Summit Therapeutics: Exercise Of Share Options

Summit Therapeutics plc
("Summit" or the "Company")

EXERCISE OF SHARE OPTIONS

Oxford, UK, 29 September 2017 - Summit Therapeutics plc (AIM: SUMM, NASDAQ: SMMT), the drug discovery and development company advancing therapies for Duchenne muscular dystrophy and C. difficile infection, announces that, following the exercise of employee share options, the Company has issued 94,425 new ordinary shares of 1p each (the "New Ordinary Shares").

Application will be made for the admission to trading on AIM of the New Ordinary Shares, which will rank pari passu with the Company's existing ordinary shares, and admission is expected to occur on or around 6 October 2017.

Following admission of the New Ordinary Shares to trading on AIM, the total number of ordinary shares with voting rights in issue will 70,443,833. This figure may be used by shareholders as the denominator for the calculations by which they will determine if they are required to notify their interest in, or a change to their interest in, the Company under the FCA's Disclosure and Transparency Rules.

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

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