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Summary of Supplement:
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Supplement contains additional information on the rationale for specific inclusion/exclusion
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related to cellular based therapy and safety issues in acute SCI trials.
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Inclusion Criteria
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Non penetrating traumatic SCI (within 14 days): The use of this criterion was
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based on the proposed immunological mechanism of the intervention and preclinical
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data which defined the treatment window. In the normal immune response,
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macrophages are most active during the sub-acute inflammatory stage. This was
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confirmed by pre-clinical studies which found the optimal window for macrophage
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implantation to be 8-10 days following injury. In addition, several of the patients
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who experienced improvement in function in the Phase 1a trial received macrophage
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injections on the 14th post-injury day.
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Penetrating trauma was excluded for several reasons: 1) such trauma carries the risk
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of microbial contamination of the spinal cord potentially leading to infection that not
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only increases pre-surgical risk factors for the patient but may also interfere with the
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activation of macrophages toward neuro-regeneration. Gunshot wounds in particular
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(for additional reasons not related to cellular therapy) were excluded after
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consultation with experts in spinal cord injury. It was felt that penetrating injuries,
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including stab wounds, have a complex pathology that may include primary
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disruption of the cord. The underlying pathology of gunshot injuries of the spinal cord
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is not well understood and may include primary disruption of neural tissue, contusive
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injury and other vascular effects. Furthermore, the ability to obtain an MRI (which
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may be contra-indicated if a bullet is close to a vital structure) and accurately apply
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the MRI eligibility criteria in this group of patients was felt to be limited by metal
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artifact.
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A single spinal cord lesion between C5 motor/C4 sensory level and T11
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neurological level by the ISNCSCI: The neurological levels chosen originally were
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C5 to T11. The upper level (C5) was chosen for safety reasons to lessen the risk that
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ascent of the neurological level caused by adverse effects of parenchymal macrophage
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injection could result in damage to the phrenic nucleus. Therefore, this criterion
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allows for a one level safety margin for respiratory status and ventilatory
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requirements. Early in the trial it was noted that many “C5” injuries were indeed C5
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motor, but had some sensory deficit in the C5 dermatome, which, by the ISNCSCI,
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would indicate the neurological level of injury was C4. After a review by the Steering
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Committee, the inclusion criterion was changed and the protocol amended to C5
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motor as it was felt that if motor function was intact at C5 despite some sensory
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impairment, there was minimal increased risk of additional respiratory compromise,
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thus meeting the original safety-based intent of the neurological level eligibility
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criterion. There also may be a question of the validity of the C5 sensory point (as
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defined in the ISNCSCI reference manual as the lateral side of the antecubital fossa1)
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and whether it is truly representative of the C5 versus the C6 dermatome in the
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majority of individuals.2 T11 was chosen as the lowest level in order to avoid conus
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medullaris and cauda equina injuries since the proposed mechanism of action was the
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promotion of axonal regeneration in the spinal cord rather than neuroprotection of
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anterior horn cells or regeneration of axons in the cauda equina. For those injuries at
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or close to T11, a careful review of the MRI was required to ensure that the lesion did
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not, in fact, extend significantly into the conus medullaris creating technical
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difficulties for the surgeons due to the diminished cross-sectional area of the conus
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and also increasing the chances of significant concomitant lower motor neuron injury.
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Complete SCI (AIS A): Participants with a complete SCI were chosen to lessen the
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risk of adverse neurological outcome since this group of patients is clearly the least
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likely to experience spontaneous improvement. Although the neurological level and
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completeness criteria were based on the ISNCSCI, one exception was discussed mid-
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study. Several cervical injury participants were examined at baseline (7-10 days post
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injury) and found to have evolving buttock or foot sensation in the absence of ano-
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rectal sensation or volition. While these patients were technically classified as
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“complete” by the International Standards, they were felt to be “in evolution” to
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incomplete status and as such, did not meet the intent of the safety-based eligibility
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criterion. As the goal of the trial was to enroll participants with clinically complete
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injuries, those individuals with a zone of partial preservation extending greater than 5
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segments below the level of injury were excluded as it was felt they were potentially
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evolving to an incomplete injury, although technically complete by the ISNCSCI.
