United States

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 6-K

REPORT OF FOREIGN PRIVATE ISSUER

PURSUANT TO RULE 13a-16 OR 15d-16

OF THE SECURITIES EXCHANGE ACT OF 1934

For the Month of August, 2016

Commission File Number: 001-35892

GW PHARMACEUTICALS PLC

(Translation of registrant’s name into English)

Sovereign House

Vision Park

Histon

Cambridge CB24 9BZ

United Kingdom

(Address of principal executive offices)

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F.

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1):

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7):

Other Events

On August 9, 2016, GW Pharmaceuticals plc (the “Company”) issued a press release announcing its third quarter financial results and operational progress and details of a conference call to be held at 8:30 a.m. EDT on August 9, 2016 to discuss the results. The press release is attached as Exhibit 99.1 and is incorporated by reference herein.

On August 9, 2016, the Company issued a press release announcing that Dr Stephen Wright has notified the Company’s Board of Directors of his intention to retire and that he plans to step down from his position as Chief Medical Officer and a member of the Board of Directors on May 1, 2017, at which time he will be 65 years old. The press release is attached as Exhibit 99.2 and is incorporated by reference herein.

The information contained in Exhibits 99.1 and 99.2 shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, unless expressly set forth by specific reference in such a filing

Exhibits

99.1 Press Release dated August 9, 2016

99.2 Press Release dated August 9, 2016

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

Exhibit 99.1

GW Pharmaceuticals plc Reports Third Quarter 2016 Financial Results and Operational Progress

- Positive Phase 3 Epidiolex pivotal trial in Lennox-Gastaut Syndrome (LGS) –

- Positive FDA pre-NDA meeting - NDA for Dravet syndrome and LGS on track for H1 2017 submission -

-Conference call today at 8:30 a.m. EDT, 1:30 p.m. BST-

London, UK, 9 August 2016: GW Pharmaceuticals plc (NASDAQ: GWPH, AIM: GWP, GW, the Company or the Group), a biopharmaceutical company focused on discovering, developing and commercializing novel therapeutics from its proprietary cannabinoid product platform, announced financial results for the third quarter ended 30 June 2016.

“We have now reported two positive Phase 3 trials for Epidiolex and are on track for an NDA filing that includes both the Dravet syndrome and Lennox-Gastaut Syndrome indications. We believe that these Phase 3 data show that Epidiolex has the potential to provide a robust and clinically meaningful reduction in seizures in these highly treatment-resistant populations together with an acceptable safety and tolerability profile,” stated Justin Gover, GW’s Chief Executive Officer. “Our recent successful financing has provided GW with the necessary capital to move forward with confidence in preparing to execute a highly successful launch.”

RECENT OPERATIONAL HIGHLIGHTS

FINANCIAL HIGHLIGHTS

Conference Call and Webcast Information

GW Pharmaceuticals will host a conference call and webcast to discuss the third quarter 2016 financial results today at 8:30 a.m. EDT / 1:30 p.m. BST. To participate in the conference call, please dial 877-407-8133 (toll free from the U.S. and Canada) or 201-689-8040 (international). Investors may also access a live audio webcast of the call via the investor relations section of the Company’s website at http://www.gwpharm.com. A replay of the call will also be available through the GW website shortly after the call and will remain available for 90 days. Replay Numbers: (toll free):1-877-660-6853, (international):1-201-612-7415. For both dial-in numbers please use conference ID # 13642862.

Enquiries:

GW Pharmaceuticals plc

(“GW” or “the Company” or “the Group”)

Financial Results for the Third Quarter Ended 30 June 2016

GW Overview

GW was founded in 1998 and 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 has established the world leading position in the development of plant-derived cannabinoid therapeutics through its proven drug discovery and development processes, intellectual property portfolio and regulatory and manufacturing expertise. The Company’s lead cannabinoid product candidate is Epidiolex®, a liquid formulation of pure plant-derived cannabidiol, or CBD, for which GW retains global commercial rights, and which is in development for a number of rare childhood-onset epilepsy disorders. GW has received Orphan Drug Designation from the U.S. Food and Drug Administration, or FDA, for Epidiolex for the treatment of Dravet syndrome, Lennox-Gastaut syndrome, or LGS, Tuberous Sclerosis Complex, or TSC, and Infantile Spasms, or IS, each of which are severe infantile-onset, drug-resistant epilepsy syndromes. Additionally, GW has received Fast Track Designation from the FDA and Orphan Designation from the European Medicines Agency,

or EMA, for Epidiolex for the treatment of Dravet syndrome.

In March 2016, GW reported positive results from the first pivotal Phase 3 trial of Epidiolex in Dravet syndrome and in June 2016 GW reported positive results from the first pivotal Phase 3 trial of Epidiolex in LGS. The Company expects to submit a New Drug Application, or NDA, to the FDA in the first half of 2017 for Epidiolex in both Dravet syndrome and LGS. GW is also building an experienced commercial team in the United States in preparation for the potential future launch of Epidiolex.

GW has a deep pipeline of additional cannabinoid product candidates with an increasing focus on orphan pediatric neurologic conditions. The Company’s pipeline includes cannabidivarin, or CBDV, which is in Phase 2 development in the field of epilepsy and is also being researched within the field of autism spectrum disorders, or ASD. In addition, GW has received Orphan Drug Designation and Fast Track Designation from the FDA for intravenous CBD for the treatment of Neonatal Hypoxic Ischemic Encephalopathy, or NHIE, which is expected to enter Phase 1 development in the fourth quarter of 2016.

Previously, 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 28 countries outside the United States.

