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**UNITED STATES**

**SECURITIES AND EXCHANGE COMMISSION**

**WASHINGTON, D.C. 20549**

 

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**FORM 20-F/A**

** **

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** **

**Amendment No. 1**

 

| **o**      | **REGISTRATION STATEMENT PURSUANT   TO SECTION 12(b) OR (g) OF THE SECURITIES EXCHANGE ACT OF 1934**                                                                                                                                       |
|------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| ** ** | ** **                                                                                                                                                                                                                                                |
| **OR**     |
| ** ** | ** **                                                                                                                                                                                                                                                |
| **x**      | **ANNUAL REPORT PURSUANT TO   SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934   For the fiscal year ended September 30, 2013                 ** |
| ** ** | ** **                                                                                                                                                                                                                                                |
| **OR**     |
| ** ** | ** **                                                                                                                                                                                                                                                |
| **o**      | **TRANSITION REPORT PURSUANT TO   SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934**                                                                                                                                                  |
| ** ** | ** **                                                                                                                                                                                                                                                |
| **OR**     |
| ** ** | ** **                                                                                                                                                                                                                                                |
| **o**      | **SHELL COMPANY REPORT PURSUANT   TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934**                                                                                                                                               |

 

Commission File Number 001-35892

 
| **GW PHARMACEUTICALS PLC**                                                                                                                                                                                                                                              |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| (Exact name of Registrant as specified in its charter)                                                                                                                                                                                                                  |
|                                                                                                                                                                                                                                                                    |
| **England and Wales**                                                                                                                                                                                                                                                   |
| (Jurisdiction of incorporation or organization)                                                                                                                                                                                                                         |
|                                                                                                                                                                                                                                                                    |
| **Porton Down Science Park, Salisbury**

**Wiltshire, SP4 0JQ**

**United Kingdom**                                                                                                                                                                                     |
| (Address of principal executive offices)                                                                                                                                                                                                                                |
|                                                                                                                                                                                                                                                                    |
| **Justin D. Gover, Chief Executive Officer**

**GW Pharmaceuticals plc**

**Porton Down Science Park, Salisbury**

**Wiltshire, SP4 0JQ**

**United Kingdom**

**Telephone No. (44) 198 055-7000**

**E-Mail: investors@gwpharm.com**

**Facsimile: (44) 198 055-7111** |
| (Name, Telephone, E-mail and/or Facsimile number and Address of   Company Contact Person)                                                                                                                                                                               |

 

Securities registered or to be registered pursuant to Section 12(b) of the Act.

 

| Title of each   class                                                                               |   | Name of each   exchange on which registered |
|-----------------------------------------------------------------------------------------------------|--------|---------------------------------------------|
| American Depositary Shares, each representing 12 Ordinary Shares, par   value £0.001 per share |   | The Nasdaq Global Market                    |

 

Securities registered or to be registered pursuant to Section 12(g) of the Act: None

 

Securities for which there is a reporting obligation pursuant to Section 15(d) of the Act: None

 

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Indicate the number of outstanding shares of each of the issuer’s classes of capital or common stock as of the close of the period covered by the annual report: 177,521,287 ordinary shares, par value £0.001 per share.

 

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act.

o Yes   x No

 

If this report is an annual or transition report, indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934.

o Yes   x No

 

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.

x Yes   o No

 

Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Web site, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files).

o Yes   o No

 

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, or a non-accelerated filer. See definition of “accelerated filer and large accelerated filer” in Rule 12b-2 of the Exchange Act. (Check one):

 

| Large accelerated filer o |   | Accelerated filer o |   | Non-accelerated filer x |
|---------------------------|--------|---------------------|--------|-------------------------|

 

Indicate by check mark which basis of accounting the registrant has used to prepare the financial statements included in this filing:

 

| U.S. GAAP o |   | International Financial Reporting Standards as issued   by the International Accounting Standards Board x |   | Other o |
|-------------|--------|-----------------------------------------------------------------------------------------------------------|--------|---------|

 

If “Other” has been checked in response to the previous question, indicate by check mark which financial statement item the registrant has elected to follow.

