6-K

UNITED STATESSECURITIES AND EXCHANGE COMMISSIONWashington, D.C. 20549

Form 6-K

REPORT OF FOREIGN PRIVATE ISSUER PURSUANT TORULE 13a-16 OR 15d-16 UNDER THESECURITIES EXCHANGE ACT OF 1934

For the month of December 2025

Commission File Number: 001-39179

Addex Therapeutics Ltd

(Translation of registrant's name into English)

Chemin des Mines 9,CH-1202 Geneva,Switzerland(Address of principal executive office)

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

Form 20-F x Form 40-F ¨

INCORPORATION BY REFERENCE

This report on Form 6-K shall be deemed to be incorporated by reference into the registration statements on Form F-3 (No. 333-291644) and S-8 (Nos. 333-272515 and 333-255124), of Addex Therapeutics Ltd (the “Company”) (including any prospectuses forming a part of such registration statements) and to be a part thereof from the date on which this report is filed, to the extent not superseded by documents or reports subsequently filed or furnished.

Entry into Amendment to At The MarketOffering Agreement with H.C. Wainwright & Co., LLC

As previously disclosed, on January 30, 2024, the Company entered into an At The Market Offering Agreement (the “Original ATM Agreement”) with H.C. Wainwright & Co., LLC (“H.C. Wainwright”) with respect to an at-the-market offering program under which the Company may offer and sell, from time to time at its sole discretion, the Company’s American Depositary Shares (the “ADSs”), each representing one hundred and twenty ordinary shares (nominal value CHF 0.01 per share) (the “Ordinary Shares”) through H.C. Wainwright as its sales agent. On December 10, 2025, the Company entered into Amendment No. 1 to the Original ATM Agreement (as amended, the “ATM Agreement”) As of the date hereof, the Company filed a prospectus supplement to increase the maximum number of Ordinary Shares issuable pursuant to the ATM Agreement, having an aggregate offering price of up to $3.3 million. The issuance and sale, if any, of the ADSs by the Company under the ATM Agreement will be made pursuant to the Company’s effective registration statement on Form F-3 (Registration Statement No. 333-291644).

H.C. Wainwright may sell the ADSs by any method permitted by law deemed to be an “at the market offering” as defined in Rule 415(a)(4) of the Securities Act of 1933, as amended, including, without limitation, sales made through The Nasdaq Capital Market or on any other existing trading market for the ADSs. H.C. Wainwright will use commercially reasonable efforts to sell the ADSs from time to time, based upon instructions from the Company (including any price, time or size limits or other customary parameters or conditions the Company may impose). The Company will pay H.C. Wainwright a commission equal to three percent (3.0%) of the gross sales proceeds of any ADSs sold through H.C. Wainwright under the ATM Agreement, and also has provided H.C. Wainwright with customary indemnification and contribution rights.

The Company is not obligated to make any sales of ADSs under the ATM Agreement. The Company or H.C. Wainwright may suspend or terminate the offering of ADSs upon notice to the other party and subject to other conditions. H.C. Wainwright will act as sales agent on a commercially reasonable efforts basis consistent with its normal trading and sales practices and applicable state and federal law, rules and regulations and the rules of the Nasdaq Stock Market.

The foregoing description of the ATM Agreement is not complete and is qualified in its entirety by reference to the full text of the ATM Agreement, a copy of which is filed in part as Exhibit 1.1 to the Company’s report on Form 6-K filed on January 30, 2024 and in part herewith as Exhibit 1.1 to this report on Form 6-K and is incorporated herein by reference. A copy of the legal opinion of Homburger AG, the Company’s Swiss counsel, relating to the underlying shares issued in connection with the ATM Agreement is attached as Exhibit 5.1 hereto.

This report on Form 6-K shall not constitute an offer to sell or the solicitation of an offer to buy the securities discussed herein, nor shall there be any offer, solicitation, or sale of the securities in any state in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state.

