Mersana Therapeutics (NASDAQ: MRSN) reporting group exits, 0% stake

Rhea-AI Filing Summary

Mersana Therapeutics, Inc. reporting persons filed Amendment No. 2 stating they no longer beneficially own any Common Stock of the issuer following the consummation of the merger described in the issuer's current report on Form 8-K filed on January 6, 2026. The filing records 0% ownership and is presented as an exit filing by 683 Capital Management, LLC, 683 Capital Partners, LP and Ari Zweiman.

Key Figures

Ownership after merger: 0% Form 8-K reference date: January 6, 2026 Signature date: 05/15/2026 +1 more

4 metrics

Ownership after merger 0% stated in Amendment No. 2 as an exit filing

Form 8-K reference date January 6, 2026 merger described in issuer's current report

Signature date 05/15/2026 dates on the Amendment No. 2 signatures

CUSIP 59045L205 Common Stock CUSIP in the filing

Key Terms

exit filing, beneficially own, Reporting Person, Form 8-K

4 terms

exit filing regulatory

"This Amendment No. 2 constitutes an exit filing for the Reporting Persons"

beneficially own regulatory

"the Reporting Persons no longer beneficially own any shares of Common Stock"

Beneficially own means having the economic rights and risks of a security—such as the right to receive dividends, sell the shares, or profit from price changes—whether or not your name appears on the official share register. Think of it like renting a car: you use it and reap the benefits even if the title lists someone else. Investors care because beneficial ownership determines who truly controls value, must be disclosed under securities rules, and can signal potential influence or trading activity that affects a stock’s price.

Reporting Person regulatory

"Each of the foregoing is referred to as a "Reporting Person" and collectively as the "Reporting Persons""

Form 8-K regulatory

"following the consummation of the merger described in the Issuer's current report on Form 8-K"

A Form 8-K is a report that companies file with the government to share important news quickly, such as changes in leadership, major business deals, or financial updates. It matters because it helps investors stay informed about significant events that could affect the company's value or stock price.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 2)

Mersana Therapeutics, Inc.

(Name of Issuer)

Common Stock, par value $0.0001 per share

(Title of Class of Securities)

59045L205

(CUSIP Number)

03/31/2026

(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)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): 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 0.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

0.00

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)

0 %

12

Type of Reporting Person (See Instructions)

IA

SCHEDULE 13G

CUSIP Number(s): 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 0.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

0.00

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)

0 %

12

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13G

CUSIP Number(s): 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 0.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

0.00

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)

0 %

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 Each of the foregoing is referred to as a "Reporting Person" and collectively as the "Reporting Persons."
(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: This Amendment No. 2 constitutes an exit filing for the Reporting Persons (as defined below). Following the consummation of the merger described in the Issuer's current report on Form 8-K, filed on January 6, 2026, the Reporting Persons no longer beneficially own any shares of Common Stock of the Issuer.
(b)	Percent of class: 0 %
(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.
	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.
	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:	05/15/2026

683 Capital Partners, LP

Signature:	Ari Zweiman
Name/Title:	Authorized Person
Date:	05/15/2026

Ari Zweiman

Signature:	Ari Zweiman
Name/Title:	Self
Date:	05/15/2026

FAQ

What did the Amendment No. 2 say about MRSN ownership?

It states the reporting persons hold 0% of Mersana common stock following a merger. The filing is an exit notice by 683 Capital affiliates and Ari Zweiman after the merger referenced in the issuer's Form 8-K dated January 6, 2026.

Who are the reporting persons named in the 13G/A for MRSN?

The reporting persons are 683 Capital Management, LLC, 683 Capital Partners, LP, and Ari Zweiman. Their principal business address is listed as 1700 Broadway, Suite 4200, New York, NY 10019 in the filing.

When did the reporting persons sign the Amendment No. 2 for MRSN?

Signatures on the amendment are dated 05/15/2026. The amendment is described as an exit filing reflecting the post-merger ownership status disclosed in the issuer's Form 8-K.

Does the Amendment No. 2 indicate any remaining shares for the filers?

No; the amendment explicitly states the reporting persons "no longer beneficially own any shares of Common Stock". The filing therefore reports zero shares and 0% ownership following the merger.