Clinical Trials for Parkinson's Disease

Clinical trials are the only path through which new treatments reach the people who need them. Every medication and procedure currently available for Parkinson's disease — from levodopa to deep brain stimulation — was proven safe and effective through clinical trials. As of early 2026, more than 200 interventional trials for Parkinson's disease are actively recruiting participants on ClinicalTrials.gov, yet most studies struggle to enroll enough volunteers. This guide explains how trials work, how to find them, and what to expect if you decide to participate.

What Is a Clinical Trial?

A clinical trial is a carefully designed research study that tests a medical intervention — a drug, device, surgical procedure, behavioral therapy, or diagnostic tool — in human volunteers. Clinical trials follow strict protocols approved by institutional review boards (IRBs) and, in the United States, are overseen by the Food and Drug Administration (FDA). These safeguards exist to protect participant safety and ensure that results are scientifically valid.

Before a treatment can be tested in humans, it must show promise in laboratory and animal studies (preclinical research). Even after preclinical success, most experimental treatments fail somewhere in the clinical trial process — this is normal and expected, not a sign that the research was wasted. Negative results are as scientifically valuable as positive ones because they help the field focus resources on more promising approaches.

Phases of Clinical Trials

Clinical trials progress through a series of phases, each with a specific purpose:

• Phase 1 (Safety): Tests safety, dosage, and side effects in a small group of 20 to 100 people, often including healthy volunteers or people with the disease. The primary question: Is this treatment safe, and what dose should be used? Duration: several months to a year.
• Phase 2 (Efficacy Signals): Tests whether the treatment works and further evaluates safety in a larger group of 100 to 300 people with the disease. The primary question: Does this treatment show evidence of benefit? Many promising treatments fail at this stage. Duration: one to three years.
• Phase 3 (Confirmatory): Confirms effectiveness, monitors side effects, and compares the treatment to existing therapies or placebo in a large group of 300 to 3,000 or more participants. This is the phase that typically determines whether the FDA will approve a treatment. Phase 3 trials are the most expensive and longest, often running two to five years. Examples in Parkinson's: the prasinezumab Phase 3 trial (900 patients, initiated November 2025) and the bemdaneprocel exPDite-2 trial.
• Phase 4 (Post-Approval): Studies that monitor long-term safety, effectiveness, and optimal use in the real-world population after a treatment has been approved.

Randomization, Placebos, and Blinding

Many clinical trials are randomized — participants are assigned by chance (like flipping a coin) to receive either the experimental treatment or a comparator (a placebo or the current standard treatment). Double-blind trials go further: neither the participant nor the research team knows who is receiving which treatment, eliminating unconscious bias in assessing results.

Receiving a placebo does not mean receiving no care. In Parkinson's trials, all participants continue their standard treatment (levodopa, dopamine agonists, etc.), and the experimental therapy is typically added on top of that baseline. You will never be asked to forgo necessary medical treatment without your explicit, informed agreement.

Some surgical trials use "sham surgery" controls, where the control group undergoes a partial procedure (such as having a small hole drilled in the skull) without the actual intervention. This design is ethically debated but scientifically important because the placebo effect in surgical trials can be substantial.

Why Participate in a Clinical Trial?

• Access to new treatments. Clinical trials offer access to therapies not yet available to the public. For Parkinson's disease, where current treatments manage symptoms but do not slow progression, experimental therapies represent the possibility of something fundamentally better.
• Contributing to science. Every trial participant advances the understanding of Parkinson's disease. Even trials with negative results inform future research. The Michael J. Fox Foundation awarded 142 new research grants totaling $101 million in late 2025 and early 2026 — most of these projects depend on volunteer participants to succeed.
• Enhanced medical monitoring. Trial participants typically receive more frequent and thorough medical attention than standard clinical care provides, including additional imaging, blood work, and specialist evaluations at no cost.
• Helping future patients. The treatments available today exist because past patients volunteered. Participation is a way of paying it forward.

How to Find Parkinson's Clinical Trials

ClinicalTrials.gov

ClinicalTrials.gov, maintained by the U.S. National Library of Medicine, is the most comprehensive listing of clinical studies worldwide. It is a legal requirement for most trials conducted in the United States to be registered here. To search:

1. Visit clinicaltrials.gov and enter "Parkinson's disease" as the condition or disease.
2. Use filters to narrow results by recruitment status (select "Recruiting" to see studies currently accepting participants), location (your city or state), study phase (Phase 1, 2, 3, or 4), and study type (interventional vs. observational).
3. Each listing includes the study purpose, eligibility criteria (age, disease stage, current medications, etc.), study locations and contact information, and the trial registration number (NCT number).
4. Use the NCT number to ask your neurologist about a specific trial or to look up published results.