EXHIBIT INDEX

Exhibit Number	Description
1.1	Amendment No. 1 to At The Market Offering Agreement, dated as of December 10,<br> 2025, by and between Addex Therapeutics Ltd and H.C. Wainwright & Co., LLC.
5.1	Opinion of Homburger AG
23.1	Consent of Homburger AG (included in Exhibit 5.1)

SIGNATURE

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.

	Addex Therapeutics Ltd
	(Registrant)
Date: December 10, 2025	/s/ Tim Dyer
	Tim Dyer
	Chief Executive Officer

Exhibit 1.1

AMENDMENTNO. 1 TOAT THE MARKET OFFERING AGREEMENT

December 10, 2025

H.C. Wainwright & Co., LLC

430 Park Avenue, 3rd Floor

New York, New York 10022

Ladies and Gentlemen:

This Amendment No. 1 to the At the Market Offering Agreement (this “Amendment”) is entered into as of the date first written above by Addex Therapeutics Ltd, a stock corporation (Aktiengesellschaft) incorporated under the laws of Switzerland (the “Company”), and H.C. Wainwright & Co., LLC, as sales agent and/or principal (the “Manager”), which are parties to that certain At the Market Offering Agreement, dated as of January 30, 2024 (the “Agreement”). All capitalized terms not defined herein shall have the meanings ascribed to them in the Agreement.

WITNESSETH THAT:

WHEREAS, Section 14 of the Agreement permits the Company and the Manager to amend the Agreement; and

WHEREAS, the Company and the Manager now desire to amend the Agreement as provided herein.

NOW, THEREFORE, in consideration of the foregoing premises and other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the Company and the Manager agree as follows:

1.	The definition of “Depositary” in Section 1 of the Agreement is amended and restated as set<br>forth below:

““Depositary” shall mean The Bank of New York Mellon.”

2.	The definition of “Depositary’s Counsel” in Section 1 of the Agreement is amended and<br>restated as set forth below:

““Depositary’s Counsel” shall mean Emmet, Marvin & Martin, LLP.”

3.	Section 2(b)(vii) of the Agreement is hereby deleted and replaced with the following:

“Unless otherwise agreed between the Company and the Manager, settlement for sales of the ADSs will occur at 10:00 a.m. (New York City time) on the second (2nd) Trading Day (or any other settlement cycle as may be in effect from time to time under Exchange Act Rule 15c6-1) following the date on which such sales are made (each, a “Settlement Date”). On or before the Trading Day prior to each Settlement Date, the Company will, or will cause its Depositary to, electronically transfer the ADSs being sold by crediting the Manager’s (or its designated broker-dealer’s) account (provided that the Manager shall have given the Company written notice of such account information at least one Trading Day prior to the Settlement Date) at The Depository Trust Company (“DTC”) by delivery order or by such other means of delivery as may be mutually agreed upon by the parties hereto which ADSs in all cases shall be freely tradable, transferable, registered ADSs in good deliverable form. On each Settlement Date, the Manager will deliver the related Net Proceeds in same day funds to an account designated by the Company. The Company agrees that, if the Company defaults in its obligation to deliver duly authorized ADSs on a Settlement Date, in addition to and in no way limiting the rights and obligations set forth in Section 7 hereto, the Company will (i) hold the Manager harmless against any loss, claim, damage, or reasonable, documented expense (including reasonable and documented legal fees and expenses), as incurred, arising out of or in connection with such default by the Company, and (ii) pay to the Manager any commission, discount or other compensation to which the Manager would otherwise have been entitled absent such default.”

4.	All references in the Agreement to the “Agreement” shall mean the Agreement as amended by<br>this Amendment; provided, however, that all references to “date of this Agreement” in the Agreement shall continue<br>to refer to the date of the Agreement, unless amended otherwise herein. Except as set forth herein, the provisions of the Agreement are<br>not amended or waived, and remain in full force and effect.
5.	Sections 13, 14, 15, 16 and 17 of the Agreement are hereby incorporated by reference herein, mutatismutandis, and apply equally to this Amendment and the Agreement as amended by this Amendment.
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If the foregoing correctly sets forth the understanding between the Company and the Manager, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding amendment to the Agreement between the Company and the Manager.

