Mereo Publicly Files Registration Statement on Form F-4 with U.S. Securities and Exchange Commission

LONDON, Jan. 25, 2019 -- Mereo BioPharma Group plc (AIM: MPH), a clinical stage, UK-based, biopharmaceutical company focused on rare diseases, announces today that a further step towards the proposed combination (the "Proposed Transaction") with OncoMed Pharmaceuticals, Inc. ("OncoMed") has been taken, with the filing by Mereo of its preliminary registration statement on Form F-4 (the "Form F-4") with the U.S. Securities and Exchange Commission (the "SEC").

The Form F-4, which remains subject to review and comment by the SEC and which may be revised further as necessary, will, when filed in definitive form, constitute the proxy statement of OncoMed for the vote of its stockholders on the Proposed Transaction and will also constitute a prospectus of Mereo in the United States.

The Proposed Transaction is expected to close in the first half of 2019, subject to the approval of OncoMed's stockholders, any approval that may be required from Mereo’s shareholders and other customary closing conditions.

The Form F-4 is available free of charge on the SEC website (www.sec.gov), on OncoMed's website (http://cms2.oncomed.com/investors/financial-information/sec-filings) and on Mereo's website (https://www.mereobiopharma.com/investors-page/sec-filings/).

In its Form F-4, Mereo is providing certain information which has not previously been publicly disseminated, including detailed information on the Proposed Transaction, certain pro forma financial statements on a combined basis, a description of the risks related to the Proposed Transaction and information regarding the remuneration of Mereo's directors and senior management for the year ended 31 December 2018.

About Mereo

Mereo is a biopharmaceutical company focused on the development and commercialisation of innovative therapeutics that aim to improve outcomes for patients with rare diseases. Mereo's strategy is to selectively acquire product candidates that have already received significant investment from pharmaceutical companies and that have substantial preclinical, clinical and manufacturing data packages. Each of Mereo's four product candidates has previously generated positive clinical data for Mereo's target indication or in a related indication. Since inception Mereo has commenced large, randomised, placebo-controlled Phase 2 clinical trials for all four of the product candidates:

• BPS-804 for osteogenesis imperfecta (OI). The Company recently announced completion of enrolment with 112 adult patients in a Phase 2b dose ranging study with some initial data expected in the H1 2019 and top-line dose ranging data in late 2019. A pediatric Phase 3 study design has also been approved by the EMA. BPS-804 has orphan designation in the US and EU and has been accepted into the PRIME and Adaptive Pathways in EU;
• MPH-966 for alpha-1 antitrypsin deficiency (AATD). The Company recently announced first patient in a Phase 2 dose ranging study in the US with data expected in late 2019;
• BCT-197 for acute exacerbations of COPD (AECOPD). The Company announced positive Phase 2 data in May 2018; and
• BGS-649 for hypogonadotropic hypogonadism (HH). The Company announced positive top-line Phase 2b data in March 2018 and positive results from the Phase 2b safety extension study in December 2018.

For Further Enquiries:

Mereo Denise Scots-Knight, Chief Executive Officer Richard Jones, Chief Financial Officer	+44 (0)333 023 7300
Cantor Fitzgerald Europe (Nominated Adviser and Joint Broker) Phil Davies Will Goode	+44 (0)20 7894 7000
RBC Capital Markets (Joint Broker) Rupert Walford Laura White	+44 (0)20 7653 4000
FTI Consulting (Public Relations Adviser to Mereo) Ben Atwell Simon Conway Brett Pollard	+44 (0)20 3727 1000
Burns McLellan (US Public Relations Adviser to Mereo) Lisa Burns Jill Steier Robert Flamm	+01 (0) 212 213 0006