UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 6-K

REPORT OF FOREIGN PRIVATE ISSUER

PURSUANT TO RULE 13a-16 OR 15d-16

OF THE SECURITIES EXCHANGE ACT OF 1934

For the month of June 2015

Commission File Number 001-36866

SUMMIT THERAPEUTICS PLC

(Translation of registrant’s name into English)

85b Park Drive

Milton Park, Abingdon

Oxfordshire OX14 4RY

United Kingdom

(Address of principal executive office)

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F:

FORM 20-F  x            FORM 40-F  ¨

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1):  ¨

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7):  ¨

Indicate by check mark whether the registrant by furnishing the information contained in this form is also thereby furnishing the information to the Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934:

YES  ¨            NO   x

If “Yes” is marked, indicate below the file number assigned to the registrant in connection with Rule 12g3-2(b):

On June 22, 2015, Summit Therapeutics plc (the “Company”) announced details of purchases of the Company’s American Depositary Shares (“ADSs”) by Mr David Wurzer, a Non-Executive Director of the Company. The press release is attached hereto as Exhibit 99.1 and incorporated by reference herein.

The information contained in Exhibits 99.1 shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such a filing.

2

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

	SUMMIT THERAPEUTICS PLC
By:	/s/ Erik Ostrowski
	Erik Ostrowski
	Chief Financial Officer

Date: June 23, 2015

EXHIBIT INDEX

Exhibit Number	Description
99.1	Press Release dated June 22, 2015 regarding ADS purchases