London, UK; Tokyo, Japan; June 30 2010: GW Pharmaceuticals plc (AIM: GWP) and Otsuka Pharmaceutical Co., Ltd. today announce that they have signed a three year extension to their global cannabinoid research collaboration. This collaboration was originally signed in July 2007 with a three year term, and the collaboration will now extend to the end of June 2013.

Under the research collaboration agreement, GW and Otsuka Pharmaceutical research a range of GW cannabinoids as potential new drug candidates in the field of Central Nervous System (CNS) disorders and oncology.

Over the next three years, Otsuka Pharmaceutical will make available a research fund of $12 million to cover research activities carried out under this Agreement. Otsuka Pharmaceutical has the discretion to increase this funding from time to time as the development of selected drug candidates advances.

Dr Geoffrey Guy, GW's Chairman, said, "Over the last three years, the GW-Otsuka research collaboration has yielded highly promising data and new intellectual property for GW cannabinoids across a range of target indications within CNS and oncology. We are very pleased that Otsuka has elected to extend this collaboration and believe that this provides a significant endorsement of the potential of GW's cannabinoid pipeline"

Dr. Taro Iwamoto, President and Representative Director of Otsuka Pharmaceutical Co., Ltd. said, "We are delighted with the progress of our collaboration with GW Pharmaceuticals in the investigation of cannabinoids as potential new medicines in the field of CNS and oncology. Over the last three years, GW and Otsuka have formed a strong close working relationship and we are excited to be extending our collaboration to develop and commercialize innovative new treatments in order to further our contribution to global well being".

The GW-Otsuka research collaboration is led by a joint research team incorporating senior scientists from both companies. This team works in close collaboration with a number of leading cannabinoid scientists around the world in the evaluation of a range of GW cannabinoids as drug candidates within the field of CNS and oncology.

The objective of this collaboration is to select 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 Pharmaceutical 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.

In addition to the research agreement, GW and Otsuka Pharmaceutical also collaborate in the development of Sativex ^®, GW's lead product, in the United States under an exclusive license agreement signed in February 2007. The initial target indication for Sativex in the US is as a treatment of pain in patients with advanced cancer, who experience inadequate analgesia during optimized chronic opioid therapy.

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.

Otsuka Pharmaceutical Co., Ltd. is a wholly owned subsidiary of Otsuka Holdings Co., Ltd., the holding company for the Otsuka Group. The Otsuka Group comprises 145 companies and employs approximately 39,000 people in 23 countries and regions worldwide. Otsuka and its consolidated subsidiaries earned ¥1,084.2 billion (approx. US $11.7 billion) in annual revenues in fiscal 2009.

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 for patients who suffer from a range of serious ailments, in particular multiple sclerosis 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