AAN 2026: Parkinson’s cell therapy trial shows sustained benefits

BlueRock Therapeutics’ investigational cell therapy bemdaneprocel continues to show potential to control motor symptoms in people with Parkinson’s disease, with the benefits of a single dose sustained for up to three years in a small Phase 1 trial.

These findings from the Phase 1 exPDite study (NCT04802733), presented by Harini Sarva, MD, a neurologist at Weill Cornell Medical Center, at the American Academy of Neurology Annual Meeting, taking place April 18-22 in Chicago and online.

Sarva’s talk was titled, “Continued Evaluation of Safety, Tolerability, and Clinical Outcomes in Participants with Parkinson’s Disease Throughout 3 Years After Bemdaneprocel Administration.”

The observed benefits of bemdaneprocel were greatest with the higher of two tested doses. An ongoing Phase 3 trial called exPDite-2 (NCT06944522) is testing the safety and efficacy of that dose in a larger group of people with Parkinson’s. The study, which started dosing last year, is enrolling about 102 participants in the U.S., Canada, and Australia.

In Parkinson’s disease, dopaminergic neurons, which produce the signaling molecule dopamine, are progressively lost, leading to movement problems and other Parkinson’s symptoms. Standard Parkinson’s treatments like levodopa aim to temporarily boost dopamine levels. However, many patients who use them experience off periods, or motor fluctuations, where movement problems get worse as the medication wears off between doses.

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Cell therapy aims to replace lost neurons

Bemdaneprocel is designed to replace lost dopaminergic neurons and provide sustained symptom control. It involves surgically implanting dopaminergic neuron precursors, derived from human embryonic stem cells, into a brain region important for motor function. There, the cells are expected to grow into mature dopaminergic neurons and restore more normal signaling.

ExPDite evaluated the cell therapy’s safety and efficacy in 12 adults with Parkinson’s disease who were experiencing motor fluctuations on standard treatments. Five people received a low dose (0.9 million cells per side of the brain) and seven received a high dose (2.7 million cells per side). All received immunosuppressive medications for a year post-transplant.

The study met its main goal of demonstrating good safety and tolerability after a year. Data up to two years showed that the therapy tended to ease or stabilize motor symptoms and shorten off episodes.

After the two-year exPDite trial, all participants enrolled in an ongoing extension study (NCT05897957), where safety and clinical outcomes are being monitored for up to five years post-transplant.

Sarva’s presentation covered data up to three years post-transplant.

Motor symptoms were assessed with the Movement Disorder Society-United Parkinson’s Disease Rating Scale (MDS-UPDRS) Part III, in both an off- and on-medication state.

As previously reported, participants in the low-dose group “maintained stability” in MDS-UPDRS scores over the three-year observation period, while those who received the higher dose saw a “trend towards improvement” in both on- and off-medication states, according to Sarva.

Researchers observed a similar pattern in data from at-home diaries. People who received the higher dose tended to report declines in daily off time and increases in on time without troublesome dyskinesia — where symptoms are well-controlled without involuntary movements — over the course of three years.

Doses of Parkinson’s medications and health-related quality of life remained relatively stable over three years in both treatment groups.

When asked whether there was evidence that the transplanted cells were still engrafted, Harva said that the combined PET scans performed each year, including at year three, showed that the cells remained engrafted and had survived.

The treatment also demonstrated “an excellent safety profile,” according to Harva, with most side effects mild to moderate.

Harva noted that while the data are promising, researchers must “take this with a grain of salt” given the small number of trial participants and their variability in age, disease duration, medication doses, and other factors. “Any one of those factors can certainly skew the data,” Harva said.

Nevertheless, the good safety profile and trends toward clinical improvement “support further development of this product,” she said.

In exPDite-2, participants will be randomly assigned to receive the high dose of bemdaneprocel or a sham surgery without any active cell therapy, which will serve as a control group for the surgical procedure. The main goal is to monitor changes in daily on-time without troublesome dyskinesia.

In response to a question about how the therapy, if it reaches the market, might compare to deep brain stimulation (DBS), Harva said there will definitely be a role for it, as some patients do not want DBS but prefer a more biological approach to restore dopamine.

She added that it is hard to know whether the therapy would be used before DBS, and that decisions should be made on a patient-by-patient basis. For patients with motor fluctuations, it could provide another treatment option. However, for those with severe dyskinesia, she said she would still recommend DBS or focused ultrasound.