Summit Therapeutics plc ( Summit or the Company ) SUMMIT THERAPEUTICS REPORTS FINANCIAL RESULTS FOR THE SECOND QUARTER ENDED 31 JULY 2015 AND OPERATIONAL PROGRESS Oxford, UK, 27 August 2015 Summit Therapeutics plc (AIM:

Summit Therapeutics plc

( Summit or the Company )

SUMMIT THERAPEUTICS REPORTS FINANCIAL RESULTS FOR THE SECOND QUARTER ENDED 31 JULY 2015 AND OPERATIONAL PROGRESS

Oxford, UK, 27 August 2015 Summit Therapeutics plc (AIM: SUMM, NASDAQ: SMMT), the drug discovery and development company advancing therapies

for Duchenne muscular dystrophy ( DMD ) and C. difficile infection ( CDI ), today reports its financial results for the second quarter and half-year ended 31 July 2015.

Mr Glyn Edwards, Chief Executive Officer of Summit commented: We have made very substantial progress with our utrophin modulator programme to

treat boys with DMD with the recent announcement that our lead candidate, SMT C1100, achieved its primary objective in a Phase 1b clinical trial, allowing us to advance this molecule into a Phase 2 open-label trial that is expected to start by the

end of this year. We further strengthened this programme with the publication of data on a second-generation utrophin modulator demonstrating its disease-modifying potential in animal models of this devastating disease. Importantly, we also received

Fast Track designation from the US FDA for SMT19969 in CDI, highlighting the promise of our novel antibiotic treatment with the potential to address disease recurrence, the key clinical issue of CDI. With top-line data from our ongoing Phase 2 proof

of concept trial in CDI expected to report in the fourth quarter of 2015, we continue to be excited about progress in both of our clinical programmes.

RECENT OPERATIONAL HIGHLIGHTS

SMT C1100 Highlights

FINANCIAL HIGHLIGHTS

Summit will host a conference call and

webcast to discuss the financial results for the second quarter and half-year ended 31 July 2015 today at 1:00pm BST / 8:00am EDT. To participate in the conference call please dial +44(0)20 7136 2050 (UK and international participants) or +1

718 354 1359 (US local number) and use the conference confirmation code 4691341. Investors may also access a live audio webcast of the call via the investors section of the Company s website www.summitplc.com. A replay of the webcast will be

available shortly after the presentation finishes.

For more information, please contact:

is seeking to treat all boys affected with the fatal disease Duchenne muscular dystrophy ( DMD ) using its pioneering utrophin modulation technology. Summit is also advancing a highly selective antibiotic to treat Clostridium

difficile infection ( CDI ).

Summit s DMD utrophin modulation programme is a treatment approach that is independent of the underlying

mutations in the dystrophin gene that cause the disease and therefore has the potential to address the entire population of DMD patients. Summit has established a leadership position in the field of utrophin modulation and is developing a robust

pipeline of first-, second- and future-generation product candidates. Summit is preparing to advance its lead utrophin modulator, SMT C1100, into Phase 2 clinical trials following the completion of a Phase 1b clinical trial in patients with DMD that

achieved its primary objective.

Summit s CDI therapy in clinical development is SMT19969, an orally administered small molecule antibiotic. SMT19969

is designed to selectively target Clostridium difficile bacteria without causing collateral damage to the healthy gut flora of patients, thereby reducing CDI recurrence rates, the key clinical issue in this disease.

Duchenne Muscular Dystrophy: Utrophin Modulation Programme

SMT C1100 is a small molecule, orally administered utrophin modulator that is being evaluated in patient clinical trials. SMT C1100 has received orphan drug

designation in the US and Europe.

