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Positive Sativex® Study Confirms Long Term Efficacy in MS Neuropathic Pain

Positive Sativex® Study Confirms Long Term Efficacy in MS Neuropathic Pain
08/09/2008

Results Support Design of Ongoing Phase III MS Spasticity Study

Porton Down, UK, 8 September 2008: GW Pharmaceuticals plc (GWP:AIM) announces positive results from a placebo-controlled "randomized withdrawal" study of Sativex® in patients with neuropathic pain due to Multiple Sclerosis (MS). This study design is described by regulators as being sufficient to satisfy the need for long-term efficacy data.

This randomized withdrawal study evaluated 42 MS patients with central neuropathic pain who had previously been in a Sativex Phase III MS neuropathic pain study and who continued to take Sativex on an open label basis for 12 weeks. They were then randomized to Sativex or placebo for a further 4 weeks in a double-blinded manner. During the randomized period, patients were not permitted to adjust their dose. The purpose of this blinded 4-week "randomized withdrawal" study was to assess the maintenance of pain control in patients who remain on Sativex versus those who switch to placebo.

In the patients who were randomized to Sativex pain scores remained stable. In the patients randomized to placebo, pain and sleep scores deteriorated. The prospectively defined primary efficacy endpoint of the study - the time to treatment failure - was statistically significantly in favour of Sativex (p=0.036). The difference between Sativex and placebo was also significant for mean pain score (p=0.028) and sleep quality (p=0.015). The results of all other symptom-related endpoints showed that Sativex patients maintained or improved their response whilst the symptoms of those who switched from Sativex to placebo worsened in the 4 weeks following cessation of active treatment. During the randomized withdrawal period, there were 2 patients with adverse events on Sativex, and 5 on placebo. One patient on placebo withdrew from the study. There was no evidence of any withdrawal syndrome.

Until now, all the evidence for long-term maintenance of efficacy of Sativex has come from long-term open-label exposurei. The results reported today confirm in the context of a placebo-controlled double-blind study that efficacy is indeed maintained in long-term use.

The results of this study are of further significance to GW since the design bears important similarities to the ongoing Phase III MS spasticity study requested by the UK regulator prior to granting approval for Sativex. This ongoing Phase III study involves all patients receiving Sativex for 4 weeks, following which Sativex responders are randomized to continue on Sativex or switch to placebo for a further 12 weeks. This study is due to report results in Q1 2009 with a regulatory submission targeted for H1 09.

Dr Stephen Wright, GW's R&D Director, said: "This is the first placebo-controlled study showing that Sativex provides long term efficacy for MS patients with neuropathic pain and supplements previously published open-label studies. In addition, these results support the design of the ongoing Phase III trial in MS spasticity. It is encouraging to note that if the difference between Sativex and placebo achieved in the results today are replicated in the ongoing Phase III MS spasticity study, this Phase III study will meet its objectives."