The hallmark motor symptoms of Parkinsons disease (PD)—such as involuntary movements (called dyskinesia), rigidity, and tremors—are the result of a progressive loss of dopamine-producing neurons in a part of the brain called the basal ganglia. For most patients with PD, managing these symptoms requires long-term treatment with levodopa—a drug that replaces dopamine in the brain—or surgical options like deep-brain stimulation (DBS).
Unfortunately, these treatment options present numerous challenges. As the disease progresses, and more dopamine-producing neurons are lost, existing treatments become increasingly less effective at managing motor symptoms. Even in earlier stages, symptom control remains imperfect, with many patients experiencing periods known as “off” times—when motor symptoms return despite medication.
A recent Phase 1 clinical trial is laying the foundation for a revolutionary new treatment option—bemdaneprocel, an injectable treatment made from stem cells. These cells develop into dopamine-producing neurons, once inside the brain. Unlike current treatments, bemdaneprocel aims to target the root cause of PD motor symptoms by replacing lost neurons. The team, which included researchers from UHN’s Krembil Research Institute (Krembil)—Drs. Alfonso Fasano, Andres Lozano and Suneil Kalia— studied whether injecting bemdaneprocel into the basal ganglia of PD patients is safe.
The trial results were promising. The treatment was well tolerated, with no off-target effects such as graft-induced dyskinesias (new dyskinesias brought on by the injected cells) observed during the 18-month follow-up period. The trial also showed that the newly developed dopamine-producing neurons remained alive 18 months post-injection. Even more importantly, the team saw clinically significant improvements in participants’ motor symptoms—including reduced “off” times. The improvements were also found to be dose-dependent, as patients in the high-dose cohort showed greater improvements than those in the low-dose cohort. Although it is unclear whether these improvements were directly caused by bemdaneprocel treatment—as participants continued taking levodopa throughout the course of this trial—these initial findings offer hope for PD patients.
Despite its small size and focus on safety, the trial’s results suggest real potential for bemdaneprocel as a future treatment. The most recent post-study follow-up, at 24-months after treatment, adds further support. Larger, longer trials will help confirm the therapy’s safety and determine if these early improvements can be replicated. This early success brings us closer to a future where people with Parkinsons have access to therapies that restore function, not just manage symptoms.
The first author on this study is Dr. Viviane Tabar, a Neurosurgeon at the Memorial Sloan Kettering Cancer Centre.
The senior authors on this study are Drs. Lorenz Studer and Claire Henchcliffe. Dr. Studer is the Director of the Center for Stem Cell Biology at the Memorial Sloan Kettering Cancer Centre. Dr. Henchcliffe is the Chair and Stanley van den Noort Professor of Neurology at the University of California Irvine School of Medicine.
Dr. Andres Lozano is the lead investigator on this study at UHN. He is a Senior Scientist at Krembil, and a Professor in the Department of Surgery in the Temerty Faculty of Medicine at the University of Toronto. Drs. Alfonso Fasano and Suneil Kalia also contributed to this study as co-investigators. Dr. Fasano is a Clinician Investigator at the Krembil Brain Institute (Krembil) at UHN, an Affiliate Scientist at the KITE Research Institute (KITE) at UHN, and a Professor in the Department of Medicine at the University of Toronto. Dr. Kalia is a Senior Scientist with Krembil and KITE, and an Associate Professor in the Department of Surgery in the Temerty Faculty of Medicine at the University of Toronto.
This work was supported by BlueRock Therapeutics and UHN Foundation.
BlueRock Therapeutics was founded in 2016 at UHN by Drs. Gordon Keller and Michael Laflamme. In 2019, BlueRock Therapeutics was fully acquired by Bayer AG.
Drs. Tabar and Lozano are scientific advisors for BlueRock Therapeutics (BlueRock). Dr. Sarva is a former consultant for BlueRock. Drs. Irion, Tomishima, Abid and Stemple are employees of BlueRock. Dr. Fasano receives royalties from Springer Nature, the company that publishes the journal, Nature. Drs. Tabar, Lozano, Fasano, Yu, Studer, and Henchcliffe also receive research funding from BlueRock outside the current study.
For a full list of competing interests, see the publication.
Tabar V, Sarva H, Lozano AM, Fasano A, Kalia SK, Yu K, Brennan C, Ma Y, Peng S, Eidelberg D, Tomishima M, Irion S, Stemple W, Abid N, Lampron A, Studer L*, Henchcliffe C*. Phase I trial of hES-cell-derived dopaminergic neurons for Parkinson’s disease. Nature. 2025 Apr 16. doi: 10.1038/s41586-025-08845-y.
*Contributed equally as senior authors on the publication.