The National Institute of Neurological Disorders and Stroke, part of the National Institutes of Health, is looking for individuals to participate in clinical studies. Participating in clinical trials allows you to play an active role in research on the nature and causes of many disorders of the brain and nervous system, and to possibly help physician-scientists develop future treatments. The information below is designed to help you quickly learn about actively recruiting research studies for which you or someone you know may be eligible.


The purpose of this study is to determine if taking inosine at doses that raise urate levels can slow the progression of Parkinson’s disease (PD).

Urate, also known as uric acid, is a natural antioxidant that is found in the blood and brain. Antioxidants are substances that prevent or slow oxidative damage to the body. Research suggests that urate also may protect brain cells that are lost due to PD. Scientific studies have shown that increased urate levels are associated with a slower rate of progression in PD, and that people with naturally high urate levels have a lower risk of developing PD.

In SURE-PD3, researchers will elevate blood urate levels with inosine. Inosine has been used by many people and earlier stage clinical trials showed that it was well tolerated and can safely raise urate levels in the body. When taken by mouth, inosine is absorbed by the body and converted into urate.

Approximately 300 participants with early-stage PD have been enrolled in this double-blinded, placebo-controlled study at 60 centers across the U.S. After 2 screening visits and DaTscan brain imaging, eligible participants were assigned to receive inosine or a placebo (an inactive substance) orally, up to three times per day for 2 years.

The duration of the study for participants is about 28 months and includes at least 12 site visits and follow-up via telephone.

Eligibility Criteria:


  • Fulfillment of diagnostic criteria for idiopathic (typical) PD with at least two of the cardinal signs of PD (e.g., tremor at rest, slowness) as assessed by the doctor/site investigator.
  • Absence of current or imminent (within 90 days of enrollment) PD disability requiring dopaminergic medication, as assessed by the site investigator.
  • Diagnosis of PD made no more than 3 years prior to first screening visit.
  • Non-fasting serum urate ≤ 5.7 mg/dL at first screening visit.


  • Normal results of a dopamine transporter (DAT) brain scan (i.e., without evidence of dopamine deficit).
  • History of gout, kidney stones containing uric acid or urate, recurrent stones of unknown type, heart attack, or stroke.
  • Low urine pH (≤ 5.0) or low kidney function (estimated glomerular filtration rate < 60 ml/min/1.73 m2).
  • Congestive heart failure with a documented ejection fraction below 45%, or a history of severe chronic obstructive pulmonary disease.
  • Signs of dementia or significant cognitive impairment (assessed as Mini Mental State Exam score < 25).
  • Use of any anti-parkinsonian medication within 60 days of baseline, or in excess of 90 days, except that a stable dose of a monoamine oxidase-B (MAO-B) inhibitors like rasagiline or selegiline is allowed.
  • Use of the following within 30 days prior to the baseline visit: inosine, more than 50 IU of vitamin E daily, or more than 300 mg of vitamin C daily, methylphenidate, amphetamines, monoamine oxidase-A inhibitors, neuroleptics or other dopamine blocking drugs.
  • Use of the following within 90 days prior to the DAT neuroimaging screening evaluation: modafinil, armodafinil, metoclopramide, alpha-methyldopa, methylphenidate, or amphetamine derivative.
  • Known unstable medical or psychiatric condition that may compromise participation in the study.
  • Participation in another investigational treatment study within 30 days prior to the baseline visit.

Study Design:

Allocation: Randomized, Endpoint Classification: Efficacy Study, Intervention Model: Parallel Assignment, Masking: Double Blind (Subject, Caregiver, Investigator, Outcomes Assessor)

Study Location:

Multiple U.S. Locations