Summit Therapeutics Reports Financial Results for the Fourth Quarter and Fiscal Year Ended 31 January 2019 and Operational Progress

Oxford, UK, and Cambridge, MA, US, 27 March 2019 - Summit Therapeutics plc (NASDAQ: SMMT, AIM: SUMM), a leader in new mechanism antibiotic innovation, today reports its financial results for the fourth quarter and fiscal year ended 31 January 2019 and provides an update on its operational progress.

“The initiation of our global Phase 3 clinical trials of ridinilazole brings us closer to becoming a fully-integrated antibiotics company. Our capabilities span discovery through late-stage clinical development with an eye towards building a focussed commercial team,” said Mr Glyn Edwards, Chief Executive Officer of Summit. “We believe our differentiated portfolio alongside our development plans aimed at demonstrating meaningful benefits to patients, physicians and payors have the potential to counter the current trends in the antibiotic sector.

“Ridinilazole has already shown clinical superiority against the standard of care in a Phase 2 clinical trial for C. difficile infection. If we were to achieve similar results in the ongoing Phase 3 clinical trials, we believe that would provide us with a compelling data package supporting the front-line use of ridinilazole in C. difficile infection. With approximately one third of patients with CDI currently experiencing unsatisfactory outcomes with the standard of care, ridinilazole has the potential to significantly improve patient outcomes.

“Further back in our pipeline are important programmes addressing other high priority targets of gonorrhoea and the ESKAPE pathogens. The unmet need here is clear, as antimicrobial resistance is having a major impact on the ability of patients to achieve cures. Our programmes aim to provide a potential treatment option that is potent across non-resistant and resistant infections due to their new mechanisms of action. Together, our pipeline comprises new mechanism antibiotics that are being developed to be the most appropriate antibiotic for the patient in question, which would support good antibiotic stewardship and potentially reduce the threat of antimicrobial resistance.”

Programme Highlights

Antibiotics Focussed Strategy

• Summit is focussed on the development of new antibiotics that will meaningfully improve patient outcomes.

• Strategy realigned after the discontinuation of ezutromid for the treatment of Duchenne muscular dystrophy in June 2018 following the report of top-line data from the Phase 2 proof of concept clinical trial, where ezutromid missed its primary and secondary endpoints.

Ridinilazole for C. difficile Infection (‘CDI’)

• Phase 3 clinical trials of ridinilazole initiated in February 2019. The trials are expected to support the front-line use of ridinilazole for the treatment of CDI. The primary endpoint for both Phase 3 clinical trials tests for superiority of ridinilazole compared to the standard of care in the treatment of CDI. Additional endpoints include ridinilazole’s impact on reducing disease recurrence and in preserving the gut microbiome, as well as health economic outcomes measures that are intended to help support commercialisation efforts.

• $12 million option exercised by BARDA in August 2018 under existing contract to support clinical and regulatory development of ridinilazole, bringing total committed BARDA non-dilutive funding to $44 million.

• PLOS One publication highlighted microbiome-preserving activity of ridinilazole over standard of care in the CoDIFy Phase 2 clinical trial.

SMT-571 for Gonorrhoea

• SMT-571 nominated to progress into IND-enabling studies for the treatment of gonorrhoea in September 2018.

• Preclinical data presented at various conferences highlighted SMT-571 as a selective and potent antibiotic with characteristics that could support its front-line use. Further data published in Journal of Antimicrobial Chemotherapy showed SMT-571 had consistently high potency across over 200 clinically relevant strains of N. gonorrhoeae, including numerous multi- and extensively-drug resistant strains.

• Up to $4.5 million of non-dilutive funding awarded by CARB-X in July 2018 to support the preclinical and Phase 1 clinical development of SMT-571.

ESKAPE Programme

• Novel targets against ESKAPE pathogens identified using the Discuva Platform.

• Discovery further highlights the power of Summit’s proprietary Discuva Platform as a potential source of new mechanism antibiotics to treat serious infectious diseases.

Financial Highlights

• Net proceeds of $24.4 million (£19.2 million) received from the sale of American Depositary Shares in a private placement that completed in January 2019.

• Profit for the year ended 31 January 2019 of £7.5 million compared to a loss of £20.2 million for the year ended 31 January 2018.

• Cash and cash equivalents at 31 January 2019 of £26.9 million compared to £20.1 million at 31 January 2018.

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 2019 today at 12:00pm GMT / 8:00am EDT. To participate in the conference call, please dial +44 (0)844 5718 892 (UK and international participants) or +1 631 510 7495 (US local number) and use the conference confirmation code 3179239. 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 Therapeutics is a leader in antibiotic innovation. Our new mechanism antibiotics are designed to become the new standards of care for the benefit of patients and create value for payors and healthcare providers. We are currently developing new mechanism antibiotics to treat infections caused by C. difficile, N. gonorrhoeae and ESKAPE pathogens and are using our proprietary Discuva Platform to expand our pipeline. For more information, visit www.summitplc.com and follow us on Twitter @summitplc.

This announcement contains inside information for the purposes of Article 7 of EU Regulation 596/2014 (MAR).

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Forward Looking Statements

Any statements in this press release about the Company’s future expectations, plans and prospects, including but not limited to, statements about the potential benefits and future operation of the BARDA or CARB-X contract, including any potential future payments thereunder, the clinical and preclinical development of the Company’s product candidates, the therapeutic potential of the Company’s product candidates, the potential of the Discuva Platform, the potential commercialisation of the Company’s product candidates, the sufficiency of the Company’s cash resources, the timing of initiation, completion and availability of data from clinical trials, the potential submission of applications for marketing approvals 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 ability of BARDA or CARB-X to terminate our contract for convenience at any time, 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 or preclinical studies will be indicative of the results of later clinical trials, expectations for regulatory approvals, laws and regulations affecting government contracts, availability of funding sufficient for the Company’s foreseeable and unforeseeable operating expenses and capital expenditure requirements and other factors discussed in the “Risk Factors” section of filings that the Company makes with the Securities and Exchange Commission, including the Company’s Annual Report on Form 20-F for the fiscal year ended 31 January 2018. Accordingly, readers should not place undue reliance on forward-looking statements or information. In addition, any forward-looking statements included in this press release represent the Company’s views only as of the date of this release and should not be relied upon as representing the Company’s views as of any subsequent date. The Company specifically disclaims any obligation to update any forward-looking statements included in this press release.