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IntroductionParkinson’s disease (PD) is a common neurodegenerative disease, which has extensive pathology that critically includes the loss of midbrain dopaminergic neurons. This loss leads to debilitating motor features such as bradykinesia and rigidity, as well as some non-motor symptoms. Intracerebral dopamine cell transplants have been explored for many years as a new approach to treating PD and initially used human fetal ventral mesencephalic tissue with inconsistent results, related in part to major logistical challenges in sourcing enough tissue of the right quality and the limited possibilities for quality control and standardisation. Dopaminergic neurons can now be derived reliably from human stem cell sources, which may overcome some of the challenges associated with fetal tissue transplantations.Methods and analysisSTEM-PD is a multi-centre, single-arm, dose-escalation, first-in-human advanced therapy investigational medicinal product (ATIMP) trial in Europe using a cell product that consists of dopaminergic neural progenitors derived from the RC17 human embryonic stem cell line. The aim of the study is to assess the safety, tolerability and feasibility of intraputamenal transplantation of this cell product in patients with moderately advanced PD. Eight participants will be recruited from two sites, Skånes University Hospital (Lund, Sweden) and Cambridge University Hospital (Cambridge, UK). The primary outcome of the trial is safety and tolerability, assessed by the number and nature of adverse events and serious adverse events, and the absence of space-occupying lesions on cranial MRI, in the first 12 months following transplantation. Secondary and exploratory outcomes, including clinical measures, changes in anti-Parkinson’s medication and measures of graft survival using positron emission tomography imaging, will be assessed at both 12 and 36 months post-grafting.Ethics and disseminationEthical approval was obtained from the Swedish Ethical Review Authority (EPM dnr 2021-06945-01) and South Central - Oxford A Research Ethics Committee (reference 23/SC/0243). Clinical Trial Authorisation was given by the Swedish Medical Products Agency (Dnr: 5.1-2022-57953) and the Medicines and Healthcare products Regulatory Agency for clinical trials authorisation (reference CTA 40773/0001/001-0001). Authorisation for transfer to Clinical Trial Regulation (EU) 536/2014 was given by the Swedish Medical Products Agency (Dnr: 5.1.1-2024-100773). Potential participants will receive verbal and written information about the trial and written informed consent will be obtained prior to enrolment. A lay summary of the results of the trial will be uploaded to the trial website which is publicly accessible. Trial results will be published in peer-reviewed journals.Trial registration numbersNCT05635409.

BACKGROUND. Recombinant human PDGF-BB (rhPDGF-BB) reduces Parkinsonian symptoms and increases dopamine transporter (DAT) binding in several animal models of Parkinson's disease (PD). Effects of rhPDGF-BB are the result of proliferation of ventricular wall progenitor cells and reversed by blocking mitosis. Based on these restorative effects, we assessed the safety and tolerability of intracerebroventricular (i.c.v.) rhPDGF-BB administration in individuals with PD. METHODS. We conducted a double-blind, randomized, placebo-controlled phase I/IIa study at two clinical centers in Sweden. Twelve patients with moderate PD received rhPDGF-BB via an implanted drug infusion pump and an investigational i.c.v. catheter. Patients were assigned to a dose cohort (0.2, 1.5, or 5 μg rhPDGF-BB per day) and then randomized to active treatment or placebo (3:1) for a 12-day treatment period. The primary objective was to assess safety and tolerability of i.c.v.-delivered rhPDGF-BB. Secondary outcome assessments included several clinical rating scales and changes in DAT binding. The follow-up period was 85 days. RESULTS. All patients completed the study. There were no unresolved adverse events. Serious adverse events occurred in three patients; however, these were unrelated to rhPDGF-BB administration. Secondary outcome parameters did not show dose-dependent changes in clinical rating scales, but there was a positive effect on DAT binding in the right putamen. CONCLUSION. At all doses tested, i.c.v. administration of rhPDGF-BB was well tolerated. Results support further clinical development of rhPDGF-BB for patients with PD. TRIAL REGISTRATION. Clinical Trials.gov NCT00866502. FUNDING. Newron Sweden AB (former NeuroNova AB) and Swedish Governmental Agency for Innovation Systems (VINNOVA).

Asymmetry of striatal dopaminergic deficits and motor symptoms is a typical characteristic of idiopathic Parkinson’s disease (PD). This study aims to characterise the trend of asymmetry in moderate-stage PD. We performed a 19-month longitudinal study in 27 patients with PET-CT imaging and appropriate clinical assessments. 11C-PE2I non-displaceable binding potential (BPND) was calculated bilaterally for the striatum at baseline and follow-up to estimate the in vivo density of striatal dopamine transporters (DAT). Changes in striatal 11C-PE2I BPND over time were more prominent in the ipsilateral as compared to contralateral side. Changes in MDS-UPDRS-III (motor component of the Movement Disorders Society Unified PD Rating Scale) were not different between the clinically most and least affected body sides. Our data support that the asymmetry in striatal dopaminergic degeneration becomes less prominent in moderate-stage PD. In contrast, during the above period, the asymmetry of motor symptoms was maintained between the clinically most and least affected body sides.

Clinical studies of Parkinson’s disease (PD) using a dopamine cell replacment strategy have been tried for more than 30 years. The outcomes following transplantation of human fetal ventral mesencephalic tissue (hfVM) have been variable, with some patients coming off their anti-PD treatment for many years and others not responding and/or developing significant side effects, including graft-induced dyskinesia. This led to a re-appraisal of the best way to do such trials, which resulted in a new European-Union-funded allograft trial with fetal dopamine cells across several centers in Europe. This new trial, TRANSEURO ( NCT01898390 ), is an open-label study in which some individuals in a large observational cohort of patients with mild PD who were undergoing identical assessments were randomly selected to receive transplants of hfVM. The TRANSEURO trial is currently ongoing as researchers have completed both recruitment into a large multicenter observational study of younger onset early-stage PD and transplantation of hfVM in 11 patients. While completion of TRANSEURO is not expected until 2021, we feel that sharing the rationale for the design of TRANSEURO, along with the lessons we have learned along the way, can help inform researchers and facilitate planning of transplants of dopamine-producing cells derived from human pluripotent stem cells for future clinical trials. The TRANSNEURO Consortium shares valuable insights that may facilitate planning of human pluripotent stem-cell-derived dopamine cell transplants for future clinical trials on Parkinson’s disease.