o Item 17   o Item 18

 

If this is an annual report, indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act).

o Yes   x No

 

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**TABLE OF CONTENTS**

 
| EXPLANATORY NOTE | 1        |
|------------------|----------|
| PART III    |     | 2 |
| Item 19     | Exhibits | 2 |

 

i

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**EXPLANATORY NOTE**

** **

This Amendment No. 1 to Form 20-F (the “Form 20-F/A”) amends the Annual Report on Form 20-F of GW Pharmaceuticals plc for the fiscal year ended September 30, 2013, originally filed with the U.S. Securities and Exchange Commission (“SEC”) on November 25, 2013 (the “Form 20-F”). The purpose of this Form 20-F/A is an exhibit-only filing to amend the Form 20-F to re-file Exhibits 4.46, 4.47, 4.48 and 4.50.

 

The Form 20-F, as amended by this Form 20-F/A, speaks as of the original filing date of the Form 20-F, does not, and does not purport to, revise, update, amend or restate the information presented in any Item of the Form 20-F or reflect any events that have occurred after the filing of the Form 20-F.

 

1

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**PART III**

 

**Item 19  Exhibits**

 
| **Exhibit   Number** | ** ** | **Description of Exhibit**                                                                                                                                                                                                                                                                                                                                           |
|----------------------|------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| ** **           | ** ** | ** **                                                                                                                                                                                                                                                                                                                                                                     |
| 1.1*                 |       | Memorandum &   Articles of Association of GW Pharmaceuticals plc. (incorporated by   reference to Exhibit 3.1 to our Registration Statement on Form F-1   (file no. 333-187356), as amended, initially filed with the SEC on   March 19, 2013).                                                                                              |
|                 |       |                                                                                                                                                                                                                                                                                                                                                                           |
| 2.1*                 |       | Form of   specimen certificate evidencing ordinary shares (incorporated by reference to   Exhibit 4.1 to our Registration Statement on Form F-1 (file   no. 333-187356), as amended, initially filed with the SEC on   March 19, 2013).                                                                                                               |
|                 |       |                                                                                                                                                                                                                                                                                                                                                                           |
| 2.2(1)*              |       | Form of   Deposit Agreement among GW Pharmaceuticals plc, Citibank, N.A., as the   depositary bank and all Holders and Beneficial Owners of ADSs issued   thereunder (incorporated by reference to Exhibit 4.2 to our Registration   Statement on Form F-1 (file no. 333-187356), as amended, initially   filed with the SEC on March 19, 2013). |
|                 |       |                                                                                                                                                                                                                                                                                                                                                                           |
| 2.3(1)*              |       | Form of   American Depositary Receipt (included in Exhibit 4.2) (incorporated by   reference to Exhibit 4.3 to our Registration Statement on Form F-1   (file no. 333-187356), as amended, initially filed with the SEC on   March 19, 2013).                                                                                                    |
|                 |       |                                                                                                                                                                                                                                                                                                                                                                           |
| 2.4*                 |       | Share   Warrant to subscribe for ordinary shares issued to Biomedical Value   Fund, L.P. dated August 2009 (incorporated by reference to   Exhibit 4.4 to our Registration Statement on Form F-1 (file   no. 333- 187356), as amended, initially filed with the SEC on   March 19, 2013).                                                        |
|                 |       |                                                                                                                                                                                                                                                                                                                                                                           |
| 2.5*                 |       | Share   Warrant to subscribe for ordinary shares issued to Biomedical Value   Fund, L.P. dated August 2009 (incorporated by reference to   Exhibit 4.5 to our Registration Statement on Form F-1 (file   no. 333- 187356), as amended, initially filed with the SEC on   March 19, 2013).                                                        |
|                 |       |                                                                                                                                                                                                                                                                                                                                                                           |
| 2.6*                 |       | Share   Warrant to subscribe for ordinary shares issued to Biomedical Offshore Value   Fund, L.P. dated August 2009 (incorporated by reference to   Exhibit 4.6 to our Registration Statement on Form F-1 (file   no. 333- 187356), as amended, initially filed with the SEC on   March 19, 2013).                                               |
|                 |       |                                                                                                                                                                                                                                                                                                                                                                           |
| 2.7*                 |       | Share   Warrant to subscribe for ordinary shares issued to Biomedical Offshore Value   Fund, L.P. dated August 2009 (incorporated by reference to   Exhibit 4.7 to our Registration Statement on Form F-1 (file   no. 333- 187356), as amended, initially filed with the SEC on   March 19, 2013).                                               |
|                 |       |                                                                                                                                                                                                                                                                                                                                                                           |
| 4.1†*           |       | License   and Distribution Agreement between Bayer AG Division Pharma and   GW Pharma Ltd., dated May 20, 2003 (incorporated by reference   to Exhibit 10.1 to our Registration Statement on Form F-1 (file   no. 333- 187356), as amended, initially filed with the SEC on   March 19, 2013).                                              |
|                 |       |                                                                                                                                                                                                                                                                                                                                                                           |
| 4.2†*           |       | Amendment   Number 1 to the License and Distribution Agreement, dated   November 4, 2003 (incorporated by reference to Exhibit 10.2 to our   Registration Statement on Form F-1 (file no. 333-187356), as   amended, initially filed with the SEC on March 19, 2013).                                                                            |