Tip: Do not be discouraged if search results seem overwhelming. Start by filtering for "Recruiting" status and your geographic area. Many trials list a toll-free contact number for inquiries.

Fox Trial Finder

The Michael J. Fox Foundation's Fox Trial Finder (foxtrialfinder.michaeljfox.org) is a free matching service specifically designed for Parkinson's disease. The process works as follows:

1. Create a profile with your basic health information: age, diagnosis date, current medications, and symptoms.
2. The system matches your profile against eligible trials and presents options ranked by relevance.
3. You receive notifications when new matching trials open.
4. Caregivers, people at genetic risk, and healthy volunteers can also create profiles — many trials need control participants.

Fox Trial Finder is an excellent starting point because it is curated for Parkinson's and presents information in plain language. However, ClinicalTrials.gov is more comprehensive and should also be checked.

Your Neurologist or Movement Disorder Specialist

Your neurologist may be conducting trials or can refer you to colleagues who are. Academic medical centers and university hospitals are the most common trial sites. If you are seen at a community practice, ask specifically whether there are trials at nearby academic centers that you might be eligible for.

The Parkinson's Foundation Helpline

The Parkinson's Foundation provides trial matching assistance through its Helpline at 1-800-4PD-INFO (1-800-473-4636), available Monday through Friday, 9 a.m. to 7 p.m. ET. Staff can help you understand trial options and navigate the enrollment process.

What to Expect as a Participant

Screening and Eligibility

Before enrollment, you undergo a screening process to determine eligibility. This typically includes a neurological examination, blood tests, cognitive assessments, brain imaging (MRI or DaTscan), and a thorough review of your medical history and current medications. Eligibility criteria vary widely by trial:

• Some trials seek recently diagnosed patients (within 2-3 years of diagnosis).
• Others seek people at specific disease stages or with particular symptoms.
• Gene therapy and stem cell trials may require patients to be levodopa-responsive.
• Genetic trials (LRRK2, GBA) may require specific genetic mutations.
• Biomarker studies may accept people who have not yet been diagnosed but have risk factors (such as REM sleep behavior disorder).

Not meeting eligibility criteria for one trial does not mean you are ineligible for all trials. Criteria are specific to each study's scientific question.

Informed Consent

Before participating, you receive a detailed informed consent document explaining the study purpose, procedures, duration, potential risks and benefits, alternatives to participation, your rights as a participant, and how your privacy is protected. Key points about informed consent:

• Take your time reading the document. There is no rush.
• Ask the research team to explain anything you do not understand.
• Discuss it with your family, your neurologist (if they are not the trial investigator), and anyone else whose input you value.
• Signing is not a permanent commitment — you can withdraw at any time for any reason.

During the Trial

Participation involves regular study visits that may include physical examinations, questionnaires, blood draws, imaging studies, and cognitive testing. Between visits, you may need to take study medication on a specific schedule, wear a monitoring device, or report symptoms through an app or diary. The time commitment varies:

• Observational studies: Typically require visits every 3-6 months with minimal intervention between visits.
• Drug trials: May require monthly or quarterly visits over 1-3 years.
• Surgical trials (gene therapy, stem cell, DBS): Require the surgical procedure plus frequent follow-up visits over 1-5 years.

Travel to the study site, parking, and time off work should be factored into your decision. Many trials offer compensation or reimbursement for travel expenses. Some newer trials incorporate telemedicine visits and home-based assessments to reduce the travel burden.

Your Rights as a Participant

• You can withdraw at any time, for any reason, without penalty and without affecting your standard medical care.
• You have the right to know all known and potential risks before agreeing to participate.
• Your personal health information is protected by federal privacy laws (HIPAA) and additional research-specific protections.
• An independent Data Safety Monitoring Board (DSMB) reviews safety data throughout the trial and can pause or stop the study if safety concerns arise.
• If significant new information emerges during the trial that affects the risk-benefit balance, you must be informed and given the opportunity to reconsider your participation.