U.S. Follow-on Offering

In July 2016, GW successfully completed a U.S. follow-on offering on the NASDAQ Global Market issuing a total of 3,220,000 American Depositary Shares (“ADSs”) at a price of $90.00 per ADS. This total included the full exercise of the underwriter’s option to purchase an additional 420,000 ADSs and resulted in total net proceeds after expenses of approximately $273.1 million (£206.4 million). The funds raised in this offering are primarily intended to support pre-launch commercialization activities for Epidiolex, further expansion of our Epidiolex manufacturing capability to meet anticipated medium and long-term demand, manufacture of Epidiolex inventory in preparation for launch, expansion of the market opportunity for Epidiolex through clinical development of other orphan indications advancement of other pipeline opportunities; and other general corporate purposes, including working capital.

Epidiolex in Dravet syndrome and LGS

GW has been conducting pre-clinical research of CBD in epilepsy since 2007. This research has shown that CBD has significant anti-epileptiform and anticonvulsant activity using a variety of in vitro and in vivo models and that it has the ability to treat seizures in acute animal models of epilepsy with significantly fewer side effects than existing AEDs.

GW’s strategy for the development of Epidiolex within the field of childhood-onset epilepsy is to initially concentrate formal development efforts on four orphan indications: Dravet syndrome, LGS, TSC, and IS, each of which are severe infantile-onset, drug-resistant epilepsy syndromes. GW expects to further expand the potential market opportunity of Epidiolex by targeting additional orphan seizure disorders.

Dravet syndrome

Dravet syndrome is a severe infantile-onset, genetic, drug-resistant epilepsy syndrome with a distinctive but complex electroclinical presentation. Onset of Dravet syndrome occurs during the first year of life with clonic seizures (jerking) and tonic-clonic (convulsive) seizures in previously healthy and developmentally normal infants. Prognosis is poor and approximately 14 percent of children die during a seizure or from Sudden Unexpected Death in Epilepsy or SUDEP. Patients develop intellectual disability and life-long ongoing seizures. There are currently no FDA-approved treatments specifically indicated for Dravet syndrome.

In March 2016, GW reported positive top-line results from the first Phase 3 pivotal efficacy and safety study in 120 patients. For the primary endpoint, patients taking Epidiolex achieved a median reduction in monthly convulsive seizures of 39 percent compared with a reduction on placebo of 13 percent, which was statistically significant (p=0.01). A series of sensitivity analyses of the primary endpoint confirmed the robustness of this result. Results from secondary efficacy endpoints reinforced the overall effectiveness observed with Epidiolex. In this study, Epidiolex was generally well tolerated, with 84 percent of adverse events reported to be mild or moderate. This trial is the largest known controlled trial in Dravet syndrome ever conducted.

In addition to this first Phase 3 trial, GW is conducting a second Phase 3 trial of Epidiolex in Dravet syndrome which is expected to recruit 150 patients. This placebo-controlled trial differs from the first Phase 3 trial in that it includes two Epidiolex dose arms, at 20 mg/kg per day and at 10 mg/kg per day. GW continues to work to enroll this trial and expects to report results from the trial in 2017.

GW is working with the investigators in the first trial on a manuscript for peer-review publication, which is expected in the fourth quarter of 2016, and presentation of data at the upcoming Annual Meeting of the American Epilepsy Society in December 2016.

LGS

LGS is a type of epilepsy with multiple types of seizures, particularly tonic (stiffening) and atonic (drop) seizures. Seizures due to LGS are hard to control and they generally require life-long treatment as LGS usually persists into the adult years. Historically patients with LGS have had few effective treatment options. Intellectual and behavioral problems associated with LGS are common and add to the complexity of this syndrome and the difficulties in managing life with LGS. Drug resistance is one of the main features of LGS.

In June 2016, GW reported positive top-line results from the first LGS Phase 3 pivotal study in 171 patients. During the treatment period, patients taking Epidiolex 20 mg/kg/day achieved a median reduction in monthly drop seizures of 44 percent compared with a reduction of 22 percent in patients receiving placebo, and the difference between treatments was statistically significant (p=0.0135). A series of sensitivity analyses of the primary endpoint confirmed the robustness of this result. Epidiolex was generally well tolerated in this trial with 78 percent of adverse events reported to be mild or moderate. GW expects presentation of additional data from this trial at the upcoming Annual Meeting of the American Epilepsy Society.

The second Phase 3 trial differs from the first Phase 3 LGS trial in that it includes two Epidiolex dose arms, at 20mg/kg and at 10mg/kg. Originally expected to recruit 150 patients, this trial reached a total of 225 patients randomized and is expected to report top-line results at the end of the third quarter of 2016.

Open Label Extension

All patients in the randomized controlled clinical trials who complete the treatment period are eligible to enroll in a long term open label extension trial. To date, 99 percent of patients who have completed the pivotal treatment period have elected to enroll in the open label extension. The withdrawal rate in this open label extension is 19 percent.

Epidiolex New Drug Application (NDA)

Following the success of the first Dravet syndrome Phase 3 trial, GW requested a pre-NDA meeting with the FDA to discuss a proposed Dravet syndrome NDA. This meeting took place in July 2016 and included some discussion of the LGS trial data. As a result of this constructive meeting, GW believes the guidance received was both positive and supportive of the Company’s proposed filing strategy to submit a single NDA that includes Phase 3 data from one Dravet trial and two LGS trials and which remains on track for a submission in the first half of 2017. Subject to satisfactory review, GW now anticipates simultaneous approval of both indications and does not expect to wait for results from the second trial in Dravet syndrome prior to this submission.

In order to support GW’s NDA, the Company expects to provide the FDA with data from ten Phase 1 and Phase 2 studies, as well as safety data in over 1,800 patients from both the expanded access program and pivotal programs, including over 450 patients with one year or more of Epidiolex continuous exposure. This data is in addition to the pivotal efficacy data.

