X0202 SCHEDULE 13D/A 0001830908 XXXXXXXX LIVE 9 American Depositary Shares, each representing 120 ordinary shares Ordinary shares 08/26/2026 false 0001574232 00654J206 Addex Therapeutics Ltd.

Chemin des Mines 9 Geneva V8 CH-1202

Timothy Mark Dyer 41 22 884 1555 c/o Addex Therapeutics Ltd Chemin des Mines 9 Geneva V8 CH-1202 0001830908 N Timothy Mark Dyer b PF OO N V8 19095510.00 0.00 19095510.00 0.00 19095510.00 N 8.98 IN Consists of 16,848,979 ordinary shares and 2,246,531 shares issuable upon exercise of options exercisable within 60 days of Agust 26, 2026. (2) Represents the percentage ownership based on 210,292,217 ordinary shares of Addex Therapeutics Ltd outstanding as of August 26, 2026, as reported in the press release on form 6K (file No.001-39179) filed on August 26, 2026. American Depositary Shares, each representing 120 ordinary shares Ordinary shares Addex Therapeutics Ltd. Chemin des Mines 9 Geneva V8 CH-1202 This Schedule 13D relates to the ordinary shares, nominal value CHF 0.01 per share (the "Shares"), of Addex Therapeutics Ltd (the "Issuer"). The Issuer's principal executive office is located at Chemin des Mines 9, CH- 1202 Geneva, Switzerland. This Amendment No.9 ("Amendment No.9") amends and restates the Statement on Schedule 13D initially filed on November 3, 2020 and amended on June 23, 2025 (as amended, the "Original Schedule 13D"). This Amendment No.9 is being filed to update the aggregate percentage of the class of securities of the Issuer owned by the Reporting Person due to the dilution caused by the Issuer's additional sales of shares from time to time since the filing of the Original Schedule 13D. The Issuer reported increased number of outstanding shares as of August 26, 2026 in the press release on form 6K (file No.001-39179) filed on August 26, 2026, causing a variation of more than one (1%) from the percentages reported in the Original Schedule 13D. Timothy Mark Dyer, an individual ("Reporting Person"). The business address of Reporting Person is c/o Addex Therapeutics Ltd, Chemin des Mines 9, CH- 1202 Geneva, Switzerland. Reporting Person is the Chief Executive Officer and a member of the Board of Directors of the Issuer. During the last five years, Reporting Person has not been (1) convicted in a criminal proceeding (excluding traffic violations or similar misdemeanors) or (2) a party to a civil proceeding of a judicial or administrative body of competent jurisdiction and as a result of such proceeding has been or is subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws. During the last five years, Reporting Person has not been (1) convicted in a criminal proceeding (excluding traffic violations or similar misdemeanors) or (2) a party to a civil proceeding of a judicial or administrative body of competent jurisdiction and as a result of such proceeding has been or is subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws. Reporting Person is a citizen of Switzerland and United Kingdom. Reporting Person is deemed to beneficially own 19,095,510 Shares of the Issuer as reflected in this Schedule 13D. Prior to May 21, 2007, Reporting Person acquired 7,811 founder shares at a purchase price of CHF 1.00. The source of funds for such purchase was Reporting Person's personal funds. On August 9, 2013, Reporting Person acquired 36,364 Shares at a purchase price of CHF 2.75 per share through participation in a private placement. The source of funds for such purchase was Reporting Person's personal funds. On June 30, 2014, Reporting Person was granted stock options from the Issuer to purchase 400,000 Shares issuable upon exercise of options as compensation for his service as Chief Executive Officer of the Issuer. On October 26, 2022, Reporting Person exercised the options and acquired 400,000 Shares that are all freely tradable. The deferred strike price was CHF 0.13 for each share acquired. On July 1, 2014, Reporting Person received 18,143 Shares as compensation for his service as Chief Executive Officer of the Issuer. On July 14, 2014, Reporting Person received 24,588 Shares as compensation for his service as Chief Executive Officer of the Issuer. On January 7, 2015, Reporting Person received 17,063 Shares as compensation for his service as Chief Executive Officer of the Issuer. On March 6, 2015, Reporting Person acquired 33,333 Shares at a purchase price of CHF 3.00 per share during a private placement. The source of funds for such purchase was Reporting Person's personal funds. On July 28, 2015, Reporting Person received 17,149 Shares as compensation for his service as Chief Executive Officer of the Issuer. On January 28, 2016, Reporting Person received 17,461 Shares as compensation for his service as Chief Executive Officer of the Issuer. On August 2, 2016, Reporting Person received 20,263 Shares as compensation for his service as Chief Executive Officer of the Issuer. On January 16, 2017, Reporting Person received 23,001 Shares as compensation for his service as Chief Executive Officer of the Issuer. On February 28, 2017, Reporting Person was granted stock options from the Issuer to purchase 229,480 Shares issuable upon exercise of options as compensation for his service as Chief Executive Officer of the Issuer. On October 26, 2022, Reporting Person exercised the options and acquired 229,480 Shares that are all freely tradable. The deferred strike price was CHF 0.13 for each share acquired. On July 28, 2017, Reporting Person received 23,187 Shares as compensation for his service as Chief Executive Officer of the Issuer. On December 23, 2017, Reporting Person was granted stock options from the Issuer to purchase 1,052,250 Shares. On October 26, 2022, Reporting Person exercised the options and acquired 1,052,250 Shares that are all freely tradable. The deferred strike price was CHF 0.13 for