683 Capital group reports 7.03% Mersana (MRSN) ownership in 13G/A filing

Rhea-AI Filing Summary

Mersana Therapeutics, Inc. reported that investment entities associated with 683 Capital have filed an amended Schedule 13G/A regarding their ownership of its common stock. As of December 31, 2025, 683 Capital Partners, LP beneficially owned 351,289 shares of common stock.

This stake represents approximately 7.03% of Mersana’s outstanding common shares, based on 4,998,750 shares outstanding as of November 7, 2025 as disclosed in the company’s Form 10-Q. The filing states the securities are not held for the purpose of changing or influencing control of the company.

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Accepted by SEC EDGAR 02/17/2026 - 10:09 AM Learn about SEC filing dates

FAQ

What ownership stake in Mersana Therapeutics (MRSN) does 683 Capital report in this Schedule 13G/A?

683 Capital-related entities report beneficial ownership of 351,289 shares of Mersana Therapeutics common stock. This represents approximately 7.03% of the company’s outstanding common shares, based on 4,998,750 shares outstanding as of November 7, 2025.

Which entities are the reporting persons in the Mersana Therapeutics (MRSN) Schedule 13G/A?

The reporting persons are 683 Capital Management, LLC, 683 Capital Partners, LP, and Ari Zweiman. 683 Capital Partners, LP directly holds the shares, while 683 Capital Management and Ari Zweiman may be deemed beneficial owners through their respective management roles.

What percentage of Mersana Therapeutics (MRSN) common stock is reported as owned by 683 Capital?

The filing states the reporting persons may be deemed to beneficially own 7.03% of Mersana’s outstanding common stock. This percentage is calculated using 4,998,750 shares outstanding as of November 7, 2025, as disclosed in Mersana’s Form 10-Q.

As of what date is 683 Capital’s ownership in Mersana Therapeutics (MRSN) measured in this filing?

The ownership information is measured as of December 31, 2025. On that date, the reporting persons may be deemed to beneficially own 351,289 shares of Mersana common stock, representing about 7.03% of the outstanding class.

Does 683 Capital seek to influence control of Mersana Therapeutics (MRSN) according to this Schedule 13G/A?

The filing certifies that the securities were not acquired and are not held for the purpose of changing or influencing control of Mersana. It also states they are not held in connection with any transaction having that control-related purpose or effect.

How are voting and dispositive powers over Mersana Therapeutics (MRSN) shares allocated among the reporting persons?

Each reporting person reports 0 shares with sole voting or dispositive power and 351,289 shares with shared voting and shared dispositive power. This reflects their indirect control through the investment management and partnership structure described in the ownership section.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 1)

Mersana Therapeutics, Inc.

(Name of Issuer)

Common Stock, par value $0.0001 per share

(Title of Class of Securities)

59045L205

(CUSIP Number)

12/31/2025

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

SCHEDULE 13G

CUSIP No. 59045L205

1

Names of Reporting Persons

683 Capital Management, LLC

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 351,289.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 351,289.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

351,289.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

7.03 %

12

Type of Reporting Person (See Instructions)

IA

SCHEDULE 13G

CUSIP No. 59045L205

1

Names of Reporting Persons

683 Capital Partners, LP

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 351,289.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 351,289.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

351,289.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

7.03 %

12

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13G

CUSIP No. 59045L205

1

Names of Reporting Persons

Ari Zweiman

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 351,289.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 351,289.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

351,289.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

7.03 %

12

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13G

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);
(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: As of December 31, 2025, 683 Capital Partners, LP beneficially owned 351,289 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 351,289 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 351,289 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 December 31, 2025, the Reporting Persons may be deemed to have beneficially owned approximately 7.03% of the outstanding Common Shares.
(b)	Percent of class: 7.03 %
(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.
Item 5.	Ownership of 5 Percent or Less of a Class.
	Not Applicable
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.
	If a group has filed this schedule pursuant to §240.13d-1(b)(1)(ii)(J), so indicate under Item 3(j) 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 to Schedule 13G filed on November 24, 2025.
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

683 Capital Management, LLC

Signature:	Ari Zweiman
Name/Title:	Managing Member
Date:	02/17/2026

683 Capital Partners, LP

Signature:	Ari Zweiman
Name/Title:	Authorized Person
Date:	02/17/2026

Ari Zweiman

Signature:	Ari Zweiman
Name/Title:	Self
Date:	02/17/2026