 

2

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| **Exhibit   Number** | ** ** | **Description of Exhibit**                                                                                                                                                                                                                                                                                                                                                                                    |
|----------------------|------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| 4.3*                 |       | Amendment   Number 2 to the License and Distribution Agreement between   GW Pharma Ltd. and Bayer Healthcare AG Division Pharma, dated   January 14, 2004 (incorporated by reference to Exhibit 10.3 to our   Registration Statement on Form F-1 (file no. 333-187356), as   amended, initially filed with the SEC on March 19, 2013).                                          |
|                 |       |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 4.4†*           |       | Amendment   Number 3 to the License and Distribution Agreement between   GW Pharma Ltd. and Bayer Healthcare AG Division Pharma, dated   March 1, 2005 (incorporated by reference to Exhibit 10.4 to our   Registration Statement on Form F-1 (file no. 333-187356), as   amended, initially filed with the SEC on March 19, 2013).                                             |
|                 |       |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 4.5†*           |       | Amendment   Number 4 to the License and Distribution Agreement between   GW Pharma Ltd. and Bayer Healthcare AG Division Pharma, dated   May 10, 2005 (incorporated by reference to Exhibit 10.5 to our   Registration Statement on Form F-1 (file no. 333-187356), as   amended, initially filed with the SEC on March 19, 2013).                                              |
|                 |       |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 4.6*                 |       | Amendment   Number 5 to the License and Distribution Agreement between   GW Pharma Ltd. and Bayer Schering Pharma AG (f/k/a Bayer AG, Bayer   HealthCare, Division Pharma), dated March 10, 2010 (incorporated by   reference to Exhibit 10.6 to our Registration Statement on Form F-1   (file no. 333-187356), as amended, initially filed with the SEC on   March 19, 2013). |
|                 |       |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 4.7†*           |       | Supply   Agreement between Bayer AG and GW Pharma Ltd., dated May 20, 2003   (incorporated by reference to Exhibit 10.7 to our Registration Statement   on Form F-1 (file no. 333-187356), as amended, initially filed with   the SEC on March 19, 2013).                                                                                                                                 |
|                 |       |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 4.8†*           |       | Amendment   Number 1 to the Supply Agreement between GW Pharma Ltd. and Bayer   Healthcare AG, dated November 4, 2003 (incorporated by reference to   Exhibit 10.8 to our Registration Statement on Form F-1 (file   no. 333-187356), as amended, initially filed with the SEC on   March 19, 2013).                                                                                 |
|                 |       |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 4.9†*           |       | Amendment   Number 2 to the Supply Agreement between GW Pharma Ltd. and Bayer   Healthcare AG, dated May 10, 2005 (incorporated by reference to   Exhibit 10.9 to our Registration Statement on Form F-1 (file   no. 333- 187356), as amended, initially filed with the SEC on   March 19, 2013).                                                                                    |
|                 |       |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 4.10†*          |       | Amendment   Number 3 to the Supply Agreement between GW Pharma Ltd. and Bayer   Schering Pharma AG (f/k/a Bayer AG, Bayer HealthCare, Division Pharma), dated   March 10, 2010 (incorporated by reference to Exhibit 10.10 to our   Registration Statement on Form F-1 (file no. 333-187356), as   amended, initially filed with the SEC on March 19, 2013).                         |
|                 |       |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 4.11†*          |       | Product   Commercialisation and Supply Consolidated Agreement between GW Pharma Limited   and Almirall Prodesfarma, S.A., dated June 6, 2006 (incorporated by   reference to Exhibit 10.11 to our Registration Statement on   Form F-1 (file no. 333-187356), as amended, initially filed with   the SEC on March 19, 2013).                                                              |
|                 |       |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 4.12†*          |       | Amendment   No. 1 to the Product Commercialisation and Supply Consolidated Agreement   between GW Pharma Ltd. and Laboratorios Almirall S.A., dated   March 4, 2009 (incorporated by reference to Exhibit 10.12 to our   Registration Statement on Form F-1 (file no. 333-187356), as   amended, initially filed with the SEC on March 19, 2013).                               |
|                 |       |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 4.13†*          |       | Amendment   to the Product Commercialisation and Supply Consolidated Agreement, dated   June 6, 2006 between GW Pharma Ltd. and Almirall S.A., dated   July 23, 2010 (incorporated by reference to Exhibit 10.13 to our   Registration Statement on Form F-1 (file no. 333-187356), as   amended, initially filed with the SEC on March 19, 2013).                              |

