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Safety and Preliminary Efficacy of Allogeneic Neural Stem Cell Transplantation in Chronic Spinal Cord Injury: A Translational Phase I/IIa Trial

Background: Given the large number of individuals living with disabling sensorimotor impairment due to spinal cord injury (SCI) approaching 2 million, viable options for regenerative repair strategies of the injured spinal cord are desperately needed. Human central nervous system stem cells (HuCNS-SC®) are self-renewing, multi-potent adult stem cells exhibiting successful engraftment, migration, and region-appropriate differentiation as demonstrated in multiple animal models for the injured brain and spinal cord.  In preclinical SCI models, improved locomotor function provided the rationale for the first human thoracic SCI clinical trial of HuCNS-SC cells.   
 
Methods: Safety and preliminary efficacy data were collected within a first ever multi-site phase I/IIa trial involving surgical transplantation of 20 million HuCNS-SC cells into the thoracic cord in 12 subjects with sensory or motor complete traumatic paraplegia.  Up to 6 years follow-up data was collected applying an extended protocol design augmenting clinical assessments through corroborating measures of sensory thresholds and neuroimaging to improve readouts of safety and efficacy. 
 
Findings: The study revealed promising short and long term surgical and medical safety.  Measures of preliminary efficacy could discern responders (5/12 patients) with reliable improvements in sensory function albeit without measurable motor changes in thoracic injuries. Imaging of the spinal cord at and rostral the site of injection revealed dynamic structural changes similar to findings in non-transplanted SCI subjects.   
 
Interpretation: Findings of safety and feasibility supported the regulatory approval for a Phase II HuCNS-SC transplantation study in cervical spinal cord injured patients.   
 
Funding: The initial study (short term follow-up of the first year; STFU) and part of the second study (long term follow-up; LTFU) was funded by Stem Cells Inc, Newark, California, USA. After dissolution of Stem Cells Inc. Q3 2016 grants from Wings for Life (WfL), and the Bright Oceans Corporation (BOCO) enabled completion of the LTFU, compilation of the full set of monitored data (initial Phase I/IIa STFU trial and LTFU study), data analysis and manuscript completion.   
 
Declaration of Interest: Armin Curt has no competing interests. Principal Investigator for multi-site Phase I/IIa trial of 12 subjects and primary author (corresponding author). Jane Hsieh, with no competing interests, is an independent consultant to the Spinal Cord Injury Center Balgrist initiating data analysis and the first draft of the manuscript, as well as coordinating contributions from collaborating authors. Martin Schubert with no competing interests, participated in care of 9 enrolled subjects, data analysis and review of manuscript. Markus Hupp has no competing interests. Participated in the care of 9 enrolled subjects and reviewed the manuscript. Susi Friedl has no competing interests. Participated in the care of 9 enrolled subjects and reviewed the manuscript. Patrick Freund has no competing interests. Collected and analyzed neuroimaging data for 9 enrolled subjects and reviewed the manuscript. Eveline Huber has no competing interests. Collected and analyzed neuroimaging data for 9 enrolled subjects and reviewed the manuscript. Dario Pfyffer has no competing interests. Collected and analyzed neuroimaging data for 9 enrolled subjects, assisted with figure creation and reviewed the manuscript. Safety of neural stem cell transplantation into the human spinal cord Draft version: V6.1 20190128 Reto Sutter has no competing interests. Collected and analysed neuroimaging data for 9 enrolled subjects and reviewed the manuscript. Catherine Jutzeler has no competing interests. Collected and analysed electrophysiological data for 9 enrolled subjects and reviewed the manuscript. Rudolf P. Wuthrich has no competing interests. Provided immunosuppression for 9 enrolled subjects and reviewed the manuscript. Kan Min has no competing conflicts of interest. Performed orthopaedic spinal surgery for 9 HuCNS-SC transplantations at Balgrist site and reviewed the manuscript. Steve Casha has no competing interests. Site investigator at University of Calgary with 2 patients enrolled and transplanted, and reviewed the manuscript. Michael Fehlings has no competing interests. Site investigator at University of Toronto with 1 patient enrolled and transplanted, and reviewed the manuscript. Raphael Guzmann has no competing interests. Performed neurosurgery and HuCNS-SC transplantation for 9 enrolled subjects and reviewed the manuscript. 
 
Ethical Approval: The study protocol and all amendments were approved by related Ethics Committees and regulatory agencies in accordance with the Declaration of Helsinki.