Stem Cell-Based Therapies to Treat Parkinson’s

Updated: June 17 2025

Parkinson’s is driven by decreased levels of dopamine, a chemical produced in the brain responsible for maintaining smooth movement and motor control, as well as influencing memory, feelings of pleasure, and motivation. In Parkinson’s, this neurodegeneration – a progressive loss of dopamine-producing neurons – can cause a range of motor and non-motor symptoms experienced by people living with the condition, significantly impacting an individual’s quality of life, relationships, and ability to perform certain functions. By the time the hallmark symptoms of Parkinson’s manifest and someone is more likely to receive a diagnosis, it is estimated that they have already lost about half of their dopamine neurons. 

Current medications for Parkinson’s typically include symptomatic treatments that focus on alleviating motor symptoms (such as tremors) by giving artificial forms of dopamine, for example, levodopa. However, disease-modifying treatments that focus on halting progression and fixing the root biological cause of the disease are currently lacking. Recently, treatments that harness the power of stem cells have been in the spotlight for their innovative and promising approaches to replace and restore those dopamine neurons that are progressively lost in the brains of people living with Parkinson’s. 

What are stem cells? 

Stem cells can be thought of as the universal cells or building blocks of our organs. They are the cells that branch out and become all other cells including brain, skin, and muscle cells. Recently, researchers have begun to focus on stem cells as a potential way to replace the damaged or lost dopamine-producing neurons that drive Parkinson’s. 

There are different sources of stem cells as well, including: adult, embryonic, and induced pluripotent stem cells. Adult stem cells are found all over the body, where they are constantly acting to replace lost or damaged cells. It’s even been estimated that our adult stem cells regenerate and replace 330 billion cells in our body every day (roughly 1% of all cells in the body). However, adult stem cells are restricted and can only replace cell types from the organ where they normally reside, and the adult stem cells naturally found in our brain are not active enough to replace the cells that are damaged in Parkinson’s. 

On the other hand, embryonic stem cells (ESCs) can generate any cell type in the entire human body (including brain cells), making them an interesting tool for therapeutic research. ESCs that are used for research come from embryonic tissues that are left unused from in vitro fertilization (IVF) procedures (and are otherwise usually destroyed). There are ethical considerations and extensive governmental regulations that must be met before these cells can be used in research to ensure proper safety and ethical sourcing. 

Induced pluripotent stem cells (iPSCs), on the other hand, are stem cells that are created in the lab by taking commonly available cells (such as skin cells or blood cells) from human tissue and turning them back into a stem cell state. These iPSCs can then be used to generate other cell types (such as dopamine-producing neurons) and transplanted back into the body. Since there is the potential to use the patient’s own cells to generate the iPSCs as well, there could be a smaller risk of rejection for the transplanted cells. 

Stem cell therapy for Parkinson’s 

For years, researchers have been working to design an effective stem cell therapy for Parkinson’s, on the basis that they can potentially create new and functional dopamine-producing cells to replace the ones that are lost or damaged in Parkinson’s. Parkinson Canada continues to fund groundbreaking research in all therapeutic areas, including stem cells, such as a project led by Dr. Tiago Cardoso at Université Laval who worked on genetic engineering of stem cells to improve cell survival and circuit formation of transplanted cells. 

Some groups have developed therapies that use ESCs to generate dopamine precursor cells in the lab that will safely graft to a patient and function in the same way as the dopamine-producing cells that were originally lost in Parkinson’s-affected brains. Due to the abilities of ESCs to self-renew and divide in the lab, they are posing a promising source of stem cells for therapeutic purposes, since every patient that is treated requires several million transplanted cells. This method allows for the production of large-scale batches of dopamine-producing cells that can be tested in animal models to ensure the cells are safe before they are used in human clinical trials. 

Several other groups have taken an approach that starts with either healthy adult donor cells (allogenic) or an individual’s own skin cells (autologous).  These iPSC-based approaches also generate dopamine precursor cells which will be transplanted into the brains of Parkinson’s patients. However, due to the personalized nature of using patient-specific iPSCs, the process can be much more laborious, time-consuming, and expensive, with some estimates putting the cost of treating one patient at $800,000. 

Two major risks of any cell transplantation therapy are: 1) the potential for tumor formation from cells that still retain stem cell-like characteristics, and 2) rejection of the transplanted cells. Therefore, before any cells are transplanted into patients, researchers implement rigorous methods in the lab that ensure the cells used for transplantation are a pure population of dopamine precursor cells. To prevent rejection of transplanted cells, many groups include the use of immunosuppressive drugs for at least 12 months. Interestingly, transplants that use the patient’s own cells as the starting material don’t need to use these immunosuppressive drugs, as was successfully shown in a clinical research study from Harvard University in one Parkinson’s patient. 

