| Item 1. | |
| (a) | Name of issuer:
Mersana Therapeutics, Inc. |
| (b) | Address of issuer's principal executive offices:
840 MEMORIAL DRIVE, CAMBRIDGE, MASSACHUSETTS
02139 |
| Item 2. | |
| (a) | Name of person filing:
683 Capital Management, LLC
683 Capital Partners, LP
Ari Zweiman |
| (b) | Address or principal business office or, if none, residence:
The principal business address for each of the Reporting Persons is 1700 Broadway, Suite 4200, New York, New York 10019. |
| (c) | Citizenship:
683 Capital Management, LLC - DELAWARE
683 Capital Partners, LP - DELAWARE
Ari Zweiman - UNITED STATES |
| (d) | Title of class of securities:
Common Stock, par value $0.0001 per share |
| (e) | CUSIP No.:
59045L205 |
| 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);
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| (b) | Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
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| (c) | Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
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| (d) | Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
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| (e) | An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
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| (f) | An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
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| (g) | A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
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| (h) | A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
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| (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);
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| (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).
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| | |
| Item 4. | Ownership |
| (a) | Amount beneficially owned:
As of November 24, 2025, 683 Capital Partners, LP beneficially owned 273,420 shares of Common Stock.
683 Capital Management, LLC, as the investment manager of 683 Capital Partners, LP, may be deemed to have beneficially owned the 273,420 shares of Common Stock beneficially owned by 683 Capital Partners, LP.
Ari Zweiman, as the Managing Member of 683 Capital Management, LLC, may be deemed to have beneficially owned the 273,420 shares of Common Stock beneficially owned by 683 Capital Management, LLC.
The following percentage is based on 4,998,750 shares of Common Stock ($0.0001 par value per share) outstanding as of November 7, 2025, as disclosed in the Issuer's Form 10-Q filed on November 14, 2025.
As of November 14, 2025, the Reporting Persons may be deemed to have beneficially owned approximately 5.47% of the outstanding Common Shares. |
| (b) | Percent of class:
5.47 %
|
| (c) | Number of shares as to which the person has:
|
| | (i) Sole power to vote or to direct the vote:
See Cover Pages Items 5-9.
|
| | (ii) Shared power to vote or to direct the vote:
See Cover Pages Items 5-9.
|
| | (iii) Sole power to dispose or to direct the disposition of:
See Cover Pages Items 5-9.
|
| | (iv) Shared power to dispose or to direct the disposition of:
See Cover Pages Items 5-9.
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| Item 5. | Ownership of 5 Percent or Less of a Class. |
| |
Not Applicable
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| Item 6. | Ownership of more than 5 Percent on Behalf of Another Person. |
| |
Not Applicable
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| Item 7. | Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person. |
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Not Applicable
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| Item 8. | Identification and Classification of Members of the Group. |
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If a group has filed this schedule pursuant to §240.13d-1(b)(1)(ii)(K), so indicate under Item 3(k) and attach an exhibit stating the identity and Item 3 classification of each member of the group. If a group has filed this schedule pursuant to §240.13d-1(c) or §240.13d-1(d), attach an exhibit stating the identity of each member of the group.
See Exhibit A. |
| Item 9. | Notice of Dissolution of Group. |
| |
Not Applicable
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Rule 13d-1(c)