Summit Therapeutics plc ( Summit or the Company ) SUMMIT THERAPEUTICS REPORTS FINANCIAL RESULTS FOR THE FOURTH QUARTER AND FISCAL YEAR ENDED 31 JANUARY 2016 Oxford, UK, 10 May 2016 Summit Therapeutics plc (AIM: SUMM, NAS

Summit Therapeutics plc

( Summit or the Company )

THERAPEUTICS REPORTS FINANCIAL RESULTS FOR THE FOURTH QUARTER AND FISCAL YEAR ENDED 31 JANUARY 2016

Oxford, UK, 10 May 2016 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 fourth quarter and fiscal year ended 31 January 2016.

Mr Glyn Edwards, Chief Executive Officer of Summit commented:

Summit s substantial clinical accomplishments over the past year have contributed to great momentum in both our DMD and CDI programmes. Notably, the successful completion of a Phase 1b trial in DMD will enable ezutromid to advance into a

Phase 2 proof of concept trial and a Phase 2 trial in CDI demonstrated statistical superiority of ridinilazole over standard of care, positioning ridinilazole as a highly promising asset in the treatment of CDI. We now look forward to what could be

a pivotal year ahead with the first look at potential proof of mechanism for ezutromid in DMD boys, and exploring a potential partnership for ridinilazole.

Utrophin Modulation Programme for DMD

Ezutromid (formerly SMT C1100) Highlights

Utrophin Modulator Pipeline: Future Generation Development

Ridinilazole (formerly

SMT19969) Highlights

Financial Highlights

Conference Call and Webcast Information

a conference call and webcast to review the financial results for the fiscal year ended 31 January 2016 today at 1:00pm BST / 8:00am EST. To participate in the conference call please dial +44 (0)20 3427 1916 (UK and international participants)

or +1 718 354 1152 (US local number) and use the conference confirmation code 2246763. 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 and commercialisation

of our product candidates, the timing of clinical results, potential third-party collaborations 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

The past year has been one of

substantial momentum for Summit in which a number of important milestones across the business have been achieved. This commenced with our successful NASDAQ initial public offering, was followed by positive clinical data in our Duchenne muscular

dystrophy ( DMD ) programme that has enabled it to progress into Phase 2 trials, and culminated in the reporting of proof of concept Phase 2 clinical data for our novel C. difficile infection ( CDI ) antibiotic.

These milestones pave the way for another exciting year to come, which is expected to feature our much anticipated first look at proof of mechanism data in

DMD and selecting a partner for Phase 3 clinical development and commercialisation to maximise the potential of our CDI antibiotic. I believe that the coming period could be a transformational year for Summit, the patients and families affected by

these two serious diseases, and our shareholders.

In DMD, we aim to treat all patients with our unique orally administered utrophin modulation approach. Utrophin is a naturally occurring protein that is

structurally and functionally similar to dystrophin, the protein which is lacking in those with DMD. Utrophin modulation has the potential to slow or stop the progression of DMD for the entire patient population, which distinguishes it from many

other treatments in development for this muscle wasting condition.

The roots of the utrophin modulation programme lie with our co-founder, Prof Kay

Davies, at the University of Oxford, who discovered utrophin and conducted the seminal work to unlock the potential of utrophin modulation as a universal treatment of DMD. Summit is focused on maintaining the Company s leadership position in

utrophin modulation, and accordingly we are committed to building a strong pipeline of utrophin modulators.

Our lead utrophin modulator, ezutromid,

successfully completed a Phase 1b clinical trial in boys with DMD in 2015. Based on the positive results from this trial, we are poised to start a Phase 2 proof of concept trial called PhaseOut DMD. This trial aims to assess the effect of ezutromid

on muscle health, function and utrophin levels and we look forward to reporting data as this trial progresses.

Simultaneously, we continue to develop our

utrophin modulator pipeline, as we seek to maximise the therapeutic promise of utrophin modulation over the long term. As such, we recently strengthened our strategic alliance with the University of Oxford by extending the term of the alliance until

November 2019. Supportive of the extension of this collaboration, we achieved the first research milestone in December 2015 by selecting two series of utrophin molecules to move into lead

optimisation studies.

