THIS ANNOUNCEMENT CONTAINS INSIDE INFORMATION AS DEFINED UNDER THE MARKET ABUSE REGULATION (EU) NO. 596/2014. UPON PUBLICATION OF THIS ANNOUNCEMENT THIS INFORMATION IS NOW CONSIDERED IN THE PUBLIC DOMAIN NOT FOR RELEASE,

THIS ANNOUNCEMENT CONTAINS INSIDE INFORMATION AS DEFINED UNDER THE MARKET ABUSE REGULATION (EU) NO. 596/2014. UPON PUBLICATION OF THIS ANNOUNCEMENT THIS

INFORMATION IS NOW CONSIDERED IN THE PUBLIC DOMAIN

NOT FOR RELEASE, PUBLICATION OR DISTRIBUTION, IN WHOLE OR IN PART, DIRECTLY OR INDIRECTLY IN, OR INTO

OR FROM ANY JURISDICTION IN WHICH THE SAME WOULD BE A VIOLATION OF THE LAWS OF SUCH JURISDICTION

MEREO ANNOUNCES INTENTION TO CONTINUE

LISTING ITS ADSs ON NASDAQ BUT PLANS CANCELLATION OF ADMISSION OF ITS ORDINARY SHARES TO TRADING ON AIM

Exclusive NASDAQ listing

should simplify trading and potentially increase liquidity

Cancellation of AIM admission has no impact on UK presence

Last day of trading on AIM will be 17 December 2020.

London and Redwood City, Calif., November 11, 2020 - Mereo BioPharma Group plc (NASDAQ: MREO, AIM: MPH)

( Mereo or the Company ), a clinical stage biopharmaceutical company focused on oncology and rare diseases, today announced the Company s intention to cancel the admission of its ordinary shares of 0.003 each

( Ordinary Shares ) to trading on AIM (the AIM Delisting ) with effect from 18 December 2020. The Company s last day of trading on AIM will be 17 December 2020. Mereo will retain its U.S. listing on NASDAQ of

American Depositary Shares (ADSs) under ticker symbol MREO. Existing holders of ADSs not also holding Ordinary Shares do not need to take any action as a result of this announcement.

Mereo s ordinary shares were admitted to trading

on AIM, a market of the London Stock Exchange, in 2016, while the Company listed its ADSs on NASDAQ in 2019. However, In the last 6 months the vast majority of trading in the Company s securities has been on NASDAQ. As a result, we now believe

it is the right time to reduce the complexity and expense of a dual listing, stated Denise Scots-Knight, Mereo s Chief Executive Officer. The proposed cancellation of the AIM admission will have no impact on Mereo s UK presence

and may improve share liquidity by funnelling trading into the market where there appears to be most demand .

The Company will today be posting

a circular to shareholders (the Circular ) which will set out further information on the process to convert Ordinary Shares into ADSs, including personalised forms for those holders of certificated Ordinary Shares who wish to convert.

Copies will also be available on Mereo s website at www.mereobiopharma.com/AIM-Delisting

The Company was founded in 2015 and its Ordinary Shares were admitted to trading on AIM in June 2016. AIM provided the Company with important access to capital

and share trading liquidity during the formative phase of Mereo s clinical development business, enabling the Company to invest in and successfully complete three Phase 2 studies on the programs purchased from Novartis, comprising setrusumab

for the treatment of osteogenesis imperfecta (OI), acumapimod for the treatment of acute exacerbations of COPD (AECOPD) and leflutrozole for the treatment of hypogonadotropic hypogonadism (HH) in obese men. In March 2017, Mereo raised

15 million on AIM enabling the Company to continue the development of setrusumab for the treatment of OI and, in October 2017, to complete the in-licensing from AstraZeneca of Mereo s fourth

development program: alvelestat, for the treatment of alpha-1 antitrypsin deficiency (AATD). At the time, almost all the Company s largest shareholders were

UK-based institutional investors, in addition to Novartis and AstraZeneca.

