Mereo BioPharma Group plc

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of

the Securities Exchange Act of 1934

Filed by the Registrant ☒

Filed by a Party other than the Registrant ☐

Check the appropriate box:

MEREO BIOPHARMA GROUP PLC

(Name of Registrant as Specified In Its Charter)

N/A

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

Payment of Filing Fee (Check the appropriate box):

MEREO BIOPHARMA GROUP PLC

Registered office: 4th Floor, One Cavendish Place, London, W1G 0QF, United Kingdom

Incorporated in England and Wales with registered no. 09481161

April 9, 2026

Dear Shareholder,

2026 Annual General Meeting of Mereo BioPharma Group plc (the “AGM” or the “Meeting”)

This letter, the notice of the AGM set out in this document (the “Notice”) and associated materials for the AGM are being sent or supplied to you because, as of 6:00 p.m. (British Summer Time) (1:00 p.m. Eastern Time) on Tuesday, April 7, 2026, you are registered in the register of members of Mereo BioPharma Group plc (the “Company”) as a holder of ordinary shares in the capital of the Company. However, this letter, the Notice and associated materials will also be available to holders of American Depositary Shares (“ADS”) representing ordinary shares and contains information relevant to holders of ADSs.

I am pleased to confirm that our AGM will take place at 2:00 p.m. (British Summer Time) (9:00 a.m. Eastern Time) on Thursday, May 14, 2026 at 5th Floor, One Cavendish Place, London W1G 0QF, United Kingdom. The Notice is set out in this document and it contains the resolutions to be proposed at the AGM (the “Resolutions”).

Action to be taken by holders of ordinary shares

If you are a holder of ADSs, please ignore this section and refer instead to the section below — “Action to be taken by holders of American Depositary Shares.”

If you are a holder of ordinary shares and are planning to attend the AGM in person (or by way of corporate representative) it would be helpful if you could inform the Company’s registrar, MUFG Corporate Markets, in advance via the Investor Centre app or at https://uk.investorcentre.mpms.mufg.com/.

Holders of ordinary shares are entitled to appoint a proxy to exercise all or any of their rights to attend and to speak and vote on their behalf at the AGM. Proxy appointment instructions may be submitted online using the Investor Centre app or at https://uk.investorcentre.mpms.mufg.com/. Alternatively, you may simply complete, sign and return the enclosed form of proxy in accordance with the instructions printed thereon. CREST members may appoint a proxy by using the CREST electronic proxy appointment service. If you are an institutional investor you may also be able to appoint a proxy electronically via the Proxymity platform. All proxies, however submitted, must be received by MUFG Corporate Marketsby no later than 2:00 p.m. (British Summer Time) (9:00 a.m. Eastern Time) on Tuesday, May 12, 2026 or 48 hours before any adjourned meeting.

If you require additional forms of proxy or assistance with how to complete, sign and return your form of proxy or assistance in submitting your proxy appointment online, please email shareholderenquiries@cm.mpms.mufg.com or call MUFG Corporate Markets' portal team on

+44 (0) 371 664 0391. Calls are charged at the standard geographic rate and will vary by provider. Calls from outside the U.K. will be charged at the applicable international rate. Lines are open 9:00 a.m. to 5:30 p.m. (British Summer Time), Monday to Friday, excluding public holidays in England and Wales.

In order to attend and vote at the AGM as an ordinary shareholder or for your proxy appointment instructions to remain valid, you must continue to be registered as a holder of ordinary shares in the Company’s register of members as of 6:00 p.m. (British Summer Time) (1:00 p.m. Eastern Time) on Tuesday, May 12, 2026 (or, if the AGM is adjourned, of 6:00 p.m. (British Summer Time) (1:00 p.m. Eastern Time) on the date which is two business days prior to the adjourned meeting). If you sell or transfer your ordinary shares on or prior to such time, any proxy appointment instructions that you submit (whether before or after you sell or transfer your ordinary shares) will be treated as invalid. Please pass this document to the person who arranged the sale or transfer for delivery to the purchaser or transferee.

The appointment of a proxy will not preclude you from attending, speaking and voting at the AGM should you wish and be entitled to do so. Please refer to the notes to the Notice for further information relating to your entitlement to attend and vote at the AGM and to appoint a proxy to attend and to speak and vote on your behalf at the AGM.

