GW Pharmaceuticals, which makes Sativex - an oral spray containing a cannabis
extract - has released disappointing results of a trial testing the drug's
benefits in treating pain in people with multiple sclerosis (MS).
The study involved 339 people experiencing neuropathic pain due to MS who have achieved inadequate pain relief with existing therapies. Half of the people in the study taking Sativex reported their pain reduced by at least 30 per cent, however the response to the placebo treatment was unusually high, making the actual benefits of the drug difficult to assess.
The latest results mean that the drug will not be made widely available to people with MS until it proves its efficacy in further trials. Other trials are currently underway looking at the effectiveness of Sativex for spasticity in people with MS.
Dr Lee Dunster, Head of Research and Information at the MS Society, said: "These results do not provide clear evidence as to the benefits of Sativex in treating pain in MS and well designed clinical trials are needed to assess the effectiveness of this therapy. We look forward to the results published later this year investigating the effect of Sativex on spasticity in people with MS."
A high placebo response during a clinical trial may occur because symptoms are eased by the simple belief that a treatment will work.
GW Pharmaceuticals stated that people with MS using the placebo took significantly more doses than those taking Sativex, confounding the overall comparison. Last year the firm adopted a fixed target dose approach in other studies of the drug, testing its effect on spasticity and cancer pain, which should prevent this situation occurring in future trials.