8-K

CYCLERION THERAPEUTICS, INC.

Date: August 25, 2026

/s/ Regina Graul, Ph.D.

Regina Graul, Ph.D.

President and Chief Executive Officer

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

PURSUANT TO SECTION 13 OR 15(d)

OF THE SECURITIES EXCHANGE ACT OF 1934

Date of Report (Date of earliest event reported): August 25, 2026

CYCLERION THERAPEUTICS, INC.

(Exact name of registrant as specified in charter)

Massachusetts

001-38787

83-1895370

(State or Other Jurisdiction

of Incorporation)

(Commission

File Number)

(I.R.S. Employer

Identification No.)

245 First Street, 18th Floor

Cambridge, Massachusetts 02142

(Address of Principal Executive Offices, including Zip Code)

(857) 327-8778

(Registrant’s telephone number, including area code)

(Former name or former address, if changed since last report.)

Securities registered pursuant to Section 12(b) of the Act:

Title of each class

Trading

Symbol(s)

Name of each exchange

on which registered

Common Stock, no par value

CYCN

The Nasdaq Capital Market

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

☒	Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐	Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐	Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐	Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 8.01

Other Events.

On August 25, 2026, the board of directors of Cyclerion Therapeutics, Inc. (the “Company”) fixed the close of business on September 4, 2026 as the record date for the Company’s previously announced distribution (the “CVR Distribution”) of contingent value rights (“CVRs”) to holders of record of the Company’s common stock and the Company’s Series A Preferred Stock, in connection with the Company’s planned merger (the “Merger”) with Korsana Biosciences, Inc. (“Korsana”).

Forward-Looking Statements

This Current Report on Form 8-K contains forward-looking statements (including within the meaning of Section 21E of the Exchange Act and Section 27A of the Securities Act) concerning Cyclerion, Korsana, the proposed transactions and other matters. These forward-looking statements include express or implied statements relating to the expected timing of the closing of the Merger; the record date for, and the expected payment date of, the CVR Distribution; the number of CVRs expected to be distributed and the anticipated terms of the CVRs, including their transferability, registration and listing status; the potential for payments to become due or to be made in respect of the CVRs; and other statements that are not historical fact. The words “anticipate,” “believe,” “contemplate,” “continue,” “could,” “estimate,” “expect,” “intends,” “may,” “might,” “plan,” “possible,” “potential,” “predict,” “project,” “should,” “will,” “would” and similar expressions (including the negatives of these terms or variations of them) may identify forward-looking statements, but the absence of these words does not mean that a statement is not forward-looking. These forward-looking statements are based on current expectations and beliefs concerning future developments and their potential effects. There can be no assurance that future developments affecting Cyclerion, Korsana or the proposed transaction will be those that have been anticipated.

The forward-looking statements contained in this Current Report on Form 8-K are based on current expectations and beliefs concerning future developments and their potential effects and therefore subject to other risks and uncertainties. These risks and uncertainties include, but are not limited to, risks associated with the possible failure to satisfy the conditions to the closing or consummation of the Merger, including Cyclerion’s failure to obtain shareholder approval for the Merger, risks associated with the potential failure to complete the financing transaction in a timely manner or at all, risks associated with the uncertainty as to the timing of the consummation of the Merger and the ability of each of Cyclerion and Korsana to consummate the transactions contemplated by the Merger, risks associated with Cyclerion’s continued listing on Nasdaq until closing of the Merger, the failure or delay in obtaining required approvals from any governmental or quasi-governmental entity necessary to consummate the Merger; the occurrence of any event, change or other circumstance or condition that could give rise to the termination of the Merger prior to the closing or consummation of the Merger, risks associated with the possible failure to realize certain anticipated benefits of the Merger, including with respect to future financial and operating results; the effect of the completion of the Merger on the combined company’s business relationships, operating results and business generally; risks associated with the combined company’s ability to manage expenses and unanticipated spending and costs that could reduce the combined company’s cash resources; risks related to the combined company’s ability to correctly estimate its operating expenses and other events; changes in capital resource requirements; risks related to the inability of the combined company to obtain sufficient additional capital to continue to advance its product candidates or its preclinical programs; the outcome of any legal proceedings that may be instituted against the combined company or any of its directors or officers related to the merger agreement or the transactions contemplated thereby; the ability of the combined company to obtain, maintain and protect its intellectual property rights, in particular those related to its product candidates; the combined company’s ability to advance the development of its product candidates or preclinical activities under the timelines it anticipates in planned and future clinical trials; the combined company’s ability to replicate in later clinical trials positive results found in preclinical studies and early-stage clinical trials of its product candidates; the combined company’s ability to realize the anticipated benefits of its research and development programs, strategic partnerships, licensing programs or other collaborations; regulatory requirements or developments and the combined company’s ability to obtain necessary approvals from the U.S. Food and Drug Administration or other regulatory authorities; changes to clinical trial designs and regulatory pathways; competitive responses to the Merger and changes in expected or existing competition; unexpected costs, charges or expenses resulting from the Merger; potential adverse reactions or changes to business relationships resulting from the completion of the Merger; legislative, regulatory, political and