Should you elect to convert your holding of ordinary shares into an interest in the capital of the Company represented by ADSs before the AGM, you will cease to be a holder of ordinary shares in your own name and will not be entitled to vote, whether in person or by proxy, at the AGM as an ordinary shareholder. However, you may be able to exercise your vote as a holder of an interest in the capital of the Company represented by ADSs — please refer to the next section — “Action to be taken by holders of American Depositary Shares.”

Action to be taken by holders of American Depositary Shares

In order to exercise your vote as a holder of an interest in ordinary shares represented by ADSs, you or your bank, broker or nominee must be registered as a holder of ADSs in the ADS registeras of 5:00 p.m. Eastern Time (10:00 p.m. British Summer Time) on Thursday, April 9, 2026(the “ADS Record Date”).

If you hold ADSs through a bank, broker or nominee as of 5:00 p.m. Eastern Time on the ADS Record Date, the materials for ADS holders, including this proxy statement, the Annual Report on Form 10-K and an ADS proxy card, will be sent to such bank, broker or nominee who should forward the materials to you – you should contact them to provide your voting instructions.

Please note that ADS proxy cards submitted by ADS holders must be received by Citibank, N.A. no later than 10:00 a.m. Eastern Time (3:00 p.m. British Summer Time) on Friday, May 8, 2026.

Contact for holders of American Depositary Shares

If you have queries about how you can deliver voting instructions, please contact Citibank, N.A. — ADR Shareholder Services by telephone on +1-877-248-4237 (toll free within the United States) or +1-781-575-4555 (for international callers) or by emailing citibank@shareholders-online.com or by mail to Citibank Shareholder Services, P.O. Box 43077, Providence, RI 02940-3077.

Contact at Mereo BioPharma

If at any point you require guidance, please contact Charles Sermon, Mereo BioPharma Group plc Company Secretary, by emailing legal@mereobiopharma.com.

Recommendation

You will find an explanatory note in relation to each of the Resolutions in the attached proxy statement. Your Board of Directors consider that each Resolution is in the best interests of the Company and is likely to promote the success of the Company for the benefit of its members as a whole. Accordingly, your directors unanimously recommend that you vote FOR the Resolutions as each of the directors with personal holdings of ordinary shares or ADSs intends to do.

Thank you for your ongoing support of Mereo BioPharma Group plc.

Yours faithfully,

/s/ Michael Wyzga

Michael Wyzga

Chairman

4th Floor, One Cavendish Place, London, W1G 0QF,

Registered Company No. 09481161

NOTICE OF 2026 ANNUAL GENERAL MEETING OF SHAREHOLDERS TO BE HELD ON THURSDAY, MAY 14, 2026

NOTICE IS HEREBY GIVEN that the Annual General Meeting of Mereo BioPharma Group plc, a public limited company incorporated under the laws of England and Wales (the “Company,” “we,” “us” and “our”), will be held at 2:00 p.m. (British Summer Time) (9:00 a.m. Eastern Time) on Thursday, May 14, 2026 at 5th Floor, One Cavendish Place, London W1G 0QF, United Kingdom to consider and, if thought fit, to pass Resolutions 1 to 10 below, as ordinary resolutions and Resolution 11 below as a special resolution.

Ordinary resolutions

That the annual report and accounts for the year ended December 31, 2025, together with the directors’ report and independent auditor’s report thereon, be received and adopted.

That PricewaterhouseCoopers LLP (“PwC”) be re-appointed as auditors to hold office from the conclusion of the annual general meeting until the conclusion of the next annual general meeting at which the Company’s annual report and accounts are presented.

That the Audit and Risk Committee be authorized to determine PwC’s remuneration for the fiscal year ending December 31, 2026.

That the directors’ remuneration report (excluding the directors’ remuneration policy), as set out in the Company’s annual report and accounts for the year ended December 31, 2025, be approved.

That the directors’ remuneration policy as set out in the Company’s annual report and accounts for

the year ended December 31, 2025, which takes effect from the end of the annual general meeting, be approved.

That the compensation of the Company's named executive officers be approved, on an advisory (non-binding) basis.