[Signature Pages Follow]

Very truly yours,
ADDEX THERAPEUTICS LTD
By:	/s/ Tim Dyer
Name:	Tim Dyer
Title:	Chief Executive Officer

[Signature Page to AmendmentNo. 1 to the At the Market Offering Agreement]

ACCEPTED as of the date first-above written:
H.C. WAINWRIGHT & CO., LLC
By:	/s/ Edward Silvera
Name:	Edward Silvera
Title:	Chief Operating Officer

[Signature Page to AmendmentNo. 1 to the At the Market Offering Agreement]

Exhibit 5.1

To:<br><br>Addex Therapeutics Ltd<br><br>  c/o Addex Pharma SA<br><br>Chemin des Aulx 12<br><br>1228 Plan-les-Ouates<br><br>Switzerland	Homburger AG<br><br> <br>Prime Tower<br><br> <br>Hardstrasse 201<br><br> <br>CH-8005 Zürich<br><br> <br><br><br> <br>homburger.ch<br><br> T +41 43 222 10 00

December 10, 2025

Addex Therapeutics Ltd / Registration Statement on Form F-3 – Exhibit 5.1

Ladies and Gentlemen

We have acted as special Swiss counsel to Addex Therapeutics Ltd, a stock corporation incorporated under the laws of Switzerland (the Company), in connection with the preparation and filing on the date hereof with the United States Securities and Exchange Commission (the SEC) of a prospectus supplement (the Prospectus Supplement). The Prospectus Supplement supplements a registration statement on Form F-3, which included a base prospectus, was filed by the Company with the SEC on November 19, 2025 and declared effective by SEC on December 5, 2025 (the Registration Statement). The Registration Statement relates to the registration under the United States Securities Act of 1933, as amended, the offer and sale by the Company, in the form of American Depositary Shares (ADSs), of (i) registered shares of the Company with a nominal value of CHF 0.01 each held by the Company directly or through a wholly owned subsidiary as treasury shares (actionspropres) (the Treasury Shares) and (ii) registered shares of the Company with a nominal value of CHF 0.01 each to be issued out of the capital band (marge de fluctuation de capital) of the Company and to be held by the Company directly or through its wholly owned subsidiary as treasury shares (the Capital Increase Shares, together with the Treasury Shares, the OfferedShares), for a proposed maximum aggregate offering price of USD 150 million. The Prospectus Supplement relates to the sale of the Offered Shares by the Company for a proposed maximum aggregate offering price of USD 3,300,000 in accordance with a New York law-governed at-the-market offering agreement dated as of January 30, 2024 by and between H.C. Wainwright & Co., LLC (the Manager) and the Company ((as amended by Amendment No. 1 to the at-the-market offering agreement dated as of December 10, 2025 by and between the Manager and the Company).

Capitalized terms used but not defined herein shall have the meaning ascribed to them in the Documents (as defined below).

A.	Basis of Opinion

This opinion is confined to and given on the basis of the laws of Switzerland in force at the date hereof. Such laws and the interpretation thereof are subject to change. In the absence of explicit statutory law, we base our opinion solely on our independent professional judgment. This opinion is also confined to the matters stated herein and the Documents (as defined below), and is not to be read as extending, by implication or otherwise, to any agreement or document referred to in any of the Documents (including, in the case of the Registration Statement, any document incorporated by reference therein or exhibited thereto) or any other matter.

For purposes of this opinion, we have only reviewed originals or copies of the following documents (collectively the Documents):

(i)	an electronic copy of the Registration<br> Statement;
(ii)	an electronic copy of the Prospectus<br> Supplement (together with the Registration Statement, the Filing Documents);
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(iii)	an electronic copy of the articles of<br> association (statuts) of the Company dated October 28, 2025, notarized by a licensed<br> notary of the Canton of Geneva on October 28, 2025 (the Articles);
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(iv)	an electronic copy of the internal regulations<br> (règlement d’organisation) of the Company in their version approved by<br> the board of directors of the Company on January 28, 2020 (the Organizational Regulations);
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(v)	an electronic copy of an internet excerpt<br> (extrait internet) from the Commercial Register of the Canton of Geneva dated as of<br> the date hereof, relating to the Company (the Internet Excerpt).
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No documents, other than the Documents, have been reviewed by us in connection with this opinion. Accordingly, we shall limit our opinion to the Documents and their legal implications under Swiss law.

