| Item 1. | |
| (a) | Name of issuer:
Cyclerion Therapeutics, Inc. |
| (b) | Address of issuer's principal executive offices:
245 First Street, 18th Floor, Cambridge, Massachusetts 02142 |
| Item 2. | |
| (a) | Name of person filing:
The reporting person is Tyndall Capital Partners, L.P. (the "Reporting Person"). As of June 30, 2025, 155,187 shares of common stock, no par value (the "Common Stock"), of Cyclerion Therapeutics, Inc. (the "Issuer") are owned by Tyndall Partners, L.P., a Delaware limited partnership ("Tyndall"). The Reporting Person is the general partner of Tyndall, and possesses the sole power to vote and the sole power to direct the disposition of all shares of Common Stock held by Tyndall. Ownership percentages are based on 3,210,094 shares of Common Stock reported as issued and outstanding as of June 30, 2025 in the Issuer's Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission on August 5, 2025. |
| (b) | Address or principal business office or, if none, residence:
150 East 58th Street, 14th Floor, New York, New York 10155 |
| (c) | Citizenship:
Delaware |
| (d) | Title of class of securities:
Common Stock, no par value |
| (e) | CUSIP No.:
23255M204 |
| Item 3. | If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a: |
| (a) |  Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
|
| (b) | Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
|
| (c) | Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
|
| (d) | Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
|
| (e) | An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
|
| (f) | An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
|
| (g) | A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
|
| (h) | A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
|
| (i) | A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
|
| (j) | A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J),
please specify the type of institution:
|
| (k) | Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
|
| | |
| Item 4. | Ownership |
| (a) | Amount beneficially owned:
155,187.00 |
| (b) | Percent of class:
4.8 % |
| (c) | Number of shares as to which the person has:
|
| | (i) Sole power to vote or to direct the vote:
155,187.00
|
| | (ii) Shared power to vote or to direct the vote:
0.00
|
| | (iii) Sole power to dispose or to direct the disposition of:
155,187.00
|
| | (iv) Shared power to dispose or to direct the disposition of:
0.00
|
| Item 5. | Ownership of 5 Percent or Less of a Class. |
| | 
Ownership of 5 percent or less of a class
|
| Item 6. | Ownership of more than 5 Percent on Behalf of Another Person. |
| |
Not Applicable
|
| Item 7. | Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person. |
| |
Not Applicable
|
| Item 8. | Identification and Classification of Members of the Group. |
| |
Not Applicable
|
| Item 9. | Notice of Dissolution of Group. |
| |
Not Applicable
|