Amendment to Registration Statement for NASDAQ

GW Pharmaceuticals Files Updated Amendment to Registration Statement for NASDAQ Global Market Listing

Porton Down, UK, 18 April 2013: GW Pharmaceuticals plc (AIM: GWP or the "Company") hereby provides notification that, further to the announcement on 19 March 2013 of the filing of a registration statement with the U.S. Securities and Exchange Commission ("SEC") for an initial public offering of American Depositary Shares ("ADSs") on the NASDAQ Global Market, the Company filed today an updated amendment to the Registration Statement with the SEC, known as a preliminary prospectus.

A copy of the preliminary prospectus may be obtained from Lazard Capital Markets LLC, Attn: Syndicate Department, 30 Rockefeller Plaza, 48th Floor, New York, NY 10020, Telephone: (800) 542-0970; from Cowen and Company, LLC, c/o Broadridge Financial Services, 1155 Long Island Avenue, Edgewood, NY,11717, Attn: Prospectus Department, Phone (631) 274-2806 / Fax (631) 254-7140; from Canaccord Genuity Inc., Attention: Syndicate Department, 99 High Street, 12th Floor, Boston, Massachusetts 02110, or by telephone at (617) 371-3900; and from Roth Capital Partners, LLC, Equity Capital Markets, 888 San Clemente Drive, Newport Beach, CA 92660, at 800-678-9147 and [email protected].

The offering is subject to market and other conditions, and there can be no assurances as to whether or when the offering may be completed or as to the actual size or terms of the offering. A registration statement relating to these securities has been filed with the SEC but has not yet become effective. These securities may not be sold nor may offers to buy be accepted prior to the time the registration statement becomes effective. This release shall not constitute an offer to sell or the solicitation of an offer to buy nor shall there be any sale of these securities in any state or jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state or jurisdiction.

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About GW Pharmaceuticals plc

Founded in 1998, GW is a biopharmaceutical company focused on discovering, developing and commercializing novel therapeutics from its proprietary cannabinoid product platform in a broad range of disease areas. GW commercialized the world's first plant-derived cannabinoid prescription drug, Sativex®, which is approved for the treatment of spasticity due to multiple sclerosis in 20 countries. Sativex®, is also in Phase 3 clinical development as a potential treatment of pain in people with advanced cancer. This Phase 3 program is intended to support the submission of a New Drug Application for Sativex® in cancer pain with the U.S. Food and Drug Administration and in other markets around the world. GW has established a world leading position in the development of plant-derived cannabinoid therapeutics and has a deep pipeline of additional cannabinoid product candidates, including two distinct compounds, GWP42004 and GWP42003, in Phase 2 clinical development for Type 2 diabetes and ulcerative colitis, respectively, and at least two additional programs expected to enter Phase 1 and Phase 2 clinical trials in the next 12 months. For further information, please visit www.gwpharm.com