GW Pharmaceuticals
Corporate brand
UnclaimedBritish biopharmaceutical company known for developing prescription medicines derived from cannabis compounds.
Last updated August 26, 2026
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Overview
GW Pharmaceuticals was a British biopharmaceutical company established in 1998 by physicians Geoffrey Guy and Brian Whittle. It developed prescription medicines based on cannabinoids and became one of the most prominent companies in the regulated medical-cannabis field. Its work was conducted within the United Kingdom’s controlled drug and medicines framework: during its founding year, GW obtained authorization from the UK Home Office and the Medicines and Healthcare products Regulatory Agency to cultivate, possess, and supply cannabis for scientific research. It also entered into a research and development agreement with Hortapharm B.V., a cannabis research company based in Amsterdam. The company’s development strategy centered on identifying, standardizing, and clinically evaluating compounds derived from the cannabis plant rather than marketing unregulated cannabis products. Its most recognized early medicine was nabiximols, sold under the brand name Sativex. Administered as an oral mouth spray, Sativex is a botanical cannabis extract containing both tetrahydrocannabinol and cannabidiol. It was authorized in the United Kingdom in 2010 for the relief of multiple-sclerosis-related symptoms, including spasticity and neuropathic pain. Sativex became historically significant as the first natural cannabis plant derivative to receive marketing approval in any country. GW later expanded its research toward purified cannabidiol for severe childhood epilepsies. The company initiated Phase 3 studies in 2015 for cannabidiol oral solution in Dravet syndrome and Lennox–Gastaut syndrome, two rare and serious seizure disorders. The US Food and Drug Administration granted the program Fast Track designation in 2015, and the resulting medicine, Epidiolex, received FDA approval in June 2018. The product was subsequently authorized in the European Union in September 2019 under the name Epidyolex. These approvals helped move cannabinoid-based medicines from a niche research area into regulated treatment for specific neurological conditions. GW became a public company when it joined the London Stock Exchange’s Alternative Investment Market in 2001. In May 2013, it added a NASDAQ listing while retaining its AIM listing, increasing its access to US healthcare investors and reflecting the growing importance of its American clinical and commercial activities. The company also pursued collaborations and development arrangements, including work associated with cannabidiol trials for children with seizure disorders and a 2020 distribution partnership with Bayer for Sativex in the United Kingdom. Jazz Pharmaceuticals acquired GW Pharmaceuticals in May 2021. Following the transaction, GW became part of Jazz’s specialty pharmaceutical portfolio, while its cannabinoid medicines and related development capabilities were incorporated into the larger company. GW’s principal historical contribution was the clinical development and regulatory validation of cannabis-derived prescription therapies, particularly Sativex and Epidiolex/Epidyolex.
History
GW Pharmaceuticals was founded in 1998 by doctors Geoffrey Guy and Brian Whittle to develop medicines derived from cannabis compounds within a regulated pharmaceutical framework. The company's formation coincided with the creation of a controlled research pathway in the United Kingdom. In its first year, GW obtained permission from the UK Home Office and the Medicines and Healthcare products Regulatory Agency to cultivate, possess, and supply cannabis for scientific research. Later in 1998, it entered into a contract with Hortapharm B.V., an Amsterdam-based cannabis research and development company. The company's early work focused on turning standardized cannabis extracts into clinically testable medicines. This approach culminated in nabiximols, marketed as Sativex, a mouth spray made from cannabis extracts containing both THC and CBD. Sativex was approved in the United Kingdom in 2010 for the treatment of symptoms associated with multiple sclerosis, including spasticity, neuropathic pain, and bladder-related symptoms. Its authorization was a major regulatory milestone because it was described as the first approval anywhere for a natural cannabis plant derivative. GW entered public markets in 2001 through a listing on the London Stock Exchange's Alternative Investment Market. In May 2013, it became dual-listed on NASDAQ and AIM. The additional US listing reflected the importance of the American market to the company's clinical development and future commercialization plans. GW subsequently broadened its research beyond botanical extracts, concentrating particularly on pharmaceutical cannabidiol for severe forms of childhood epilepsy. In 2014, the company entered into a deal connected with clinical-trial development in New York involving cannabidiol for children with seizures and other medical complications. In 2015, it began Phase 3 trials of cannabidiol oral solution in Dravet syndrome and Lennox–Gastaut syndrome. The FDA granted the program Fast Track designation that year. The resulting product, Epidiolex, was approved by the FDA in June 2018 for specified seizure disorders. European authorization followed in September 2019 under the name Epidyolex. GW continued commercial development of its earlier product alongside the cannabidiol program. In 2020, it concluded a partnership with Bayer for distribution of Sativex in the United Kingdom. The arrangement illustrated the company's use of larger pharmaceutical partners to support market access for specialist medicines. In May 2021, Jazz Pharmaceuticals acquired GW Pharmaceuticals. The acquisition ended GW's independent existence as a publicly traded biopharmaceutical company and placed its products and cannabinoid-focused expertise within Jazz Pharmaceuticals. Historically, GW is associated with the transition of cannabis-derived compounds from controlled research material into approved prescription medicines, especially in multiple sclerosis symptom management and rare epileptic disorders.