Epidiolex Follow-On Indications

TSC

TSC is a genetic disorder that causes non-malignant tumors to form in many different organs, primarily in the brain, eyes, heart, kidney, skin and lungs. The brain and skin are the most affected organs. The most common symptom of TSC is epilepsy, which occurs in 75 to 90 percent of patients, about 70 percent of whom experience seizure onset in their first year of life. There are significant co-morbidities associated with TSC including cognitive impairment in 50 percent, autism spectrum disorders in up to 40 percent and neurobehavioral disorders in over 60 percent of individuals with TSC.

A number of patients with TSC have been treated with Epidiolex in the expanded access program. At the 69th Annual Meeting of the American Epilepsy Society, safety and efficacy data on 10 patients diagnosed with TSC from the expanded access program were presented by Massachusetts General Hospital for Children (Geffrey et al) on Epidiolex treatment of refractory epilepsy in these patients. In this poster, there was a response rate of 50%, 50%, 40%, 60% and 66% at 2, 3, 6, 9, and 12 months of treatment with Epidiolex, respectively. Side effects were seen in five patients (50%) and most were resolved with anti-epileptic drug or CBD dose adjustment.

In April 2016, GW commenced a Phase 3 trial of Epidiolex in patients with TSC. This dose-ranging trial is a 16-week comparison of Epidiolex versus placebo in a total of approximately 200 patients, aged one to 65 years, to assess the safety and efficacy of Epidiolex as an adjunctive anti-epileptic treatment. The primary measure of this trial is the percentage change from baseline in seizure frequency during the treatment period. Primary endpoint seizures include focal motor seizures with or without impairment of consciousness or awareness and generalized convulsive seizures.

Infantile Spasms (IS)

An infantile spasm is a specific type of seizure seen in an epilepsy syndrome of infancy and childhood known as West syndrome. West syndrome is characterized by infantile spasms, developmental regression, and a specific pattern on electroencephalography, or EEG, testing called hypsarrhythmia (chaotic brain waves). The onset of infantile spasms is usually in the first year of life, typically between 4 to 8 months of age.

In December 2015, at the Annual Meeting of the American Epilepsy Society, safety and efficacy data on nine patients suffering from epileptic spasms from the Epidiolex expanded access program were presented by Massachusetts General Hospital for Children (Abati et al). Epilepsy spasms often remain refractory to standard AEDs. According to this poster, Epidiolex exerted its effects in a short time course, with a response rate of 67 percent after two weeks and 78 percent after one month. Three of nine patients became spasm-free after two weeks of Epidiolex treatment.

GW expects to commence a two-part Phase 3 trial of Epidiolex in patients with IS in the fourth quarter of 2016.

Epidiolex Manufacturing

GW is currently manufacturing Epidiolex through utilization of in-house and external third party facilities for various steps in the production process. The Company expects to satisfy near-term requirements for Epidiolex from these current facilities but is also in the process of scaling-up various parts of the production process both in-house and with external third parties. GW is actively scaling its growing and manufacturing of Epidiolex to meet anticipated commercial demand, if approved. In 2015, GW’s production of CBD botanical raw materials increased by a factor of approximately 20 times) compared with the previous year and is expected to double in 2016, equating to approximately 1.6 million 100mg/ml bottles of Epidiolex. With expectations of significant demand for Epidiolex upon potential approval, GW plans to continue expansion of Epidiolex plant growing capacity well beyond this 2016 goal. GW believes it is on track to be ready for FDA pre-approval inspection anticipated in the second half of 2017.

Epidiolex Commercialization

GW is planning to commercialize Epidiolex in the United States and elsewhere using its own sales and marketing organization. In June 2015, the Company appointed Julian Gangolli to the newly created position of President, North America and is leading GW’s commercial organization in the United States, which is based in the Company’s office at Carlsbad, California. GW has also recruited a number of U.S. medical affairs, clinical trials and commercial staff, many of whom have strong epilepsy knowledge and experience. With the success of both Dravet syndrome and LGS Phase 3 trials, the Company expects to expand this organization over the next 12 months. The creation of the medical affairs team has allowed GW to open scientific and consultative communications with key stakeholders, such as the patient and physician communities in the United States.

The Company expects to implement a “high efficiency” commercial deployment model expected to include a dedicated sales force of approximately 50 to 60 sales professionals targeting approximately 4,000 – 5,000 U.S. physicians. This commercial organization will be defined by a “high touch” patient, payor and physician communication, education and distribution model, and one in which the medical affairs organization will play a significant role in establishing strong relationships with physicians and patient organizations.

Outside the United States, GW is taking the initial steps toward preparations for Epidiolex commercialization in Europe. The Company has begun to hire key staff in medical affairs and marketing disciplines to begin laying the groundwork for a more comprehensive commercial organization.

U.S. Expanded Access Program (EAP)

In parallel with GW’s formal clinical trial program, the FDA has granted 20 intermediate expanded access Investigational New Drug Applications (INDs) to independent physician investigators in the U.S to treat a total of 465 children and young adults suffering from intractable epilepsy with Epidiolex. In addition, the FDA has granted further intermediate INDs to treat 455 additional patients under expanded access programs supported by six U.S. states and for which GW is supplying Epidiolex. The FDA may authorize expanded access programs to facilitate access to investigational drugs for treatment use for patients with a serious or immediately life-threatening disease or condition who lack therapeutic alternatives. The FDA has also authorized to physicians 14 individual emergency INDs and 3 individual patient non-emergency INDs. As at 1 August 2016, approximately 500 patients were on EAP treatment at 32 U.S. clinical sites.

Mechanism of action

There is a significant effort utilizing in vitro, in vivo and other models of epilepsy to identify the mechanisms of action that underpin the clinical effectiveness of Epidiolex (and other cannabinoids) in epilepsy, including investigation of the effect of cannabinoids on epilepsy associated gene expression. As recently reported in Neurotherapeutics (Ibeas et al 2015), CBD is likely to be acting via more than one mechanism of action with the effect of reducing neuronal hyperexcitability. Importantly, the anti-seizure effects of CBD are not dependent on cannabinoid receptors, nor on sodium channels.

