A Study to Evaluate the Efficacy and Safety of Intravenous (IV) Prasinezumab in Participants With Early-Stage Parkinson's Disease
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MK-0947 PN-002: An Open-label Study to Evaluate Brain α-synuclein Deposition Using Positron Emission Tomography (PET) and [¹⁸F]MK-0947 in Participants With Parkinson's Disease (PD)
What is Parkinson's disease, and why research matters
Parkinson's starts when a protein called alpha synuclein misfolds and clumps inside brain cells, and the dopamine producing cells in a region called the substantia nigra begin to die. By the time the first tremor appears, roughly half of those cells are already gone. That is why researchers are so focused on the years before diagnosis: constipation, loss of smell, acting out dreams during sleep, and depression can show up a decade early, and a test that detects misfolded alpha synuclein in spinal fluid, published in 2023, can now identify the disease biologically.
Treatment today manages symptoms very well for years, but nothing yet slows the disease itself. That is the gap research is built around. Between August 2024 and February 2025, the FDA approved three new medicines, including a 24 hour pump that delivers levodopa under the skin for people with advanced disease. Deep brain stimulation, an implanted device, has 5 year data showing lasting benefit, and a newer adaptive version adjusts itself in real time. And a surprising amount of current research is about exercise, which is the one intervention with evidence that it may slow progression, now being tested as a treatment with a dose, like a drug.
Types of Parkinson's disease clinical trials
Disease modifying trials. The holy grail: medicines meant to slow or stop the loss of dopamine cells. Antibodies against alpha synuclein, drugs targeting the LRRK2 gene, and repurposed medicines are all in trials. These usually enroll people diagnosed within the last few years, run for 1 to 2 years, and measure how fast symptoms progress. No such drug is approved yet.
Symptom treatment trials. New pills, patches, and pumps that control tremor, stiffness, and "off" periods when levodopa wears off. Also trials for the non movement symptoms that often matter most: constipation, depression, sleep problems, and thinking changes.
Cell and gene therapy trials. Early stage studies that implant lab grown dopamine cells into the brain to replace the ones lost, or deliver genes that help remaining cells survive. The first stem cell therapy reached Phase 3 in 2025. These require brain surgery and enroll carefully selected participants.
Device and stimulation trials. Deep brain stimulation refinements, adaptive stimulation that responds to brain signals, wearable sensors, and non invasive stimulation devices worn at home.
Exercise and rehabilitation trials. One of the most active areas. Studies test how much exercise, how intense, and how early, including in people with early signs but no diagnosis yet. Music based walking programs and digital coaching are also under study.
Biomarker and early detection studies. Finding Parkinson's before the tremor: skin and colon biopsies for misfolded alpha synuclein, imaging, gut microbiome studies, and large cohorts followed for years. Many enroll people at risk who have no symptoms.
Who can participate in Parkinson's clinical trials?
Parkinson's studies usually look at three things. How long ago you were diagnosed, because disease modifying trials want early disease, often within 2 or 3 years, while pump and device studies want people with advanced disease and motor fluctuations. Your stage, described with the Hoehn and Yahr scale from 1 to 5, and often your score on a movement exam called the MDS-UPDRS. And your current medicines: some trials need people not yet on levodopa, others need people whose levodopa is wearing off between doses. Exercise and biomarker studies frequently have the widest doors, and some enroll people with early warning signs like loss of smell or a sleep disorders but no diagnosis. Eligibility always varies by study.
The stages of Parkinson's, and why they matter for trials
Doctors describe Parkinson's with the Hoehn and Yahr scale:
- Stage 1. Symptoms on one side of the body only, usually mild tremor or stiffness. Daily life is barely affected.
- Stage 2. Both sides affected, posture and walking may change, balance still intact.
- Stage 3. Balance problems begin and falls become a risk, but the person is still independent.
- Stage 4. Severe symptoms; standing and walking are possible but need help.
- Stage 5. Wheelchair or bed bound without assistance.
Progression varies enormously: some people stay at stage 1 or 2 for a decade or more. Disease modifying trials mostly enroll stages 1 and 2. Pump, device, and cell therapy studies enroll later stages with motor fluctuations. Knowing your stage and how long since diagnosis tells you at a glance which studies fit.
How to enroll in a Parkinson's clinical trial
Enrolling in a Parkinson's study through our platform takes about 5 minutes, and a family member can help. Here is how it works:
Identify your trial. Use the search bar or filters. Titles often say "early Parkinson's," "advanced Parkinson's with motor fluctuations," or "prodromal" (early signs, no diagnosis yet), so you can tell quickly which ones fit.
Select your preferred location. Enter your city or state in the filter on the left. Cell therapy and device trials run at specialized movement disorder centers, while exercise and digital studies are often closer to home or remote.
Explore study details. Click "Learn More" for goals, procedures, and eligibility, including how long since diagnosis is required, which medicines are allowed, and whether imaging, spinal fluid tests, or surgery are involved.
Complete the health profile. Click "Get started" to begin the 5-step application. Have three things ready: the year you were diagnosed, your current Parkinson's medicines and whether they wear off between doses, and your Hoehn and Yahr stage if your neurologist has told you. Those answers decide eligibility for most Parkinson's studies.
Submit the application. A clinical trial coordinator reviews it and contacts you about whether you may qualify. Nothing is decided until you have gone through informed consent, and participation is voluntary at every step.