Types of Parkinson's Trials

Parkinson's clinical trials are not limited to testing new drugs:

• Interventional drug trials: Testing new medications, including disease-modifying therapies (prasinezumab, LRRK2 inhibitors), symptomatic treatments (tavapadon), and repurposed drugs (GLP-1 agonists).
• Device and surgical trials: Testing adaptive DBS, focused ultrasound, and drug delivery devices.
• Cell therapy and gene therapy trials: Testing stem cell transplants (bemdaneprocel) and gene therapy (AB-1005, AADC, GBA).
• Observational studies: Tracking disease progression, symptoms, and biomarkers over time without any intervention. The PPMI (Parkinson's Progression Markers Initiative) is the largest and most impactful example. These are lower risk and scientifically essential.
• Exercise and rehabilitation trials: Testing specific exercise programs, physical therapy approaches, or speech therapy techniques.
• Caregiver studies: Research on caregiver interventions, stress reduction, and support strategies. Caregivers can directly participate in research.
• Genetic studies: Studying how genetic risk factors influence disease progression and treatment response. Programs like PD GENEration (Parkinson's Foundation) offer free genetic testing and counseling while contributing to research.

Major Trials Currently Recruiting (Early 2026)

The following are among the most significant Parkinson's trials recruiting participants as of early 2026. This list is not exhaustive; check ClinicalTrials.gov and Fox Trial Finder for a complete, up-to-date listing.

• Prasinezumab Phase 3 (Roche): Anti-alpha-synuclein antibody. 900 participants, 2-year treatment. For people with early Parkinson's disease.
• exPDite-2 (BlueRock/Bayer): Bemdaneprocel stem cell therapy, Phase 3. The first large-scale cell therapy trial for Parkinson's.
• REGENERATE-PD: AB-1005 GDNF gene therapy, Phase 2, enrolling across four countries.
• BEACON (Denali): The LRRK2 inhibitor BIIB122 continues here in LRRK2-variant carriers after its Phase 2b LUMA trial in idiopathic Parkinson's failed and was discontinued in May 2026.
• SLEIPNIR (Cure Parkinson's): A platform trial designed to test multiple disease-modifying drugs efficiently.
• PPMI (Michael J. Fox Foundation): The landmark observational study tracking disease biomarkers and progression. Enrolling people with and without Parkinson's.

Evaluating a Clinical Trial

Before agreeing to participate, consider the following questions:

• Is the trial registered on ClinicalTrials.gov? (All legitimate U.S. trials should be.)
• Is it conducted at a reputable academic medical center or hospital?
• Has it been approved by an institutional review board (IRB)?
• What phase is the trial? (Phase 1 carries the most uncertainty; Phase 3 has a better-established safety profile.)
• Is there a placebo group, and what is the chance of receiving the placebo?
• What is the time commitment, including travel?
• What are the known risks and potential benefits?
• Will I be told my individual results?
• What happens to my care after the trial ends?

Discuss these questions with your neurologist. Be wary of any "trial" that charges you to participate (legitimate trials do not charge for the experimental treatment), is not registered on ClinicalTrials.gov, or makes guarantees about outcomes.

The Importance of Diverse Participation

Parkinson's clinical trials have historically underrepresented women, Black and Hispanic individuals, and people from rural communities. This limits the applicability of results — a treatment proven effective in a predominantly white, urban, male study population may not work the same way for everyone, and important safety signals may be missed.

Researchers, advocacy organizations, and the FDA are actively working to improve diversity in Parkinson's trials through outreach, decentralized trial designs (allowing remote participation), translated materials, and partnerships with community health centers. If you belong to an underrepresented group, your participation is especially valuable. The Parkinson's Foundation Helpline (1-800-4PD-INFO) can help connect you with studies actively seeking diverse participants.

Common Concerns Addressed

"Will I Get a Placebo Instead of Real Treatment?"

Some trials use placebos, but you will always be informed in advance if this is possible. You will never be asked to stop your current Parkinson's medications unless that is specifically part of the study design and clearly explained in the informed consent. Most Parkinson's trials use an "add-on" design where the experimental treatment is added to your existing medication regimen. Many trials with placebo groups offer an open-label extension phase afterward, where all participants receive the active treatment.

"Is It Safe?"

All clinical trials carry some risk — that is inherent in testing something new. Multiple layers of oversight protect you: IRB approval, FDA regulatory review, ongoing DSMB monitoring, and the research team's vigilance. Phase 1 trials carry the highest uncertainty because the treatment has never been tested in humans before, while Phase 3 trials test treatments whose safety profile is better established through years of prior testing.

"I Live Far from a Major Medical Center"

Geographic barriers are real, but several developments are improving access. Many trials now incorporate telemedicine visits, home-based nursing assessments, and wearable device monitoring to reduce required travel. Some trials reimburse travel expenses or provide transportation assistance. Fox Trial Finder allows you to search by location and may identify satellite sites closer to you.