SMMT Summit Therapeutics Inc

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

UNDER THE SECURITIES EXCHANGE ACT OF 1934

For the month of January 2020.

Commission File Number 001-36866

SUMMIT THERAPEUTICS PLC

(Translation of registrant’s name into English)

136a Eastern Avenue

Milton Park, Abingdon

Oxfordshire OX14 4SB

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  ☒            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):  ☐

On January 23, 2020, Summit Therapeutics plc (the “Company”) issued a press release announcing the expansion by the Biomedical Advanced Research and Development Authority (“BARDA”), a division of the U.S. Department of Health and Human Services, Office of the Assistant Secretary for Preparedness and Response, of its award to the Company for the clinical and regulatory development of ridinilazole, the Company’s product candidate for the treatment of C. difficile infection. The related press release is attached hereto as Exhibit 99.1.

This Report on Form 6-K, including Exhibit 99.1, is hereby incorporated by reference into the Company’s Registration Statement on Form F-3 (File No. 333-232074).