Preliminary Results from Sativex® Phase III Multiple Sclerosis spasticity study
GW to evaluate optimal regulatory filing strategy with marketing partners

Porton Down, UK, 17 March 2006 - GW Pharmaceuticals plc (AIM: GWP) today announces preliminary results from a Phase III study of Sativex® in the relief of spasticity in people with Multiple Sclerosis (MS). This study is one of a number of Phase III studies which are currently taking place to support approval of Sativex across Europe in a range of target indications.

Analysis of the per protocol population (those patients that complied with the study protocol) showed a positive and statistically significant improvement in the primary outcome measure (p<0.05). Analysis of the Intention to Treat (ITT) population (all study patients regardless of whether they complied with the protocol) was in favour of Sativex but not to a degree that reached statistical significance (p>0.05).

Dr Stephen Wright, R&D Director at GW, said:

"The study supports the significant positive data already generated from previous GW studies in people with MS who have failed to respond to currently available anti-spasticity treatments. This is a high need patient population and we are considering the regulatory impact of this new study in light of the different outcomes of the two statistical analyses and in the context of our overall regulatory strategy for Sativex. Whilst this study may provide GW with a regulatory route in Europe for the spasticity indication, the bulk of our positive clinical data relates to neuropathic pain. We have two further Phase III neuropathic pain studies due to report later this year and we need to consider with our marketing partners the relative benefits of awaiting that data before submitting the next regulatory filing."

The trial reported today was a randomized placebo-controlled parallel group study in 335 people with spasticity due to MS. All patients entering the study were taking best available anti-spasticity medication and remained on such medication through the trial. Hence, any improvements seen in the trial were obtained over and above currently available treatment. The primary outcome measure was the improvement in spasticity as measured on a 0-10 numeric rating scale. The duration of treatment in the study was 14 weeks.

In this trial, the primary endpoint, and two key secondary endpoints (the Responder Analysis and the Carer Global Impression of Change), in the per protocol analysis achieved statistical significance, whereas the outcomes in the ITT analysis were positive but non-significant. The lack of significance in the ITT analysis was not due to a lack of effect of Sativex, but rather was due to a larger than expected placebo response, thus reducing the size of the difference between the two groups. Had the placebo response been the same as in GW’s previous completed Phase III spasticity study, the ITT analysis in this new study would also have been statistically significant.

Separately, a pooled analysis across the three Sativex MS spasticity studies now completed, incorporating a total of 652 patients, shows Sativex to be significantly superior to placebo (p<0.05).

As in previous studies, adverse event data in this latest trial showed the medicine to be generally well tolerated.

Professor Mike Barnes, Professor of Neurological Rehabilitation, University of Newcastle, and President of the World Federation of neuro-rehabilitation, said:

“This study explored the effects of Sativex in a high need patient population who, by definition, had exhausted all available anti-spasticity medication and yet remained in need of treatment. As a clinician, the positive per protocol result confirms to me that Sativex has a valuable role in treating those patients for whom there are no further treatment options available."

Sativex is approved and marketed in Canada in the indication of MS neuropathic pain. In the last eighteen months, GW has put in place a substantial Phase III clinical programme for global regulatory success for Sativex in multiple indications. In addition to MS spasticity, the following Phase III trials are ongoing or planned:

- two Phase III peripheral neuropathic pain studies, due to complete later this year
- a further Phase III trial in MS neuropathic pain due to complete in mid-2007
- a Phase III clinical programme for the treatment of cancer pain

Dr Geoffrey Guy, Executive Chairman of GW, said:

"This study is one of several studies included within our comprehensive Phase III clinical programme for Sativex across multiple indications including neuropathic pain and spasticity in multiple sclerosis, peripheral neuropathic pain and cancer pain. GW's regulatory strategy in Europe is directed towards approval of Sativex in all the major countries and not just the UK. On this basis, GW, together with our marketing partners and the relevant regulatory authorities, will evaluate the relative strengths of a regulatory submission for the relief of spasticity or neuropathic pain. We will proceed so that the next regulatory filing in Europe has the maximum chance of success across the indications and across the major markets.

"GW has recently achieved a number of significant milestones. Sativex is now approved in Canada for the relief of neuropathic pain in MS. In the US, the FDA has permitted Sativex to enter directly into Phase III trials and in Continental Europe, GW has signed an exclusive marketing agreement with Almirall Prodesfarma for Sativex. The Company continues to make excellent progress towards realising its global ambitions."

There will be a conference call for analysts today at 8.30am. Please contact Gemma Cross Brown at Financial Dynamics on +44 (0) 20 7831 3113 for details. A recording of this call will be accessible on the press releases page in the investor relations section of the GW website ( later this morning.