Closing of U.S. Follow-on Offering of Nasdaq ADSs

GW Pharmaceuticals plc Announces the Closing of its U.S. Follow-on Offering of American Depositary Shares (ADSs) on the Nasdaq Global Market and Full Exercise of Underwriters' Option to Purchase Additional ADSs

Offering raises $101.1 million

London, UK, January 14, 2014: GW Pharmaceuticals plc (Nasdaq: GWPH, AIM: GWP, "GW" or the "Company"), a biopharmaceutical company focused on discovering, developing and commercializing novel therapeutics from its proprietary cannabinoid product platform, announced today the closing of its previously announced follow-on offering on the NASDAQ Global Market of 2,441,110 American Depositary Shares (ADSs) and the full exercise by the underwriters of their option to purchase 366,165 additional ADSs at a price of $36.00 per ADS raising gross proceeds of $101.1 million (before deducting underwriting discount, commissions and offering expenses). Application has been made for the aggregate number of 33,687,300 ordinary shares of 0.1p each represented by the offered ADSs and the additional ADSs to be admitted to trading on AIM and admission is expected to occur on January 15, 2014.

Morgan Stanley & Co. LLC and Cowen and Company, LLC are acting as joint book-running managers for the offering. Piper Jaffray & Co. is acting as lead manager and Canaccord Genuity Inc. is acting as co-lead manager.

A registration statement relating to these securities was declared effective by the Securities and Exchange Commission on January 8, 2014. Copies of the final prospectus relating to this offering may be obtained from: Morgan Stanley & Co. LLC, Attention: Prospectus Department, 180 Varick Street, 2nd Floor, New York, New York 10014; from Cowen and Company, LLC, c/o Broadridge Financial Services, 1155 Long Island Avenue, Edgewood, NY, 11717, Attn: Prospectus Department; from Piper Jaffray & Co., Attention: Prospectus Department, 800 Nicollet Mall, J12S03, Minneapolis, MN 55402; or from Canaccord Genuity Inc., Attention: Syndicate Department, 99 High Street, 12th Floor, Boston, Massachusetts 02110.

This press 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 other jurisdiction in which such an offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state or other jurisdiction.

This press release is not directed to, or intended for distribution or use by, any person or entity that is a citizen or resident or located in any locality, state, country or other jurisdiction where such distribution, publication, availability or use would be contrary to law or regulation or which would require any registration or licensing within such jurisdiction.

The distribution of this press release into jurisdictions other than the UK may be restricted by law. Persons into whose possession this announcement come should inform themselves about and observe any such restrictions.

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 24 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 a deep pipeline of additional cannabinoid product candidates, including Epidiolex which has received Orphan Drug Designation from the FDA for the treatment of Dravet syndrome, a severe infantile-onset, genetic, drug-resistant epilepsy syndrome. Our product pipeline also includes compounds in Phase 1 and 2 clinical development for glioma, ulcerative colitis, type‑2 diabetes, and schizophrenia.

For further information, please contact:

Enquiries:

For readers in the European Economic Area:

In any EEA Member State that has implemented the Prospectus Directive, this communication is only addressed to and directed at qualified investors in that Member State within the meaning of the Prospectus Directive. The term "Prospectus Directive" means Directive 2003/71/EC (and amendments thereto, including Directive 2010/73/EU, to the extent implemented in each relevant Member State), together with any relevant implementing measure in the relevant Member State.

For readers in the United Kingdom:

This communication, in so far as it constitutes an invitation or inducement to enter into investment activity (within the meaning of s21 Financial Services and Markets Act 2000 as amended) in connection with the securities which are the subject of the offering referred to above or otherwise, is being directed only at (i) persons who are outside the United Kingdom or (ii) persons who have professional experience in matters relating to investments who fall within Article 19(5) ("Investment professionals") of the Financial Services and Markets Act 2000 (Financial Promotion) Order 2005 (the "Order") or (iii) certain high value persons and entities who fall within Article 49(2)(a) to (d) ("High net worth companies, unincorporated associations etc") of the Order; or (iv) any other person to whom it may lawfully be communicated (all such persons in (i) to (iv) together being referred to as "relevant persons"). The ADSs are only available to, and any invitation, offer or agreement to subscribe, purchase or otherwise acquire such ADSs will be engaged in only with, relevant persons. Any person who is not a relevant person should not act or rely on this communication or any of its contents.