 

3

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| **Exhibit   Number** | ** ** | **Description of Exhibit**                                                                                                                                                                                                                                                                                                                                                                                    |
|----------------------|------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| 4.14†*          |       | Supplementary   Agreement to the Product Commercialisation and Supply Consolidated Agreement,   dated June 6, 2006 between GW Pharma Ltd. and Almirall S.A.,   dated November 17, 2011 (incorporated by reference to Exhibit 10.14   to our Registration Statement on Form F-1 (file no. 333-187356), as   amended, initially filed with the SEC on March 19, 2013).            |
|                 |       |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 4.15†*          |       | Amendment   and Supplementary Agreement to the Product Commercialisation and Supply   Consolidated Agreement, dated June 6, 2006 between GW Pharma Ltd.   and Almirall S.A., dated March 13, 2012 (incorporated by reference   to Exhibit 10.15 to our Registration Statement on Form F-1 (file no. 333-187356),   as amended, initially filed with the SEC on March 19, 2013). |
|                 |       |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 4.16†*          |       | Research   Collaboration and Licence Agreement between GW Pharma Ltd. and GW   Pharmaceuticals plc and Otsuka Pharmaceutical Co., Ltd., dated   July 9, 2007 (incorporated by reference to Exhibit 10.16 to our   Registration Statement on Form F-1 (file no. 333-187356), as   amended, initially filed with the SEC on March 19, 2013).                            |
|                 |       |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 4.17†*          |       | Amendment   No. 1 to Research Collaboration and Licence Agreement, dated   March 14, 2008 (incorporated by reference to Exhibit 10.17 to our   Registration Statement on Form F-1 (file no. 333-187356), as   amended, initially filed with the SEC on March 19, 2013).                                                                                                                   |
|                 |       |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 4.18†*          |       | Amendment   No. 2 to Research Collaboration and Licence Agreement, dated   June 29, 2010 (incorporated by reference to Exhibit 10.18 to our   Registration Statement on Form F-1 (file no. 333-187356), as   amended, initially filed with the SEC on March 19, 2013).                                                                                                                    |
|                 |       |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 4.19†*          |       | Development   and License Agreement between GW Pharma Ltd. and   GW Pharmaceuticals Plc and Otsuka Pharmaceutical Co., Ltd.,   dated February 14, 2007 (incorporated by reference to Exhibit 10.19   to our Registration Statement on Form F-1 (file no. 333-187356), as   amended, initially filed with the SEC on March 19, 2013).                             |
|                 |       |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 4.20†*          |       | Amendment   No. 1 to Development and License Agreement, dated November 1, 2008   (incorporated by reference to Exhibit 10.20 to our Registration   Statement on Form F-1 (file no. 333-187356), as amended, initially   filed with the SEC on March 19, 2013).                                                                                                                            |
|                 |       |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 4.21†*          |       | Letter   amending Development and License Agreement, dated October 21, 2010   (incorporated by reference to Exhibit 10.21 to our Registration   Statement on Form F-1 (file no. 333-187356), as amended, initially   filed with the SEC on March 19, 2013).                                                                                                                                    |
|                 |       |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 4.22†*          |       | Distribution   and License Agreement, dated April 8, 2011, by and between GW   Pharma Ltd. and Novartis Pharma AG (incorporated by reference to   Exhibit 10.22 to our Registration Statement on Form F-1 (file   no. 333- 187356), as amended, initially filed with the SEC on   March 19, 2013).                                                                                        |
|                 |       |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 4.23†*          |       | Manufacturing   and Supply Agreement, dated November 9, 2011, by and between Novartis   Pharma AG and GW Pharma Ltd. (incorporated by reference to   Exhibit 10.23 to our Registration Statement on Form F-1 (file   no. 333-187356), as amended, initially filed with the SEC on   March 19, 2013).                                                                                      |
|                 |       |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 4.24†*          |       | Production   Supply Agreement, dated March 7, 2007 (incorporated by reference to   Exhibit 10.24 to our Registration Statement on Form F-1 (file   no. 333-187356), as amended, initially filed with the SEC on   March 19, 2013).                                                                                                                                                             |
|                 |       |                                                                                                                                                                                                                                                                                                                                                                                                                    |
| 4.25†*          |       | Lease,   dated July 6, 2009 (incorporated by reference to Exhibit 10.25 to   our Registration Statement on Form F-1 (file no. 333-187356), as   amended, initially filed with the SEC on March 19, 2013).                                                                                                                                                                                      |