In this opinion, Swiss legal concepts are expressed in English terms and not in their original language. These concepts may not be identical to the concepts described by the same English terms as they exist under the laws of other jurisdictions.

B.	Assumptions

In rendering the opinion below, we have assumed the following:

(a)	all documents produced to us as originals<br> are authentic and complete, and all documents produced to us as copies (including, without<br> limitation, electronic copies) conform to the original;

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(b)	all documents produced to us as originals<br> and the originals of all documents produced to us as copies were duly executed and certified,<br> as applicable, by the individuals purported to have executed or certified, as the case may<br> be, such documents;
(c)	the Filing Documents are unchanged and correct,<br> complete and up-to-date and in full force and effect as of the date hereof and no changes<br> have been made which should have been or should be reflected in the Filing Documents as of<br> the date hereof;
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(d)	all signatures appearing on all original<br> documents or copies thereof which we have examined are genuine and authentic;
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(e)	to the extent relevant for purposes of this<br> opinion, any and all information contained in the Documents is, and all material statements<br> made to us in connection with the Documents are and will be, true, complete and accurate<br> at all relevant times;
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(f)	prior to the issuance of any Capital Increase<br> Shares, the shareholders' meeting will have resolved to increase the capital band (if the<br> Capital Increase Shares will exceed the amount of the existing capital band), and the board<br> of directors of the Company will have resolved in the presence of a notary on the execution<br> of the corresponding capital increase, validly excluded the existing shareholders' pre-emptive<br> subscription rights (droits de souscription préférentiel) for purposes<br> of offering as contemplated in the Registration Statement, issued a capital increase report<br> with respect to the corresponding capital increase and made the corresponding declarations<br> required for implementing the corresponding capital increase (constatations relatives à l’augmentation du capital) in the presence of a notary and the board resolutions,<br> and such further resolutions and ascertainments will not have been amended and will be in<br> full force and effect until the issuance of all Capital Increase Shares;
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(g)	the Company has not entered and will not<br> enter into any transaction which could be construed as repayment of share capital (restitution des versements);
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(h)	all authorizations, approvals, consents,<br> licenses, exemptions, other than as required by mandatory Swiss law applicable to the Company<br> or the Articles, and other requirements for the filing of the Filing Documents and for any<br> other activities carried on in view of, or in connection with, the performance of the obligations<br> expressed to be undertaken by the Company in the Filing Documents have been duly obtained<br> or fulfilled in due time and are and will remain in full force and effect, and any related<br> conditions to which the parties thereto are subject have been satisfied;
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(i)	the Articles, the Organizational Regulations<br> and the Internet Excerpt are unchanged and correct, complete and up-to-date and in full force<br> and effect as of the date hereof, and no changes have been made which should have been or<br> should be reflected in the Articles, the Organizational Regulations or the Internet Excerpt<br> as of the date hereof;
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(j)	the Offered Shares have not been and will<br> not be publicly offered, directly or indirectly, in Switzerland within the meaning of article<br> 3 lit. h of the Swiss Financial Services Act of June 15, 2018, as amended (FinSA),<br> except under an exemption from the prospectus requirements under the FinSA;
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(k)	the Company is, at the date hereof, not insolvent<br> (in the sense of article 725 of the Swiss Code of Obligations of March 30, 1911,<br> as amended (CO)) or over-indebted (in the sense of article 725b CO);
(l)	the Company intends to produce and publish<br> financial statements in accordance with articles 958 et seqq. CO at least annually;<br> and
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(m)	no laws (other than those of Switzerland)<br> affect any of the conclusions stated in this opinion.
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C.	Opinion
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Based on the foregoing assumptions and subject to the qualifications set out below, we express the following opinion:

