London, UK; Tokyo, Japan; 9 July 2007: GW Pharmaceuticals plc (AIM: GWP) and Otsuka Pharmaceutical Co., Ltd. today announce that they have signed a global cannabinoid research collaboration in the field of Central Nervous System (CNS) and oncology in order to research, develop and commercialize a range of candidate cannabinoid products.

The research collaboration agreement follows the signature in February 2007 of an exclusive license and development agreement between GW and Otsuka to develop and market Sativex^®, GW' s lead product, in the United States.

The cannabinoid research collaboration has an initial term of three years, during which Otsuka will make available a research fund of $9 million, which may be increased from time to time by Otsuka, to cover research activities carried out by GW and its scientific collaborators under this agreement.

The GW-Otsuka collaboration research team, which incorporates senior scientists from both companies, will evaluate a range of GW cannabinoids as drug candidates within the field of CNS and oncology, with a view to selecting the most promising candidates for full clinical development, regulatory approval and global commercialization. Products selected for full development will be the subject of a license from GW. Under the terms of each product license, Otsuka will fund the global development and commercialization of such products, and GW will receive license fees, milestone payments and a long term commercial supply price and royalty. The financial terms of each license are to be agreed at the time of selection of each product for global development.

Dr Geoffrey Guy, GW' s Chairman, said, "Otsuka is a world leader in the field of CNS and we are delighted to be working with such a prestigious company to enhance and develop our product pipeline. The relationship between GW and Otsuka commenced earlier this year with the signature of the Sativex US license agreement, and this new research collaboration will serve to enhance further the close relationship between our two companies.

"Over the last few years, GW has been undertaking a primary cannabinoid research programme addressing a range of therapeutic areas under the direction of Professor Roger Pertwee and in collaboration with a number of other world leading cannabinoid scientists. This collaboration with Otsuka will enable GW to accelerate and expand this programme in order to develop and commercialise novel cannabinoid medicines in the exciting areas of CNS and oncology."

Mr. Tatsuo Higuchi, President of Otsuka Pharmaceutical Co., Ltd. said, "Otsuka strives to contribute to the health of people around the world through the creation of innovative products in an effort to address unmet medical needs. We are delighted to be embarking on this great opportunity with GW Pharmaceuticals to further investigate cannabinoids, which are considered to be a significant potential source of new medicines in the field of CNS and oncology. At the same time, we anticipate that our further contribution to global well being will be significant as a result of this research collaboration."

Notes to Editors

About Cannabinoids

The cannabinoid (CB) receptor system is a complex and far-reaching system which has only started to become understood in the last decade or so. To date, CB₁ and CB₂ receptors have been identified and cloned. Initially, the chemicals which affect these receptors ("cannabinoids") were identified only within the cannabis plant, but extensive scientific investigation has now elaborated a series of endogenous chemicals which maintain this 'endocannabinoid system' . These endogenous cannabinoids are produced in human tissues, exert their actions within those tissues and are then destroyed locally. This allows the system to function in a fine-tuning, modulatory role, and abnormalities of the endocannabinoid system have now been found in several important diseases. Originally, it was believed that these receptors acted largely within the brain, but it is becoming increasingly clear that they are present at many different sites, in many different body systems.

The importance of the integrity of this system of receptors in maintaining several critical areas of mental and physical well-being is becoming clearer because of the type of research that GW and its collaborators are performing. Equally, this research work has identified several important disease areas where the administration of cannabinoids as medicines may lead to desirable therapeutic consequences. Cannabinoid modulators are showing promise in chronic painful conditions, in movement disorders, and in disorders of cell proliferation such as cancer. Furthermore, the role of cannabinoids in the brain may offer therapeutic promise in disorders of behaviour and mood. This is an area of active scientific discovery and therapeutic research which may deliver a range of new treatments to meet unmet medical needs.

About Sativex US License Agreement

On February 14 2007, GW and Otsuka entered into an exclusive license agreement to develop and market Sativex, GW' s lead product, in the US.

In 2006, the Food & Drug Administration (FDA) permitted Sativex to enter directly into Phase III clinical trials in the US for the treatment of pain in patients with advanced cancer that has not been adequately relieved by opioid medications. GW and Otsuka currently plan for the first US pivotal efficacy clinical trial to be a Phase II/III cancer pain dose ranging study, to commence in the near future.

About Otsuka Pharmaceutical Co., Ltd

Founded in 1964, Otsuka Pharmaceutical Co., Ltd. is a global healthcare company with the corporate philosophy: 'Otsuka - people creating new products for better health worldwide.' Otsuka researches, develops, manufactures and markets innovative and original products, with a focus on pharmaceutical products for the treatment of diseases and consumer products for the maintenance of everyday health. Otsuka is committed to being a corporation that creates global value, adhering to the high ethical standards required of a company involved in human health and life, maintaining a dynamic corporate culture, and working in harmony with local communities and the natural environment.

The Otsuka Pharmaceutical Group comprises 99 companies and employs approximately 31,000 people in 17 countries and regions worldwide. Otsuka and its consolidated subsidiaries earned US$7.2 billion in annual revenues in fiscal 2006.

Focusing on the central nervous system, the circulatory, respiratory, and digestive systems, ophthalmology and dermatology, Otsuka' s pharmaceutical product business engages in the research and development, manufacture and sale of pharmaceuticals, aiming to maximize the assets of a global network to address unmet medical meets. For additional information, visit www.otsuka-global.com

About GW

GW was founded in 1998 and listed on the AiM, a market of the London Stock Exchange, in June 2001. Operating under license from the UK Home Office, the company researches and develops cannabinoid pharmaceutical products that alleviate pain and other neurological symptoms in patients who suffer from serious ailments. GW has assembled a team of over 100 scientists with extensive experience in developing 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.