each share acquired. On December 23, 2017, Reporting Person acquired 108,000 Shares through the exercise of options of which 53,000 and 55,000 were received on June 1, 2010, and November 15, 2011, respectively. The exercise price was CHF 1.00 for the Shares acquired and the source of funds for such purchase was Reporting Person's personal funds. On January 4, 2018, Reporting Person received 24,519 Shares as compensation for his service as Chief Executive Officer of the Issuer. On August 15, 2018, Reporting Person received 18,226 Shares as compensation for his service as Chief Executive Officer of the Issuer. On March 28, 2018, Reporting Person acquired 31,948 Shares at a purchase price of CHF 3.13 per share through participation in a private placement. The source of funds for such purchase was Reporting Person's personal funds. On June 1, 2018, Reporting Person was granted stock options from the Issuer to purchase 1,199,662 Shares. On October 26, 2022, Reporting Person exercised the options and acquired 1,199,662 Shares that are all freely tradable. The deferred strike price was CHF 0.13 for each share acquired. On January 1, 2019, Reporting Person was granted stock options from the Issuer to purchase 243,506 Shares. On October 26, 2022, Reporting Person exercised the options and acquired 243,506 Shares that are all freely tradable. The deferred strike price was CHF 0.13 for each share acquired. On January 4, 2019, Reporting Person received 14,136 Shares as compensation for his service as Chief Executive Officer of the Issuer. On April 1, 2020, Reporting Person was granted stock options from the Issuer to purchase 698,011 Shares. On October 26, 2022, Reporting Person exercised the options and acquired 698,011 Shares that are all freely tradable. The deferred strike price was CHF 0.13 for each Share acquired. On May 17, 2021, Reporting Person was granted stock options from the Issuer to purchase 700,000 Shares. On October 26, 2022, Reporting Person exercised the options and acquired 700,000 Shares that are all freely tradable. The deferred strike price was CHF 0.13 for each share acquired. On April 12, 2022, Reporting Person was granted stock options from the Issuer to purchase 2,051,972 Shares. On October 26, 2022, Reporting Person exercised the options and acquired 2,051,972 Shares that are all freely tradable. The deferred strike price was CHF 0.13 for each share acquired. On October 5, 2022, Reporting Person was granted stock options from the Issuer to purchase 2,830,873 Shares. On October 26, 2022, Reporting Person exercised the options and acquired 2,830,873 Shares. Of these shares 58,977 are not freely tradable as of August 26, 2026. The deferred strike price was CHF 0.13 for each share acquired. On May 12, 2023, Reporting Person was granted stock options from the Issuer to purchase 7,008,033 Shares. On November 27, 2023, Reporting Person exercised the options and acquired 7,008,033 Shares. Of these shares 1,168,005 are not freely tradable as of August 26, 2026. The deferred strike price was CHF 0.043 for each share acquired. On January 8, 2024, Reporting Person was granted a stock option from the Issuer to purchase 3,369,796 shares at an exercise price of CHF 0.05. The shares underlying this option vest in 48 equal monthly installments, subject to Timothy Mark Dyer's continuous service as Chief Executive Officer of the issuer. As of August 26, 2026, 2,246,531 Shares are issuable upon exercise of options as compensation for his service as Chief Executive Officer of the Issuer. Unless specifically stated above, Reporting Person paid no compensation for the Shares. The Reporting Person acquired the securities of the Issuer at founding, through the exercise of options, acquisitions through participation in private placements and in consideration for his services as Chief Executive Officer of the Issuer. The reporting person also received shares issuable upon exercise of options. The terms of the Reporting Person's employment arrangements for 2025 were set forth in the Issuer's Annual Report on Form 20-F for such period filed by the Issuer with the Securities and Exchange Commission on May 15, 2026. Except in respect of such employment arrangements as set forth therein, the Reporting Person does not have any present plans which relate to or would result in: However, the Reporting Person reserves the right to change its plans at any time, as it deems appropriate, in light of its ongoing evaluation of (i) its business and liquidity objectives? (ii) the Issuer's financial condition, business, operations, competitive position, prospects and/or Share price? (iii) industry, economic and/or securities markets conditions? (iv) alternative investment opportunities? and (v) other relevant factors. As of the date hereof, Reporting Person beneficially owns 19,095,510 Shares, which represents approximately 8.89% of the Issuer's Shares, consisting of (i) 16,848,979 Shares (ii) 2,246,531 Shares issuable upon exercise of options exercisable within 60 days of August 26, 2026. Reporting Person may be deemed to hold sole voting and dispositive power over his 19,095,510 Shares of the Issuer. Other than the acquisition of the shares as reported herein, and as described under Item 4, Reporting Person has not effected any transactions in the shares of the Issuer during the past 60 days or since the most recent filing of Schedule 13D, whichever is less. To the best knowledge of Reporting Person, no person other than the Reporting Person has the right to receive, or the power to direct the receipt of, dividends from, or the proceeds from the sale of the 19,095,510 Shares reported in Item 5(a). Not applicable. The information furnished in Item 3 is incorporated into this Item 6 by reference. Not applicable. Timothy Mark Dyer /s/ Timothy Mark Dyer 08/27/2026