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    SEC Form SCHEDULE 13G filed by Mereo BioPharma Group plc

    1/9/26 5:24:27 PM ET
    $MREO
    Biotechnology: Pharmaceutical Preparations
    Health Care
    Get the next $MREO alert in real time by email



    SECURITIES AND EXCHANGE COMMISSION
    Washington, D.C. 20549


    SCHEDULE 13G


    UNDER THE SECURITIES EXCHANGE ACT OF 1934
    Mereo BioPharma Group plc

    (Name of Issuer)


    Ordinary Shares

    (Title of Class of Securities)


    589492107

    (CUSIP Number)


    01/02/2026

    (Date of Event Which Requires Filing of this Statement)


    Check the appropriate box to designate the rule pursuant to which this Schedule is filed:
    Checkbox checked   Rule 13d-1(b)
    Checkbox checked   Rule 13d-1(c)
    Checkbox not checked   Rule 13d-1(d)






    SCHEDULE 13G

    CUSIP No.
    589492107


    1Names of Reporting Persons

    EcoR1 Capital, LLC
    2Check the appropriate box if a member of a Group (see instructions)

    Checkbox checked  (a)
    Checkbox not checked  (b)
    3Sec Use Only
    4Citizenship or Place of Organization

    DELAWARE
    Number of Shares Beneficially Owned by Each Reporting Person With:
    5Sole Voting Power

    0.00
    6Shared Voting Power

    74,500,000.00
    7Sole Dispositive Power

    0.00
    8Shared Dispositive Power

    74,500,000.00
    9Aggregate Amount Beneficially Owned by Each Reporting Person

    74,500,000.00
    10Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

    Checkbox not checked
    11Percent of class represented by amount in row (9)

    9.4 %
    12Type of Reporting Person (See Instructions)

    IA, OO

    Comment for Type of Reporting Person:  These Ordinary Shares are held through 14,900,000 American Depositary Shares of the Issuer, each representing 5 Ordinary Shares. Percentage calculated based on 795,658,504 Ordinary Shares outstanding on November 7, 2025, as reported in the Form 10-Q filed by the Issuer for the quarter ended September 30, 2025.


    SCHEDULE 13G

    CUSIP No.
    589492107


    1Names of Reporting Persons

    Oleg Nodelman
    2Check the appropriate box if a member of a Group (see instructions)

    Checkbox checked  (a)
    Checkbox not checked  (b)
    3Sec Use Only
    4Citizenship or Place of Organization

    UNITED STATES
    Number of Shares Beneficially Owned by Each Reporting Person With:
    5Sole Voting Power

    0.00
    6Shared Voting Power

    74,500,000.00
    7Sole Dispositive Power

    0.00
    8Shared Dispositive Power

    74,500,000.00
    9Aggregate Amount Beneficially Owned by Each Reporting Person

    74,500,000.00
    10Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

    Checkbox not checked
    11Percent of class represented by amount in row (9)

    9.4 %
    12Type of Reporting Person (See Instructions)

    HC, IN

    Comment for Type of Reporting Person:  These Ordinary Shares are held through 14,900,000 American Depositary Shares of the Issuer, each representing 5 Ordinary Shares. Percentage calculated based on 795,658,504 Ordinary Shares outstanding on November 7, 2025, as reported in the Form 10-Q filed by the Issuer for the quarter ended September 30, 2025.


