoms. Treatments to date have largely focused on dopamine replacement strategies or deep brain stimulation, both symptomatic treatments.

As neurodegenerative diseases progress, there are major changes throughout the body and brain. These changes are transmitted in the body via the circulatory system between organs, tissues and cells. Recent findings from multiple laboratories have shown that infusions of young plasma into aging rodents can have beneficial effects on cognitive functions. This suggests that the circulating components of plasma can improve cognitive and disease-relevant symptoms. This has motivated the field to treat multiple disorders with blood products and their constituent active components.

The established safety of blood transfusions allows the investigators to test whether infusions of young plasma can ease the neurological symptoms in human subjects with neurodegenerative diseases. A related study of plasma infusions has already been completed at Stanford in patients with Alzheimer's disease (ClinicalTrials.gov identifier NCT02256306).

The investigator proposes to test the safety and efficacy of transfusing young plasma into PD participants, in order to establish its effects on motor and cognitive functions in participants in a Phase 1 study. The successful completion of this study will inform the design of future, larger and multicenter studies with the goal to determine whether infusions of young plasma can ameliorate the neurodegenerative symptoms and underlying pathophysiology in Parkinson's disease.

Inclusion Criteria:

• A diagnosis of clinically probable or established Parkinson's Disease (MDS criteria)
• Subject must be on a stable dose of dopaminergic medication and/or Deep Brain Stimulation (DBS) parameters for at least 4 weeks prior to screening and for the duration of the study
• Subject must be competent to sign consent
• Subject must be willing to commit to being available for testing and infusions for 6 consecutive weeks (2 testing consecutive weeks, 4 infusion consecutive weeks) followed by two visits a month after final infusion.
• The availability of a study partner who knows the patient well and is willing to accompany the subject to all trial (optional if participant is able to consent and travel by self)

Exclusion Criteria:

• The participation in any other interventional clinical trial
• The inability to travel to Stanford
• Inability to walk without assistance in the off or on medication state
• The clinically determined presence of dementia
• A clinical suspicion/diagnosis of Multiple System Atrophy (MSA), Progressive Supranuclear Palsy (PSP), Lewy Body Dementia (LBD), Essential Tremor (ET)
• Subject's pregnancy or likelihood of pregnancy within the next 6 months.
• Subject's positive test results for Hepatitis B, Hepatitis C or HIV at screening
• Any other condition or situation that the investigator believes may interfere with the safety of the subject or the intent and conduct of the study
• Subject's medical history of:

Stroke Anaphylaxis Gout- may cause an increase in uric acid Prior adverse reaction to any human blood product Any history of a blood coagulation disorder or hypercoagulability Congestive heart failure Uncontrolled hypertension Renal failure Prior intolerance to intravenous fluids Recent history of uncontrolled atrial fibrillation immunoglobulin A deficiency (by history)

• Subject's relation to medications or other treatments:
• Any concurrent use of an anticoagulant therapy. Antiplatelet drugs (e.g., aspirin or clopidogrel) are acceptable.
• The use of Inosine, which may alter urate levels
• Initiation or change in the dosage of a cholinesterase inhibitor or memantine during the trial. A participant already on a cholinesterase inhibitor or memantine must be on a stable dose for at least one month prior to Screening.
• Concurrent participation in another interventional treatment trial for Parkinson's disease. If there was prior participation, the last dose of the investigational agent must have been at least 6 months prior to Screening.
• Treatment with any human blood product, including intravenous immunoglobulin, during the 6 months prior to Screening or during the trial.
• Concurrent daily treatment with benzodiazepines, typical or atypical antipsychotics, long-acting opioids, or other medications that, in the investigator's opinion, interfere with cognition. Intermittent treatment with short-acting benzodiazepines or atypical antipsychotics may be permitted, provided that no dose is administered within the 72 hours preceding any cognitive assessment.

Participants who completed the study

Adverse events were monitored during the entirety of the trial, starting at baseline and continuing through the 4 week post-infusion mark (8 week total).

Adverse events were categorized using the CTCAE v4.0.