- Positive unanimous vote at Epidiolex® (cannabidiol) FDA Advisory Committee meeting -

- NDA PDUFA goal date scheduled for June 27, 2018 -

- Conference call today at 4:30 p.m. EST -

LONDON and CARLSBAD, Calif., May 08, 2018 (GLOBE NEWSWIRE) -- GW Pharmaceuticals plc (NASDAQ:GWPH) (GW, the Company or the Group), a biopharmaceutical company focused on discovering, developing and commercializing novel therapeutics from its proprietary cannabinoid product platform, announces financial results for the second quarter ended 31 March 2018.

“The positive outcome of the Epidiolex FDA Advisory Committee meeting was a momentous event for GW. The strength and consistency of the clinical data, together with the public presentations that featured very moving personal stories of the challenges associated with managing these difficult forms of epilepsy, led to a unanimous vote in support of approval,” stated Justin Gover, GW’s Chief Executive Officer. “With our late June FDA decision date nearing, our commercial team is busy preparing to launch Epidiolex in the second half of this year. Should Epidiolex be approved, we believe that this will signal a major vote of confidence in GW’s cannabinoid platform to discover and develop prescription medicines that meet exacting regulatory standards and will serve us to accelerate a number of important pipeline programs that have the potential to offer additional value.”

OPERATIONAL HIGHLIGHTS

Epidiolex (CBD) orphan epilepsy program in Dravet syndrome, Lennox-Gastaut syndrome (LGS), Tuberous Sclerosis Complex (TSC) and infantile spasms (IS) Regulatory NDA for the adjunctive treatment of seizures associated with LGS and Dravet PDUFA goal date of June 27, 2018 Positive, unanimous vote in support of approval by FDA Advisory Committee Conditional grant of rare pediatric disease designation by FDA European submission accepted for review by the EMA. Expected decision in Q1 2019 Manufacturing FDA pre-approval cGMP inspections successfully completed with no 483 citations Clinical data Second Phase 3 LGS trial accepted for publication. Paper expected to be released shortly New data presented at the American Academy of Neurology (AAN) Annual Meeting

- Long-term safety and efficacy data in patients LGS and Dravet syndrome presented

- Abuse liability data Clinical trials Phase 3 trial in Tuberous Sclerosis Complex ongoing with data expected H1 2019 Second Phase 3 trial in Dravet syndrome enrollment complete with data expected H2 2018 Part A of two-part Phase 2/3 trial in Infantile Spasms nearing completion; based on currently available data unlikely to proceed into Part B Expanded access program and open label extension Over 2,000 patients now have been exposed to Epidiolex treatment Commercial U.S. Sales leadership team in place and preparing for launch Active engagement with U.S. payors is ongoing Commercial footprint established in top 5 EU markets Life-cycle management Several new formulations of CBD in development including modified liquid formulations, a solid dose form and an intravenous formulation Intellectual property 7 key favorable patent application decisions by USPTO related to the use of CBD in epilepsy 5 patent grants following March 2018 Notices of Allowance 2 new Notices of Allowance issued by USPTO Additional patent applications under review and being filed as new data is generated

Pipeline progress Sativex ® (nabiximols) for Multiple Sclerosis spasticity U.S. development and commercialization rights wholly owned by GW Three positive Phase 3 trials completed in Europe Plans to engage with FDA in H2 2018 with a view to commencing a single U.S. pivotal trial CBDV in Autism Spectrum Disorders 10-patient investigator-initiated expanded access program for seizures associated with autism underway. Data expected Q4 2018. Investigator-led 100 patient placebo-controlled trial in autism spectrum disorder due to commence in Q3 2018 Open label study in Rett syndrome due to commence Q3 and Phase 2 placebo-controlled trial in Rett syndrome due to commence in Q4 2018 Orphan Drug Designation from FDA and EMA for CBDV for the treatment of Rett syndrome CBD:THC in Glioblastoma Phase 2 study showed significant increase in one year survival compared to placebo Pivotal clinical development program plans under development Orphan Drug Designation from both FDA and EMA for CBD:THC to treat glioblastoma Neonatal Hypoxic-Ischemic Encephalopathy (NHIE) intravenous CBD program Phase 1 trial complete Orphan Drug and Fast Track Designations granted from FDA and EMA Phase 2 trial in planning



