Intravenous human umbilical cord-derived mesenchymal stem cell transplantation for ischemic stroke (MERIT): A phase 1 trial.

Umbilical cord-derived mesenchymal stem cells (UC-MSCs) hold promise as a potential therapy for ischemic stroke, but the optimal transplantation strategy remains to be explored. This open-label, single-arm, phase 1 study enrolls 18 patients with subacute ischemic stroke and National Institutes of Health Stroke Scale (NIHSS) scores of 6-20 (median, 9; interquartile range, 8-12). The patients receive a single intravenous transplantation of 50, 100, or 200 million UC-MSCs (n = 6 for each dose) and are followed for 24 weeks. The primary outcome is safety and tolerability, with secondary assessment of preliminary efficacy and exploratory analyses of immunological changes. Possible treatment-related adverse events include dizziness, nausea, sweating, fatigue, and epilepsy. No serious adverse event occurs. A reduction in NIHSS score by 1-5 points is observed in 14 patients during follow-up. In conclusion, intravenous administration of UC-MSCs is well-tolerated in subacute ischemic stroke. The trial is registered on ClinicalTrials.gov (NCT05697718).