CBDV (cannabidivarin) Development Program

In addition to Epidiolex, GW’s product candidates also include the cannabinoid GWP42006, which features cannabidivarin (CBDV) as the primary molecular entity. CBDV bears similarities in chemical structure to CBD and has also shown anti-epileptic properties across a range of in vitro and in vivo models of epilepsy. GWP42006 was also found to provide additional efficacy when combined with drugs currently used to control epilepsy. Positive results using genetic biomarkers for response have been identified.

GW has also evaluated GWP42006 in both general and syndromic pre-clinical models of Autism Spectrum Disorders (ASD) yielding promising signals on cognitive and social endpoints as well as repetitive behaviors. These animal models include both genetically determined and chemically-induced models of neurobehavioral abnormalities, and include Rett syndrome and Fragile X syndrome among others.

GW has completed a Phase 1 trial of GWP42006 in 66 healthy subjects. In this trial, GWP42006 was well tolerated even at the highest tested dose. There were no serious or severe adverse events reported, nor any withdrawals due to adverse events.

GW is now pursuing multiple development programs for GWP42006 both within adult and childhood epilepsy and in childhood behavioral disorders:

• In epilepsy, GW is recruiting a Phase 2 trial of GWP42006. This is a double-blind, randomized, placebo-controlled two-part trial to investigate the pharmacokinetics, followed by efficacy and safety of GWP42006 as add-on therapy in patients with inadequately controlled focal seizures. The first part of this trial has completed enrollment of 32 patients and the dose-ranging pharmacokinetic and safety data has been reviewed by an independent panel. GW has commenced the efficacy part of the trial and expects to recruit an additional 100 patients. Data from this part of the trial is expected in the first half of 2017.

• In October 2015, GW announced that it had signed a Memorandum of Understanding (MOU) with the NSW Government in Australia to advance a research program for Epidiolex and CBDV in children with severe, drug resistant childhood epilepsy. The MOU facilitates a world first, Phase 2 clinical trial in children for GWP42006.

• GW is conducting pre-clinical research into CBDV within the field of ASD. Many of the pediatric intractable epilepsy conditions within the Epidiolex expanded access program share considerable overlap with ASD and these conditions often fall within the orphan disease space. Initial clinical observations from treating physicians suggest a potential role for cannabinoids in addressing problems associated with ASD such as deficits in cognition, behavior and communication. GW is working with investigators and early open-label clinical experience is expected to commence in the second half of 2016, with Phase 2 placebo-controlled trials within ASD expected to commence in the first half of 2017.

Other Orphan/Neurology Pipeline Programs

Neonatal Hypoxic-Ischemic Encephalopathy (NHIE)

NHIE is acute or sub-acute brain injury resulting from deprivation of oxygen during birth (hypoxia). GW estimates 6,500 to 12,000 cases of NHIE occur in the U.S. each year. Of these, 35% are expected to die in early life and 30% are expected to develop persistent neurologic disability. There are currently no FDA-approved medicines specifically indicated for NHIE.

GW held a pre-IND meeting with the FDA to discuss the development program for an intravenous CBD formulation (GWP42003) in the treatment of NHIE. GW has received Orphan Drug Designation and Fast Track Designation from the FDA for CBD for the treatment of NHIE. GW has also received Orphan Drug Designation from the EMA for CBD for the treatment of perinatal asphyxia, an alternate term that describes the same condition.

GW expects to commence a Phase 1 trial of GWP42003 in healthy volunteers for an intravenous CBD formulation in the treatment of NHIE in the fourth quarter of 2016.

Glioma

GW is testing its product candidate GWP42002:GWP42003 (THC/CBD) in the treatment of recurrent glioblastoma multiforme, or GBM, a particularly aggressive brain tumor which is considered a rare disease by the FDA and the EMA. The Company has received Orphan Drug Designation from the FDA for GWP42002:GWP42003 for the treatment of glioma. In pre-clinical models, GW has shown these cannabinoids used together to be orally active in the treatment of glioma xenografts and have shown tumor response to be positively associated with tissue levels of cannabinoids.

GW has completed recruitment of 27 patients into a placebo-controlled Phase 1b/2a trial in recurrent GBM. This study first evaluated the safety of CBD:THC taken in combination with dose-intense temozolomide, and then initiated a placebo-controlled phase. Data from this trial is expected in the fourth quarter of 2016.

Other Pipeline Programs

Sativex for Cerebral Palsy in Children

GW is currently conducting a Phase 2 clinical trial of Sativex to assess the efficacy, safety and tolerability of Sativex as an adjunctive treatment to existing anti-spasticity medications in children aged 8 to 18 years with spasticity due to cerebral palsy or traumatic central nervous system injury who have not responded adequately to existing anti-spasticity medications. This trial is a randomized, double-blind, placebo-controlled trial followed by a 24-week open label extension phase and has completed enrollment of 72 patients. GW expects to report data from this trial in the fourth quarter of 2016.

Schizophrenia

GW’s product candidate, an oral formulation of GWP42003 (CBD), has shown notable anti-psychotic effects in accepted pre-clinical models of schizophrenia and in September 2015, GW announced positive top line results from an exploratory Phase 2a placebo-controlled clinical trial of CBD in 88 patients with schizophrenia who had previously failed to respond adequately to first line anti-psychotic medications. GW is evaluating appropriate next steps regarding product development in schizophrenia with future research likely focused on pediatric orphan neuropsychiatric indications.

Type 2 Diabetes

GW is testing its product candidate GWP42004 in the treatment of type 2 diabetes. GWP42004 is an orally administered product which features plant-derived tetrahydrocannabivarin (THCV) as its active ingredient.