That Justin Roberts be re-appointed as a director of the Company.

That Dr. Daniel Shames be re-appointed as a director of the Company.

That Marc Yoskowitz be re-appointed as a director of the Company.

That the Directors be generally and unconditionally authorized in accordance with section 551 of the Companies Act 2006 (the “Act”) to exercise all the powers of the Company to allot shares in the Company or to grant rights to subscribe for, or to convert securities into, shares in the Company up to a maximum aggregate nominal amount of £3,591,354.73, such authority to expire on June 30, 2029, save that the Company may, before such expiry, make offers or agreements which would, or might, require shares to be allotted or rights to subscribe for or to convert any securities into shares to be granted after such expiry and the Directors may allot shares or grant such rights under any such offer or agreement as if the authority conferred by this Resolution had not expired. Such authority shall replace the authority granted pursuant to section 551 of the Act at the annual general meeting of the Company held on May 22, 2023 to the extent not utilized at the date this Resolution is passed.

Special resolution

That, subject to Resolution 10 being passed, the Directors be generally empowered pursuant to section 570 and section 573 of the Act to allot equity securities for cash pursuant to the authority given by Resolution 10 and to sell equity securities held as treasury shares for cash pursuant to section 727 of the Act, in each case as if section 561(1) of the Act did not apply to any such allotment or sale, provided that this power shall be limited to the allotment or sale of equity securities up to an aggregate nominal value of £3,591,354.73, such power to expire on June 30, 2029, save that the Company may, before such expiry, make offers or agreements which would or might require equity securities to be allotted and equity securities held as treasury shares to be sold after such expiry, and the Directors may allot equity securities and sell equity securities held as treasury shares in pursuance of any such offer or agreement as if the power conferred hereby had not expired. Such power shall replace the power granted pursuant to section 570 and section 573 of the Act at the annual general meeting of the Company held on May 22, 2023 to the extent not utilized at the date this Resolution is passed.

Notes:

The following notes apply to ordinary shareholders. Holders of ADSs should review the information in the section of the letter accompanying this Notice titled “Action to be taken by holders of American Depositary Shares” for voting and other relevant information for the Meeting.

Entitlement to Attend and Vote

To be entitled to attend and vote at the Meeting (and for the purposes of the determination by the Company of the votes that may be cast in accordance with Regulation 41 of the Uncertificated Securities Regulations 2001), only those members registered in the Company’s register of members at 6:00 p.m. (British Summer Time) (1:00 p.m. Eastern Time) on Tuesday, May 12, 2026 (or, if the Meeting is adjourned at 6:00 p.m. (British Summer Time) (1:00 p.m. Eastern Time) on the date which is two business days prior to the adjourned meeting) shall be entitled to attend and vote at the Meeting. Changes to the register of members of the Company after the relevant deadline shall be disregarded in determining the rights of any person to attend and vote at the Meeting.

Appointment of Proxies

If you are a member of the Company at the time set out in note 1 above, you are entitled to appoint a proxy to exercise all or any of your rights to attend, speak and vote at the Meeting. You can appoint a proxy only using the procedures set out in these notes and the notes to the form of proxy for use at the Meeting. In order to be valid, proxy appointment instructions must be received by the Company’s registrar, MUFG Corporate Markets, by no later than 2:00 p.m. (British Summer Time) (9:00 a.m. Eastern Time) on Tuesday, May 12, 2026 or 48 hours before any adjourned meeting.

A proxy does not need to be a member of the Company but must attend the Meeting to represent you. If you wish your proxy to speak on your behalf at the Meeting you will need to appoint your own choice of proxy (not the Chair of the Meeting) and give your instructions directly to them.

You may appoint more than one proxy provided each proxy is appointed to exercise rights attached to different ordinary shares. You may not appoint more than one proxy to exercise rights attached to any one ordinary share. To appoint more than one proxy, please indicate on your proxy submission how many ordinary shares it relates to.

A vote withheld is not a vote in law, which means that the vote will not be counted in the calculation of votes for or against the Resolution. If no voting indication is given, your proxy will vote or abstain from voting at their discretion. Your proxy will vote (or abstain from voting) as they think fit in relation to any other matter which is put before the Meeting.

