PHASE 2B ASTEROID STUDY 12-MONTH TOPLINE RESULTS

NOVEMBER 11, 2019

DISCLAIMER

1Mereo BioPharma Group plc

This presentation has been prepared by Mereo BioPharma Group plc (the “Company”) solely for your information and for the purpose of providing background information on the Company, its business and the industry in which it operates or any particular aspect thereof. For the purposes of this notice, “presentation” means this document, any oral presentation, any question and answer session and any written or oral material discussed or distributed during any related presentation meeting.This presentation has not been independently verified and no representation or warranty, express or implied, is made or given by or on behalf of the Company or any of its subsidiary undertakings, or any of any such person’s directors, officers, employees, agents, affiliates or advisers, as to, and no reliance should be placed on, the accuracy, completeness or fairness of the information or opinions contained in this presentation and no responsibility or liability is assumed by any such persons for any such information or opinions or for any errors or omissions. All information presented or contained in this presentation is subject to verification, correction, completion and change without notice. In giving this presentation, none of the Company or any of its subsidiary undertakings, or any of any such person’s directors, officers, employees, agents, affiliates or advisers, undertakes any obligation to amend, correct or update this presentation or to provide the recipient with access to any additional information that may arise in connection with it. To the extent available, the data contained in this presentation has come from official or third party sources. Third party industry publications, studies and surveys generally state that the data contained therein have been obtained from sources believed to be reliable, but that there is no guarantee of the accuracy or completeness of such data. While the Company believes that each of these publications, studies and surveys has been prepared by a reputable source, the Company has not independently verified the data contained therein. In addition, certain of the data contained in this presentation come from the Company’s own internal research and estimates based on the knowledge and experience of the Company’s management in the market in which the Company operates. Further, certain of the data has been provided to the Company by contract research organizations that the Company retains to conduct clinical trials, or by other third parties contracted by the Company. While the Company believes that such internal research and estimates and such other data are reasonable and reliable, they, and, where applicable, their underlying methodology and assumptions, have not been verified by any independent source for accuracy or completeness and are subject to change without notice. Accordingly, undue reliance should not be placed on any of the data contained in this presentation.

FORWARD-LOOKING STATEMENTS

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PHASE 2B ASTEROID STUDY: SETRUSUMAB DEMONSTRATES CLEAR DOSE-DEPENDENT BONE BUILDING AND TREND IN FRACTURE REDUCTION IN ADULT OI PATIENTS

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• Dose-dependent and statistically significant improvement in areal bone mineral density (BMD) over baseline at the lumbar spine, as measured by two-dimensional dual-energy X-ray absorptiometry (DXA)

• DXA is a well-established method for measuring BMD in clinical trials and measures total bone (trabecular and cortical) mineral density

• The mean increase in areal BMD reached 8.8% at 12 months in highest dose cohort (p<0.001), the largest increase in areal BMD observed in any clinical trial in adult OI patients

• Areal BMD as measured by DXA increased with duration of treatment across all three dose cohorts in a dose dependent manner; statically significant increases also seen at the femoral neck and hip

• Effect was consistent across all OI subtypes represented in the study population (I, III & IV)

• Trend of decrease in fractures observed in highest dose cohort

• Setrusumab was safe and well tolerated with no cardiac-related safety concerns observed in the study

• These results are supportive of progression of setrusumab into a pediatric pivotal study in OI with a primary endpoint of fracture rate over 12 months of treatment as originally planned

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KEY LEARNINGS: HR-pQCT MEASUREMENT

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• Primary endpoint of the ASTEROID study: Change in Trabecular Volumetric Bone Mineral Density (Tr vBMD) of the radius (wrist) over baseline after 12 months of treatment as measured by High Resolution peripheral Quantitative Computed Tomography (HR-pQCT)

• HR-pQCT is a relatively new and cutting-edge technology in bone research and useful to investigate bone biology, although it has not been widely used in clinical studies

• Two types of bone: trabecular (Tr) and cortical – HR-pQCT can discriminate between these

• The patient population in the ASTEROID study was highly heterogenous, presenting with a wide range of measurable trabecular bone at the radius at baseline

• Very low to very high baseline measurements (range=18.2 to 279) - outside the ranges in published literature for both OI and normal individuals1

• As a result, changes in Tr vBMD could not be detected and the study did not meet this endpoint at any of the three setrusumab dose levels

