Objective: The STEM-PD trial evaluates safety, tolerability, and feasibility of intraputaminal transplantation of STEM-PD, a dopaminergic(DA) progenitor product derived from a clinical-grade human embryonic stem cell (hESC) line, in patients with moderate Parkinson’s disease (PD). This is a 3-year first-in-human (FIH), open-label, multicentre, single-arm, dose-escalation study. We report 12-month primary safety and interim efficacy data.

Background: PD is characterized by progressive degeneration of nigral dopaminergic neurons causing disabling motor symptoms. Cell replacement strategies aim to restore dopaminergic function. Early trials using fetal ventral mesencephalic tissue demonstrated survival of transplanted neurons and symptomatic benefit in some patients but were limited by ethical, logistical, and standardization challenges. Pluripotent stem cell–derived products offer a scalable alternative. STEM-PD is a cryopreserved, off-the-shelf DAprogenitor product derived from hESCs (NCT05635409).

Method: Participants were recruited at Skåne University Hospital (Lund, Sweden) and Cambridge University Hospital (UK). Participants received bilateral intraputaminal grafts at two escalating doses (n=4/n=4) transplanted sequentially with predefined safety intervals.  Immunosuppression (basilixumab, tacrolimus, prednisolone, azathioprine) was for 12 month. The primary endpoint was safety, defined as the incidence and nature of adverse events (AEs) and serious adverse events (SAEs) within 12 months and absence of space-occupying lesions on MRI. Secondary endpoints include OFF-medication motor function, levodopa equivalent daily dose (LEDD), and graft survival assessed by [18F]F-DOPA and dopamine transporter PET ([18F]FE-PE2i). Assessments include MRI, PET imaging, MDS-UPDRS III (ON/OFF), Hauser diary, dyskinesia and cognitive/psychiatric tests, and quality-of-life measures.

Results: Seven participants completed 12-month follow-up. No SAEs related to the cell product occurred. [18F]F-DOPA PET demonstrated indications of early graft survival. Six of seven participants substantially reduced LEDD. No graft-induced dyskinesias were observed. Follow-up to 36 months will assess long-term safety, clinical outcomes, and dopaminergic function.

Conclusion: These findings support further clinical development of STEM-PD and evaluation in larger patient cohorts.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/stem-pd-an-open-label-phase-i-ii-trial-of-transplanted-human-pluripotent-stem-cell-derived-dopaminergic-progenitor-cells-in-parkinsons-disease/