 

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| **Exhibit   Number** | ** ** | **Description of Exhibit**                                                                                                                                                                                                                                                                                   |
|----------------------|------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| 4.26†*          |       | Lease,   dated October 9, 2009 (incorporated by reference to Exhibit 10.26   to our Registration Statement on Form F-1 (file no. 333-187356), as   amended, initially filed with the SEC on March 19, 2013).                                                                                  |
|                 |       |                                                                                                                                                                                                                                                                                                                   |
| 4.27†*          |       | Lease,   dated April 6, 2011 (incorporated by reference to Exhibit 10.27 to   our Registration Statement on Form F-1 (file no. 333-187356), as   amended, initially filed with the SEC on March 19, 2013).                                                                                    |
|                 |       |                                                                                                                                                                                                                                                                                                                   |
| 4.28†*          |       | Lease,   dated October 12, 2011 (incorporated by reference to Exhibit 10.28   to our Registration Statement on Form F-1 (file no. 333-187356), as   amended, initially filed with the SEC on March 19, 2013).                                                                                 |
|                 |       |                                                                                                                                                                                                                                                                                                                   |
| 4.29†*          |       | Lease,   dated January 6, 2012 (incorporated by reference to Exhibit 10.29   to our Registration Statement on Form F-1 (file no. 333-187356), as   amended, initially filed with the SEC on March 19, 2013).                                                                                  |
|                 |       |                                                                                                                                                                                                                                                                                                                   |
| 4.30†*          |       | Agreement   for Lease, dated April 4, 2012 (incorporated by reference to   Exhibit 10.30 to our Registration Statement on Form F-1 (file   no. 333-187356), as amended, initially filed with the SEC on   March 19, 2013).                                                                    |
|                 |       |                                                                                                                                                                                                                                                                                                                   |
| 4.31*                |       | Occupational   Underlease, dated August 11, 2010 (incorporated by reference to   Exhibit 10.31 to our Registration Statement on Form F-1 (file   no. 333-187356), as amended, initially filed with the SEC on   March 19, 2013).                                                              |
|                 |       |                                                                                                                                                                                                                                                                                                                   |
| 4.32*                |       | Lease,   dated May 24, 2011 (incorporated by reference to Exhibit 10.32 to   our Registration Statement on Form F-1 (file no. 333-187356), as   amended, initially filed with the SEC on March 19, 2013).                                                                                     |
|                 |       |                                                                                                                                                                                                                                                                                                                   |
| 4.33*                |       | Tenancy   Agreement, dated November 19, 2012 (incorporated by reference to   Exhibit 10.33 to our Registration Statement on Form F-1 (file   no. 333-187356), as amended, initially filed with the SEC on   March 19, 2013).                                                                  |
|                 |       |                                                                                                                                                                                                                                                                                                                   |
| 4.34*                |       | Service   Agreement by and between GW Pharma Ltd., and Adam George, dated   June 1, 2012 (incorporated by reference to Exhibit 10.34 to our   Registration Statement on Form F-1 (file no. 333-187356), as   amended, initially filed with the SEC on March 19, 2013).                   |
|                 |       |                                                                                                                                                                                                                                                                                                                   |
| 4.35†*          |       | Service   Agreement by and between GW Pharma Ltd., and Chris Tovey, dated   July 11, 2012 (incorporated by reference to Exhibit 10.35 to our   Registration Statement on Form F-1 (file no. 333-187356), as   amended, initially filed with the SEC on March 19, 2013).                  |
|                 |       |                                                                                                                                                                                                                                                                                                                   |
| 4.36*                |       | Service   Agreement by and between GW Research Ltd. and Dr. Geoffrey Guy,   dated March 14, 2013 (incorporated by reference to Exhibit 10.36 to   our Registration Statement on Form F-1 (file no. 333- 187356), as   amended, initially filed with the SEC on March 19, 2013).     |
|                 |       |                                                                                                                                                                                                                                                                                                                   |
| 4.37*                |       | Service   Agreement by and between GW Research Ltd. and Justin Gover, dated   February 26, 2013 (incorporated by reference to Exhibit 10.37 to   our Registration Statement on Form F-1 (file no. 333-187356), as   amended, initially filed with the SEC on March 19, 2013).            |
|                 |       |                                                                                                                                                                                                                                                                                                                   |
| 4.38*                |       | Service   Agreement by and between GW Research Ltd. and Dr. Stephen Wright,   dated January 18, 2013 (incorporated by reference to Exhibit 10.38   to our Registration Statement on Form F-1 (file no. 333- 187356),   as amended, initially filed with the SEC on March 19, 2013). |

 

