Mereo BioPharma (NASDAQ: MREO) holder discloses 8.18% ADS stake

Rhea-AI Filing Summary

Mereo BioPharma Group plc received a Schedule 13G filing from investment firm 683 Capital and related parties reporting a significant passive stake. As of January 6, 2026, 683 Capital Partners, LP beneficially owned 65,083,815 ordinary shares, represented by 13,016,763 American Depositary Shares (ADS), which equals about 8.18% of the ordinary shares.

The percentage is based on 795,658,504 ordinary shares outstanding as of November 7, 2025. 683 Capital Management, LLC, as investment manager, and Ari Zweiman, as managing member, may each be deemed to share beneficial ownership. The filing certifies that the securities were not acquired and are not held for the purpose of changing or influencing control of Mereo BioPharma.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

Mereo BioPharma Group plc

(Name of Issuer)

American Depositary Shares, each representing five ordinary shares, nominal value of 0.003 GBP per share

(Title of Class of Securities)

589492107

(CUSIP Number)

12/29/2025

(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. 589492107

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 65,083,815.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 65,083,815.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

65,083,815.00

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)

8.18 %

12

Type of Reporting Person (See Instructions)

IA

SCHEDULE 13G

CUSIP No. 589492107

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 65,083,815.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 65,083,815.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

65,083,815.00

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)

8.18 %

12

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13G

CUSIP No. 589492107

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 65,083,815.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 65,083,815.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

65,083,815.00

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)

8.18 %

12

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13G

Item 1.
(a)	Name of issuer: Mereo BioPharma Group plc
(b)	Address of issuer's principal executive offices: ONE CAVENDISH PLACE, FOURTH FLOOR, LONDON, UNITED KINGDOM W1G 0QF
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: American Depositary Shares, each representing five ordinary shares, nominal value of 0.003 GBP per share
(e)	CUSIP No.: 589492107
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: CUSIP 589492107 relates to the American Depositary Shares, each representing five ordinary shares, nominal value of GBP 0.003 per share. As of January 6, 2026, 683 Capital Partners, LP beneficially owned 65,083,815 Ordinary Shares represented by 13,016,763 ADS. 683 Capital Management, LLC, as the investment manager of 683 Capital Partners, LP, may be deemed to have beneficially owned the 65,083,815 Ordinary Shares 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 65,083,815 Ordinary Shares beneficially owned by 683 Capital Management, LLC. The following percentage is based on 795,658,504 Ordinary Shares (GBP 0.003 par value per share) outstanding as of November 7, 2025, as disclosed in the Issuer's Form 10-Q filed on November 10, 2025. As of January 6, 2026, the Reporting Persons may be deemed to have beneficially owned approximately 8.18% of the outstanding Ordinary Shares.
(b)	Percent of class: 8.18 %
(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)(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

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:	01/06/2026

683 Capital Partners, LP

Signature:	Ari Zweiman
Name/Title:	Authorized Person
Date:	01/06/2026

Ari Zweiman

Signature:	Ari Zweiman
Name/Title:	Self
Date:	01/06/2026

Exhibit Information

JOINT FILING AGREEMENT The undersigned hereby agree that the statement on Schedule 13G with respect to the Ordinary Shares, par value 0.003 GBP per share, of Mereo BioPharma Group plc dated as of January 6, 2026 is, and any further amendments thereto signed by each of the undersigned shall be, filed on behalf of each of the undersigned pursuant to and in accordance with the provisions of Rule 13d-1(k)(2) under the Securities Exchange Act of 1934, as amended. Dated: January 6, 2026 683 CAPITAL MANAGEMENT, LLC By: /s/ Ari Zweiman Ari Zweiman, Managing Member 683 CAPITAL PARTNERS, LP By: /s/ Ari Zweiman Ari Zweiman, Authorized Person /s/ Ari Zweiman Ari Zweiman

FAQ

What ownership stake in Mereo BioPharma (MREO) does 683 Capital report?

The filing reports that the reporting persons may be deemed to beneficially own 65,083,815 ordinary shares of Mereo BioPharma, represented by 13,016,763 ADS, equal to about 8.18% of the ordinary shares.

Who are the reporting persons in this Mereo BioPharma (MREO) Schedule 13G?

The reporting persons are 683 Capital Management, LLC, 683 Capital Partners, LP, and Ari Zweiman, who may each be deemed to share beneficial ownership of the same block of Mereo BioPharma ordinary shares.

How is the 8.18% ownership in Mereo BioPharma (MREO) calculated?

The 8.18% figure is based on 795,658,504 ordinary shares outstanding as of November 7, 2025, as disclosed in Mereo BioPharma’s Form 10-Q, and the reported beneficial ownership of 65,083,815 ordinary shares.

Is 683 Capital’s position in Mereo BioPharma (MREO) reported as passive or active?

The certification states that the securities were not acquired and are not held for the purpose of changing or influencing control of Mereo BioPharma and are not held in connection with a transaction having that purpose or effect, indicating a passive filing.

What class of Mereo BioPharma (MREO) securities is covered by this Schedule 13G?

The Schedule 13G covers American Depositary Shares (ADS) of Mereo BioPharma Group plc, with each ADS representing five ordinary shares, nominal value 0.003 GBP per share, under CUSIP 589492107.

What voting and dispositive power do the reporting persons have over Mereo BioPharma (MREO) shares?

Each reporting person reports 0 shares with sole voting or dispositive power and 65,083,815 ordinary shares with shared voting and shared dispositive power.