Duchenne Muscular Dystrophy Program Developing utrophin modulator therapies for the potential treatment of all DMD patients

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Thank you to the patients and their families, and the organisations who have supported our program Action Duchenne "A Brave New World"3November 2015

Utrophin and Dystrophin Two proteins, one major function – stabilise muscle fibre membranes Description of hypothesis Confirmation of approach in vivo Utrophin modulator pipeline November 20154Action Duchenne "A Brave New World"

Comparison Between Dystrophin and Utrophin Function November DystrophinUtrophin Muscle specific transcripts  Early foetal muscle expression  Mature muscle expression  Mature fibre localisationComplete lengthNMJ, MTJ Fibre repair  Specific fibre binding sitesCostamere Protein binding partners Dystrophin Protein Complex  nNOS  Microtubules  Actin  Action Duchenne "A Brave New World"

Dystrophin or Utrophin Protein: Maintaining the Function of Muscle Fibers Contractile apparatus Dystrophin or Utrophin Costamere Section through a muscle fibre Finite number of springs Finite number of binding sites Contraction and relaxation stress transmitted through costamere anchor sites Muscle fibre membrane November 2015Action Duchenne "A Brave New World"6 No springs Structural failure No dystrophin (Duchenne) Structural failure Fewer springs Still functional but lower weight capacity Less dystrophin (Becker) Still functional but lower stress tolerance

Utrophin is Functionally Equivalent to Dystrophin in Developing and Repairing Muscle >Modulation of utrophin protein has potential to compensate for lack of dystrophin November 20157Action Duchenne "A Brave New World"

Summit’s Utrophin Modulation Approach Utrophin gene expression is switched off in myonuclei once repair to a damaged region of the fibre has been made Exactly same mechanism operating in DMD muscle Development of an oral drug treatment where the drug enters muscle fibre myonuclei, via blood circulation, to switch on and maintain utrophin gene expression continuously Mouse dosed orally with SMT C1100 Each “dot” radiolabelled SMT C1100 * Example positive C1100 myonuclei Action Duchenne "A Brave New World"8November 2015 * *

Utrophin Modulators Increase Utrophin Expression Along Muscle Fibres in mdx Models >Utrophin localised along the entire length of the membrane with drug treatment >Reconstruction of the dystrophin protein complex >Stabilises membrane reducing rate of degeneration mdx control mdx + SMT C1100mdx + 2 nd Generation β-dystroglycan (EDL) Utrophin (TA) November 2015 Source: Human Mol Genet, (2015), 24 (15) Action Duchenne "A Brave New World"

Increased Resistance to Muscle damage November 2015 Source: Human Mol Genet (2015), 24 (15), : PLoS ONE (2011), 6 (5), e Utrophin Modulation Protected Against Loss of Muscle Function in mdx Disease Model Action Duchenne "A Brave New World"

Utrophin Modulator Pipeline November 2015Action Duchenne "A Brave New World"11

Our Utrophin Development Pipeline Action Duchenne "A Brave New World"12 Discovery Clinical Trial Preparation Phase 1Phase 2 SMT C1100 Second Generation Future Generations PRODUCT >Disease modifying approach >Potential to treat all DMD patients regardless of the dystrophin mutation November 2015

SMT C1100 Overview Molecule: First-generation, small molecule utrophin modulator Status: >Met primary objective in Phase 1b modified diet clinical trial >Received Orphan Drug Designation from the FDA and Orphan Medicinal Product Designation from the EMA Clinical Data-to-Date: >Well-tolerated in ~100 healthy volunteers and 24 DMD patients >Phase 1b modified diet clinical trial demonstrated improved drug exposure in patients following specific dietary guidance November 2015 >>> Next Milestone: Phase 2 proof of concept trial expected to start Q Action Duchenne "A Brave New World"

Phase 1b Modified Diet Trial Design Evaluated plasma levels of SMT C1100 in DMD patients following specific dietary guidance providing for a balanced diet of fats, proteins and carbohydrates Study Design:>12 ambulatory DMD patients aged 5-13 years old >Placebo controlled, dose escalating trial >14 days of oral dosing Primary Objective:>PK of SMT C1100 Secondary Objectives:>Safety/tolerability of SMT C1100 >Evaluate variability in steady state PK >Evaluate CK levels as a potential biomarker of SMT C1100 activity November Action Duchenne "A Brave New World"

Modified Diet Phase 1b Results: Increased Exposure in Patients who had Participated in First Phase 1b Trial >All seven patients who participated in previous Phase 1b trial had increased exposures when following dietary guidance >Seven of the 12 patients had higher exposure after Day 14 compared to Day 1, which was not observed in previous trials of SMT C1100 November 2015 >>>Potential for all DMD patients to benefit from continued utrophin production >>>Data support advancement to Phase 2 proof of concept trial * (Fixed Dose) 15Action Duchenne "A Brave New World" * Excludes 1 patient who had AUC >1215 in both studies

Next Steps: Phase 2 Proof of Concept Trial >Trial to evaluate clinical benefit of SMT C1100 in patients with DMD >Expected initiation Q >Plan to report interim data periodically Planned Study Design:Open label trial expected to enrol up to 40 ambulatory DMD patients aged 5-10 years old 48 week trial Sites in Europe and US PK not part of inclusion criteria November Action Duchenne "A Brave New World"

Phase 2 Proof of Concept Trial: Range of Mechanism and Efficacy Measures Planned MECHANISM Utrophin protein levels Muscle fibre regeneration MUSCLE HEALTH Magnetic Resonance Imaging (MRI) Serum biomarkers FUNCTION Six minute walk test North Star Ambulatory Assessment November Action Duchenne "A Brave New World"