Glossary Placebo-controlled Principal investigator Statistical significance A type of clinical trial in which a group of participants is randomly assigned to receive a placebo (inactive substance) for comparison to the standard of care (control) or intervention. The researcher, often a doctor, who oversees and leads an entire clinical trial or study. A number that refers to whether the study’s results are highly likely to be true or could have occurred purely by chance. Note that statistically significant does not necessarily mean highly important. See also: placebo Placebo effect A beneficial physical or emotional change that occurs after taking a placebo (inactive substance). This phenomenon is thought to result, at least in part, from expectations of benefit. (In other words, the more a person believes they will benefit, the more likely it is they will experience benefit.) To separate out this effect from a drug or therapy’s true benefits, clinical trials typically use placebo-controlled designs. See also: placebo; placebo-controlled Positron Emission Tomography (PET) scan A Positron Emission Tomography (PET) scan is a specialized imaging test that uses a small amount of radioactive medication to study the function of the brain. For example, researchers are looking to visualize alpha-synuclein protein in the brain with PET scans; this could serve as a biomarker and way to measure the impact of drugs in trials. See also: alpha-synuclein, biomarker Pre-clinical Research that is not conducted on humans. Before a drug can enter clinical trials, pre-clinical models must first evaluate its feasibility and safety. Protocol The written description of a clinical trial or study that describes its objectives, design and methods, as well as inclusion and exclusion criteria. See also: exclusion criteria; inclusion criteria Randomized A strategy in which participants are assigned to one group in a clinical trial or study by a methodological process that mimics chance. In placebo- controlled interventional trials, one group of participants is randomized to an intervention and another is assigned to placebo. See also: placebo Recruiting A term used to indicate that a study is open for enrollment and needs participants. Repurposing Taking an existing drug that has been developed (and typically FDA-approved) for one condition and using it to treat another. Clinical trials are necessary to repurpose, or reposition, a therapy to ensure that it is safe and efficacious in those with Parkinson’s. SNCA A gene that directs the production of the alpha-synuclein protein. A mutation in the SNCA gene is the basis for a rare, inherited form of Parkinson’s. See also: alpha-synuclein 48 Navigating Clinical Trials: A Guide for Parkinson’s Patients and Families Study funder The study funder provides financial support for research. Funding can come from a variety of individuals or organizations, including foundations, pharmaceutical companies and federal agencies, such as the National Institutes of Health. Study sponsor The study sponsor is the individual or organization who oversees the study. The sponsor initiates, conducts and is responsible for the research. Symptomatic therapy A treatment that eases the symptoms of a disease but does not address the underlying disease process. All currently available Parkinson’s therapies are symptomatic; they do not slow disease progression. Telemedicine A field of medicine that delivers health care through electronic, two-way, real-time interactive communication between individuals and their physicians or other providers. Tolerability The degree to which effects of a drug or therapy can be tolerated by a patient, or how much these effects impact a person’s lifestyle or day-to-day activities.