In March 2014, GW commenced a placebo-controlled Phase 2 dose ranging trial of GWP42004. The primary objective of this trial was to compare the change in glycemic control in patients with type-2 diabetes when treated with one of three doses of GWP42004 or placebo as add-on therapy, to metformin with the primary endpoint being change from baseline to the end of treatment in mean glycosylated hemoglobin A1c (HbA1c) level. The safety and tolerability of GWP42004 compared with placebo was also being assessed. This trial is now completed and a preliminary analysis of the topline data shows that this trial did not meet its primary endpoint. The drug was well tolerated with no serious adverse events. GW is undertaking further evaluation of the data to determine whether to pursue further development of GWP42004 within the field of type-2 diabetes.

MANAGEMENT’S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION

AND RESULTS OF OPERATIONS

The following discussion and analysis should be read in conjunction with the condensed consolidated financial information contained herein, which has been prepared in accordance with International Accounting Standard 34, Interim Financial Reporting. GW presents its condensed consolidated financial information in pounds sterling.

Solely for the convenience of the reader, unless otherwise indicated, all pound sterling amounts stated in the Condensed Consolidated Balance Sheet as at 30 June 2016, the Condensed Consolidated Income Statement and the Condensed Consolidated Cash Flow Statement for the three and nine months ended 30 June 2016 have been translated into U.S. dollars at the rate on 30 June 2016 of $1.32993 to £1.00. These translations should not be considered representations that any such amounts have been, could have been or could be converted into U.S. dollars at that or any other exchange rate as at that or any other date.

Overview

GW generates revenue from Sativex product sales, license fees, collaboration fees, technical access fees, development and approval milestone fees, research and development fees and royalties.

The principal factors affecting GW’s profitability and operating cash flow are the amount and timing of GW-funded research and development and capital expenditure, the rate of growth of Sativex product revenues, and the amount of development and approval milestone receipts from the Company’s commercial partners.

Expenditure on research and development activities is recognized as an expense in the period in which the expense is incurred. GW incurs research and development expenditures that are funded from GW’s own cash resources. This typically relates to core research and development spend on the Company’s staff and research facilities plus spend on the Epidiolex development program and certain pipeline product Phase 2 trials, currently in the areas of adult epilepsy and glioma. GW refers to this as “GW-funded research and development expenditure.”

A proportion of GW’s research and development expenditure is funded by the Company’s collaboration partners. GW refers to this as “development-partner funded research and development expenditure”. Most of this expenditure during the period relates to the Sativex cancer pain development for the U.S. market which is wholly funded by Otsuka.

Sales, general and administrative expenses consist primarily of salaries, employer payroll taxes and benefits related to GW’s executive, finance, business development and support functions. Other sales, general and administrative expenses include costs associated with managing commercial activities and the costs of compliance with the day-to-day requirements of being a listed public company on NASDAQ in the U.S. and on the AIM Market in the United Kingdom, including insurance, general administration overhead, investor relations, legal and professional fees, audit fees and fees for taxation services.

Net foreign exchange gains/losses primarily result from unrealized gains/losses on translating the Group’s U.S. dollar denominated cash deposits to pounds sterling at the closing U.S. dollar to pounds sterling exchange rate.

As a UK resident Group with operations in the U.S., GW is subject to both UK and U.S. corporate taxation. GW’s tax recognized represents the sum of the tax currently payable or recoverable, and deferred tax. Deferred tax assets are recognized only to the extent that it is probable that taxable profits will be available against which deductible temporary differences can be utilized. As a company that carries out extensive research and development activities, GW benefits from the UK research and development tax credit regime, whereby the Company’s principal research subsidiary company, GW Research Limited, is able to surrender the trading losses that arise from its research and development activities for a cash rebate. This has resulted in a tax credit for each of the periods reported herein, as disclosed in the tax benefit line of the condensed consolidated income statements.

Results of Operations:

Comparison of the three months ended 30 June 2016 and 30 June 2015:

Revenue

Total revenue for the three months to 30 June 2016 was £2.3 million, compared to £8.6 million for the three months ended 30 June 2015. This decrease of £6.3 million primarily comprises:

Other revenue streams, individually, did not change by a material amount.

Cost of sales

Cost of sales for the three months ended 30 June 2016 of £0.7 million is consistent with the £0.7 million recorded in the three months ended 30 June 2015.

Research and development expenditure

Total research and development expenditure for the three months ended 30 June 2016 of £25.6 million increased by £4.8 million compared to the £20.8 million incurred in the three months ended 30 June 2015.

Partner funded research and development expenditure decreased by £6.8 million to £0.4 million for the three months ended 30 June 2016 from £7.2 million for the three months ended 30 June 2015. This decrease reflects the conclusion and close out of the Sativex Phase 3 cancer pain clinical trials.

GW-funded research and development expenditure increased by £11.5 million to £25.2 million for the three months ended 30 June 2016 from £13.7 million for the three months ended 30 June 2015. The increase is due to:

Sales, general and administrative expenses

Sales, general and administrative expenses for the three months ended 30 June 2016 of £5.6 million increased by £2.6 million compared to the £3.0 million incurred in the three months ended 30 June 2015. This net increase is due to:

Net foreign exchange gains / (losses)

Net foreign exchange gains for the three months ended 30 June 2016 was a gain of £11.2 million, compared to the £8.9 million loss recorded for the three months ended 30 June 2015. The gain or loss recognized relates to the remeasurement of the Group’s U.S. dollar denominated cash deposits to pounds sterling in the period to 30 June 2016. The Sterling to U.S. dollar exchange rate has moved from 1.4365 at 31 March 2016 to 1.32993 at 30 June 2016. Dollar denominated cash deposits totalled $215.8 million at 31 March 2016 and $204.5 million at 30 June 2016.

Taxation

The tax benefit was £6.1 million for the three months ended 30 June 2016. This represents an increase of £2.8 million compared to a £3.3 million benefit recorded in the three months ended 30 June 2015.

