Riluzole is a drug approved by the U.S. Food and Drug Administration (FDA) to treat amyotrophic lateral sclerosis (ALS). It is being studied as a potential treatment for patients with primary progressive multiple sclerosis (PPMS) and secondary progressive multiple sclerosis (SPMS).
How riluzole works
Riluzole acts to block the release of a neurotransmitter, glutamate, from nerve cells as well as blocking glutamate binding to its receptors.
A neurotransmitter is a molecule that nerve cells use to communicate. A nerve cell releases the neurotransmitter that is then picked up by receptors on a neighboring cell. Normally, excess glutamate is quickly removed, but if it builds up, it can cause damage to the surrounding nerve cells, as glutamate repeatedly binds to the receptors.
MS symptoms are primarily caused by demyelination (damage to the myelin sheath, a protective layer surrounding the nerve fibers), but the death of nerve cells themselves can also contribute to the symptoms of the disease. Riluzole could have a neuroprotective effect in MS patients, preventing nerve cell death caused by excessive glutamate release.
Riluzole in clinical trials
A double-blind, randomized, placebo-controlled Phase 2 trial (NCT00501943) assessing the effect of riluzole compared to a placebo (as an add-on therapy to Avonex) over a three-year period in early RRMS patients has been completed. The trial enrolled 43 patients with an onset of MS less than one year before.
The results, published in the scientific journal Annals of Clinical and Translational Neurology, revealed no clinical benefit of riluzole treatment compared to a placebo. The primary endpoint of change in brain volume revealed no significant difference in the rate of decline, suggesting that riluzole did not have a neuroprotective effect in patients with early MS. Riluzole was safe and well tolerated and only a few side effects associated with the treatment were recorded.
An uncontrolled pilot study involving 16 people with PPMS showed more positive results and suggested that riluzole may be able to decrease the number of new T1 lesions in the brain and may slow spinal cord atrophy. No side effects associated with the treatment were reported. The study has limitations due to its small size and lack of controls, therefore no statistical analyses could be performed. A larger study is needed to confirm these results.
Currently, a large-scale randomized, double-blind, placebo-controlled Phase 2 study (NCT0190259) called MS-SMART is ongoing to test the safety and efficacy of three different drugs (riluzole, amiloride, and fluoxetine) compared to a placebo in patients with SPMS.
The trial has enrolled 440 participants with SPMS in the U.K. who will be randomly assigned one of the three drugs or a placebo for a two-year period. Outcomes such as a change in brain volume will be used to determine the effectiveness of the treatment. The trial is expected to be completed by July 2018.
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