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Exclusion Criteria
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Fever (>38.4 °C), 24 hours prior to scheduled tissue harvest: Febrile patients were
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excluded to minimize the risk of product contamination with bacteria that might be
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circulating in the blood.
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Blood transfusion within 3 days prior to scheduled tissue harvest: As this was an
autologous therapy, it was necessary to ensure the blood required to isolate the
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monocytes was a true autologous sample. Estimates on the half life of circulating
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monocytes range from 4.5 -20 hours.3,4
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Human immunodeficiency virus (HIV), hepatitis B and C positive: As the basis
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for the therapy is immunological, the cells involved in the immune system response
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could not be compromised by HIV. Patients with HIV, Hepatitis B or C were
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excluded to minimize risks to manufacturing staff processing the autologous blood
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sample (handling potentially contaminated blood).
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Previous or concomitant treatment with:
o Immune modulators or experimental drugs 60 days prior to study
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enrollment
o Acute immune modulators (i.e. dexamethasone, methylpredisolone
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(MPSS)) within 5 days prior to scheduled skin harvest
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These exclusions were to ensure the macrophage and immune responses were not
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compromised. An exception was the standard use of MPSS in the 24-48 hours
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following SCI, as the mean half-life 3.54 days in patients with acute spinal cord
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injury; therefore immune system response would no longer be impacted by day 7-8
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following injury.5 Dexamethasone and other immune modulators such as
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fludrocortisone, also required a 5 day window for clearance prior to skin and blood
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harvest.
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Hematopoetic inducers (e.g. erythropoietin [Procrit]) following injury: This was
added to the list of exclusions as a protocol amendment after discovering technical
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difficulties during the cell separation procedure in participants who had received
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hematopoetic inducers.
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Longitudinal dimension of injury determined by MRI > 3 cm and anatomical
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transection of the cord visualized by MRI: A contusion size ≤ 3 cm without spinal
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cord transection was determined based on Phase 1a data. In that study, a lesion size
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of one vertebral segment was used in order to target a “moderate” size lesion,
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eliminating the most severe contusions. As the length of one vertebral segment
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varies depending on the location in the spinal column and based on individual
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characteristics of the participant (height), a more objective measurement was chosen
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for Phase 2. The MRI criterion of no transection was chosen, because an individual
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with transection of the long tracts was less likely to benefit from the intervention.
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Additionally, it was noted in the Phase I trial that for the one participant with spinal
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cord transection noted intra-operatively, it was difficult to accurately inject the
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macrophages due to the condition of the cord, nor did this individual demonstrate
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recovery.
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References:
1. American Spinal Injury Association. International standards for neurological
classification of spinal cord injury, revised 2000, reprinted 2002. Chicago, IL:
American Spinal Injury Association; 2002.
2. Browne BJ, Jacobs SR, Herbison GJ, Ditunno JF. Pin sensation as a predictor of
extensor carpi radialis recovery in spinal cord injury. Arch Phys Med Rehabil 1993;
74: 14-18.
3. Weinberg JB (ed). Mononuclear phagocytes. In: Greer J (ed). Wintrobe’s Clinical
Hematology. 11th edn. Lippincott Williams and Wilkins: Philadelphia, PA, 2004, pp
355-378.
4. Guyton AC, Hall JE (eds). Resistance of the body to infection. In: Textbook of
Medical Physiology. 10th edn. W.B. Saunders Company: Philadelphia, PA, 2000, pp
392-401.
5. Segal JL, Maltby BF, Langdorf MI, Jacobsen R, Brunnemann SR, Jusko WJ.
Methylprednisone disposition kinetics in patients with acute spinal cord injury.
Pharmacotherapy 1998;18(1): 16-22.
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