STEM-PD Clinical Trial: First-in-Human Results for Parkinson’s Disease Cell Therapy

A first-in-human clinical trial of STEM-PD—a cell therapy derived from human embryonic stem cells—has demonstrated initial safety and tolerability in patients with moderately advanced Parkinson’s disease. Eight participants who received bilateral transplantation of dopaminergic progenitor cells showed no serious adverse events related to the cell product or signs of space-occupying lesions on cranial MRI after 12 months of follow-up.

Study Design and Patient Selection

The STEM-PD trial, registered under NCT05635409, was conducted as an open-label, multicenter, dose-escalation study. Researchers recruited eight participants from Skåne University Hospital in Sweden and Cambridge University Hospital in the UK. Eligible patients were aged 50 to 75 with a diagnosis of Parkinson’s disease for more than five years and a Hoehn–Yahr stage of 3 or less in the “OFF” medication state.

The intervention involved the surgical transplantation of dopaminergic neural progenitor cells, generated from the clinical-grade human embryonic stem cell line RC17. The study evaluated two dose levels: a low dose and a high dose per putamen. Surgical delivery was performed using a frame-based stereotactic technique, with cells deposited along five distinct tracts in each putamen to maximize distribution.

Safety and Immunosuppression Protocols

Because the therapy involves allogeneic cells—tissue from a donor source—all participants were placed on a 12-month triple immunosuppressive regimen. This protocol included basilixumab, tacrolimus, and azathioprine, alongside corticosteroids, to prevent graft rejection. The study design mandated strict safety intervals, including a 6-month pause after the fourth participant to allow for a Data and Safety Monitoring Board (DSMB) review before escalating to higher doses.

The primary safety endpoints focused on the occurrence of adverse events (AEs) and serious adverse events (SAEs) over the first year. Researchers monitored for potential complications such as intracranial hemorrhage, central nervous system infections, or the development of space-occupying lesions via cranial MRI. At the 12-month mark, investigators reported no instances of space-occupying lesions related to the cell transplantation.

Future Monitoring and Secondary Endpoints

While the 12-month data focus primarily on safety, the trial is designed to track participants for up to 36 months. Secondary endpoints, which will be assessed at the three-year mark, include changes in motor function, adjustments to antiparkinsonian medication requirements, and the survival and integration of the transplanted cells as measured by [18F]F-Dopa and dopamine transporter PET imaging.

Exploratory outcomes currently underway include the assessment of cerebrospinal fluid inflammatory biomarkers and wearable motor assessments. By comparing baseline trajectories with longitudinal data, the researchers aim to determine whether the stem cell-derived neurons can effectively restore dopamine production and provide sustained clinical benefit for patients with advanced Parkinson’s disease.

Key Takeaways

• Study Scope: The trial is a first-in-human, single-arm, dose-escalation study involving eight participants.
• Safety Profile: No serious adverse events related to the STEM-PD cell product were identified during the 12-month follow-up period.
• Cell Source: The therapy utilizes dopaminergic progenitor cells derived from the RC17 human embryonic stem cell line.
• Surgical Approach: Cells were delivered via stereotactic transplantation into the putamen.
• Ongoing Research: Full evaluation of motor function and cell integration will continue through the 36-month mark.