NSI‐566 is a stable, primary adherent neural stem cell line derived from a single human fetal spinal cord and expanded epigenetically with no genetic modification. This cell line is being tested in clinical trials in the U.S. for treatment of amyotrophic lateral sclerosis and spinal cord injury. In a single‐site, phase I study, we evaluated the feasibility and safety of NSI‐566 transplantation for the treatment of hemiparesis due to chronic motor stroke and determined the maximum tolerated dose for future trials. Three cohorts (n = 3 per cohort) were transplanted with one‐time intracerebral injections of 1.2 × 107, 2.4 × 107, or 7.2 × 107 cells. Immunosuppression therapy with tacrolimus was maintained for 28 days. All subjects had sustained chronic motor strokes, verified by magnetic resonance imaging (MRI), initiated between 5 and 24 months prior to surgery with modified Rankin Scores [MRSs] of 2, 3, or 4 and Fugl‐Meyer Motor Scores of 55 or less. At the 12‐month visit, the mean Fugl‐Meyer Motor Score (FMMS, total score of 100) for the nine participants showed 16 points of improvement (p = .0078), the mean MRS showed 0.8 points of improvement (p = .031), and the mean National Institutes of Health Stroke Scale showed 3.1 points of improvement (p = .020). For six participants who were followed up for 24 months, these mean changes remained stable. The treatment was well tolerated at all doses. Longitudinal MRI studies showed evidence indicating cavity‐filling by new neural tissue formation in all nine patients. Although this was a small, one‐arm study of feasibility, the results are encouraging to warrant further studies. stem cells translational medicine 2019;8:999–1007
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