We are very excited about the progress made in 2015 in our utrophin modulator programme and are equally excited about our

activities related to its future development. Our strategy is focussed on independently developing these utrophin modulators through clinical trials, and if successful, commercialising them ourselves in Europe and in the United States. We believe

this is achievable as DMD is an orphan disease with a concentrated network of physicians and patient groups that gives us the ability to retain the commercial value of this promising therapeutic approach.

In CDI, our novel antibiotic, ridinilazole, continues to impress. We were pleased to report excellent top-line Phase 2 clinical trial results, which have

enhanced our belief in the promise of ridinilazole as a new therapeutic approach capable of not only treating the initial CDI infection, but also reducing the high rates of recurrent disease experienced in CDI. In this trial, ridinilazole

demonstrated a large numerical reduction in rates of recurrent disease over the standard of care, vancomycin. We believe this was a result of this highly selective antibiotic s ability to preserve a patient s gut microbiome which plays a

vital role in protecting against CDI.

With these data, we believe ridinilazole offers a clear advantage over conventional broad spectrum antibiotics used

to treat CDI. While continuing to explore all options, our preferred path forward for ridinilazole is to seek a partner for Phase 3 development and commercialisation. We will consider a number of factors as we seek to select a partner who we believe

will maximise ridinilazole s potential for patients and our shareholders.

Operationally, we strengthened our business across several fronts. We achieved a major milestone in March 2015, when we successfully completed our NASDAQ

initial public offering, which strengthened our cash position and broadened our access to a wider network of specialist healthcare investors. This listing complements our existing listing on AIM, a market of the London Stock Exchange.

We are also building on and strengthening our team as clinical programmes continue to progress. This included the appointment of rare disease drug development

expert and paediatrician, Dr Ralf Rosskamp, as our Chief Medical Officer in September. His expertise brings great value to our team as we embark on mid-stage clinical trials with our utrophin modulator programme. In addition, we have added valued

members to our teams to support our clinical and preclinical activities. I believe these additions will help Summit to succeed in reaching its planned milestones.

We were pleased to welcome Mr David Wurzer,

who is a seasoned biotechnology and pharmaceutical executive, to our Board as a Non-Executive Director in February 2015. David s financial background is helping to ensure the board has the right composition to fulfil its regulatory obligations

as a dual-listed company.

In summary, Summit s strong progress in 2015 has brought us one step closer to being able to make a meaningful impact on the lives of patients and

families affected by DMD and CDI. We have entered another potentially pivotal year, where we hope to see the first signs of proof of mechanism for ezutromid and utrophin modulation.

I would like to thank all of our shareholders for their continued support. I also want to extend my sincerest

gratitude to our patients and their families, and the nurses and doctors who have been involved in our clinical trials. We would not be where we are without their commitment. Finally, I would like to thank the Summit team for the hard work and

dedication over the past year that has brought us to this exciting stage in Summit s development.

We look forward to updating you on our quest to

advance the current state of care in DMD and CDI.

Frank Armstrong, FRCPE, FFPM

Non-Executive Chairman

The period under review has shown 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 successfully completed patient clinical trials. The Company also achieved a significant milestone

following the completion of a United States ( US ) initial public offering ( IPO ) of shares on NASDAQ.

Summit is seeking to treat all patients affected with the fatal disorder DMD using its utrophin modulation technology. Summit is also advancing a highly

selective antibiotic to treat CDI.

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

dystrophin gene that cause the disease. Therefore, this approach has the potential to benefit the entire patient population. Summit has established a leadership position in the field of utrophin modulation and is developing a pipeline of first-,

second- and future-generation product candidates. Summit expects to commence enrolment of patients into a Phase 2 proof of concept trial evaluating its lead utrophin modulator, ezutromid during the second quarter of 2016 following the successful

completion of a Phase 1b modified diet clinical trial in patients with DMD.

Summit s CDI therapy is ridinilazole, a novel class antibiotic that has

the potential to treat the initial infection and reduce recurrent disease, the key clinical issue in CDI. In the recent Phase 2 proof of concept clinical trial, ridinilazole achieved statistical superiority in sustained clinical response over the

antibiotic vancomycin, the current standard of care in CDI. Ridinilazole is now being prepared for Phase 3 clinical trials.

Dystrophy: Utrophin Modulation 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, and 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 in the case of a healthy individual, replaced by the 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