FINANCIAL HIGHLIGHTS

Cash and cash equivalents at 31 March 2018 of £346.8 million ($487.2 million) compared to £241.2 million as at 30 September 2017



Revenue for the six months ended 31 March 2018 of £8.1 million ($11.4 million) compared to £3.7 million for the six months ended 31 March 2017



Loss for the six months ended 31 March 2018 of £109.6 million ($154.0 million) compared to £50.0 million for the six months ended 31 March 2017

Solely for the convenience of the reader, the above balances have been translated into U.S. dollars at the rate on 31 March 2018 of $1.40495 to £1. 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.

Conference Call and Webcast Information

GW Pharmaceuticals will host a conference call and webcast to discuss the second quarter 2018 financial results today at 4:30 pm EST. 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):1-877-481-4010 or 919-882-2331 (international). For both dial-in numbers please use conference ID # 13679685 and PIN: 29077.

About GW Pharmaceuticals plc and Greenwich Biosciences

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, along with its U.S. subsidiary Greenwich Biosciences, is advancing an orphan drug program in the field of childhood-onset epilepsy with a focus on Epidiolex (cannabidiol), for which GW has submitted regulatory applications in the U.S. and Europe for the adjunctive treatment of Lennox-Gastaut syndrome and Dravet syndrome. The Company continues to evaluate Epidiolex in additional rare epilepsy conditions and currently has ongoing clinical trials in Tuberous Sclerosis Complex and Infantile Spasms. GW commercialized the world’s first plant-derived cannabinoid prescription drug, Sativex® (nabiximols), which is approved for the treatment of spasticity due to multiple sclerosis in numerous countries outside the United States and for which the company is now planning a U.S. Phase 3 trial. The Company has a deep pipeline of additional cannabinoid product candidates which includes compounds in Phase 1 and 2 trials for epilepsy, glioblastoma, and schizophrenia. 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 timing and outcomes of regulatory or intellectual property decisions, 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 the Company’s regulatory processes, and the level of 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 including the most recent Form 20-F filed on 4 December 2017. 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.

Enquiries:

GW Pharmaceuticals plc Stephen Schultz, VP Investor Relations (U.S.) 917 280 2424 / 401 500 6570 U.S. Media Enquiries:

Sam Brown Inc. Healthcare Communications Christy Curran

Mike Beyer 615 414 8668

312 961 2502 EU Media Enquiries:

FTI Consulting Ben Atwell

Simon Conway +44 (0) 3727 1000









GW Pharmaceuticals plc Condensed consolidated income statement Three months ended 31 March 2018 and 2017 Three months

ended Three months

ended Three months

ended 31 March 31 March 31 March 2018 2018 2017 $000’s £000’s £000’s Revenue 3,351 2,385 1,627 Cost of sales (1,637 ) (1,165 ) (687 ) Research and development expenditure (46,057 ) (32,782 ) (27,157 ) Sales, general and administrative expenses (24,779 ) (17,637 ) (9,290 ) Net foreign exchange loss (20,533 ) (14,615 ) (3,988 ) Operating loss (89,655 ) (63,814 ) (39,495 ) Interest expense (327 ) (233 ) (153 ) Interest and other income 1,862 1,325 313 Loss before tax (88,120 ) (62,722 ) (39,335 ) Tax benefit 80 57 4,968 Loss for the period (88,040 ) (62,665 ) (34,367 ) Loss per share – basic and diluted (26.0c) (18.5p) (11.3p) Loss per ADS – basic and diluted(1) (312.0c) (222.0p) (135.6p) Weighted average ordinary shares outstanding (in millions) – basic and diluted 338.2 303.7

All activities relate to continuing operations.

