Successful Completion of Preclinical Development Studies in Summit Corporation’s C. Difficile Program

Oxford, UK, 4 April 2012, Summit (AIM: SUMM), a UK drug discovery company, today announces that is has successfully completed formal preclinical development studies on its drug candidate, SMT 19969, which is being developed as a new antibiotic to treat infections caused by the hospital ‘superbug’, Clostridium difficile (‘C. difficile’). On the basis of these preclinical data, Summit intends to seek regulatory approval to progress SMT 19969 into human clinical trials.

Clostridium difficile infection (‘CDI’) represents a serious medical issue in both hospitals and long-term care homes and increasingly in the wider community. In Europe and North America, the annual cost of care is estimated to be over $7 billion. Existing treatment options are limited and do not address the major issues of recurrent disease or the established and emerging hyper-virulent strains of C. difficile. The disease can prove fatal with over 2,700 deaths due to CDI being reported in the UK in 2010.

SMT 19969 is a novel antibiotic with an exceptionally narrow spectrum of activity that has the potential to reduce rates of recurrent disease and become the front-line treatment for CDI. Summit nominated SMT 19969 to enter formal preclinical development in May 2011 and the successful completion of these studies is another significant milestone for the programme. Preclinical development studies are designed to assess if drug candidates meet the requisite safety profile for evaluation in clinical trials in human subjects. The results of these studies showed that SMT 19969 has an excellent safety profile and support preparation of a Clinical Trial Application (‘CTA’) to seek approval from the Medicines and Healthcare Products Regulatory Authority (‘MHRA’) for entry into human clinical trials.

The development of SMT 19969 through preclinical development has been supported by a prestigious Seeding Drug Discovery Award from the Wellcome Trust.

Richard Storer, DPhil, Chief Scientific Officer of Summit commented: “Our C. difficile programme continues to make excellent progress as illustrated by the successful completion of formal preclinical development of our lead candidate SMT 19969. C. difficile infection is a serious healthcare threat and we believe that SMT 19969 has the ideal profile to address the key clinical issues and to become the front-line antibiotic for the treatment of this disease. We are excited about the prospects for SMT 19969 and look forward to advancing this programme into human clinical trials.”

For more information, please contact:

Summit

Barry Price, PhD / Glyn Edwards / Richard Pye, PhD

Tel: +44 (0)1235 443 939

Singer Capital Markets

(Nominated Adviser and Joint broker)

Shaun Dobson / Claes Spång

Tel: +44 (0)203 205 7500

Hybridan LLP

(Joint broker)

Claire Louise Noyce / Deepak Reddy

Tel: +44 (0)207 947 4350

Peckwater PR

(Financial public relations)

Tarquin Edwards

Tel: +44 (0)7879 458 364

tarquin.edwards@peckwaterpr.co.uk

About C. difficile infection

Clostridium difficile infection (‘CDI’) is a significant healthcare issue in hospitals, long-term care homes and there is growing concern about its spread to the wider community. It is a serious illness caused by infection of the inner lining of the colon by the C. difficile bacteria, which produces toxins that cause inflammation of the colon, severe diarrhoea and, in the most serious cases, death.

Patients typically develop CDI following the use of broad-spectrum antibiotics (e.g. cephalosporins and fluoroquinolones) that disrupt the normal gastrointestinal (gut) flora and so allow C. difficile bacteria to flourish. Broad spectrum antibiotics are associated with recurrent disease which represents the major clinical issue in treating CDI because repeat episodes of infection are often more severe. The severity of the disease is also increasing due to infection from hyper-virulent strains such as BI/NAP1/027. The limited treatment options currently available are failing to address these clinical challenges.

About SMT 19969

SMT 19969 is a small molecule, novel antibiotic that is being developed for the treatment of Clostridium difficile infection (‘CDI’). Results from in vivo and in vitro non-clinical efficacy studies have shown that SMT 19969 has an superior profile compared to antibiotics that are currently on the market to treat CDI. The molecule combines potent activity against C. difficile, including hyper- virulent, endemic and emerging strains, with exceptionally high levels of antibacterial selectivity. This selectivity results in a lack of disruption to the healthy gut bacteria and this is important in naturally preventing recurrence of CDI to improve the prognosis for patients. In addition, SMT 19969 is targeted exclusively to the site of infection by being retained in the GI tract. Also it shows exceptionally low levels of resistance development and has an excellent safety profile.

About Summit

Summit is an Oxford, UK based drug discovery Company with an innovative Seglin™ technology platform for the discovery of new medicines and a portfolio of drug programme assets. Summit’s programme portfolio consists of a number of drug programmes targeting high-value areas of unmet medical need including Duchenne Muscular Dystrophy and C. difficile infection. Summit is listed on the AIM market of the London Stock Exchange and trades under the ticker symbol SUMM. Further information is available at www.summitplc.com.

About The Wellcome Trust

The Wellcome Trust is a global charitable foundation dedicated to achieving extraordinary improvements in human and animal health. It supports the brightest minds in biomedical research and the medical humanities. The Trust’s breadth of support includes public engagement, education and the application of research to improve health. It is independent of both political and commercial interests. www.wellcome.ac.uk

Forward Looking Statements

This document contains “forward-looking statements” within the meaning of the U.S. Private Securities Litigation Reform Act of 1995. Forward-looking statements can be identified by words such as “anticipates”, “intends”, “plans”, “seeks”, “believes”, “estimates”, “expects” and similar references to future periods, or by the inclusion of forecasts or projections. Forward-looking statements are based on the Company’s current expectations and assumptions regarding our business, the economy and other future conditions. Because forward-looking statements relate to the future, by their nature, they are subject to inherent uncertainties, risks and changes in circumstances that are difficult to predict. The Company’s actual results may differ materially from those contemplated by the forward-looking statements. The Company cautions you therefore that you should not rely on any of these forward-looking statements as statements of historical fact or as guarantees or assurances of future performance. Important factors that could cause actual results to differ materially from those in the forward-looking statements and regional, national, global political, economic, business, competitive, market and regulatory conditions.

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