• Importantly, when combined with % change in cortical vBMD of the radius, a dose-dependent percentage increase in total vBMD was observed, reaching statistical significance in the high and medium dose cohorts (but not at low dose)

Conclusion: total vBMD increases were driven by the ability of setrusumab to build cortical bone

1Kocijan et al Osteoporos Int. Oct 2015; 2431-40

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THERE ARE CURRENTLY NO FDA OR EMA APPROVED THERAPIES FOR OSTEOGENESIS IMPERFECTA (OI)

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• OI is rare genetic bone disease characterized by frequent bone fractures, brittle teeth, and other physical symptoms

• Setrusumab (BPS-804) is a monoclonal antibody targeting sclerostin, functioning as a strong bone-building agent that also reduces the resorption of bone, creating a dual-action anabolic effect to build overall bone density

• Setrusumab received PRIME (Priority Medicine) designation by the European Medicines Agency (EMA) and Orphan Drug status in EU and US

6.2OI cases per 100,000 population in the US 1

10OI cases per 100,000 population in the EU 2

Prevalence:

85% - 90%linked to a gene mutation that

produces abnormal type 1 collagen 1, 2

72% - 77%of total OI population 3

OI types I, III and IV occur in

1. Based on Osteogenesis Imperfecta Foundation estimates; 2. Based on Orphanet estimates; 3. Shapiro J (2014) Osteogenesis Imperfecta: A Translational Approach to Brittle Bone Disease. Academic Press. Chapter 2: p15-22

SETRUSUMAB (BPS804) – ASTEROID STUDY

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Treatment Period = 12 months

28 dayscreening

High dose open label

High dose blinded (31pts)

Medium dose blinded (29pts)

Low dose blinded (30pts)

Placebo

Patients on placebo given high dose open label and new participants randomized 1:1:1:1

Follow-Up Period = 12 months

Option to receive zoledronic acid at M12 and M18 –discretion of physician

DXA and HR-PQCT scans at 18 and 24 months

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PATIENT BASELINE DEMOGRAPHICS

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Randomized Portion

High Dose(n=31)

Medium Dose(n=29)

Low Dose(n=30)

Age (years)

Mean 40.6 40.4 47.2

Min, Max 19, 73 20, 67 31, 74

Sex, n

Male 14 9 9

Female 17 20 21

Height & Weight, n

Mean height (cm) 150.3 150.59 150.74

Mean weight (kg) 63.15 65.13 64.84

OI Type, n

Type I 18 18 19

Type III/IV 13 11 11

Withdrawal*(n=1)

Discontinued(n=10)

Enrolled patients (n=112)

Three-Arm Blinded Dose Ranging

(n=80)

Open Label ArmTop dose

(n=21)

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TRABECULAR VOLUMETRIC BONE MINERAL DENSITY (TR VBMD) AND TOTAL VOLUMETRIC BONE MINERAL DENSITY (TOTAL VBMD) AS MEASURED BY HR-PQCT

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Baseline

Trabecular vBMD

mgHA/cm3

Mean % Change in

Trabecular vBMD

at 12 months

Mean % Change in

Total vBMD at 12

months

36 – 279 0.7% (SD 5.1) +4.11% (p=0.004)

18 - 213 -0.8% (SD 4.2) +4.85% (p=0.028)

50 - 182 -0.6% (SD 2.8) -0.18% (p=0.18)

Dose Cohort

High (n=27/28)

Medium (n=20/22)

Low (n=22/24)

Expected baseline for OI patients 60—114 and for normal individuals 149-190*

*Bone structure assessed by HRpQCT in adult patients with different types of OI: https://www.ncbi.nlm.nih.gov/pubmed/25956285

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AREAL BONE MINERAL DENSITY AS MEASURED BY DXAPER PROTOCOL

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Dose CohortMean % Change in Areal BMD

6 months

Mean % Change in Areal BMD

12 months

High (n=23) +4.4% (p<0.001) +8.8% (p<0.001)

Medium (n=17) +3.61% (p<0.001) +6.8% (p<0.001)

Low (n=21) +1.52% (p=0.057) +2.6% (p=0.057

Increase in areal BMD at the lumbar spine as measured by DXA by dose cohort all OI subtypes

OI TypeMean % Change in Areal BMD

6 months

Mean % Change in Areal BMD 12

months

Type 1 (n=17) +4.1% +8.8%

Type III & IV (n=6) +5.4% +9.8%

Increase in areal BMD at the vertebrae as measured by DXA by OI subtype at the high dose