(1) Each ADS represents 12 ordinary shares

Condensed consolidated statement of comprehensive loss For the three months ended 31 March 2018 and 2017 Three months

ended

31 March

2018

£000’s Three months

ended

31 March

2017

£000’s Loss for the period (62,665 ) (34,367 ) Items that may be reclassified subsequently to profit or loss Exchange loss on retranslation of foreign operations (753 ) (177 ) Other comprehensive loss for the period (753 ) (177 ) Total comprehensive loss for the period (63,418 ) (34,544 )





GW Pharmaceuticals plc Condensed consolidated income statement Six months ended 31 March 2018 and 2017 Six months

ended Six months

ended Six months

ended 31 March 31 March 31 March 2018 2018 2017 $000’s £000’s £000’s Revenue 11,404 8,117 3,683 Cost of sales (2,877 ) (2,048 ) (1,402 ) Research and development expenditure (88,594 ) (63,058 ) (52,071 ) Sales, general and administrative expenses (49,211 ) (35,027 ) (15,974 ) Net foreign exchange (loss)/gain (24,120 ) (17,168 ) 7,827 Operating loss (153,398 ) (109,184 ) (57,937 ) Interest expense (660 ) (470 ) (243 ) Interest and other income 3,550 2,527 586 Loss before tax (150,508 ) (107,127 ) (57,594 ) Tax (expense)/benefit (3,497 ) (2,489 ) 7,631 Loss for the period (154,005 ) (109,616 ) (49,963 ) Loss per share – basic and diluted (47.4c) (33.7p) (16.5p) Loss per ADS – basic and diluted (1) (568.8c) (404.4p) (198.0p) Weighted average ordinary shares outstanding (in millions) – basic and diluted 325.0 303.2

All activities relate to continuing operations.

(1) Each ADS represents 12 ordinary shares

Condensed consolidated statement of comprehensive loss For the six months ended 31 March 2018 and 2017 Six months

ended

31 March

2018

£000’s Six months

ended

31 March

2017

£000’s Loss for the period (109,616 ) (49,963 ) Items that may be reclassified subsequently to profit or loss Exchange (loss)/gain on retranslation of foreign operations (940 ) 241 Other comprehensive (loss)/gain for the period (940 ) 241 Total comprehensive loss for the period (110,556 ) (49,722 )





GW Pharmaceuticals plc Condensed consolidated statement of changes in equity Six months ended 31 March 2018 and 2017 Called-up Share share premium Other Accumulated capital account reserves deficit Total £000’s £000’s £000’s £000’s £000’s Balance at 1 October 2016 302 556,477 19,538 (177,827 ) 398,490 Exercise of share options 2 88 - - 90 Share-based payment transactions - - - 4,768 4,768 Loss for the period - - - (49,963 ) (49,963 ) Deferred tax attributable to unrealized share option gains - - - 595 595 Other comprehensive income - - 241 - 241 Balance at 31 March 2017 304 556,565 19,779 (222,427 ) 354,221 Balance at 1 October 2017 304 556,570 18,822 (297,521 ) 278,175 Exercise of share options 2 - - - 2 Issue of share capital 33 223,037 - - 223,070 Expense of new equity issue - (926 ) - - (926 ) Share-based payment transactions - - - 8,969 8,969 Loss for the period - - - (109,616 ) (109,616 ) Deferred tax attributable to unrealized share option gains - - - 675 675 Other comprehensive loss - - (940 ) - (940 ) Balance at 31 March 2018 339 778,681 17,882 (397,493 ) 399,409





GW Pharmaceuticals plc Condensed consolidated balance sheets As at 31 March 2018 and 30 September 2017 As at

