MPH.L Regulatory News (MPH)

Mereo BioPharma Group plc

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

Completion of Patient Enrolment in Phase 2b study

of BPS-804 for the treatment of Osteogenesis Imperfecta

Six month efficacy data from top dose open label cohort expected H1 2019

Top-line results expected H2 2019

London, 15 October 2018 - Mereo BioPharma Group plc (AIM: MPH), a clinical stage UK based biopharmaceutical company focused on rare diseases, today announced it has successfully completed patient enrolment in the potentially pivotal adult phase 2b ASTEROID clinical study of BPS-804 (Setrusumab) for the treatment of osteogenesis imperfecta (OI), an orphan genetic disorder known as brittle bone disease.

A total of 112 adult patients have been enrolled into this multi-centre, randomised, double-blind, dose-finding study, which is being conducted in the US and Europe. The study has 4 arms and includes an open-label arm which is expected to report six-month data on the top dose in H1 2019 and 12-month data in H2 2019. Top-line 12 month data from the blinded dose ranging part of the study is expected in Q4 2019. BPS-804 has been granted Orphan Drug Designation by the US FDA and the EMA. BPS-804 has also been accepted into the EMA's Adaptive Pathways Programme and granted PRIority MEdicines (PRIME) designation.

The study's primary endpoint is change from baseline of Bone Mineral Density (BMD) after 12 months as measured by High Resolution peripheral Quantitative Computed Tomography (HR-pQCT) and the secondary endpoints of BMD using traditional two-dimensional dual-energy X-ray absorptiometry (DXA) measurement together with measurement of serum bone biomarkers. Bone microarchitecture assessed by HRpQCT has been shown to be a predictor of fracture risk in postmenopausal women (The OFLEY study1). In a previous study in OI patients, BPS-804 showed a statistically significant improvement in BMD and on bone biomarkers.

In August 2018, the Company's Paediatric Investigation Plan (PIP) was approved by the European Medicine Agency. Mereo plans to commence this registration trial in approximately 160 children with severe disease aged 5-18 years old in 2019. The primary endpoint will be fracture rate over a 12-month period.

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

"This is another important milestone in the development of BPS-804 for Osteogenesis Imperfecta, which is a serious, debilitating and painful orphan disease for which there are currently no EMA or FDA approved treatments. We believe BPS-804's mechanism of action is specifically suited to OI and has the potential to become a novel treatment option that could reduce fractures and improve quality of life of these patients. We look forward to announcing data from this study during the course of 2019."

About BPS-804 (Setrusumab)

BPS-804 is a fully humanised monoclonal antibody that inhibits sclerostin, a protein which inhibits the activity of bone-forming cells. The mechanism of action of BPS-804 could be particularly well suited for the treatment of OI and has the potential to become a novel treatment that could reduce fractures and improve patient quality of life.

About OI

OI is a rare genetic disorder that is characterized by fragile bones and reduced bone mass resulting in bones that break easily, loose joints and weakened teeth. In severe cases patients may experience hundreds of fractures in a lifetime. In addition, people with OI often suffer muscle weakness, early hearing loss, fatigue, curved bones, scoliosis, respiratory problems and short stature. The majority of cases of OI (estimated at approximately 90%) are caused by a dominant mutation in a gene coding for type I collagen, a key component of healthy bone. Current treatment of OI is supportive, focusing on minimizing fractures and maximizing mobility, but to date, there are no EMA or FDA approved treatments.

1 Bone microarchitecture assessed by HRpQCT as Predictor of Fracture Risk in Postmenopausal Women: The OFELY Study Journal of Bone Mineral Research 9 March 2017

About Mereo BioPharma

Mereo is a biopharmaceutical company focused on the development and commercialization of innovative therapeutics that aim to improve outcomes for patients with rare diseases. The portfolio currently consists of four clinical-stage product candidates, each of which were acquired from large pharmaceutical companies: BPS-804 (setrusumab) for the treatment of osteogenesis imperfecta ("OI"); MPH-966 (alvelestat) for the treatment of severe alpha-1 antitrypsin deficiency ("AATD"); BCT-197 for the treatment of acute exacerbations of chronic obstructive pulmonary disease, ("AECOPD"); and BGS-649 for the treatment of hypogonadotropic hypogonadism ("HH") in obese men. Each of the Company's product candidates has generated positive clinical data for Mereo's target indication or in a related indication. The Company'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. Since inception the Company has commenced large, randomized, placebo-controlled Phase 2 clinical trials for all four of the product candidates and has previously announced positive top-line results from two of its clinical trials: a Phase 2 trial with BCT-197 in December 2017 and a Phase 2b dose-ranging study with BGS-649 in March 2018.

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