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| **Exhibit   Number** | ** ** | **Description of Exhibit**                                                                                                                                                                                                                                                                                  |
|----------------------|------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| 4.39*                |       | Letter   of Appointment by and between GW Pharmaceuticals plc and James Noble,   dated February 26, 2013 (incorporated by reference to Exhibit 10.39   to our Registration Statement on Form F-1 (file no. 333- 187356),   as amended, initially filed with the SEC on March 19, 2013). |
|                 |       |                                                                                                                                                                                                                                                                                                                  |
| 4.40*                |       | Letter   of Appointment by and between GW Pharmaceuticals plc and Tom Lynch,   dated February 26, 2013 (incorporated by reference to Exhibit 10.40   to our Registration Statement on Form F-1 (file no. 333- 187356),   as amended, initially filed with the SEC on March 19, 2013).   |
|                 |       |                                                                                                                                                                                                                                                                                                                  |
| 4.41**               |       | Service   Agreement by and between GW Pharmaceuticals Inc. and Cabot Brown, dated   November 7, 2013.                                                                                                                                                                                                       |
|                 |       |                                                                                                                                                                                                                                                                                                                  |
| 4.42*                |       | Long   Term Incentive Plan (incorporated by reference to Exhibit 10.42 to our   Registration Statement on Form F-1 (file no. 333-187356), as   amended, initially filed with the SEC on March 19, 2013).                                                                                          |
|                 |       |                                                                                                                                                                                                                                                                                                                  |
| 4.43*                |       | GW   Pharmaceuticals All Employee Share Scheme (incorporated by reference to   Exhibit 10.43 to our Registration Statement on Form F-1 (file   no. 333-187356), as amended, initially filed with the SEC on   March 19, 2013).                                                                    |
|                 |       |                                                                                                                                                                                                                                                                                                                  |
| 4.44*                |       | GW   Pharmaceuticals Approved Share Option Scheme 2001 (incorporated by reference   to Exhibit 10.44 to our Registration Statement on Form F-1 (file   no. 333-187356), as amended, initially filed with the SEC on   March 19, 2013).                                                            |
|                 |       |                                                                                                                                                                                                                                                                                                                  |
| 4.45*                |       | GW   Pharmaceuticals Unapproved Share Option Scheme 2001 (incorporated by   reference to Exhibit 10.45 to our Registration Statement on   Form F-1 (file no. 333-187356), as amended, initially filed with   the SEC on March 19, 2013).                                                          |
|                 |       |                                                                                                                                                                                                                                                                                                                  |
| 4.46†           |       | Lease,   dated May 24, 2013.                                                                                                                                                                                                                                                                                     |
|                 |       |                                                                                                                                                                                                                                                                                                                  |
| 4.47†           |       | Lease,   dated May 24, 2013.                                                                                                                                                                                                                                                                                     |
|                 |       |                                                                                                                                                                                                                                                                                                                  |
| 4.48†           |       | Lease,   dated May 24, 2013.                                                                                                                                                                                                                                                                                     |
|                 |       |                                                                                                                                                                                                                                                                                                                  |