In the three months ended 30 June 2016, GW recorded a tax benefit of £6.1 million made up of: (i) the recognition of an accrued £4.8 million research and development tax credit expected to be claimable by GW Research Limited in respect of research and development expenditure incurred in the three months ended 30 June 2016; (ii) the recognition of £0.3 million of research and development federal tax credits in respect of the year ended 30 September 2015 for the Group’s U.S. subsidiary, GW Pharmaceuticals Inc.; and (iii) recording of £1.0 million of current tax credit in respect of activities of the Group’s U.S. subsidiary, GW Pharmaceuticals Inc. during the year ended 30 September 2016.

In the three months ended 30 June 2015, GW recorded a tax benefit of £3.3 million comprising the recognition of an accrued £3.4 million research and development tax credit expected to be claimable by GW Research Limited in respect of the research and development expenditure incurred in the three months ended 30 June 2015. This was offset by a £0.1 million reduction in the deferred tax asset held by the Group’s commercial subsidiary GW Pharma Limited, as the company utilizes brought forward losses to offset against its current period profits.

Loss

The Group reported a loss after tax for the three months ended 30 June 2016 of £12.2 million compared with a loss after tax for the three months ended 30 June 2015 of £21.4 million.

Results of Operations:

Comparison of the nine months ended 30 June 2016 and 30 June 2015:

Revenue

Total revenue for the nine months to 30 June 2016 was £8.6 million, compared to £22.9 million for the nine months ended 30 June 2015. This decrease of £14.3 million primarily comprises:

Other revenue streams, individually, did not change by a material amount.

Cost of sales

Cost of sales for the nine months ended 30 June 2016 of £1.9 million is consistent with the £1.9 million recorded in the nine months ended 30 June 2015.

Research and development expenditure

Total research and development expenditure for the nine months ended 30 June 2016 of £75.5 million increased by £24.2 million compared to the £51.3 million incurred in the nine months ended 30 June 2015.

Partner funded research and development expenditure decreased by £14.8 million to £3.9 million for the nine months ended 30 June 2016 from £18.7 million for the nine months ended 30 June 2015. This decrease reflects the conclusion and close out of the Sativex Phase 3 cancer pain clinical trials.

GW-funded research and development expenditure increased by £39.0 million to £71.6 million for the nine months ended 30 June 2016 from £32.6 million for the nine months ended 30 June 2015. The increase is due to:

Sales, general and administrative expenses

Sales, general and administrative expenses for the nine months ended 30 June 2016 of £12.5 million increased by £4.9 million compared to the £7.6 million incurred in the nine months ended 30 June 2015. This net increase reflects:

Net foreign exchange gains / (losses)

Net foreign exchange gains for the nine months ended 30 June 2016 was a gain of £19.3 million, compared to a £0.7 million loss recorded for the nine months ended 30 June 2015. In both periods the gain recognized relates to the remeasurement of the Group’s US dollar denominated cash deposits to pounds sterling at the closing US dollar to Sterling exchange rate at 31 March. The Sterling to U.S. dollar exchange rate has moved from 1.5127 at 30 September 2015 to 1.32993 at 30 June 2016. Dollar denominated cash deposits totalled $274.9 million at 30 September 2015 and $204.5 million at 30 June 2016.

Taxation

The tax benefit was £15.0 million for the nine months ended 30 June 2016, which represents an increase of £8.9 million compared to a £6.1 million benefit recorded in the nine months ended 30 June 2015.

In the nine months ended 30 June 2016, GW recorded a tax benefit of £15.0 million comprising: (i) the recognition of an accrued £13.4 million research and development tax credit expected to be claimable by GW Research Limited in respect of the research and development expenditure incurred in the nine months ended 30 June 2016; (ii) the recognition of an additional £0.6 million of research and development tax credits in respect of the year ended 30 September 2015 in its principal research subsidiary, GW Research Limited, as part of the process for finalising tax returns for that period; (iii) the recognition of £0.3 million of research and development federal tax credits in respect of the year ended 30 September 2015 in its U.S. subsidiary, GW Pharmaceuticals Inc., following the submission of an orphan drug tax credit claim and; (iv) recording of £0.7 million of current tax credit in respect of activities of GW Pharmaceuticals Inc. for the year ended 30 September 2016.

In the nine months ended 30 June 2015, GW recorded a tax benefit of £6.1 million made up of: (i) the recognition of an accrued £6.1 million research and development tax credit expected to be claimable by GW Research Limited in respect of the research and development expenditure incurred in the nine months ended 30 June 2015; (ii) the recognition of an additional £0.2 million of research and development tax credits in respect of the year ended 30 September 2014 in its principal research subsidiary, GW Research Limited, as part of the process for finalising tax returns for that period and; (iii) recording of £0.2 million of deferred tax expense due to the fact that previously recognized losses have been utilized to offset profits earned in the nine months ended 30 June 2015 by GW Pharma Limited.

Loss

The Group reported a loss after tax for the nine months ended 30 June 2016 of £46.7 million compared with a loss after tax for the nine months ended 30 June 2015 of £32.3 million.

Liquidity and Capital Resources

Cash Flow

Net cash outflow from operating activities for the nine months ended 30 June 2016 of £57.2 million was £33.1 million higher than the £24.1 million outflow from operating activities for the nine months ended 30 June 2015, principally reflecting the increase in investment in Epidiolex and other pipeline research and development activities, an increased foreign exchange gain on the Group’s U.S. dollar denominated cash deposits and additional tax benefits.

Capital expenditure for the nine months ended 30 June 2016 of £6.3 million, consisting primarily of ongoing upgrades to our cannabinoid extraction and Epidiolex manufacturing and growing facilities, was £7.8 million lower than the £14.1 million for the nine months ended 30 June 2015 due to the stage of completion of the construction of these facilities.

