The active component of cannabis does not slow progression in MS
31st May, 2012
Disappointing news from the UK this week suggests that the active component of cannabis, THC, does not slow progression in MS.
British researchers, led by Prof John Zajicek of the Peninsula Medical School in Plymouth, have released the much anticipated results from the CUPID trial (Cannabinoid Use In Progressive Inflammatory brain Disease). The data has not yet been published in a peer-reviewed journal, but Prof Zjicek has presented the results to colleagues at the conference of the Association of British Neurologists in Brighton this week.
Some early studies of cannabinoids, including human trials and laboratory models of MS had suggested that THC may protect neurons from degeneration (Journal of Neuroimmunology) and (Lancet). However, these results have not been borne out in the current clinical trial in people with progressive MS.
The study set out to investigate whether THC is safe and effective in slowing progression in people with MS over a three year period. They also aimed to examine the value of the trial design which used methods such as patient-based assessments as well as traditional clinical outcome measures.
493 people with primary or secondary progressive MS were recruited from 27 centres across UK between May 2006 and July 2008. All participants in the trial were required to be able to walk (with aids if needed). Participants were randomly assigned to receive THC capsules or placebo (dummy) capsules, to be taken by mouth over three years. 329 people were allocated to receive the THC capsules and 164 were allocated to the placebo group. The study was ‘double-blind’, meaning that neither the participants nor the doctors and nurses involved at the study sites knew who was assigned to the treatment group.
The Expanded Disability Status Scale (EDSS) and the Multiple Sclerosis Impact Scale (MSIS-29) were used as the primary outcome measures. The MSIS-29 is questionnaire designed specifically for MS and was completed by the participants. The study also collected information on a range of ‘secondary’ measures including a timed walk, peg test and number test. Participants also provided their own assessment of their MS via regular questionnaires. In addition, some centres in the multi-centre trial conducted annual MRI scans on the participants.
Overall the study found no evidence that THC has an effect on MS progression as measured by either the EDSS or MSIS-29 questionnaire responses. There was some evidence that THC might have a beneficial effect in people whose MS was less advanced. However, as this was only found in a small group of people in this study it will require confirmation by further studies.
The findings are disappointing, but the study team do not rule out further follow-up on this work. In particular the lessons learned in relation to the design of clinical trials for progressive MS will be very important for the research community.