Advances in stem cell biology have generated intense interest in the prospect of transplanting stem cells into the nervous system for the treatment of neurodegenerative diseases. Here, we report the results of an ongoing phase

ObjectiveThe US Food and Drug Administration–approved trial, “A Phase 1, Open-Label, First-in-Human, Feasibility and Safety Study of Human Spinal Cord-Derived Neural Stem Cell Transplantation for the Treatment of Amyotrophic Lateral Sclerosis, Protocol Number: NS2008-1,” is complete. Our overall objective was to assess the safety and feasibility of stem cell transplantation into lumbar and/or cervical spinal cord regions in amyotrophic lateral sclerosis (ALS) subjects.MethodsPreliminary results have been reported on the initial trial cohort of 12 ALS subjects. Here, we describe the safety and functional outcome monitoring results for the final trial cohort, consisting of 6 ALS subjects receiving 5 unilateral cervical intraspinal neural stem cell injections. Three of these subjects previously received 10 total bilateral lumbar injections as part of the earlier trial cohort. All injections utilized a novel spinal-mounted stabilization and injection device to deliver 100,000 neural stem cells per injection, for a dosing range up to 1.5 million cells. Subject assessments included detailed pre- and postsurgical neurological outcome measures.ResultsThe cervical injection procedure was well tolerated and disease progression did not accelerate in any subject, verifying the safety and feasibility of cervical and dual-targeting approaches. Analyses on outcome data revealed preliminary insight into potential windows of stem cell biological activity and identified clinical assessment measures that closely correlate with ALS Functional Rating Scale-Revised scores, a standard assessment for ALS clinical trials.InterpretationThis is the first report of cervical and dual-targeted intraspinal transplantation of neural stem cells in ALS subjects. This approach is feasible and well-tolerated, supporting future trial phases examining therapeutic dosing and efficacy.

Gene therapy for motor neuron diseases requires efficient gene delivery to motor neurons (MNs) throughout the spinal cord and brainstem. The present study compared adeno-associated viral (AAV) vector serotypes 1, 6, 8, and 9 for spinal cord delivery in adult mice, by the intraparenchymal or intrathecal route of administration. Whereas intraparenchymal injections resulted in local transduction of the lumbar segment of the spinal cord, intrathecal injections led to a broader distribution, transducing cells along the sacral, lumbar, and lower thoracic spinal cord. Overall, AAV6 and AAV9 performed better than the other serotypes. Dramatic differences in cell-specific expression patterns could be observed when constructs bearing the chicken β-actin (Cba) versus cytomegalovirus (CMV) promoter were compared. In summary, intrathecal delivery of AAV6 or AAV9 vectors containing the CMV promoter yielded the strongest levels of biodistribution and MN transduction in the spinal cord.

Adeno-associated viral vector 9 (AAV9) has recently been shown to penetrate the blood--brain barrier via intravascular administration, making it a good candidate for diffuse gene delivery. However, the potential side effects of systemic delivery are unknown. Intrathecal viral vector administration may be more invasive than intravenous injections, but it requires far less vector and it can be performed on an outpatient basis, making it an ideal route of delivery for clinical translation. A total of 12 domestic farm pigs (o20 kg) underwent a single-level lumbar laminectomy with intrathecal catheter placement for AAV9 delivery. Animals were perfused and the tissue was harvested 30 days after treatment. Gene expression was assessed by anti-green fluorescent protein immunohistochemistry. Although a single lumbar injection resulted in gene expression limited to the lumbar segment of the spinal cord, three consecutive boluses via a temporary catheter resulted in diffuse transduction of motor neurons (MNs) throughout the cervical, thoracic and lumbar spinal cords. We now present the first successful robust transduction of MNs in the spinal cord of a large animal via intrathecal gene delivery using a self-complementary AAV9. These promising results can be translated to many MN diseases requiring diffuse gene delivery.

This study provides Class IV evidence that for patients with ALS, spinal cord transplantation of human stem cells can be safely accomplished and does not accelerate the progression of the disease. This study lacks the precision to exclude important benefit or safety issues.