Summit Therapeutics plc ( Summit or the Company ) SUMMIT THERAPEUTICS REPORTS FINANCIAL RESULTS FOR THE FISCAL YEAR ENDED 31 JANUARY 2015 Oxford, UK, 6 May 2015 Summit Therapeutics plc (AIM: SUMM, NASDAQ: SMMT), the drug

Summit Therapeutics plc

( Summit or the Company )

THERAPEUTICS REPORTS FINANCIAL RESULTS FOR THE FISCAL YEAR ENDED 31 JANUARY 2015

Oxford, UK, 6 May 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 fiscal year

ended 31 January 2015.

Dr Frank Armstrong, Non-Executive Chairman of Summit commented: It has been a year of substantial progress

that has seen Summit s lead product candidates for the treatment of DMD and CDI progress into clinical trials in patients, expansion of our operations into the United States and receipt of strong financial backing from new and existing

investors that culminated in the successful offering on NASDAQ. It is my belief that Summit is well placed to achieve a number of key clinical milestones in the coming year as we seek to establish the potential of our two programmes as potential

life-changing treatments.

DUCHENNE MUSCULAR DYSTROPHY PROGRAMME

C. DIFFICILE INFECTION PROGRAMME

OPERATIONAL HIGHLIGHTS

FINANCIAL HIGHLIGHTS

NASDAQ INITIAL PUBLIC OFFERING

Conference Call and Webcast Information

Summit will host a conference call and webcast to review the financial results for the fiscal year ended 31 January 2015 today at 1:00pm BST / 8:00am EST.

To participate in the conference call please dial +44 (0)20 7136 2055 (UK and international participants) or +1 718 354 1158 (US local number) and use the conference confirmation code 5108710. 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.

About Summit Therapeutics

Summit is a biopharmaceutical company focused on the discovery, development and commercialization 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

www.summitplc.com and Summit can be followed on Twitter (@summitplc).

For more information, please contact:

Forward Looking Statements

Any statements in this press release about our future expectations, plans and prospects, including statements about clinical development of our product

candidates, the timing of clinical results and expectations regarding the sufficiency of our cash balance to fund operating expenses and capital expenditures, and other statements containing the words anticipate, believe,

continue, could, estimate, expect, intend, may, plan, potential, predict, project, should, target,

would, and similar expressions, constitute forward-looking statements within the meaning of The Private Securities Litigation Reform Act of 1995. Actual results may differ materially from those indicated by such forward-looking

statements as a result of various important factors, including: the uncertainties inherent in the initiation of future clinical trials, availability and timing of data from ongoing and future clinical trials and the results of such trials, whether

preliminary results from a clinical trial will be predictive of the final results of that trial or whether results of early clinical trials will be indicative of the results of later clinical trials, expectations for regulatory approvals,

availability of funding sufficient for our foreseeable and unforeseeable operating expenses and capital expenditure requirements and other factors discussed in the Risk Factors section of filings that we make with the Securities and

Exchange Commission. In addition, any forward-looking statements included in this press release represent our views only as of the date of this release and should not be relied upon as representing our views as of any subsequent date. We

specifically disclaim any obligation to update any forward-looking statements included in this press release.

CHAIRMAN S STATEMENT

I am pleased to report that it has been a year of substantial progress that has seen Summit s lead product candidates progress into clinical trials in

patients, expansion of our operations into the United States and receipt of strong financial backing from investors that culminated in the successful NASDAQ initial public offering.

It is my belief that Summit is in a strong position to achieve a number of key clinical milestones in the coming year that have the potential to benefit

patients and their families, along with our shareholders.

Our novel utrophin modulation programme for the treatment of Duchenne muscular dystrophy ( DMD ) provides Summit with the opportunity to treat all

patients with this devastating muscle wasting condition. Utrophin modulation is a scientific approach that has the potential to slow or even stop progression of DMD and would be applicable to all DMD patients, regardless of the underlying genetic

faults. It would also potentially be complementary to other disease modifying approaches in development that only target small sub-sets of DMD patients.

We are seeking to capitalise on this opportunity by developing a pipeline of utrophin modulator drugs. Summit has an established leadership position in this

field of research, strengthened through our strategic alliance with the University of Oxford. This includes the research team of co-founder and scientific adviser Professor Kay Davies who pioneered utrophin modulation as a DMD treatment approach.

Our strategic ambition for the DMD programme is to independently develop a utrophin modulator drug through clinical trials and, if successful,

commercialise it ourselves in the United States and Europe. We believe this is achievable as DMD is an orphan disease with a concentrated network of clinicians and patient advocacy groups that gives us the ability to retain the commercial value of

this promising therapeutic approach.

Our lead utrophin modulator, SMT C1100, progressed into clinical trials in patients during 2014. Further clinical

data is anticipated during 2015 as we work towards commencing a Phase 2 proof of concept efficacy trial that will seek to validate the potential of utrophin modulation as a new treatment paradigm for all DMD patients. Our earlier-stage pipeline

continues to advance in parallel as we seek to identify second and future generation utrophin based therapies in order to maintain our leadership position in this research field.