Net cash flow from financing activities decreased by £128.2 million to a £0.2 million inflow in the nine months ended 30 June 2016 compared to a £128.4 million inflow for the nine months ended 30 June 2015 principally reflecting a new equity fundraising in the comparative period which resulted in a £127.5 million inflow, a decrease in proceeds on share option exercise of £0.5 million and an increase in repayments of fit out funding by £0.2 million in the current period.

As at 30 June 2016, GW had a closing cash position of £191.2 million compared to £234.9 million as at 30 September 2015.

Property, plant and equipment

Property, plant and equipment at 30 June 2016 increased by £9.8 million to £38.5 million from £28.7 million at 30 September 2015. This increase reflects the occupation of the Group’s new cannabinoid extraction facilities, and further expansion growing facilities for Epidiolex production.

Inventories

Inventories at 30 June 2016 decreased by £0.3 million to £4.5 million compared with the £4.8 million at 30 September 2015. Inventories consist of finished goods, consumable items and work in progress and are stated net of a £nil million realizable value provision (30 September 2015: £0.1 million). During the nine months ended 30 June 2016, the provision for inventories reduced by £0.1 million as a result of having utilized some of the Group’s previously provided for inventory in research and development.

Trade receivables and other assets

Trade receivables and other receivables at 30 June 2016 increased by £1.0 million to £3.9 million from £2.9 million at 30 September 2015. This is due to an increase in prepaid costs in relation to goods, services and deposits paid for capital expenditure not yet received by the group.

Trade and other payables

Current trade and other payables at 30 June 2016 increased by £8.7 million to £32.7 million from £24.0 million at 30 September 2015. This increase reflects a £9.1 million increase in trade payables and accruals as a result of the continued expansion of GW funded clinical trials and manufacturing capability offset by a £0.4 million decrease in the provision held for revenue rebates to our commercial partners.

Non-current trade and other payables at 30 June 2016 remained consistent at £8.4 million compared with £8.4 million at 30 September 2015.

Headcount

Average headcount for the nine months ended 30 June 2016 was 429 (30 June 2015: 313).

Guidance

The Group remains on track to meet the expenditure guidance given with its second quarter results in May 2016, albeit that the exchange rate gain of £11.2 million experienced in the third quarter has reduced the projected net cash outflow for the 2016 financial year.

Subject to further exchange rate related volatility the Group’s fourth quarter expenditure plans remain consistent with previous guidance.

RISKS AND UNCERTAINTIES

A detailed analysis of the risks that the Group faces is set out in the Group’s Annual Report on Form 20-F filed by the Company with the SEC on 7 December 2015. The following summary of key risks for the Group are as highlighted below:

Clinical

Regulatory & Legislative

Orphan drug designation and intellectual property

Manufacturing

Marketing and Commercialization

Safety

Staffing and systems

Funding

Risk in Relation to the Use of Financial Instruments

Credit Risk

Liquidity Risk

Market Price Risk

Exchange Rate Risk

Overseas entity

GW continues to face a number of potential risks and uncertainties which could have a material impact on the Group’s performance over the remaining three months of the financial year and could cause actual results to differ materially from expected and historical results.

The directors are satisfied that the Group has sufficient resources to continue in operation for the foreseeable future, a period of not less than 12 months from the date of this report. Accordingly, they continue to adopt the going concern basis in preparing the financial information for the 9 and 3 months ended 30 June 2016.

The directors do not consider that the principal risks and uncertainties have changed since the Annual Report on Form 20-F for the year ended 30 September 2015 was filed by the Group with the SEC on 7 December 2015.

Related party transactions

The Group did not enter into any significant related party transactions during the period.

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 28 countries outside the United States. GW is advancing an orphan drug program in the field of childhood epilepsy with a focus on Epidiolex® (cannabidiol), which is in Phase 3 clinical development for the treatment of Dravet syndrome and Lennox-Gastaut syndrome and which is also expected to enter Phase 3 clinical trials in the treatment of Tuberous Sclerosis Complex. GW has a deep pipeline of additional cannabinoid product candidates which includes compounds in Phase 1 and 2 trials for glioma, schizophrenia and epilepsy. For further information, please visit www.gwpharm.com.

Forward-looking statements

This news release contains forward-looking statements that reflect GW's current expectations regarding future events, including statements regarding financial performance, the timing of clinical trials, the relevance of GW products commercially available and in development, the clinical benefits of Sativex® and Epidiolex® and the safety profile and commercial potential of Sativex and Epidiolex. 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 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, Epidiolex and other products by consumer and medical professionals. A further list and description of risks and uncertainties associated with an investment in GW can be found in GW’s filings with the U.S. Securities and Exchange Commission. Existing and prospective investors are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date hereof. GW undertakes no obligation to update or revise the information contained in this press release, whether as a result of new information, future events or circumstances or otherwise.

GW Pharmaceuticals plc

Condensed consolidated income statement

Three months ended 30 June 2016

All activities relate to continuing operations.

Condensed consolidated statement of comprehensive loss

For the three months ended 30 June 2016

GW Pharmaceuticals plc

Condensed consolidated income statement

Nine months ended 30 June 2016

All activities relate to continuing operations.

Condensed consolidated statement of comprehensive loss

For the nine months ended 30 June 2016

GW Pharmaceuticals plc

Condensed consolidated statement of changes in equity

Nine months ended 30 June 2016

GW Pharmaceuticals plc

Condensed consolidated balance sheets

As at 30 June 2016

GW Pharmaceuticals plc

Condensed consolidated cash flow statements

For the nine months ended 30 June 2016

1. Significant accounting policies

Basis of preparation

These unaudited condensed consolidated interim financial statements for the three and nine month periods ended 30 June 2016 and 30 June 2015 of GW Pharmaceuticals plc and subsidiaries (collectively, the “Group”) have been prepared in accordance with International Accounting Standard 34 – “Interim Financial Reporting” (“IAS 34”), as issued by the International Accounting Standards Board (“IASB”) and as endorsed by the European Union. These statements were approved by the Board on 9 August 2016.