Early clinical trial results show promise 

BlueRock Therapeutics recently published results from a Phase I clinical trial, in which 12 Parkinson’s patients both in Canada and the United States received a surgical transplantation of either a low dose (1.8 million cells) or high dose (5.4 million cells) of the stem cell-derived therapeutic bemdaneprocel. These patients were followed for 18 months to evaluate overall safety and tolerability. Changes in motor symptoms, along with several other measures, were also evaluated. 

Over the follow-up period, it was reported that none of the patients had any serious adverse events related to the therapeutic. Imaging scans used to visualize and assess dopamine activity also showed that the after the 18 months of follow-up, transplanted dopamine cells were likely surviving and engrafting in the patients’ brains. Although more data will be needed, some trends in improvement in motor symptoms were experienced by patients. With these findings in place, BlueRock Therapeutics is expanding this work to a Phase III clinical trial to begin in mid-to-late 2025. The expanded trial plans to involve 102 patients and will evaluate changes in ON-time, as well as changes in movement and quality of life scores, plus continued monitoring of safety and tolerability of the therapy. 

The CiRA group in Kyoto, Japan has also concluded a Phase I/IIa clinical trial, with the goal of testing their iPSC-based stem cell therapy in seven Parkinson’s patients. Initial results were recently published in April of 2025, finding no serious adverse effects while the grafts appeared to successfully hold and slightly increase in volume over the 24-month follow-up period. Four patients also demonstrated improvements in their motor function during the same period. They have not yet announced if they intend to begin more advanced trials based on these results. 

The STEM-PD group has also begun a Phase I/IIa clinical trial in Sweden. They have performed cell transplantation surgeries on four patients with moderately advanced Parkinson’s. They were injected with the low dose (7 million cells) and monitored for 6-10 months for safety. Regrettably, STEM-PD has announced that one of the participants in their study has died due to an opportunistic infection, but not as a result of the stem cell therapeutic nor the surgical implantation.  They plan to continue with the next cohort of four more participants, who will receive a higher dose (14.2 million cells) of the therapeutic. PET imaging 6-12 months after implantation in the current cohort demonstrated dopamine cell survival, and evaluation will continue for a total duration of three years to fully evaluate how effective this treatment is at reducing clinical motor symptoms such as time spent in the “OFF” state. 

Aspen Neuroscience has begun a Phase I/IIa clinical trial of a treatment taking skin cells from individual Parkinson’s patients to generate iPSCs and then grow millions of dopamine-producing cells for transplantation back into the patient’s own brain. The company has transplanted the first 2 cohorts of patients with the therapy and plans to follow them for the next three years to determine the safety and efficacy of the treatment, with data to be presented at the 2025 International Conference on Parkinson’s Disease and Movement Disorders in October of 2025. Initial results have demonstrated that the therapeutic was well-tolerated with no adverse effects in participants. 

S.BIOMEDICS has begun their TED-A9 Phase I/IIa stem cell study utilizing ESCs to replace dopamine neurons in participant brains. They have completed dosing and early monitoring of 12 participants so far: six in the low-dose group (3.15 million cells) and six in the high-dose group (6.30 million cells). At the initial study follow-up of 12 months, no adverse effects were observed, appeared to be successfully engrafting, and many participants demonstrated improvements in wearing-off and motor symptoms like freezing of gait. They plan to continue monitoring the participants for another four years for a five-year total study period. 

Lastly, the Mass General Brigham healthcare and research network in Boston has received FDA approval for a stem cell study using iPSCs and has begun dosing the first three participants with a dopamine replacement therapeutic derived from stem cells derived from the participant’s own blood. Once all six planned participants have been dosed, they plan to track the participants for 12 months, with another check-in at 18 months to determine safety and efficacy of the therapeutic, and if there are any changes in symptoms. 

It is important to note that stem cell transplantation approaches are still experimental, and none have been approved by Health Canada or the FDA for widescale use in PD. It’s still a developing field, and while there are many promising therapeutics currently making their way through the clinical trial pipeline, nothing is available yet for standard clinical use. It is recommended that people living with Parkinson’s be cautious of any group that is selling a cell transplantation product or surgery for Parkinson’s that is not associated with an approved clinical trial, and to discuss these treatments further with their medical team. 

Across these 6 active clinical trials, 54 people living with Parkinson’s will have been dosed with new stem cell-based therapeutics to replace the dopamine-producing neurons that have been lost. And across the stem cell therapy field as a whole, 1200 participants have been collectively dosed across 115 clinical trials, to treat various forms of cancer, blindness, spinal cord injury and now Parkinson’s. Future plans are also on the way for many more participants in more advanced trials as the overall safety and efficacy of these treatments continue to be demonstrated. It’s very encouraging to see promising advancements in the field toward developing true disease-modifying therapies, both in the studies we’ve highlighted here and many others happening elsewhere. As these Phase I/II trials conclude and advance into more large-scale and comprehensive trials, we look forward to seeing how these therapeutics develop and will continue to advocate for this research to take place in Canada to ensure the benefits are brought to our communities affected by Parkinson’s.