Riluzole in Spinal Cord Injury Study

At present there are over 1 million people living with Spinal Cord Injury (SCI) in North America alone, with annual costs for the acute treatment and chronic care of these patients totaling four billion dollars USD. The worldwide prevalence of SCI is unknown, with estimates ranging up to 250 million individuals. The incidence of SCI in developed countries has been estimated to be between 10 - 40 cases per million inhabitants. In spite of the immense impact of SCI at a personal and societal level, an effective and safe pharmacologic treatment for SCI, shown to improve neurological and functional outcomes at long-term follow-up, remains absent.

The final degree of neurological tissue destruction that occurs after traumatic SCI is a product of both primary and secondary injury mechanisms. The primary mechanical injury to the cord initiates a subsequent signaling cascade of deleterious down-stream events, known collectively as secondary injury mechanisms. These secondary injury mechanisms include ischemia, interstitial and cellular ionic imbalance, free radical formation, glutamatergic excitotoxicity, lipid peroxidation and generation of arachidonic acid metabolites. Although little can be done from a therapeutic standpoint to correct damage sustained during the primary injury, by mitigating the evolution of secondary injury events there is opportunity to preserve remnant viable neurological tissue and improve neurologic outcomes. There is convincing evidence from the preclinical realm that the pharmacologic agent riluzole attenuates certain aspects of the secondary injury cascade leading to diminished neurological tissue destruction in animal SCI models. Riluzole, a sodium channel blocking benzothiazole anticonvulsant, specifically exerts its neuroprotective effect by helping to maintain neuronal cellular ionic balance and by reducing the release of excitotoxic glutamate in the post-SCI setting. Several preclinical studies in the rodent SCI model have associated administration of riluzole with increased neural tissue preservation at the site of injury, in addition to improved behavioral outcomes, in comparison to administration of placebo or other sodium channel blocking drugs. In the clinical realm, while riluzole has not been studied extensively in the context of SCI, it has been widely used in the treatment of amyotrophic lateral sclerosis (ALS). A 2007 Cochrane review, summarizing the findings of 4 placebo-controlled randomized trials, concluded that at a dose of 100 mg daily, riluzole is safe and improves median survival by 2-3 months in patients with ALS. In regards to adverse events (AEs), riluzole was well tolerated, although treated patients were 2.6 times more likely to experience a three-fold increase in serum alanine transaminase (ALT) as compared to patients treated with placebo. However, this effect was found to be uniformly reversible with cessation of riluzole therapy and was only reported after several months of medication administration. Recently, the clinical safety and pharmacokinetic profile of riluzole have been studied in a multi-center pilot study in the context of traumatic SCI. A total of 36 patients received an oral dose of riluzole 50 mg twice daily for 2 weeks, with treatment initiated within 12 hours of injury for all patients. The 12 hour dosing window, as well as the 2 week duration of therapy, was chosen to match the period of medication administration to the known period of glutamatergic excitotoxicity after SCI (several minutes after injury until 2 weeks after injury). With the final analysis currently undergoing peer review, completion of this study has confirmed the acceptable safety profile of riluzole administration previously documented in the ALS literature, and has established the feasibility of conducting a large-scale efficacy trial investigating this therapy.

At present, there is no specific pharmacological therapy that is given uniformly to all patients with traumatic SCI. As a result, a placebo-controlled comparison group is ethical and justifiable.

The aim of the current trial is to evaluate efficacy and safety of riluzole in the treatment of patients with acute SCI.

The primary objective of the current Phase II/III trial is to evaluate the superiority of riluzole, at a dose of 2 x 100 mg the first 24 hours followed by 2 x 50 mg for the following 13 days after injury, as compared to placebo, in change between 180 days and baseline in motor outcomes as measured by International Standards for Neurological Classification of Spinal Cord Injury Examination (ISNCSCI) Motor Score, in patients with acute traumatic SCI, presenting to the hospital less than 12 hours after injury.

Secondary objectives are to evaluate the effects of riluzole on overall neurologic recovery, sensory recovery, functional outcomes, quality of life outcomes, health utilities, mortality, and adverse events. The working hypothesis is that the riluzole treated subjects will experience superior motor, sensory, functional, and quality of life outcomes as compared to those receiving placebo, with an acceptable safety profile.