31 March As at

31 March As at

30 September 2018 2018 2017 Non-current assets $000’s £000’s £000’s Intangible assets - goodwill 7,320 5,210 5,210 Other intangible assets 2,723 1,938 1,049 Property, plant and equipment 67,862 48,302 43,666 Deferred tax asset 9,899 7,046 6,282 87,804 62,496 56,207 Current assets Inventories 4,896 3,485 4,244 Taxation recoverable 30,105 21,428 20,072 Trade receivables and other current assets 19,450 13,844 11,217 Cash and cash equivalents 487,235 346,798 241,175 541,686 385,555 276,708 Total assets 629,490 448,051 332,915 Current liabilities Trade and other payables (43,071 ) (30,656 ) (33,119 ) Current tax liabilities (3,333 ) (2,372 ) (838 ) Obligations under finance leases (296 ) (211 ) (205 ) Deferred revenue (1,145 ) (815 ) (2,307 ) (47,845 ) (34,054 ) (36,469 ) Non-current liabilities Trade and other payables (11,744 ) (8,359 ) (9,256 ) Obligations under finance leases (6,530 ) (4,648 ) (4,755 ) Deferred revenue (2,221 ) (1,581 ) (4,260 ) Total liabilities (68,340 ) (48,642 ) (54,740 ) Net assets 561,150 399,409 278,175 Equity Share capital 476 339 304 Share premium account 1,094,010 778,681 556,570 Other reserves 25,123 17,882 18,822 Accumulated deficit (558,459 ) (397,493 ) (297,521 ) Total equity 561,150 399,409 278,175





GW Pharmaceuticals plc Condensed consolidated cash flow statements For the six months ended 31 March 2018 and 2017 Six months ended Six months ended Six months ended 31 March 31 March 31 March 2018 2018 2017 $000’s £000’s £000’s Loss for the period (154,005 ) (109,616 ) (49,963 ) Adjustments for: Interest and other income (3,550 ) (2,527 ) (586 ) Interest expense 660 470 243 Tax expense/(benefit) 3,497 2,489 (7,631 ) Depreciation of property, plant and equipment 4,350 3,096 2,310 Impairment of property, plant and equipment - - 95 Reversal of impairment of property, plant and equipment - - (216 ) Amortization of intangible assets 270 192 87 Net foreign exchange losses/(gains) 24,120 17,168 (7,827 ) Increase in provision for inventories 5,292 3,767 47 Decrease in deferred signature fees (4,159 ) (2,960 ) (823 ) Share-based payment charge 12,601 8,969 4,768 Loss on disposal of property, plant and equipment 6 4 564 (110,918 ) (78,948 ) (58,932 ) Increase in inventories (4,228 ) (3,009 ) (442 ) Increase in trade receivables and other assets (586 ) (417 ) (1,667 ) Decrease in trade and other payables and deferred revenue (5,165 ) (3,676 ) (4,108 ) Research and development tax credits received 242 172 - Income taxes paid (1,710 ) (1,217 ) (828 ) Net cash outflow from operating activities (122,365 ) (87,095 ) (65,977 ) Investing activities Interest received 1,439 1,024 437 Purchases of property, plant and equipment (15,034 ) (10,701 ) (8,995 ) Purchases of intangible assets (1,201 ) (855 ) (428 ) Net cash outflow from investing activities (14,796 ) (10,532 ) (8,986 ) Financing activities Proceeds on exercise of share options 1 1 90 Proceeds of new equity issue 313,403 223,070 - Expenses of new equity issue (1,203 ) (856 ) (134 ) Interest paid (660 ) (470 ) (462 ) Repayments of fit out funding (270 ) (192 ) (656 ) Repayment of obligations under finance leases (142 ) (101 ) (82 ) Net cash inflow/(outflow) from financing activities 311,129 221,452 (1,244 ) Effect of foreign exchange rate changes on cash and cash equivalents (25,573 ) (18,202 ) 8,100 Net increase/(decrease) in cash and cash equivalents 148,395 105,623 (68,107 ) Cash and cash equivalents at beginning of the period 338,840 241,175 374,392 Cash and cash equivalents at end of the period 487,235 346,798 306,285