Certain information and footnote disclosures normally included in financial statements prepared in accordance with International Financial Reporting Standards (“IFRS”) as issued by the IASB and as adopted by the European Union have been condensed or omitted as permitted by IAS 34. The balance sheet as at 30 September 2015 was derived from the audited financial statements.

The significant accounting policies and methods of computation adopted in the preparation of these condensed consolidated interim financial statements are consistent with those used in the preparation of the Group’s annual audited financial statements for the year ended 30 September 2015 in accordance with IFRS, as issued by the IASB and as adopted by the European Union. These condensed consolidated interim financial statements include all adjustments necessary to fairly state the results of the interim period and the Group believes that the disclosures are adequate to make the information presented not misleading. Interim results are not necessarily indicative of results to be expected for the full year.

The Group has not adopted early any standard, interpretation or amendment that was issued but is not yet effective.

The information for the period ended 30 September 2015 does not constitute statutory accounts as defined in section 434 of the Companies Act 2006.

Solely for the convenience of the reader, unless otherwise indicated, all pound sterling amounts stated in the Condensed Consolidated Balance Sheet as at 30 June 2016, the Condensed Consolidated Income Statement and the Condensed Consolidated Cash Flow Statement for the three and nine months ended 30 June 2016 have been translated into U.S. dollars at the rate on 30 June 2016 of $1.32993 to £1.0000. These translations should not be considered representations that any such amounts have been, could have been or could be converted into U.S. dollars at that or any other exchange rate as at that or any other date.

The Directors do not consider the business to be seasonal or cyclical.

Going concern

At 30 June 2016 the Group had cash and cash equivalents of £191.2 million. The Directors have considered the financial position of the Group, its cash position and forecast cash flows for the 12-month period from the date of this report when considering going concern. They have also considered the Group’s key risks and uncertainties affecting the likely development of the business, and the subsequent completion in July 2016 of a follow-on offering, raising total net proceeds after expenses of $273.1 million (£206.4 million). In the light of this review, the Directors have a reasonable expectation that the Company and the Group have adequate resources to continue in operational existence for at least a 12-month period from the date of this report. Accordingly, they continue to adopt the going concern basis in preparing these financial statements.

2. Segmental Information

Operating Segments

Information reported to the Company’s Board of Directors, the chief operating decision maker for the Group, for the purposes of resource allocation and assessment of segment performance is focused on the stage of product development. The Group’s reportable segments are as follows:

The accounting policies of the reportable segments are consistent with the Group’s accounting policies. Segment result represents the result of each segment without allocation of share-based payment expenses, and before sales, general and administrative expenses, foreign exchange gain/loss, interest expense, interest income and tax.

No measures of segment assets and segment liabilities are reported to the Group’s Board of Directors in order to assess performance and allocate resources. There is no intersegment activity and all revenue is generated from external customers.

2. Segmental Information (continued)

Segmental revenues and results

For the Three Months Ended 30 June 2016

2. Segmental Information (continued)

Segmental revenues and results

For the Three Months Ended 30 June 2015

2. Segmental Information (continued)

Segmental revenues and results

For the Nine Months Ended 30 June 2016

2. Segmental Information (continued)

Segmental revenues and results

For the Nine Months Ended 30 June 2015

2. Segmental Information (continued)

Revenues from the Group’s largest customer are included within the above segments as follows:

Revenues from the Group’s second largest customer, the only other customer where revenues account for more than 10% of the Group’s revenues, are included within the above segments as follows:

Geographical analysis of turnover by destination of customer

3. Research and development expenditure

4. Tax benefit

The research and development tax credit relates to research and development expenditure claimed under the Finance Act 2000 in the UK, or claimed under the orphan credit scheme in the United States. In April 2016, the Group received £13.3 million in respect of research and development expenditure incurred in the UK for the year ended 30 September 2015.

In the three and nine months ended 30 June 2016 and 2015, the Group recognized the full estimated benefit for qualifying research and development expenditures incurred during each period. Any difference in the credit ultimately received is recorded as an adjustment in respect of prior year.

The carrying amount of deferred tax assets is reviewed at each balance sheet date and amended to the extent that sufficient future taxable profits will be available to allow all or part of the asset to be recovered.

5. Loss per share

The calculations of loss per share are based on the following results and numbers of shares.

6. Inventories

Inventory is stated net of a provision for inventories, calculated in accordance with the Group’s accounting policy. The movement in the provision for inventories is as follows:

The reversal of write-down of inventories is as a result of an increased level of utilization, reducing the level of work in progress expected to expire before use.

Inventories with a carrying value of £2.1 million are considered to be recoverable after more than one year from the condensed consolidated balance sheet date, but within the Group’s normal operating cycle (30 September 2015: £2.7 million).

7. Trade receivables and other receivables

8. Trade and other payables

Fit out funding represents £9.0 million (30 September 2015: £8.8 million) owed to the Group’s landlord reflecting the liability to repay the £7.8 million of fit out funding received to fund the expansion and upgrades to manufacturing facilities and associated accrued interest of £1.4 million (30 September 2015: £1.0 million), , net of payments to date of £0.2 million. The repayments of this liability commenced on 27 May 2016 after the Group commenced occupying the facility. Repayments will continue over a 15-year term.

Other creditors and accruals includes £3.7 million of accrued capital expenditure (30 September 2015: £1.2 million).

9. Deferred revenue

Deferred revenues result mainly from the unamortized portion of up-front license fees received in 2005 of £12.0 million from Almirall S.A. and collaboration and technical access fees from other Sativex licensees.

Advance research and development fees represent amounts received from Otsuka for activities to be carried out on behalf of Otsuka. These amounts will be recognized as revenue in future periods as the services are rendered.

10. Amounts payable under finance leases