| 4.49**               |       | Lease,   dated August 1, 2013.                                                                                                                                                                                                                                                                                   |
|                 |       |                                                                                                                                                                                                                                                                                                                  |
| 4.50†           |       | Lease,   dated July 16, 2013.                                                                                                                                                                                                                                                                                    |
|                 |       |                                                                                                                                                                                                                                                                                                                  |
| 8.1**                |       | List of   Subsidiaries.                                                                                                                                                                                                                                                                                               |
|                 |       |                                                                                                                                                                                                                                                                                                                  |
| 12.1**               |       | Section 302   Certificate.                                                                                                                                                                                                                                                                                       |
|                 |       |                                                                                                                                                                                                                                                                                                                  |
| 12.2**               |       | Section 302   Certificate.                                                                                                                                                                                                                                                                                       |
|                 |       |                                                                                                                                                                                                                                                                                                                  |
| 13.1**               |       | Section 906   Certificate.                                                                                                                                                                                                                                                                                       |
|                 |       |                                                                                                                                                                                                                                                                                                                  |
| 13.2**               |       | Section 906   Certificate.                                                                                                                                                                                                                                                                                       |

 

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| *      | Previously   filed.                                                                                                                                                                                             |
|--------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|   |                                                                                                                                                                                                            |
| **     | Previously   filed with the initial filing of the Company’s Annual Report on Form 20-F for   the year ended September 30, 2013, originally filed on November 25, 2013.                                     |
|   |                                                                                                                                                                                                            |
| † | Confidential   treatment requested.                                                                                                                                                                             |
|   |                                                                                                                                                                                                            |
| (1)    | Incorporated   by reference to the Registration Statement on Form F-6 (File   No. 333-187978), filed with the Securities and Exchange Commission with   respect to ADSs representing ordinary shares. |

 

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**Signature**

 

The registrant hereby certifies that it meets all of the requirements for filing on Form 20-F and that it has duly caused and authorized the undersigned to sign this Amendment No. 1 to Form 20-F on its behalf.

 
| ** **              | **GW PHARMACEUTICALS PLC** |
|-------------------------|---------------------------------|
| ** **              | ** **                      |
| ** **              | ** **                      |
|                    | By:                             | /s/   JUSTIN GOVER |
|                    |                            | Name: | Justin   Gover |
|                    |                            | Title: | *Chief Executive Officer* |
|                    |                            |   | * * |
| Date: January   6, 2014 |                            |   |   |

 

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