Update on acumapimod Phase 2 Study

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Mereo BioPharma Group plc

("Mereo" or the "Company" or the "Group")

Update on acumapimod Phase 2 Study

Completion of Patient Enrolment of a Phase 2 Dose-Ranging Study

of acumapimod for the treatment of AECOPD

Top line results expected H2 2017

London, 15 May 2017 - Mereo BioPharma Group plc (AIM: MPH), a clinical stage, UK-based, biopharmaceutical company focused on rare and specialty diseases, today announced, that it has successfully completed patient enrolment in the AETHER, multi-centre, double-blind, placebo-controlled Phase 2 dose-ranging study of acumapimod (BCT-197), for the treatment of patients with acute exacerbations of chronic obstructive pulmonary disease (AECOPD). Acumapimod is a novel, orally active p38 MAP kinase inhibitor in development as a first-line acute therapy for AECOPD.

A total of 282 patients have been enrolled to explore two different dosing regimens versus placebo, on top of standard of care, in patients presenting with an AECOPD in the hospital setting. The study aims to determine the most appropriate dosing regimen of acumapimod. The primary end point is forced expiratory volume in one second (FEV1). Following a 5-day dosing period, patients are being followed for 26 weeks to explore a number of additional end points including hospital stay times, patient reported outcomes and recurrence rates of AECOPD. Top-line data from this study is expected in the second half of 2017.

Alastair Mackinnon, Chief Medical Officer of Mereo BioPharma Group plc commented:

"This is another important milestone in our strategy of rapidly developing our portfolio of assets acquired from big pharma, following on from the recent initiation of a potentially pivotal Phase 2b study for BPS-804 in the orphan disease osteogenesis imperfecta. COPD is a chronic and debilitating condition, characterised by acute exacerbations which can result in hospitalisation and accelerate long term lung function decline. The treatment paradigm for AECOPD has not advanced in over a decade in the US or Europe and there is a growing need for new therapies. In previous Novartis studies, acumapimod was shown to have a statistically significant and clinically meaningful impact on FEV1 in AECOPD patients and to be a powerful anti-inflammatory. We believe it has the potential to be an important new treatment to improve the quality of life of these patients whilst also reducing healthcare costs."

About acumapimod (BCT-197)

Acumapimod is an orally active p38 MAP kinase inhibitor in development as a first-line acute therapy, alongside existing treatment for AECOPD. p38 MAP kinase is central in the acute inflammatory pathway. It is rapidly activated in response to viral and bacterial infections, pollutants and other noxious agents which are the key drivers of acute inflammation underlying the pathology of COPD exacerbations. p38 is activated in COPD and AECOPDs and is inversely correlated with measure of lung function. The higher the p38 MAP kinase activation, the lower lung function is expected to be. COPD patients are usually treated with corticosteroids to control the inflammation including during exacerbations. Steroid resistance however, is common and despite this treatment, there remains a considerable unmet need for improved management and outcome from AECOPDs . Mereo believes acumapimod, through targeting the pathways that drive the pathological mechanism behind acute exacerbations, offers a potential new treatment for controlling the inflammation.

Previous studies undertaken by Novartis, showed acumapimod demonstrated a statistically significant reduction of the inflammatory marker TNFα and a clinically meaningful increase in forced expiratory volume in one second (FEV1), a clinically relevant endpoint in the treatment of COPD. In studies to date, acumapimod has been shown to be safe and well tolerated in the target patient population.

About AECOPD

Chronic obstructive pulmonary disease (COPD) is a non-reversible, progressive lung disease that is estimated to affect 210 million people world wide1 and is a leading cause of death. An AECOPD is characterised by a sudden worsening in the COPD patient's symptoms of dyspnoea, cough and sputum production. Acute exacerbations last for several days and require a step up of medication and often hospitalisation. AECOPDs occur in the natural course of the disease and are commonly triggered by infections and air pollution. Both airway and systemic inflammation are characteristic drivers of the disease

1 Epidemiology and Prevalence of Chronic Obstructive Pulmonary Disease, Enrique Diaz-Guzman, MD, David M. Mannino, MD March 2014, Clinics in Chest Medicine

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About Mereo

Mereo is a UK-based biopharmaceutical company focused on the development of innovative medicines that aim to address unmet medical needs in rare and specialty disease areas and improve patient quality of life. The Company seeks to selectively acquire development-stage product candidates from large pharmaceutical companies and to rapidly progress these product candidates to subsequent value inflection points.

Mereo combines the operational discipline and efficiency of a small company with the financial resources to conduct comprehensive clinical studies. The Company has the option to directly commercialise products, for example in orphan diseases, in addition to partnering or divesting its products.

Mereo's initial portfolio consists of three mid-late stage clinical assets that were acquired from Novartis in July 2015. BPS-804 is being developed for the prevention of fractures resulting from osteogenesis imperfecta (brittle bone disease); acumapimod (BCT-197), is being developed to treat inflammation in patients with an AECOPD; and BGS-649 is a once-weekly pill to restore normal testosterone levels in men with hypogonadotropic hypogonadism.

In H1 2016 the Company initiated a Phase 2 study with acumapimod and a Phase 2b study with BGS-649. Mereo recently announced commencement of the first pivotal trial for BPS-804. Additional product opportunities, from a range of large pharmaceutical and biotechnology companies, are under active evaluation.