- 2021
Acquisition by Jazz Pharmaceuticals
[1]Jazz Pharmaceuticals acquired GW Pharmaceuticals, integrating the company into its specialty-pharmaceutical operations.
- 2019
Epidyolex authorized in Europe
[1]The cannabidiol medicine received European authorization under the brand name Epidyolex.
- 2018
Epidiolex approved in the United States
[1]The FDA approved Epidiolex for specified severe childhood seizure disorders.
- 2015
Phase 3 cannabidiol trials begin
[1]GW began late-stage trials of cannabidiol oral solution for Dravet syndrome and Lennox–Gastaut syndrome.
- 2013
NASDAQ and AIM dual listing
[1]The company became dual-listed on NASDAQ and AIM.
- 2010
Sativex approved in the United Kingdom
[1]Nabiximols, marketed as Sativex, received UK approval for symptoms associated with multiple sclerosis.
- 2001
AIM listing
[1]GW Pharmaceuticals listed on the Alternative Investment Market of the London Stock Exchange.
- 1998
Company founded and UK cannabis research authorization obtained
[1]Geoffrey Guy and Brian Whittle founded GW Pharmaceuticals. The company obtained UK authorization to cultivate, possess, and supply cannabis for scientific research.
- 1998
Research agreement with Hortapharm
[1]GW entered into a contract with Amsterdam-based cannabis research and development company Hortapharm B.V.
Products and positioning
Evidence-led biopharmaceutical developer specializing in regulated cannabinoid medicines for neurological conditions, including multiple-sclerosis symptoms and rare childhood epilepsies.
Cannabinoid oral spray · 2010
Sativex
Sativex is the trade name for nabiximols, a botanical cannabis extract delivered as a mouth spray. It contains cannabinoid constituents including THC and CBD and was developed to address symptoms associated with multiple sclerosis. The product received UK approval in 2010 for symptoms including spasticity, neuropathic pain, and overactive-bladder-related problems. Its approval made it a landmark regulated cannabis-derived medicine.
Purified cannabidiol oral solution · 2018
Epidiolex
Epidiolex is GW's cannabidiol oral solution for specified severe seizure disorders. GW began Phase 3 development in 2015 for Dravet syndrome and Lennox–Gastaut syndrome, and the US FDA approved the product in June 2018. The medicine represented GW's move from botanical cannabis extracts toward a more precisely characterized cannabinoid pharmaceutical for rare neurological diseases.
Purified cannabidiol oral solution · 2019
Epidyolex
Epidyolex is the European brand name for GW's cannabidiol oral solution. It received European authorization in September 2019 for specified rare epilepsy indications. The product is the same core cannabidiol medicine known as Epidiolex in the United States, with regional naming reflecting different regulatory markets.
Brand decisions
2021
Accept acquisition by Jazz PharmaceuticalsM&ABackground
GW had developed approved cannabinoid medicines and a specialist neurological-drug portfolio but was operating as an independent public company.
Action taken
Jazz Pharmaceuticals acquired GW Pharmaceuticals in May 2021.
Aftermath
GW's products and development capabilities became part of Jazz Pharmaceuticals, ending GW's independent public-company status.
2020
Partner with Bayer for UK Sativex distributionStrategyBackground
GW sought commercial distribution support for Sativex in its home market.
Action taken
GW concluded a partnership with Bayer covering distribution of Sativex in the United Kingdom.
Aftermath
The arrangement gave the specialist medicine access to the distribution capabilities of a larger pharmaceutical company.
2015
Advance cannabidiol into Phase 3 developmentOtherBackground
GW was seeking to develop a cannabinoid medicine for severe childhood epilepsies, particularly Dravet syndrome and Lennox–Gastaut syndrome.
Action taken
The company initiated Phase 3 trials of cannabidiol oral solution and pursued FDA Fast Track designation.
Aftermath
The program led to the later US approval of Epidiolex and European authorization of Epidyolex.
Recent events
Reported
Jazz Pharmaceuticals completes acquisition of GW Pharmaceuticals[2]
Jazz Pharmaceuticals announced that it completed its acquisition of GW Pharmaceuticals.
Jazz Pharmaceuticals announces acquisition of GW Pharmaceuticals[3]
Jazz Pharmaceuticals and GW Pharmaceuticals announced a definitive agreement for Jazz to acquire GW for $220 per American Depositary Share, in a transaction valued at $7.2 billion. The transaction was subject to shareholder, court and regulatory approvals and was expected to close in the second quarter of 2021.
Sources3 sources
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