economic developments; and those risks and uncertainties and other factors more fully described in filings with the Securities and Exchange Commission, including reports filed on Form 10-K, 10-Q and 8-K and in other filings made by Cyclerion with the SEC from time to time and available at www.sec.gov. These forward-looking statements are based on current expectations, and with regard to the proposed transaction, are based on Cyclerion’s current expectations, estimates and projections about the expected date of closing of the proposed transaction and the potential benefits thereof, its business and industry, management’s beliefs and certain assumptions made by Cyclerion, all of which are subject to change. Such forward-looking statements are made as of the date of this Current Report on Form 8-K, and the parties undertake no obligation to update such statements to reflect subsequent events or circumstances, except as otherwise required by securities and other applicable law.

No Offer or Solicitation

This Current Report on Form 8-K is not intended to and does not constitute (i) a solicitation of a proxy, consent or approval with respect to any securities or in respect of the proposed transaction or (ii) an offer to sell or the solicitation of an offer to subscribe for or buy or an invitation to purchase or subscribe for any securities pursuant to the proposed transaction or otherwise, nor shall there be any sale, issuance or transfer of securities in any jurisdiction in contravention of applicable law. No offer of securities shall be made except by means of a prospectus meeting the requirements of the Securities Act or an exemption therefrom. Subject to certain exceptions to be approved by the relevant regulators or certain facts to be ascertained, the public offer will not be made directly or indirectly, in or into any jurisdiction where to do so would constitute a violation of the laws of such jurisdiction, or by use of the mails or by any means or instrumentality (including without limitation, facsimile transmission, telephone and the internet) of interstate or foreign commerce, or any facility of a national securities exchange, of any such jurisdiction.

NEITHER THE SEC NOR ANY STATE SECURITIES COMMISSION HAS APPROVED OR DISAPPROVED OF THE SECURITIES OR DETERMINED IF THIS CURRENT REPORT ON FORM 8-K IS TRUTHFUL OR COMPLETE.

Important Additional Information About the Proposed Transaction

This Current Report on Form 8-K does not substitute for the Form S-4, proxy statement/prospectus or for any other document that Cyclerion has filed or may file with the SEC in connection with the proposed transaction. In connection with the proposed transaction between Cyclerion and Korsana, Cyclerion has filed relevant materials with the SEC, including the Form S-4 that contains a proxy statement/prospectus.

CYCLERION URGES INVESTORS AND STOCKHOLDERS TO READ THE FORM S-4, PROXY STATEMENT/PROSPECTUS AND ANY OTHER RELEVANT DOCUMENTS THAT HAVE BEEN OR MAY BE FILED WITH THE SEC, AS WELL AS ANY AMENDMENTS OR SUPPLEMENTS TO THOSE DOCUMENTS, CAREFULLY AND IN THEIR ENTIRETY IF AND WHEN THEY BECOME AVAILABLE BECAUSE THEY CONTAIN OR WILL CONTAIN IMPORTANT INFORMATION ABOUT CYCLERION, KORSANA, THE PROPOSED TRANSACTION AND RELATED MATTERS.

Investors and stockholders can obtain free copies of the Form S-4 and other documents filed by Cyclerion with the SEC (when they become available) through the website maintained by the SEC at www.sec.gov. In addition, investors and stockholders should note that Cyclerion communicates with investors and the public using its website (www.cyclerion.com) and the investor relations website (www.cyclerion.com/investor-resources) where anyone is able to obtain free copies of the Form S-4 and other documents filed by Cyclerion with the SEC and stockholders are urged to read the Form S-4 and the other relevant materials when they become available before making any voting or investment decision with respect to the proposed transaction.

Participants in the Solicitation

Cyclerion, Korsana and their respective directors and executive officers may be deemed to be participants in the solicitation of proxies from stockholders in connection with the proposed transaction. Information about Cyclerion’s directors and executive officers including a description of their interests in Cyclerion is included in Cyclerion’s Annual Report on Form 10-K, as filed with the SEC on March 30, 2026 and amended on April 30, 2026, and in subsequent reports filed with the SEC. Additional information regarding these persons and their interests in the proposed transaction are included in the Form S-4 relating to the proposed transaction filed with the SEC. These documents can be obtained free of charge from the sources indicated above.

SIGNATURES

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