SCISSOR-Spinal Cord Injury Study on Small molecule-derived Rho inhibition: a clinical study protocol

Abstract

Introduction: The approved analgesic and anti-inflammatory drugs ibuprofen and indometacin block the small GTPase RhoA, a key enzyme that impedes axonal sprouting after axonal damage. Inhibition of the Rho pathway in a central nervous system-effective manner requires higher dosages compared with orthodox cyclooxygenase-blocking effects. Preclinical studies on spinal cord injury (SCI) imply improved motor recovery after ibuprofen/indometacin-mediated Rho inhibition. This has been reassessed by a meta-analysis of the underlying experimental evidence, which indicates an overall effect size of 20.2% regarding motor outcome achieved after ibuprofen/indometacin treatment compared with vehicle controls. In addition, ibuprofen/indometacin may also limit sickness behaviour, non-neurogenic systemic inflammatory response syndrome (SIRS), neuropathic pain and heterotopic ossifications after SCI. Consequently, 'small molecule'-mediated Rho inhibition after acute SCI warrants clinical investigation.

Methods and analysis: Protocol of an investigator-initiated clinical open-label pilot trial on high-dose ibuprofen treatment after acute traumatic, motor-complete SCI. A sample of n=12 patients will be enrolled in two cohorts treated with 2400 mg/day ibuprofen for 4 or 12 weeks, respectively. The primary safety end point is an occurrence of serious adverse events, primarily gastroduodenal bleedings. Secondary end points are pharmacokinetics, feasibility and preliminary effects on neurological recovery, neuropathic pain and heterotopic ossifications. The primary safety analysis is based on the incidence of severe gastrointestinal bleedings. Additional analyses will be mainly descriptive and casuistic.

Ethics and dissemination: The clinical trial protocol was approved by the responsible German state Ethics Board, and the Federal Institute for Drugs and Medical Devices. The study complies with the Declaration of Helsinki, the principles of Good Clinical Practice and all further applicable regulations. This safety and pharmacokinetics trial informs the planning of a subsequent randomised controlled trial. Regardless of the result of the primary and secondary outcome assessments, the clinical trial will be reported as a publication in a peer-reviewed journal.

Trial registration number: NCT02096913; Pre-results.

Keywords: Heterotopic ossifications; Neuropathic pain; Neuroprotection; Plasticity; ibuprofen.

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Figures

Figure 1

Pharmacological targets of ibuprofen. Intracellular signalling cascades converge at the GTPase RhoA, which is activated after SCI by myelin and scar-associated proteins (for review, see refs. 5, 7 and 29). Downstream to Rho, the activated ROCK inhibits axonal regrowth, promotes neurodegeneration, contributes to the development of neuropathic pain and tissue loss and impedes neurorestoration and functional recovery (reviewed by Watzlawick et al). This pathway can be blocked by the ROCK inhibitors Y-27632 and fasudil or the specific Rho inhibitors P21CIP1/WAF1, C3 transferase, and by the R(−) and S(−) enantiomers of ibuprofen, as the most convincing Rho inhibitor among individual drugs from the group of NSAIDs. Ibuprofen-mediated Rho inhibition depends on the upregulation of PPARγ. Treatment with PPARγ agonists was demonstrated to have anti-inflammatory effects and to protect tissue and thereby motor function in other CNS injury conditions (reviewed by McTigue). It is not yet clear whether the inhibition of NF-κB as a further target of R(−)/S(+) ibuprofen is independent of PPARγ. Notably, PPARγ inhibits gene expression by antagonising the activities of the proinflammatory transcription factors NF-κB. Another pathway, mainly operated by the S enantiomer of ibuprofen, is the inhibition of COX 1/2 and consequently of the prostaglandin E2 production, which activates NF-κB or counterregulates it at very high concentrations. COX 1/2 and NF-κB are associated with inflammation-induced neuropathic pain, neurodegeneration, sickness behaviour and the systemic inflammatory response syndrome. Systemic inflammation contributes to neurogenic heterotopic ossificastions. Taken together, Rho-blocking NSAIDs have the potential to decrease the systemic and acute CNS inflammatory response by targeting at least two separate pathways, PPARγ and COX 1/2. The suspected side effect of neuroprotective anti-inflammatory therapy, that is, that it further limits the regeneration capacity of spared axons, is suggested to be abrogated by Rho inhibition. CNS, central nervous system; COX, cyclooxygenase; GDP, guanosine diphosphate; GTP, guanosine triphosphate; NSAIDs, non-steroid anti-inflammatory drugs; PPARγ, peroxisome proliferator-activated receptor γ; NF-κB, nuclear factor κB; RGMa, repulsive guidance molecule A; ROCK, Rho-associated coiled kinase; SCI, spinal cord injury.

Figure 2

Systematic review preclinical study selection chart. To identify animal studies reporting the effect of ibuprofen or indometacin treatment for neurobehavioral recovery after SCI, the following search term was used for PubMed, EMBASE and ISI Web of science (search conducted on 18 May 2015): (Ibuprofen OR Indometacin OR NSAID OR nonsteroidal anti-inflammatory drugs) AND (SCI OR hemisection OR contusion OR dorsal column injury OR transection OR corticospinal tract injury OR compression OR spinal cord lesion). Search results were limited to animals. Studies were included if they reported the effects of ibuprofen or indometacin in animal models after various types of SCIs. We included SCI experiments comparing functional motor outcome between a group of animals receiving treatment and a control group receiving no treatment (sham group). Non-traumatic models of SCI were excluded, as well as studies reporting only combined treatments. Studies had to report the number of animals for each group, the mean effect size and its variance. Studies were excluded due to inappropriate outcome scales, combination of treatments and statistical inconsistencies. SCI, spinal cord injury.

Figure 3

Meta-analysis of preclinical effects on motor recovery. Improvement in neurobehavioral score is ranked by effect size (ES). The overall number of included animals was n=255 (median n=12, range 8–73). Black dots represent studies using ibuprofen and white dots show indometacin studies. The horizontal bar represents the 95% CI of the ES. Details on the design of the included studies are summarised in table 1.

Figure 4

Longitudinal clinical trial design. Diagram of frequency and scope of trial procedures. The evaluation for eligibility should start as early as possible after acute SCI. The baseline will be obtained at the day of the inclusion from day 4 and latest at day 21 post trauma, in any case as early as possible. Start of the study medication is directly after the baseline assessment. The duration of the intervention is 4 weeks for cohort I and 12 weeks for cohort II. Frequent safety laboratory measurements are performed. Samples for pharmacokinetic measurements are collected two times in cohort I and three times in cohort II. The follow-up visits for the determination of secondary end points are performed at week 4 (±3 days) and after the end of the intervention at week 24 (±14 days). Final safety laboratory measurements will be performed 4 weeks after the end of the study medication. SCI, spinal cord injury.