Our novel antibiotic SMT19969 for the treatment of C. difficile infection ( CDI ) has the potential to address another healthcare threat that

is poorly served by current treatments. In 2014 an investigational new drug application ( IND ) in the US was opened for SMT19969. SMT19969 has progressed into a Phase 2 proof of concept trial and with enrolment and dosing on-going,

top-line data is expected to be reported in the second half of 2015. In addition, a separate open label Phase 2 trial is being undertaken that we anticipate will inform our future clinical development plans for this novel antibiotic.

Our strategic objective with SMT19969 is to maximise its commercial potential either independently or through establishing collaboration partnerships. The

board of directors will continue to evaluate the relative merits of these options and seek to provide the greatest value for patients and our shareholders.

We were pleased to complete our NASDAQ initial public offering in March 2015. The offering has provided the Company with additional funds and increased access

to a wider network of specialist healthcare investors. This new capital has enhanced our immediate ability to advance the development of our two product candidates and our earlier stage pipeline of utrophin modulators. The NASDAQ listing also

complements our listing on AIM, a market of the London Stock Exchange.

The Company expanded during the year to support the progression of our two

clinical programmes. We now have operations in the United States through our office in Cambridge, Massachusetts. This physical presence in the United States will support greater interactions with academic, clinical and business leaders in our two

areas of therapeutic development. The operations team in the UK and US continues to be strengthened to support our efforts of reaching key inflection points in our two programmes. In February 2015, the Company changed its name to Summit Therapeutics

plc. This new name directly references our sector of business and I believe will help increase our profile and marketability with investors and the wider life sciences industry.

I was pleased to welcome a number of new

faces to the Board of Directors with Mr Leopoldo Zambeletti, Ms Valerie Andrews and Mr David Wurzer joining as Non-Executive Directors. They each have a wealth of experience in the global life sciences industry and will be of great assistance as we

pursue our business strategy. In addition, Mr Jim Mellon stepped down from the Board, and I would like to thank him for his efforts during his time as a Non-Executive Director.

The Company has made good

progress and is well positioned to achieve a number of important clinical milestones over the coming year. I would like to thank all our shareholders for their continued support, which has been essential in the advancement of our two programmes. I

would also like to thank all the patients and their families, and the doctors and nurses, who have been involved in our various clinical trials. Finally, I would like to thank all our staff for their continued dedication and commitment that has

enabled the Company to progress over the last year. We are all excited about our future prospects as we look to meet the needs of patients and their families affected by two serious diseases.

Frank Armstrong, FRCPE, FFPM

Non-Executive Chairman

It has been a period of significant progress across all areas of the business. Summit s utrophin modulation programme for the treatment of Duchenne

muscular dystrophy ( DMD ) and novel antibiotic for the treatment of C. difficile infection ( CDI ) have each advanced into patient clinical trials. The Company also achieved a significant milestone following the

completion of a US initial public offering ( IPO ) of shares on NASDAQ. This IPO has strengthened the financial resources of the Company and will support its future clinical development plans as Summit seeks to exploit the promise of its

DMD and CDI programmes.

seeking to treat all boys afflicted 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 so has the potential to address the entire population of DMD patients. Summit has established a leadership position in the field of utrophin modulation. Summit is currently evaluating its

most advanced product candidate, SMT C1100, in clinical trials in DMD patients and, in parallel, Summit is also developing an earlier stage pipeline of second and future generation utrophin modulators.

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 gut flora of patients, and thereby reduce CDI recurrence rates, the key clinical issue in this disease.

Nasdaq Listing And Equity Offering

completed a US initial public offering on the NASDAQ Global Market issuing 3,967,500 American Depositary Shares ( ADSs ) at an offering price of $9.90 per ADS in March 2015. Total gross proceeds were $39.3 million ( 25.8 million).

Each ADS represents five Ordinary Shares of 1 pence each in the capital of the Company. The ADSs trade on NASDAQ under the symbol SMMT and this listing complements the listing of the Company s Ordinary Shares on AIM, a market of the

London Stock Exchange, that trade under the symbol SUMM .

The NASDAQ listing was an important strategic event for Summit. The Company believes

that it will provide greater access to the large number of specialist healthcare investors in the US, as well as increase liquidity in the trading of its shares.

The funds raised in the US IPO have strengthened the financial position of the Company and will support the on-going clinical development of its lead product

candidates, SMT C1100 and SMT19969. The additional funds will also support the parallel development of its pipeline of future generation utrophin modulators as the Company seeks to maintain its leadership position in this field of DMD research.

Duchenne Muscular Dystrophy Programme

DMD is the most common and most severe form of muscular dystrophy. The disease predominately affects males and results in the progressive wasting of

muscles throughout the body. DMD typically results in death by the time patients reach their late twenties. Patients with DMD are unable to produce dystrophin, a protein essential for maintaining healthy muscle function.

Utrophin is a naturally occurring protein that is functionally and structurally similar to dystrophin. Utrophin plays an active role in the development of new

muscle fibres, both in foetal development and in the repair of damaged muscle fibres. Utrophin production is switched off in mature muscle fibres and replaced by production of dystrophin. Utrophin modulation has the potential to maintain the

production of utrophin in all skeletal muscles, including the diaphragm, and the heart to compensate for the absence of functional dystrophin in DMD patients and so restore and maintain healthy muscle function. A key benefit of utrophin modulation

is that it is independent of the underlying genetic fault in the dystrophin gene and so has the potential to treat the entire patient population.

C1100 Clinical Trial Activities

Initial Phase 1b Clinical Trial in DMD Patients