The use of a synthetic marijuana derivative in treating multiple sclerosis (MS) is being questioned after the first major non-commercial study of its main active ingredient, tetrahydrocannabinol (THC), found the drug had little effect in slowing the course of the disease.
Researchers in England enrolled nearly 500 patients over an eight year span. People with progressive MS received either THC capsules or a placebo for three years to see how their MS changed over this period.
Overall, the study found no evidence to support the effectiveness of THC on MS progression, using either a disability scale administered by neurologists or a patient reported scale measuring the drug’s impact.
There was some evidence to suggest a beneficial effect in patients at the lower end of the disability scale, but the benefit was only found in a small group of people rather than the whole population.
“Our research has shown that, although there is a suggestion of benefit to those at the lower end of the disability scale, there is little evidence to suggest that THC has a long term impact on the slowing of progressive MS,” said John Zajicek, a professor of Clinical Neuroscience at Plymouth University Peninsula Schools of Medicine and Dentistry.
Multiple sclerosis is the most common cause of neurological disability in young adults. It is generally regarded as an autoimmune disease, with early episodes of inﬂammation causing nerve damage, which worsens as the disease progresses.
Initial relapses are often replaced by secondary gradual progression after several years. Although therapies for the inﬂammatory phase are available, none has been shown to slow disease progression in the absence of relapses.
Another finding in the study, reported in The Lancet Neurology, was that MS in the study population progressed more slowly than expected, making it more of a challenge to determine a treatment’s effectiveness.
Researchers say in addition to evaluating the potential neuroprotective effects and safety of THC over the long-term, one of the aims was to improve the way that clinical trial research is done. They hope by exploring newer methods of measuring MS, and using the latest statistical methods, to make the most of every piece of information collected.
“Progression of MS is thought to be due to death of nerve cells, and researchers around the world are desperately searching for treatments that may be neuroprotective,” said Zajicek.
Prior studies have often yielded contradictory results of the efficacy of synthetic THC as a treatment for MS.
In 2012, German researchers found that Sativex, a mouth spray containing cannabinoids, reduces chronic pain and symptoms of muscle spasticity in MS patients.
But in that same year, a British medical journal reported there was little evidence supporting the use of the medical marijuana spray to treat muscle pain and spasticity in MS patients.
Undaunted, British-based GW Pharmaceuticals (NASDAQ:GWPH) just announced plans to expand marketing authorization of the drug into France for the treatment of spasticity. Sativex is already approved as a treatment for MS spasticity in 21 countries, including 17 countries in Europe.
Multiple sclerosis is a chronic disease which attacks the body’s central nervous system and destroys the myelin sheath that protects the nerve cells. An estimated 400,000 Americans have the disease and more than 2 million worldwide.