    SCHEDULE 13G

    CUSIP No.
    589492107


    1Names of Reporting Persons

    EcoR1 Capital Fund Qualified, L.P.
    2Check the appropriate box if a member of a Group (see instructions)

    Checkbox not checked  (a)
    Checkbox not checked  (b)
    3Sec Use Only
    4Citizenship or Place of Organization

    DELAWARE
    Number of Shares Beneficially Owned by Each Reporting Person With:
    5Sole Voting Power

    0.00
    6Shared Voting Power

    69,802,840.00
    7Sole Dispositive Power

    0.00
    8Shared Dispositive Power

    69,802,840.00
    9Aggregate Amount Beneficially Owned by Each Reporting Person

    69,802,840.00
    10Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

    Checkbox not checked
    11Percent of class represented by amount in row (9)

    8.8 %
    12Type of Reporting Person (See Instructions)

    PN

    Comment for Type of Reporting Person:  These Ordinary Shares are held through 13,960,568 American Depositary Shares of the Issuer, each representing 5 Ordinary Shares. Percentage calculated based on 795,658,504 Ordinary Shares outstanding on November 7, 2025, as reported in the Form 10-Q filed by the Issuer for the quarter ended September 30, 2025.


    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:

    EcoR1 Capital, LLC, a Delaware limited liability company ("EcoR1") EcoR1 Capital Fund Qualified, L.P., a Delaware limited partnership ("Qualified Fund") Oleg Nodelman Qualified Fund is filing this statement jointly with the other reporting persons, but not as a member of a group, and it expressly disclaims membership in a group. In addition, the filing of this Schedule 13G on behalf of Qualified Fund should not be construed as an admission that it is, and it disclaims that it is, a beneficial owner, as defined in Rule 13d-3 under the Act, of any securities covered by this Schedule 13G. Each reporting person also disclaims beneficial ownership of the securities reported herein except to the extent of that person's pecuniary interest therein.
    (b)Address or principal business office or, if none, residence:

    357 Tehama Street #3 San Francisco, CA 94103
    (c)Citizenship:

    See Item 4 of the cover sheet for each reporting person.
    (d)Title of class of securities:

    Ordinary Shares
    (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)Checkbox not checked   Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
    (b)Checkbox not checked   Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
    (c)Checkbox not checked   Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
    (d)Checkbox not checked   Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
    (e)Checkbox checked   An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
    (f)Checkbox not checked   An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
    (g)Checkbox checked   A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
    (h)Checkbox not checked   A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
    (i)Checkbox not checked   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)Checkbox not checked   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)Checkbox not checked   Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
     
    Item 4.Ownership
    (a)Amount beneficially owned:

    EcoR1: 74,500,000 Oleg Nodelman: 74,500,000 Qualified Fund: 69,802,840
    (b)Percent of class:

    EcoR1: 9.4% Oleg Nodelman: 9.4% Qualified Fund: 8.8%
    (c)Number of shares as to which the person has:
     (i) Sole power to vote or to direct the vote:

    EcoR1: 0 Oleg Nodelman: 0 Qualified Fund: 0

     (ii) Shared power to vote or to direct the vote:

    EcoR1: 74,500,000 Oleg Nodelman: 74,500,000 Qualified Fund: 69,802,840

     (iii) Sole power to dispose or to direct the disposition of:

    EcoR1: 0 Oleg Nodelman: 0 Qualified Fund: 0

     (iv) Shared power to dispose or to direct the disposition of:

    EcoR1: 74,500,000 Oleg Nodelman: 74,500,000 Qualified Fund: 69,802,840

    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.


    EcoR1 is the general partner and investment adviser of investment funds, including Qualified Fund. Mr. Nodelman is the control person of EcoR1.
    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 acquired and are held in the ordinary course of business and 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. 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.

     
    EcoR1 Capital, LLC
     
    Signature:/s/ Oleg Nodelman
    Name/Title:Manager
    Date:01/09/2026
     
    Oleg Nodelman
     
    Signature:/s/ Oleg Nodelman
    Name/Title:Reporting person
    Date:01/09/2026
     
    EcoR1 Capital Fund Qualified, L.P.
     
    Signature:/s/ Oleg Nodelman
    Name/Title:Manager of the General Partner, EcoR1 Capital, LLC
    Date:01/09/2026
    Exhibit Information

    EXHIBIT 99 - AGREEMENT REGARDING JOINT FILING OF STATEMENT ON SCHEDULE 13D OR 13G

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