TRIAL PHASE Definitions

Food and Drug Administration (FDA) categories for describing the clinical trial of a drug based on the study's characteristics, such as the objective and number of participants. There are five phases:
Early Phase 1: Exploratory study involving very limited human exposure to the drug, with no therapeutic or diagnostic goals (for example, screening studies, microdose studies)
Phase 1: Studies that are usually conducted with healthy volunteers and that emphasize safety. The goal is to find out what the drug's most frequent and serious adverse events are and, often, how the drug is metabolized and excreted.
Phase 2: Studies that gather preliminary data on effectiveness (whether the drug works in people who have a certain disease or condition). For example, participants receiving the drug may be compared with similar participants receiving a different treatment, usually an inactive substance (called a placebo) or a different drug. Safety continues to be evaluated, and short-term adverse events are studied.
Phase 3: Studies that gather more information about safety and effectiveness by studying different populations and different dosages and by using the drug in combination with other drugs.
Phase 4: Studies occurring after FDA has approved a drug for marketing. These including postmarket requirement and commitment studies that are required of or agreed to by the sponsor. These studies gather additional information about a drug's safety, efficacy, or optimal use.


66 exercise-related trials as of 1/22/19

6 gene therapy trials as of 1/22/19


      Status of PD Clinical Trials Registered on (as of Feb. 2019)


* 26 trials are combined Phase 1/Phase 2 OR combined Phase 2/3. 

Note: 465 total active trials includes 285 recruiting, 67 not yet recruiting, 25 enrolling by invitation and 88 no longer recruiting.

An INTERVENTIONAL STUDY (or Clinical Trial) is a clinical study in which participants are assigned an intervention such as a medication, device, or procedure, so that researchers can evaluate its effects on biomedical or health-related outcomes.  Participants may receive diagnostic, therapeutic, or other types of interventions.  See trial phase descriptions at bottom of page. 


As of January 22, 2019, there were 465 active PD interventional studies worldwide listed on This includes trials that are recruiting, not yet recruiting, enrolling by invitation or no longer recruiting.

... and click on country to view by state and by individual trial.


6 telemedicine/telehealth trials

as of 1/22/19

10 alpha synuclein trials as of 1/22/19

PHASE Not Applicable

Parkinson's Disease interventional studies

8 cognitive therapy trials as of 1/22/19

Analyzing the Parkinson's disease clinical trial pipeline to facilitate patient collaboration in research.


66 DBS-related trials as of 1/22/19

To view publications of completed studies, you can search PubMed to find publication abstracts and authors, as well as links to full publications. Helpful keywords to use in a search are trial name, trial NCT# (i.e., trial ID), principal investigator name, and sponsor name.  PubMed is a free resource developed by the National Center for Biotechnology Information (NCBI) at the U.S. NIH.