Issue of Warrants

Mereo BioPharma Group plc

 ("Mereo" or the "Company")

Issue of Warrants

London, May 7, 2019 - Mereo BioPharma Group plc (AIM: MPH, NASDAQ:MREO), a clinical stage UK based biopharmaceutical company focused on rare diseases, announces that, in connection with the revisions made to its loan agreement with Silicon Valley Bank and Kreos Capital V (UK) Limited, as announced in their FY18 results statement issued on April 29, 2019, the Company has issued warrants giving the Lenders the right to subscribe for 321,444 shares at a price of 295 pence per share, currently equivalent to approximately 0.3% of the issued share capital of the Company. These warrants will be capable of exercise from issue until May 3, 2029.

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About Mereo

Mereo 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 that have substantial preclinical, clinical and manufacturing data packages. Mereo's four product candidates have previously generated positive clinical data for Mereo's target indications or in related indications. Mereo has commenced randomized Phase 2 clinical trials for all four of the product candidates. In connection with the merger with OncoMed, Mereo added two candidates to its pipeline, Navicixizumab and Etigilimab.

· BPS-804 for osteogenesis imperfecta (OI). In October 2018, the Company announced completion of enrollment of 112 adult patients in a Phase 2b dose ranging study with initial data expected in Q2 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 U.S. and the 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 dosing of the first patient in a Phase 2 dose ranging study in the U.S. with data expected around the end of 2019;

· BCT-197 for severe exacerbations of COPD. The Company announced positive Phase 2 data in May 2018 and recently announced the outline of the pivotal Phase 3 study including the primary and key secondary endpoints following the successful end of Phase 2 Type B meeting with the FDA;

· 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;

· Navicixizumab has completed a Phase 1a single-agent clinical trial in patients with advanced solid tumors and is currently in a Phase 1b trial in combination with a standard paclitaxel regimen in patients with platinum-resistant ovarian cancer. This study recently completed enrolment; and

· Etigilimab has completed a single-agent Phase 1a trial in patients with advanced or metastatic solid tumors and is currently in a Phase 1b combination study with nivolumab. Etigilimab is part of OncoMed's prior collaboration with Celgene. Celgene has the option to obtain an exclusive licence to develop and commercialize the product. If Celgene exercises such option, OncoMed (now a wholly-owned indirect subsidiary of Mereo) will be eligible to receive a $35 million opt in payment.