Update on Admission

Summit Therapeutics plc

(“Summit Therapeutics” or the “Company”)

Subscription to Raise $25m

Oxford, UK, and Cambridge, MA, US, 8 January 2019 - Summit Therapeutics (AIM: SUMM, NASDAQ: SMMT), a leader in antibiotic innovation, announces that admission to AIM of the 78,125,000 new ordinary shares of one penny each in the Company (“New Ordinary Shares”) in the form of 15,625,000 American Depositary Shares in connection with the proposed subscription to raise $25 million, approved by Summit Therapeutics shareholders on 4 January 2019 (the “Subscription”), is now expected to occur on or around 9 January 2019.

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 for 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 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 Announcement about the Company’s future expectations, plans and prospects, including but not limited to, whether or not the Company will consummate the Subscription, 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 risk that the closing conditions to the Subscription are not satisfied, the ability of BARDA or CARB-X to terminate the Company’s 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 Announcement 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 Announcement.

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