SEC Form SC 13D/A filed by Summit Therapeutics Inc. (Amendment)

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

(Rule 13d-101)

INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT

TO § 240.13d-1(a) AND AMENDMENTS THERETO FILED PURSUANT TO

§ 240.13d-2(a)

(Amendment No. 8)¹

Summit Therapeutics Inc.

(Name of Issuer)

Common Stock, par value $0.01 per share

(Title of Class of Securities)

86627T108

(CUSIP Number)

ADAM W. FINERMAN, ESQ.

BAKER HOSTETLER LLP

45 Rockefeller Plaza

New York, New York 10111

(212) 589-4233

(Name, Address and Telephone Number of Person

Authorized to Receive Notices and Communications)

February 7, 2023

(Date of Event Which Requires Filing of This Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box ¨.

Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See § 240.13d-7 for other parties to whom copies are to be sent.

¹ The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

CUSIP No. 86627T108

* The 175,864,281 shares of Common Stock beneficially owned consist of (i) 162,532,792 shares of Common Stock previously owned by the Reporting Person, (ii) 9,346,434 shares of Common Stock, representing the number of shares of Common Stock issued to the Reporting Person as payment of interest in connection with the NPA (as defined below) and (iii) includes the exercise of warrants to buy 3,985,055 shares of Common Stock, which are exercisable until December 24, 2029.

CUSIP No. 86627T108

The following constitutes the Schedule 13D/A filed by the undersigned (as amended hereby, the “Schedule 13D”).

Item 5(a) is hereby amended and restated to read as follows:

The aggregate percentage of Common Stock reported owned by the Reporting Person is based on 221,241,725 shares of Common Stock outstanding as of February 6, 2023, which is the total number of shares of Common Stock disclosed by the Issuer in the Issuer’s Prospectus filed with the Securities and Exchange Commission on February 7, 2023.

Percentage: Approximately 78.1%.

CUSIP No. 86627T108

SIGNATURES

After reasonable inquiry and to the best of his knowledge and belief, the undersigned certifies that the information set forth in this statement is true, complete and correct.

Dated: February 16, 2023