In recognition of the on-going capital requirements for the business, the Company announced a merger with Oncomed Pharmaceuticals, Inc, a US NASDAQ listed company, in December 2018. This merger completed in April 2019 with an initial

public offering of ADSs on NASDAQ, resulting in Mereo achieving dual-listed status. The liquidity in the trading of Mereo s Ordinary Shares was enhanced by the NASDAQ listing and the Company s shareholder base began to shift towards US

investors. In February 2020, the Company raised a total of $6 million ( 4.6 million) from two new US investors, and then, in June 2020, the Company completed a further private placement of $70 million ( 56 million) from a group

comprised almost exclusively of US investors. This demand from US investors has led to a rapid and significant increase in the proportion of Mereo s Ordinary Shares that are currently held via ADSs and traded on NASDAQ.

As at 9 November 2020, being the last practicable date prior to the date of this announcement, 51.27 per cent. of the Company s Ordinary Shares

are held in ADS form and tradeable on NASDAQ. By reference to the volume of underlying Ordinary Shares, approximately 79 per cent. of trading in the past six months has taken place on NASDAQ. All shareholders who have not already converted

their Ordinary Shares into ADSs are currently able to do so at any time.

The AIM Rules for Companies require that, unless London Stock Exchange plc

otherwise agrees, the cancellation of a company s shares from trading on AIM requires the consent of not less than 75 per cent. of votes cast by its shareholders given in a general meeting. However, in the Company s case, given that

the listing of its ADSs on NASDAQ enables shareholders to continue to trade their shares in the Company in that format and, further, that there is a process available to shareholders to convert their Ordinary Shares into ADSs prior to the AIM

Delisting, London Stock Exchange plc has agreed that shareholder consent in a general meeting is not required for Mereo to proceed with the AIM Delisting.

Reasons for the AIM Delisting

The Board of Directors of

the Company has decided to implement the AIM Delisting for the following reasons:

Accordingly, the Directors believe that it is no longer in the best interests of the Company or its

shareholders as a whole for the Company to retain admission of Ordinary Shares to trading on AIM. However, the Company is providing an opportunity for shareholders to convert their Ordinary Shares into ADSs without cost, prior to the AIM Delisting

becoming effective on 18 December 2020.

Effect of the AIM Delisting

Shareholders will no longer be able to buy and sell Ordinary Shares on AIM after 17 December 2020. Holders of Ordinary Shares should read

Information for holders of Ordinary Shares below which explains in more detail the process of converting Ordinary Shares into ADSs.

company incorporated in England and Wales, the Company will continue to be subject to the requirements of the Companies Act 2006.

Delisting taking effect, the Company will no longer be subject to the AIM Rules for Companies or be required to retain the services of an independent nominated adviser ( Nomad ). The Company will also no longer be subject to the QCA

Corporate Governance Code or be required to comply with the continuing obligations set out in the FCA s Disclosure Guidance and Transparency Rules ( DTRs ) or, provided the Company s securities remain outside the scope of the

regulation, the EU Market Abuse Regulation ( MAR ). In addition, the Company and its shareholders will no longer be subject to the provisions of the DTRs relating to the disclosure of changes in significant shareholdings in Mereo. The

Company will, however, continue to comply with all regulatory requirements for the NASDAQ listing of its ADSs, including all applicable rules and regulations of the SEC.

Shareholders who continue to hold Ordinary Shares will continue to be notified in writing of the availability of key documents on our website, including

publication of Annual Reports and Annual General Meeting documentation. Holders of ADSs will be able to continue to access all such information via the Mereo website. Holders of Ordinary Shares and ADSs will both be eligible to receive any future

dividends that may be declared.

Following the AIM Delisting, as the Company will remain a public limited company incorporated in England and Wales but

its securities will not be admitted to trading on a regulated market or multilateral trading facility in the United Kingdom (or a stock exchange in the Channel Islands or the Isle of Man), the City Code on Takeovers and Mergers (the

Code ) will only apply to the Company if it is considered by the Panel on Takeovers and Mergers (the Panel ) to have its place of central management and control in the United Kingdom (or the Channel Islands or the Isle of Man).

This is known as the residency test . The way in which the test for central management and control is applied for the purposes of the Code may be different from the way in which it is applied by the United Kingdom tax authorities, HM

Revenue & Customs ( HMRC ). Under the Code, the Panel looks to where the majority of the directors of the Company are resident, amongst other factors, for the purposes of determining where the Company has its place of central

management and control.