SMT C1100: Phase 1b Modified Diet Clinical Trial

Earlier this month, Summit reported that it achieved the primary objective of its Phase 1b modified diet clinical trial of SMT C1100 in patients with DMD. The

placebo controlled trial was designed to increase plasma levels of SMT C1100 in patients by recommending a diet with balanced proportions of fat, proteins and carbohydrates combined with consuming a small glass of full fat milk at the time of

Initial analysis shows that six of 12 patients achieved the desired plasma level after receiving the higher dose of 2,500 mg of SMT C1100 twice

daily for 14 days. In a prior Phase 1b trial, only two of 12 patients dosed with SMT C1100 achieved the desired plasma level.

tolerated at all doses tested in the modified diet trial with no serious adverse events reported. This outcome increases the human safety database for this investigational drug.

The trial enrolled a total of 12 patients with DMD between the ages of five and 13 who were divided equally into three dose cohorts. Patients were randomised

to three groups over 14-day treatment periods during which each patient received a low dose of SMT C1100, a high dose of SMT C1100 and a placebo. There was a wash-out period of at least 14 days between each of the treatment periods. The trial was

conducted at four sites in the United Kingdom. The trial also measured enzyme biomarkers of muscle damage, such as creatine kinase. In this modified diet study, there was no change in the measured enzyme levels when patients received SMT C1100

compared to when they received a placebo. The Company plans to evaluate levels of creatine kinase as well as additional biomarkers over a longer duration of exposure to SMT C1100 in future clinical trials.

Summit expects to report further data from this trial at an upcoming medical meeting.

SMT C1100: Phase 2 Clinical Trial Plans

progress SMT C1100 into Phase 2 clinical trials. Summit plans to commence a Phase 2 open-label trial during the fourth quarter of 2015. The trial will evaluate the longer-term benefits of SMT C1100 on muscle health, function and safety. Summit also

plans to initiate a larger, multinational Phase 2 placebo-controlled trial that is expected to include sites in the US and Europe.

As part of the Company s strategy to maintain its leadership position in the field of utrophin modulation research, Summit is advancing

a pipeline of second- and future-generation utrophin modulators. The second generation utrophin modulators are structurally related to SMT C1100 but are designed to have more favourable pharmaceutical properties to achieve higher drug uptake.

In July 2015, new positive preclinical data on a second-generation utrophin modulator was published in the peer-reviewed journal Human Molecular Genetics. The

data showed that treatment of the in vivo mdx disease model for five weeks resulted in increased utrophin expression that was localised along the entire length of the muscle fibre membrane. This addressed the primary cause of fibre

degeneration and resulted in reduced regeneration and necrosis, enhanced protection of the muscle against contraction-induced damage and improved muscle function. Increases in utrophin were observed in skeletal muscle, including the diaphragm, and

the heart. Summit believes that these data further support the potential of utrophin modulation as a treatment approach for DMD regardless of the underlying genetic mutation.

In parallel to the current clinical development of SMT C1100, Summit is also working to identify an optimised formulation of this drug. The Company is working

with leading formulation companies to identify potential new formulations to progress into human clinical trials.

Intellectual Property

In July, Summit announced that the European Patent Office ( EPO ) had granted a key composition of matter patent for SMT C1100. The patent, EPO

number 1986633, will provide a period of exclusivity until 2027 and means SMT C1100 has intellectual property protection in major territories including the US and Japan.

C. difficile Infection Programme

SMT19969: Phase 2 Clinical Programme

antibiotic for the treatment of CDI that is currently being evaluated in a Phase 2 proof of concept clinical trial being conducted in the US and Canada. This trial, named CoDIFy, is a double-blind, randomised active-control trial evaluating the

efficacy of SMT19969 against the current standard of care, the antibiotic vancomycin. CoDIFy is enrolling up to 100 patients with half the patients receiving ten days of dosing with SMT19969, and the remaining patients receiving ten days of dosing

The primary endpoint of the trial is sustained clinical response, which is defined as clinical cure based on the resolution of diarrhoea

at the test of cure visit on day 12 and no recurrence of CDI within 30 days after the end of treatment. The trial will examine a number of secondary endpoints including the safety and tolerability of SMT19969, and its impact on the gut flora of

Summit expects to report top-line results from this trial in the fourth quarter of 2015.

