UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 6-K

REPORT OF FOREIGN PRIVATE ISSUER

PURSUANT TO RULE 13a-16 or 15d-16

UNDER THE SECURITIES EXCHANGE ACT OF 1934

For the month of May, 2020

Commission File Number: 001-38452

MEREO BIOPHARMA GROUP PLC

(Translation of registrant’s name into English)

4^th Floor, One Cavendish Place,

London, W1G 0QF, United Kingdom

(Address of principal executive office)

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F.

Form 20-F  ☒            Form 40-F  ☐

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1):  ☐

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7):  ☐

Exhibit Index

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

Date: May 22, 2020

Exhibit 99.1

Annual General Meeting

London and Redwood City, Calif., May 22, 2020 – Mereo BioPharma Group plc (NASDAQ: MREO, AIM: MPH) “Mereo” or “the Company”, a clinical-stage biopharmaceutical company focused on oncology and rare diseases, announces that it will be holding its Annual General Meeting (“AGM”) on 29 June 2020 at 3:00 p.m. at 1 Cavendish Place, London W1G 0QF, United Kingdom. A formal notice of AGM will be announced and posted to shareholders (or a notification of the availability of the notice of AGM will be posted to shareholders, where appropriate) in due course, and will also be available on the Company’s website at www.mereobiopharma.com.

On 23 March 2020, the UK Government published compulsory measures on staying at home and away from others (social distancing) to address the spread of COVID-19. In accordance with these measures, it is currently expected that Mereo’s AGM will be held as a closed meeting and ordinary shareholders will not be allowed to attend the AGM in person. Accordingly, all shareholders are encouraged to appoint the Chairman of the AGM as their proxy to vote on the resolutions to be proposed. The Company will arrange for a quorum of two qualifying persons to be present at the AGM. If COVID-19 social distancing measures remain in place at the time of the AGM, any ordinary shareholder seeking to attend the AGM in person will be refused entry.

The Company will continue to monitor UK government advice and in the event that Mereo’s AGM arrangements have to change, the Company will announce the change via a regulatory news service announcement and post details on the Investors section of its website at www.mereobiopharma.com.

About Mereo BioPharma

Mereo BioPharma is a biopharmaceutical company focused on the development and commercialization of innovative therapeutics that aim to improve outcomes for patients with rare diseases. Mereo’s strategy is to selectively acquire product candidates for rare diseases that have already received significant investment from pharmaceutical and large biotechnology companies and that have substantial preclinical, clinical and manufacturing data packages. The Company also acquired two clinical stage oncology products as a result of the merger with Oncomed Pharmaceuticals Inc. in 2019. Mereo’s lead rare disease product candidate, setrusumab, has completed a Phase 2b dose-ranging study in adults with osteogenesis imperfecta (“OI”) and a pivotal Phase 3 study design in paediatrics has been agreed with the FDA and EMA. Mereo’s second lead product candidate, alvelestat, is being investigated in a Phase 2 proof-of-concept clinical trial in patients with alpha-1 antitrypsin deficiency (“AATD”). Mereo’s lead oncology product candidate, etigilimab, an anti-TIGIT, has entered Phase 1b for a range of solid tumor types and the second product candidate, navicixizumab, has been licensed to Oncologie Inc. for up to $300M in milestone payments. Following successful completion of Phase 2, Mereo is seeking partnerships for it’s two additional clinical-stage product candidates; acumapimod for the treatment of acute exacerbations of chronic obstructive pulmonary disease (“AECOPD”), leflutrozole for the treatment of hypogonadotropic hypogonadism (“HH”) in obese men. Mereo continues to evaluate financing options through a combination of partnering and equity offering alongside prioritisation of the product candidate portfolio.

Additional Information

The person responsible for arranging the release of this information on behalf of the Company is Charles Sermon, General Counsel.

Forward-Looking Statements

This Announcement contains “forward-looking statements.” All statements other than statements of historical fact contained in this Announcement are forward-looking statements within the meaning of Section 27A of the United States Securities Act of 1933, as amended (the “Securities Act”), and Section 21E of the United States Securities Exchange Act of 1934, as amended (the “Exchange Act”). Forward-looking statements usually relate to future events and anticipated revenues, earnings, cash flows or other aspects of our operations or operating results. Forward-looking statements are often identified by the words “believe,” “expect,” “anticipate,” “plan,” “intend,” “foresee,” “should,” “would,” “could,” “may,” “estimate,” “outlook” and similar expressions, including the negative thereof. The absence of these words, however, does not mean that the statements are not forward-looking. These forward-looking statements are based on the Company’s current expectations, beliefs and assumptions concerning future developments and business conditions and their potential effect on the Company. While management believes that these forward-looking statements are reasonable as and when made, there can be no assurance that future developments affecting the Company will be those that it anticipates.

All of the Company’s forward-looking statements involve known and unknown risks and uncertainties (some of which are significant or beyond its control) and assumptions that could cause actual results to differ materially from the Company’s historical experience and its present expectations or projections. The foregoing factors and the other risks and uncertainties that affect the Company’s business, including those described in its Annual Report on Form 20-F, Reports on Form 6-K and other documents filed from time to time by the Company with the United States Securities and Exchange Commission (the “SEC”) and those described in other documents the Company may publish from time to time should be carefully considered. The Company wishes to caution you not to place undue reliance on any forward-looking statements, which speak only as of the date hereof. The Company undertakes no obligation to publicly update or revise any of our forward-looking statements after the date they are made, whether as a result of new information, future events or otherwise, except to the extent required by law.

Mereo BioPharma Contacts:

Investors:

investors@mereobiopharma.com

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