September 4, 2026

Stem cell research is opening new possibilities for understanding Parkinson’s disease and developing treatments that may one day replace some of the neurons lost to the condition. It’s very exciting! While this therapy remains experimental and is not yet an approved treatment for Parkinson’s, recent clinical trials have produced encouraging early results that are worth paying attention to.  

 Why Stem Cells are Important to Parkinson’s Research 
Parkinson’s disease develops when dopamine-producing neurons in a region of the brain called the substantia nigra become damaged and die. Since dopamine helps coordinate movement, declining levels lead to symptoms such as slowness, stiffness, and tremor. 

Current treatments include levodopa and deep brain stimulation. These help patients manage symptoms, but do not replace the neurons that have been lost or stop Parkinson’s from progressing. Stem cells are of particular interest because they can be guided in a laboratory to develop into many specialized cell types, including dopamine-producing neurons. 

Researchers are applying this in two main ways: creating laboratory models of Parkinson’s and developing experimental cell-replacement therapies. 

Studying Parkinson’s in the Laboratory 
One important development is the creation of induced pluripotent stem cells, or iPS cells. Scientists can take an adult cell from a person’s skin or blood and reprogram it into a stem-cell-like state. The cell can then be directed to develop into neurons that produces dopamine. 

When the original cell comes from someone living with Parkinson’s, the resulting neurons carry that person’s genetic information. Researchers can study these cells to investigate why certain neurons are vulnerable, and examine how genetic variants affect Parkinson’s, to aid in testing medications. This gives scientists access to living human neurons that would otherwise be extremely difficult to study. The National Institute of Neurological Disorders and Stroke supports the use of stem cell models to investigate neurological conditions and accelerate the development of therapies.  

Neurons grown in a lab cannot reproduce every aspect of Parkinson’s or the complexity of a living brain, however, they provide an important bridge between studies involving animals and clinical research involving people. 

Replacing Lost Neurons 
The more ambitious application of stem cell research is cell replacement. Researchers begin with pluripotent stem cells, which can develop into nearly any type of cell. These may be embryonic stem cells or iPS cells created by reprogramming adult cells. 

Scientists expose the stem cells to a carefully controlled sequence of biological signals that directs them to become immature dopamine-producing neurons. These neuron progenitors are then surgically implanted into the part of the brain involved in movement. The goal is for the cells to survive, mature, connect with existing brain circuits, and provide a more consistent source of dopamine. 

The transplanted cells are not expected to eliminate Parkinson’s. They do not address all the biological processes behind the disease. They are primarily intended to improve symptoms related to dopamine loss. Parkinson’s also causes many non-movement symptoms that may not respond to dopamine cell replacement. 

Clinical Trial Results 
Several small, early-stage trials have now shown that laboratory-produced dopamine neuron progenitors can survive after transplantation into the human brain. 

In a U.S. and Canadian Phase I trial, twelve people received an embryonic stem cell product called bemdaneprocel. Researchers reported evidence the transplanted cells survived and produced dopamine. The study met its initial safety and tolerability goals, and no adverse events were attributed to the treatment during the initial follow-up period. Some participants also experienced improvements in movement measurements.  

A separate Japanese Phase I/II trial involved seven participants who received dopamine progenitor cells made from iPS cells. Researchers reported that the cells produced dopamine. Some participants showed improvements in movement symptoms, but the number of participants was too small to establish effectiveness.  

Results from the European STEM-PD trial were published in July 2026. Eight participants received dopamine progenitor cells derived from embryonic stem cells, and seven completed the twelve-month evaluation. Imaging provided evidence of cell survival in several participants, and six of the seven reduced their Parkinson’s medication. No serious adverse events were attributed to the cell product, but one participant died from an infection while receiving immunosuppressive treatment. Researchers emphasized that longer follow-up and larger controlled studies are needed. 

The Important Work Ahead 
These trials represent important progress in the field of stem cell applications. Researchers have demonstrated that standardized, stem-cell-derived dopamine progenitors can be manufactured, delivered to the brain, and monitored after transplantation. They have not yet found that the approach provides lasting benefits or is appropriate for widespread clinical use, but these preliminary results seem promising. Still to come is evidence of the treatment’s long-term safety, effectiveness, and ideal dosage, while addressing risks associated with surgery, immune rejection, and immunosuppression. Larger controlled trials and longer follow-up will determine whether it can safely provide lasting benefits for people living with Parkinson’s. 

No stem cell product is currently approved by the FDA to treat Parkinson’s, and unapproved treatments offered outside legitimate clinical trials may carry serious health and financial risks. Anyone considering a study should consult a movement disorder specialist and confirm that it is registered with ClinicalTrials.gov. 

To learn more about this topic, register for our upcoming webcast with Dr. Marina Emborg, a leader in stem cell neuroscience research.  

Sources 

National Institute of Neurological Disorders and Stroke. “Parkinson’s Disease.” National Institutes of Health. 

 National Institute of Neurological Disorders and Stroke. “Focus on Stem Cell Research.” National Institutes of Health. 

 Tabar, V., et al. “Phase I Trial of Human Embryonic Stem Cell-Derived Dopaminergic Neurons for Parkinson’s Disease.” Nature, April 16, 2025. 

 Doi, D., et al. “Phase I/II Trial of iPS-Cell-Derived Dopaminergic Cells for Parkinson’s Disease.” Nature, April 16, 2025. 

 Paul, G., et al. “Human Embryonic Stem Cell-Derived Dopaminergic Cells for Parkinson’s Disease: A Phase I/II Open-Label Trial.” Nature Medicine, July 9, 2026. 

 ClinicalTrials.gov. “A Study of Bemdaneprocel in Participants with Parkinson’s Disease.” Identifier NCT04802733. U.S. National Library of Medicine. 

ClinicalTrials.gov. “STEM-PD: Stem Cell-Based Transplantation for Parkinson’s Disease.” Identifier NCT05635409. U.S. National Library of Medicine. 

 U.S. Food and Drug Administration. “Consumer Alert on Regenerative Medicine Products Including Stem Cells and Exosomes.” 

 ClinicalTrials.gov. “Learn About Clinical Studies.” U.S. National Library of Medicine.