Exclusive Licence Agreement Signed with Novartis

GW Signs Exclusive Licence Agreement to Commercialise Sativex® in Australia, Asia, Middle-East and Africa

Porton Down, UK; 11 April 2011: GW Pharmaceuticals plc (AIM:GWP) today announces that it has entered into an exclusive licence agreement for Novartis Pharma AG to commercialise Sativex® in Australia and New Zealand, Asia (excluding Japan, China and Hong Kong), Middle East (excluding Israel/Palestine) and Africa.

Under the terms of the agreement, Novartis will have exclusive commercialisation rights to Sativex® and will also be responsible for regulatory filings and act as Marketing Authorisation holder for Sativex®. GW will be responsible for the manufacture and supply of Sativex® to Novartis.

Sativex® has been developed as a treatment for spasticity due to Multiple Sclerosis (MS). It is anticipated that regulatory filings for Sativex® in MS will begin in some of the countries in the above region during 2011. Sativex® is also in Phase III clinical development for the treatment of cancer pain.

Under the agreement, GW will receive an upfront payment of $5 million and will be eligible for additional payments totaling $28.75 million upon the achievement of certain approval and commercial milestones. In addition, GW will receive royalties on net sales of Sativex®.

Justin Gover, GW's Managing Director, said, "We are delighted to have entered into this agreement with Novartis. As one of the world's leading pharmaceutical companies with a strategic focus in both MS and oncology, Novartis represents an excellent commercial partner for Sativex in these important and growing international markets."

Sativex® is licensed to Otsuka Pharmaceutical Co. Ltd in the United States, to Almirall S.A. in Europe (excluding the United Kingdom), to Bayer HealthCare AG in the UK and Canada, and to Neopharm Group in Israel/Palestine.

Enquiries:

Notes to Editors

Sativex®

Sativex® is an endocannabinoid modulator made of two actives - THC (delta-9-tetrahydrocannabinol) and CBD (cannabidiol) - which was developed and is manufactured by GW.

Sativex® is indicated as an add-on treatment for patients with moderate to severe spasticity due to multiple sclerosis (MS) who have not adequately responded to other anti-spasticity medications and who have demonstrated a clinically significant improvement in symptoms related to spasticity during an initial treatment testing periodi.

Sativex® contains active ingredients known as 'cannabinoids' which are extracted from the plant Cannabis Sativa grown and processed under strictly controlled conditions. Cannabinoids react with cannabinoid receptors that exist naturally throughout our body, including the brain.ii A receptor is a site located in a brain cell in which certain substances can stick or "bind" for a while. If this happens, this binding has an effect on the cell and the nerve impulses it produces, causing a 'dimming-down' of the spasticity symptom. In patients who respond to Sativex®, this is the effect that improves their spasticity symptoms and helps them cope with their daily activities.iii

Sativex® is approved in the UK, Spain, Canada and New Zealand in the treatment of spasticity due to MS. In addition, a further six European countries (Germany, Italy, Sweden, Denmark, Austria and the Czech Republic) have recently recommended Sativex® for approval and are expected to grant national licences in mid-2011.

Spasticity

Spasticity is a symptom defined by patients and carers as muscle spasms, seizing-up, stiffness and/or difficulty in moving muscles and it is one of the most common symptoms of MS, occurring in up to 75% of MS sufferers in the course of the disease. Spasticity can affect many aspects of the daily lives of patients with MS and is one of the main factors contributing to their distress and disability.iv

Cancer Pain

Sativex® recently commenced a Phase III trials programme in cancer pain, which is being performed in conjunction with GW's licensing partner for Sativex® in the US, Otsuka Pharmaceutical Co. Ltd. The programme includes two Phase III randomised placebo-controlled multi-centre multinational trials as well as a long term extension study. Each Phase III trial will include approximately 370 patients and will evaluate the efficacy and safety of Sativex versus placebo over a 5 week treatment period.

Studies suggest that more than one-third of patients with cancer, and more than three-quarters of those with advanced disease, have chronic pain. Large surveys indicate that optimal opioid therapy does not yield sufficient relief in a substantial proportion of these patients.

About GW Pharmaceuticals

GW Pharmaceuticals plc (AIM:GWP) was founded in 1998 and is listed on the AIM, a market of the London Stock Exchange. Operating under licence from the UK Home Office, the company researches and develops cannabinoid pharmaceutical products for patients who suffer from a range of serious ailments, in particular MS and cancer pain. GW has assembled a large in-house scientific team with expertise in cannabinoid science as well as experience in the development of both plant based prescription pharmaceutical products and medicines containing controlled substances. GW occupies a world leading position in cannabinoids and has developed an extensive international network of the most prominent scientists in the field.

For further information, please visit www.gwpharm.com

This news release may contain forward-looking statements that reflect GWs current expectations regarding future events, including development and regulatory clearance of the GW's products. Forward-looking statements involve risks and uncertainties. Actual events could differ materially from those projected herein and depend on a number of factors, including (inter alia), the success of the GW's research strategies, the applicability of the discoveries made therein, the successful and timely completion of uncertainties related to the regulatory process, and the acceptance of Sativex® and other products by consumer and medical professionals.

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i Patient leaflet

ii GW Pharmaceuticals: Cannabinoid Science: Mechanism of action. Available at. http://www.gwpharm.com/mechanism-of-action.aspx (latest access: 23/03/2011).

iii GW Pharmaceuticals: Cannabinoid Science: Cannabinoid Compounds. Available at http://www.gwpharm.com/types-compounds.aspx (Last accessed:23/03/2011).

iv Rizzo MA et al. Prevalence and treatment of spasticity reported by multiple sclerosis patients. Mult Scler 2004;10:589-595.