Accordingly, following the AIM Delisting, the Panel has confirmed to the Company that the Code will not apply to the Company, and

the Company and its shareholders will therefore not have the benefit of the protections the Code affords, including, but not limited to, the requirement that a person who acquires an interest in Ordinary Shares carrying 30 per cent. or more of

the voting rights in the Company must make a cash offer to all other shareholders at the highest price paid in the 12 months before the offer was announced.

Notwithstanding the above, the Company may become subject to the Code in the future if any changes to the Board composition result in the majority of the

Directors being resident in the United Kingdom, Channel Islands or the Isle of Man.

Information for holders of Ordinary Shares

The Company s Ordinary Shares will continue to be traded on AIM until market close (4.30 p.m. London time) on 17 December 2020. Thereafter, holders

of unconverted Ordinary Shares can still hold the Ordinary Shares, but there will be no public market in the United Kingdom on which the Ordinary Shares can be traded, and the Ordinary Shares will not be tradeable on NASDAQ in this form.

In order to sell Ordinary Shares on a public market following the AIM Delisting, selling shareholders will need to convert their Ordinary Shares into ADSs.

Each ADS represents five Ordinary Shares. This conversion can be made at any time, including before the AIM Delisting, subject in all cases to the provisions of, and the limitations set forth in, the Company s deposit agreement of 23 April

2019 with Citibank, N.A., as depositary (the Depositary ), which governs the Company s ADSs (the Deposit Agreement ). A copy of the Deposit Agreement has been filed with the SEC under cover of a Registration Statement on

Form F-6. You may obtain a copy of the Deposit Agreement from the SEC s website (www.sec.gov). Please refer to Registration Number 333-249338 when retrieving such

The Board considers that shareholders should consider converting their Ordinary Shares into ADSs prior to the AIM Delisting on 18 December

2020 for the following reasons:

Shareholders who do not elect to participate in the block transfer process can utilise the services of a

broker who is able to facilitate conversion at the shareholder s convenience.

Shareholders whose Ordinary Shares are held in uncertificated form in

CREST and who wish to convert their Ordinary Shares into ADSs, should contact their broker without delay to request that their Ordinary Shares are converted.

Mereo advises holders of Ordinary Shares which are not in ADS form to seek independent financial advice regarding the AIM Delisting and the conversion of

their Ordinary Shares into ADSs.

Information on the process to convert Ordinary Shares into ADSs and the forms to be completed will accompany the

Circular. The information and forms, and contacts at the Company s registrar, Link Group, in respect of completion of the block transfer participation request form for certificated holders, and the Company s ADS depositary, Citibank, in

respect of the conversion of Ordinary Shares to ADSs, are included on Mereo s website at www.mereobiopharma.com/AIM-Delisting

Many investors purchase AIM-quoted shares because they are classed as unlisted/unquoted securities which may qualify individuals who are UK tax resident and UK domiciled for relief from inheritance taxation and certain other preferential

tax benefits. Mereo cannot and does not provide any form of taxation advice to shareholders and therefore shareholders are strongly advised to seek their own taxation advice to confirm the consequences of continuing to hold unlisted Ordinary Shares

or converting Ordinary Shares into ADSs.

The following summary does not constitute legal or tax advice and is not exhaustive. The Company s

understanding of the current position for UK individuals who are UK domiciled under UK taxation law is as follows but it should be noted that the Company has not taken steps to confirm the current position with HMRC. Therefore, the following should

not be relied upon by shareholders without taking further advice (and the Company accepts no liability in respect of any such reliance on any information provided herein on taxation matters):

It is recommended that shareholders obtain appropriate professional advice in

respect of the application of other UK taxes.

Shareholders who elect to convert their holdings of Ordinary Shares to NASDAQ listed ADSs prior to the AIM

Delisting should not incur a stamp duty, or SDRT, charge. It is expected that shareholders who elect to convert their holdings of Ordinary Shares to NASDAQ listed ADSs following the AIM Delisting may incur a stamp duty, or SDRT, charge at the rate

of 1.5 per cent. of the market value of the Ordinary Shares being converted.

If you are in any doubt as to your tax position you should consult an

appropriate professional adviser immediately.

time in this announcement are to London time unless otherwise stated.

(2) Each of the times and dates in the above timetable are subject to change. If