1.	The Treasury Shares have been validly issued,<br> fully paid as to their nominal value and are non-assessable.
2.	The Capital Increase Shares, if and when (i) issued<br> and paid for pursuant to the Articles and Swiss law and (ii) registered in the Commercial<br> Register of the Canton of Geneva and entered into the Company’s book of uncertificated<br> securities (registre des droits-valeurs), will have been validly issued, fully paid<br> as to their nominal value and non-assessable.
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D.	Qualifications
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The above opinions are subject to the following qualifications:

(a)	The lawyers of our firm are members of the<br> Zurich bar and do not hold themselves out to be experts in any laws other than the laws of<br> Switzerland. Accordingly, we are opining herein as to Swiss law only and we express no opinion<br> with respect to the applicability or the effect of the laws of any other jurisdiction to<br> or on the matters covered herein
(b)	We express no opinion as to whether the Filing<br> Documents are accurate, true, correct, complete or not misleading. In particular, and without<br> limitation to the foregoing, we express no opinion on whether the Filing Documents provide<br> sufficient information for investors to reach an informed assessment of the Company, any<br> companies within the Company’s consolidation perimeter and the Offered Shares.
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(c)	When used in this opinion, the term "non-assessable"<br> means that no further contributions have to be made to the Company by the relevant holder<br> of the Offered Shares.
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(d)	We express no opinion as regards the exclusion<br> of shareholders’ pre-emptive subscription rights (droits de souscription préférentiel)<br> in connection with the offering and issuance of the Offered Shares.
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(e)	We express no opinion as to the future availability<br> of the capital band of the Company.
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(f)	Any Offered Shares issued or to be issued<br> by the Company will not be fully fungible and will not rank pari passu with the existing<br> and outstanding registered shares of the Company until such Offered Shares have been duly<br> entered into the Company’s book of uncertificated securities (registre des droits-valeurs)<br> and the main register (registre principal) maintained by the relevant third party<br> and all steps have been taken in order for such Offered Shares to constitute intermediated<br> securities (titres intermédiés) in accordance with the Swiss Federal<br> Act on Intermediated Securities of October 3, 2008, as amended.
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(g)	As long as the Offered Shares are not duly<br> recorded in the main register and credited to one or more securities accounts, they do not<br> exist as intermediated securities. As a consequence, our opinions do not extend to legal<br> consequences attached to the Offered Shares in their form as intermediated securities.
(h)	The exercise of voting rights and rights<br> related thereto with respect to any Offered Shares is only permissible after registration<br> in the Company’s share register (registre des actions) as a shareholder with<br> voting rights in accordance with the provisions of, and subject to the limitations provided<br> in, the Articles.
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(i)	When used in this opinion, the term "validly<br> issued" means that the issuance of the Offered Shares is valid between the Company and<br> the party having subscribed for the Offered Shares. With regard to any third parties, the<br> issuance of the Offered Shares will only be valid on the business day in Switzerland following<br> the day of publication of the corresponding capital increase in the Swiss Official Gazette<br> of Commerce.
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(j)	We express no opinion as to the conditions,<br> restrictions or consequences applicable to the acquisition of treasury shares (actions propres) by the Company, whether such acquisition is made directly or through one or<br> more controlled undertakings.
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(k)	We express no opinion as to regulatory matters<br> or as to any commercial, accounting, calculating, auditing, tax or other non-legal matter.
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* * *

We have issued this opinion as of the date hereof and we assume no obligation to advise you of any changes that are made or brought to our attention hereafter.

This letter is addressed to you in connection with the Prospectus Supplement. We consent to the filing of this letter as an exhibit to the Prospectus Supplement. No other person may rely on this opinion for any purpose. Without our prior written consent, this opinion may not (in full or in part) be copied, furnished or quoted to any other person except your advisors and representatives in connection with the matters set forth herein.

This opinion shall be governed by and construed in accordance with the laws of Switzerland. We confirm our understanding that all disputes arising out of or in connection with this opinion shall be subject to the exclusive jurisdiction of the courts of the Canton of Zurich, Switzerland, venue being Zurich 1.

Sincerely<br> yours
/s/<br> Homburger AG

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