Appointment of Proxy Using Hard Copy Proxy Form

A form of proxy for use at the Meeting has been provided. Instructions for its use are set out in the form. If you require additional forms of proxy or assistance with how to complete, sign and return a form of proxy or assistance in submitting your proxy appointment online, please call MUFG Corporate Markets’ general helpline team on +44 (0) 371 664 0391. Calls are charged at the standard geographic rate and will vary by provider. Calls from outside the U.K. will be charged at the applicable international rate. Lines are open 9:00 a.m. to 5:30 p.m. (British Summer Time), Monday to Friday, excluding public holidays in England and Wales. Alternatively, you can request additional forms of proxy via email at shareholderenquiries@cm.mpms.mufg.com or via postal address to MUFG Corporate Markets, PXS 1, Central Square, 29 Wellington Street, Leeds LS1 4DL, United Kingdom. In the case of a member which is a company, the form of proxy must be executed under its common seal or signed on its behalf by an officer of the company or an attorney for the company. Any power of attorney or any other authority under which the proxy form is signed (or a duly certified copy of such power or authority) must be included with the form of proxy.

Appointment of a Proxy Online

Shareholders can vote online via the Investor Centre, a free app for smartphone and tablet provided by MUFG Corporate Markets (the Company's registrar). It allows you to securely manage and monitor your shareholdings in real time, take part in online voting, keep your details up to date, access a range of information including payment history and much more. The app is available to download on both the Apple App Store and Google Play, or by scanning the relevant QR code below. Alternatively, you may access the Investor Centre via a web browser at: https://uk.investorcentre.mpms.mufg.com/. Shareholders can use this service to vote or appoint a proxy online. Such instructions must be received by no later than 2:00 p.m. (British Summer Time) (9:00 a.m. Eastern Time) on Tuesday, May 12, 2026 or 48 hours before any adjourned meeting. Shareholders will need to use the unique personal identification Investor Code (“IVC”) printed on your share certificate. If you need help with voting online, please contact MUFG Corporate Markets’ portal team on +44 (0) 371 664 0391 or via email at shareholderenquiries@cm.mpms.mufg.com. Calls are charged at the standard geographic rate and will vary by provider. Calls from outside the U.K. will be charged at the applicable international rate. Lines are open 9:00 a.m. to 5:30 p.m. (British Summer Time), Monday to Friday, excluding public holidays in England and Wales.

Appointment of Proxies Through CREST

CREST members who wish to appoint a proxy or proxies by utilizing the CREST electronic proxy appointment service may do so for the Meeting and any adjournment(s) of it by using the procedures described in the CREST Manual (available from www.euroclear.com). CREST Personal Members or other CREST sponsored members, and those CREST members who have appointed a voting service provider(s), should refer to their CREST sponsor or voting service provider(s), who will be able to take the appropriate action on their behalf.

In order for a proxy appointment made by means of CREST to be valid, the appropriate CREST message (a CREST Proxy Instruction) must be properly authenticated in accordance with Euroclear UK & International Limited’s (EUI) specifications and must contain the information required for such instructions, as described in the CREST Manual. The message must be transmitted so as to be received by the issuer’s agent (ID: RA10) by no later than 2:00 p.m. (British Summer Time) (9:00 a.m. Eastern Time) on Tuesday, May 12, 2026 or 48 hours before any adjourned meeting. For this purpose, the time of receipt will be taken to be the time (as determined by the time stamp applied to the message by the CREST Applications Host) from which the issuer’s agent is able to retrieve the message by enquiry to CREST in the manner prescribed by CREST. After this time, any change of instructions to proxies appointed through CREST should be communicated to the appointee through other means. CREST members and, where applicable, their CREST sponsors or voting service providers should note that EUI does not make available special procedures in CREST for any particular messages. Normal system timings and limitations will therefore apply in relation to the input of CREST Proxy Instructions. It is the responsibility of the CREST member concerned to take (or, if the CREST member is a CREST personal member or sponsored member or has appointed a voting service provider(s), to procure that their CREST sponsor or voting service provider(s) take(s)) such action as shall be necessary to ensure that a message is transmitted by means of the CREST system by any particular time.

