Parkinson's disease is driven by the loss of dopamine-producing neurons, and existing drugs that replace the missing dopamine tend to lose effectiveness over time. The STEM-PD trial, led by Professor Malin Parmar at Lund University with clinical partners at Skåne University Hospital and the University of Cambridge, took a more radical approach: transplanting dopamine progenitor cells, derived from human embryonic stem cells, directly into patients' brains. It was the first pluripotent stem cell trial approved in Sweden and the first for Parkinson's disease in Europe.
Eight patients received the cells at two different doses, followed by twelve months of immunosuppression, and seven completed the full year of follow-up. No serious side effects directly linked to the cell product were observed, no graft-induced involuntary movements appeared, and dopamine PET imaging gave early indications of graft survival at six and twelve months. Six of the seven patients who completed follow-up substantially reduced their dopaminergic medication, although the trial's primary purpose was safety rather than efficacy.
The results, published in Nature Medicine, carry particular resonance in Lund, where transplantation of fetal dopamine cells for Parkinson's was pioneered roughly forty years ago. The programme now moves toward a larger phase II trial under a commercial partner, with long-term monitoring of the first cohort continuing. With only eight participants, clinical benefit remains unproven, but the trial establishes that a scalable, stem-cell-derived product can be manufactured, implanted and tolerated, a foundational step for regenerative medicine in neurodegenerative disease.