Summit Therapeutics Announces Exercise of Over-Allotment Option

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

SUMMIT THERAPEUTICS ANNOUNCES EXERCISE OF OVER-ALLOTMENT OPTION

Oxford, UK, 18 March 2015 - Summit Therapeutics plc (NASDAQ: SMMT, AIM: SUMM), the drug discovery and development company advancing therapies for Duchenne muscular dystrophy and C. difficile infection, today announced that the underwriters of its initial public offering have exercised in full their over-allotment option to purchase an additional 517,500 American Depositary Shares ("ADSs") at the initial public offering price of $9.90 per ADS, less underwriting discounts and commissions.  After the over-allotment closing, the total number of ADSs sold by Summit in its initial public offering has increased to 3,967,500. 

All of the ADSs in the offering were sold by Summit and are trading on the NASDAQ Global Market under the ticker symbol "SMMT".  Summit's ordinary shares will continue to trade on the AIM market of the London Stock Exchange under the ticker symbol "SUMM". Each ADS represents five ordinary shares of Summit. 

Application has been made for the 2,587,500 new ordinary shares in the Company, represented by the 517,500 ADSs, to be admitted to trading on the AIM market and it is expected that dealing in these ordinary shares will commence at 8:00am GMT on 20 March 2015.  Following the close of the offering, the issued share capital of the Company will consist of 60,955,197 ordinary shares and 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 change to their interest in, the Company, under the Disclosure and Transparency Rules.

JMP Securities and Oppenheimer & Co. acted as joint book-running managers for the offering. Needham & Company acted as lead manager. 

This press release does not constitute a prospectus and does not constitute or form part of any offer or invitation to sell or issue, or the solicitation of an offer to purchase or acquire, any of the ordinary shares or ADSs or any other securities in the United States of America or in any other jurisdiction. Securities may not be offered or sold in the United States of America absent registration or an exemption from registration under the United States Securities Act of 1933, as amended (the "Securities Act").  A registration statement relating to these securities was declared effective by the United States Securities and Exchange Commission on 4 March 2015. 

The public offering of securities in the United States has been made only by means of a prospectus. Such prospectus contains detailed information about the issuer and its management and financial statements. Copies of the final prospectus relating to this offering may be obtained from JMP Securities LLC, Prospectus Department, 600 Montgomery Street, 10th Floor, San Francisco, CA 94111, telephone: +1 (415) 835-8985; from Oppenheimer & Co. Inc., Syndicate Prospectus Department, 85 Broad Street, 26th Floor, New York, NY 10004, telephone: +1 (212) 667-8563 and from Needham & Company, LLC, Prospectus Department, 445 Park Avenue, 4th floor, New York, NY 10022, telephone: +1 (800) 903-3268.

This press release is being issued pursuant to and in accordance with Rule 135e under the Securities Act.

For readers in the United Kingdom
This communication, in so far as it constitutes an invitation or inducement to enter into investment activity (within the meaning of s21 Financial Services and Markets Act 2000 as amended ("FSMA")) in connection with the securities which are the subject of the offering described in this press release or otherwise, is being directed only at (i) persons who are outside the United Kingdom and to whom such invitation or inducement may be lawfully addressed or (ii) persons who have professional experience in matters relating to investments who fall within Article 19(5) ("Investment professionals") of the Financial Services and Markets Act 2000 (Financial Promotion) Order 2005 (the "Order") or (iii) certain high value persons and entities who fall within Article 49(2)(a) to (d) ("High net worth companies, unincorporated associations etc") of the Order; or (iv) any other person to whom it may lawfully be communicated (all such persons in (i) to (iv) together being referred to as "relevant persons"). The ADSs will only be available to, and any invitation, offer or agreement to subscribe, purchase or otherwise acquire such ADSs will be engaged in only with, relevant persons. Any person who is not a relevant person should not act or rely on this document or any of its contents. This communication does not contain an offer or constitute any part of an offer to the public within the meaning of ss85 and 102B of FSMA or otherwise.

For readers in the European Union ('EU')
In any EU Member State that has implemented the Prospectus Directive, this communication is only addressed to and directed at qualified investors in that Member State within the meaning of the Prospectus Directive. The term "Prospectus Directive" means Directive 2003/71/EC (and amendments thereto, including Directive 2010/73/EU, to the extent implemented in each relevant Member State), together with any relevant implementing measure in the relevant Member State.

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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.

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