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Dose CohortMean % Change in Areal

BMD at 12 months

High (n=21) +3.2% (p=0.022)

Medium (n=14) +3.6%

Low (n=18) +2.2%

Increase in areal BMD at the femoral neck as measured by DXA by dose cohort

Dose CohortMean % Change in Areal

BMD at 12 months

High (n=21) +2.3% (p=0.009)

Medium (n=14) +2.6%

Low (n=18) +2.0%

Increase in areal BMD at the total hip as measured by DXA by dose cohort

AREAL BONE MINERAL DENSITY AS MEASURED BY DXAPER PROTOCOL

COMPARISON OF HIGH DOSE SETRUSUMAB DATA WITH TERIPARATIDE ON DEXA

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LumbarSpine

Femoral Neck

Total Hip

8.8% 3.2% 2.3%

8.6% 3.2% 2.1%

9.8% 3.2% 2.9%

Setrusumab (high dose) Teriparatide1

Overall

Type I

Type III/IV

LumbarSpine

Femoral Neck

Total Hip

4.7% 1.2% 0.8%

5.6% 2.8% 1.8%

2.8% -4.9% -2.9%

Overall

Type I

Type III/IV

High dose clearly more efficacious than teriparatide in all types and at all anatomical sites

1Orwell et al. Evaluation of teriparatide treatment in adults with osteogenesis imperfecta. J Clin Invest. 2014 Feb;124(2):491-8

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FRACTURES

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Dose CohortPercentage of patients

fracturingOccurrence rate

High (n=27) 15% 0.16

Medium (n=20) 35% 0.49

Low (n=22) 23% 0.39

Percentage of patients with at least one fracture and occurrence rate per patient year

• Although the ASTEROID study was not statistically powered to show a difference in fracture rates, a trend of reduction in fractures was observed in the high dose cohort

• Fractures in the study included both X-ray confirmed as well as those confirmed by a local radiologist dependent on the nature of the fracture

SETRUSUMAB WAS SAFE AND WELL TOLERATED

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• The adverse event profile was balanced across the arms• No cardiac events of a safety concern - 9 AEs that were reported as potentially cardiac discussed at the

DMC (including cardiology review), and none were concluded to represent a CV safety concern• There were 5, 8 and 4 serious treatment emergent adverse events in the high, medium and low dose

groups, three of which were initially recorded as related. • Two events occurred in one patient, these were headache and hydrocephalus. The patient had a

history of basilar invagination, subdural haematoma and subdural haemorrhage; Neurologist and DMC concluded events unlikely related to study drug. There was a temporary interruption to study drug but the patient restarted treatment and continued study with no complications.

• The other SAE recorded initially recorded as related was of anaphylactic reaction, which occurred 2 days following infusion. This was the patients 6th infusion. As the reaction was 2 days following the infusion and the patient had had 5 previous doses, it is unlikely to be a drug reaction and the

patient continued therapy, with out symptoms or signs with repeat infusions.

SETRUSUMAB – ASTEROID STUDY – CONTINUATION PART

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• Continuation following 12 months treatment with setrusumab• Follow-up period off drug for 12 months

• Patients have option to receive bisphosphonates at end of treatment or at 6 months post-treatment (month 12 or 18) – investigators’ decision

• DEXA and HR-pQCT scans conducted at 6 and 12 months post setrusumab treatment • Bone biomarkers CTX1 and P1NP measured 2 and 6 months post setrusumab treatment • Fracture data also being collected

• Examines potential “off effect” of setrusumab• May inform further adult drug ‘holiday’ and chronic dosing schedules• Majority of patients – 81 – have taken this option to date

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Planned enrollment:

24 patients 5-18 years

Total Study duration

~165 Severe OI PatientsTypes I, III and IV

One month dose finding – 3 doses versus placebo

Additional 128 patients Randomized 1:1 placebo to selected dose

52Weeks

Primaryendpoints

• Fracture rate versus placebo at 12 months

Secondaryendpoints

• BMD by DXA scans 12 months

• Bone biomarkers

• PRO and quality of life

• HR-pQCT sub-study

Pivotal study approved in EU and Canada

Exploring extension into the U.S.

SETRUSUMAB PEDIATRIC PHASE 3 PIVOTAL STUDY READY TO BEGIN

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