Intellectual Property and Regulatory

received notification that the US Food and Drug Administration ( FDA ) had granted Fast Track designation to SMT19969. Fast Track designation is awarded to expedite the development and regulatory review of drugs intended to treat serious

or life-threatening conditions and that demonstrate the potential to address unmet medical needs. SMT19969 is also designated a Qualified Infectious Disease Product or QIDP under the Generating Antibiotics Incentives Now Act which allows

Summit to benefit from a number of incentives supporting the development of new antibiotics.

In April, a key patent protecting the use of SMT19969 in the

treatment of CDI was issued to Summit by the US Patent and Trademark Office. Summit believes this patent, which provides protection through until December 2029, significantly strengthens the intellectual property estate protecting the use of SMT

The development of SMT19969 is supported by a 4.0 million Wellcome Trust Translational Award through to completion of the Phase 2

proof of concept clinical trial.

Other Operating Income

Other operating income for the

three months ended 31 July 2015 was 0.4 million compared to 0.5 million for the three months ended 31 July 2014. Other operating income for the six months ended 31 July 2015 was 0.8 million compared

to 1.1 million for the six months ended 31 July 2014. Income recognised as part of the Wellcome Trust Translational Award was lower in both the three months ended 31 July 2015 and the six months ended 31 July 2015 as a

result of a lower contribution rate ascribed to Phase 2 activities as compared to Phase 1 activities under the terms of the funding agreement. The Company has received 3.9 million out of the 4.0 million awarded by the

Wellcome Trust to date. Income recognised as part of funding from Innovate UK for the DMD programme was lower in both the three months ended 31 July 2015 and the six months ended 31 July 2015, in line with the achievement of milestones to

date under the terms of the funding agreement. The Company was awarded up to 2.4 million in funding from Innovate UK and has received 1.2 million to date.

Research and Development Expenses

development expenses increased by 1.7 million to 4.2 million for the three months ended 31 July 2015 from 2.5 million for the three months ended 31 July 2014. Research and development expenses increased

by 2.4 million to 7.4 million for the six months ended 31 July 2015 from 5.0 million for the six months ended 31 July 2014. These increases reflected increased expenditure related to the Company s

CDI and DMD programme activities as well as an increase in staff related costs.

General and Administration Expenses

General and administration expenses decreased by 0.6 million to 1.0 million for the three months ended 31 July 2015 from

1.6 million for the three months ended 31 July 2014. General and administration expenses decreased by 0.4 million to 2.1 million for the six months ended 31 July 2015 from 2.5 million for the

six months ended 31 July 2014. These decreases were primarily due to the provision of 0.7 million for milestone payments owed to two US DMD patient groups as part of funding agreements recognised in July 2014, offset by costs

associated with being a publicly traded company in the US following the Company s NASDAQ listing, as well as expenses associated with the Company s US office which opened last year.

Operating Activities

Net cash outflow from operating activities increased by 1.7 million to 7.0 million for the six months ended 31 July 2015 compared

to an outflow of 5.3 million for the six months ended 31 July 2014. This was driven by an increase in operating expenses and working capital requirements, offset by the receipt in July 2015 of a 1.4 million research and

development tax credit.

Investing Activities

cash outflow from investing activities for the six months ended 31 July 2015 and inflow for the six months ended 31 July 2014 includes the net amount of bank interest received on cash deposits less amounts paid to acquire property and

Financing Activities

from financing activities for the six months ended 31 July 2015 and the six months ended 31 July 2014 relates to proceeds received from the sale of the Company s equity securities and the exercise of share options. The Company

received net proceeds of 22.1 million from the sale of equity securities including the exercise of share options during the six months ended 31 July 2015 compared with net proceeds of 20.7 million received from the sale

of equity securities during the six months ended 31 July 2014.

About Summit Therapeutics

Summit is a biopharmaceutical company focused on the discovery, development and commercialisation of novel medicines for indications for which there are no

existing or only inadequate therapies. Summit is conducting clinical programs focused on the genetic disease Duchenne muscular dystrophy and the infectious disease C. difficile infection. Further information is available at