In this connection, CREST members and, where applicable, their CREST sponsors or voting service providers are referred, in particular, to those sections of the CREST Manual concerning practical limitations of the CREST system and timings. The Company may treat as invalid a CREST Proxy Instruction in the circumstances set out in Regulation 35(5)(a) of the Uncertificated Securities Regulations 2001.

Appointment of Proxies via Proxymity

If you are an institutional investor you may also be able to appoint a proxy electronically via the Proxymity platform, a process which has been agreed by the Company and approved by the registrar. For further information regarding Proxymity, please go to www.proxymity.io. Your proxy must be received by no later than 2:00 p.m. (British Summer Time) (9:00 a.m. Eastern Time) on Tuesday, May 12, 2026 or 48 hours before any adjourned meeting. Before you can appoint a proxy via this process you will need to have agreed to Proxymity’s associated terms and conditions. It is important that you read these carefully as you will be bound by them and they will govern the electronic appointment of your proxy. An electronic proxy appointment via the Proxymity platform may be revoked completely by sending an authenticated message via the platform instructing the removal of your proxy vote.

Appointment of Proxy by Joint Members

In the case of joint holders, where more than one of the joint holders purports to appoint a proxy, only the appointment submitted by the most senior holder will be accepted. Seniority is determined by the order in which the names of the joint holders appear in the Company’s register of members in respect of the joint holding, the first-named being the most senior.

Changing Proxy Instructions

To change your proxy instructions simply submit a new proxy appointment using the methods set out above. Note that the cutoff times for receipt of proxy appointments (see above) also apply in relation to amended instructions; any amended proxy appointment received after the relevant cut-off time will be disregarded. Where you have appointed a proxy using a hard-copy form of proxy and would like to change the instructions using another form of proxy, please contact MUFG Corporate Markets as per the communication methods shown in note 6. If you submit more than one valid proxy appointment, the appointment received last before the latest time for the receipt of proxies will take precedence.

Termination of Proxy Appointments

In order to revoke a proxy instruction, you will need to inform the Company by sending a signed hard copy notice clearly stating your intention to revoke your proxy appointment to MUFG Corporate Markets, at the address shown in note 6 above. In the case of a member which is a company, the revocation notice must be executed under its common seal or signed on its behalf by an officer of the company or an attorney for the company. Any power of attorney or any other authority under which the revocation notice is signed, or a duly certified copy of such power or authority, must be included with the revocation notice. The revocation notice must be received by MUFG Corporate Markets no later than 48 hours before the Meeting. If you attempt to revoke your proxy appointment but the revocation is received after the time specified then, subject to the paragraph directly below, your proxy appointment will remain valid. Completion of a proxy will not preclude you from attending the Meeting and voting in person if you so wish.

Corporate Representatives

A corporation which is a member can appoint one or more corporate representatives who may exercise, on its behalf, all its powers as a member provided that no more than one corporate representative exercises powers over the same ordinary share.

Issued Shares and Total Voting Rights

As at close of business on the day immediately prior to the date of posting of this Notice, the Company’s issued share capital comprised 798,078,829 ordinary shares. Each ordinary share carries the right to one vote at a general meeting of the Company and, therefore, the total number of voting rights in the Company as at close of business on the day immediately prior to the date of posting of this Notice is 798,078,829.

Electronic Address

You may not use any electronic address (within the meaning of section 333(4) of the Companies Act 2006 (the “Act”)) provided in this Notice (or in any related documents including any form of proxy) to communicate with the Company for any purposes other than those expressly stated.

Website Publication of Audit Concerns

Under section 527 of the Act, members meeting the threshold requirement set out in that section have the right to require the Company to publish on a website a statement setting out any matter relating to: (a) the audit of the Company’s accounts (including the auditor’s report and the conduct of the audit) that are to be laid before the meeting; or (b) any circumstance connected with an auditor of the Company ceasing to hold office since the previous meeting at which annual reports and accounts were laid in accordance with section 437 of the Act. The Company may not require the shareholders requesting any such website publication to pay its expenses in compliance with sections 527 or 528 of the Act. Where the Company is required to place a statement on a website under section 527 of the Act, it must forward the statement to the Company’s auditor not later than the time when it makes the statement available on the website. The business which may be dealt with at the AGM includes any statement that the Company has been required, under section 527 of the Act, to publish on a website.

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