Summit Therapeutics Inc.

CERTIFICATE OF AMENDMENT

TO THE

RESTATED CERTIFICATE OF INCORPORATION

OF

Pursuant to Section 242 of the

General Corporation Law of the State of Delaware

Summit Therapeutics Inc. (the “Corporation”), a corporation organized and existing under and by virtue of the General Corporation Law of the State of Delaware, does hereby certify as follows:

1. A resolution was duly adopted by the Board of Directors (the “Board”) of the Corporation pursuant to Section 242 of the General Corporation Law of the State of Delaware setting forth an amendment to the Restated Certificate of Incorporation of the Corporation, dated September 18, 2020, as amended by that Amendment to the Restated Certificate of Incorporation, dated July 27, 2022 and as further amended by that Amendment No. 2 to Restated Certificate of Incorporation, dated January 19, 2023 (the “Restated Certificate”)and declaring said amendment to be advisable. The stockholders of the Corporation duly approved said proposed amendment at a special meeting of the stockholders called and held on November 4, 2026, upon notice in accordance with Section 222 of the General Corporation Law of the State of Delaware, by voting the necessary number of shares as required by statute in favor of such amendment. The resolution setting forth the amendment is as follows:

RESOLVED, that the first paragraph of Article FOURTH of the Restated Certificate be deleted in its entirety and replaced with the following language:

“FOURTH: The total number of shares of all classes of capital stock that the Corporation shall have authority to issue is 2,020,000,000 shares, consisting of (i) 2,000,000,000 shares of Common stock, $0.01 par value per share (the “Common Stock”), and (ii) 20,000,000 shares of Preferred stock, $0.01 par value per share (the “Preferred Stock”).”

2. This Certificate of Amendment shall become effective upon filing with the Secretary of State of the State of Delaware.

IN WITNESS WHEREOF, this Certificate of Amendment has been executed by a duly authorized officer of the Corporation on this day of , 2026.

SUMMIT THERAPEUTICS INC.

By:

Name:

Title:

SUMMIT THERAPEUTICS INC.

601 BRICKELL KEY DRIVE, SUITE 1000

MIAMI, FL 33131

VOTE BY INTERNET

Before The Meeting - Go to www.proxyvote.com or scan the QR Barcode above

Use the Internet to transmit your voting instructions and for electronic delivery of information up until 11:59 P.M. Eastern Time on November 3, 2026. Have your proxy card in hand when you access the website and follow the instructions to obtain your records and to create an electronic voting instruction form.

During The Meeting - Go to www.virtualshareholdermeeting.com/SMMT2026SM

You may attend the meeting via the Internet and vote during the meeting. Have the information that is printed in the box marked by the arrow available and follow the instructions.

ELECTRONIC DELIVERY OF FUTURE STOCKHOLDER COMMUNICATIONS

If you would like to reduce the costs incurred by Summit Therapeutics Inc. in mailing proxy materials, you can consent to receiving all future proxy statements, proxy cards and annual reports electronically via e-mail or the Internet. To sign up for electronic delivery, please follow the instructions above to vote using the Internet and, when prompted, indicate that you agree to receive or access stockholder communications electronically in future years.

VOTE BY PHONE - 1-800-690-6903

Use any touch-tone telephone to transmit your voting instructions up until 11:59 P.M. Eastern Time on November 3, 2026. Have your proxy card in hand when you call and then follow the instructions.

VOTE BY MAIL

Mark, sign and date your proxy card and return it in the postage-paid envelope we have provided or return it to Summit Therapeutics Inc., c/o Broadridge, 51 Mercedes Way, Edgewood, NY 11717.

TO VOTE, MARK BLOCKS BELOW IN BLUE OR BLACK INK AS FOLLOWS:

T04503-S50999

KEEP THIS PORTION FOR YOUR RECORDS

THIS PROXY CARD IS VALID ONLY WHEN SIGNED AND DATED.

DETACH AND RETURN THIS PORTION ONLY

SUMMIT THERAPEUTICS INC.

THE BOARD OF DIRECTORS RECOMMENDS A VOTE “FOR” ITEM 1

Vote on Proposal

For Against Abstain

1. To approve an amendment to the Company’s Restated Certificate of Incorporation to increase the number of authorized shares of common stock by 1,000,000,000 (from 1,000,000,000 to 2,000,000,000).

The shares represented by this proxy when properly executed will be voted in the manner directed herein by the undersigned stockholder(s). If no direction is made, this proxy will be voted “FOR” Item 1 in accordance with the recommendation of the Company’s Board of Directors. The proxies are also authorized to vote upon such other matters as may properly come before the Special Meeting or any adjournment or postponement thereof in accordance with their discretion.

Please sign your name exactly as it appears hereon. When signing as attorney, executor, administrator, trustee or guardian, please add your title as such. When signing as joint tenants, all parties in the joint tenancy must sign. If a signer is a corporation or partnership, please sign in full corporate or partnership name by duly authorized officer.

Signature [PLEASE SIGN WITHIN BOX] Date

Signature (Joint Owners) Date

Important Notice Regarding the Availability of Proxy Materials for the Special Meeting:

The Proxy Statement is available at www.proxyvote.com.

T04504-S50999

SUMMIT THERAPEUTICS INC. SPECIAL MEETING OF STOCKHOLDERS

THIS PROXY IS SOLICITED BY THE BOARD OF DIRECTORS

The stockholder(s) hereby appoint(s) Robert W. Duggan, Mahkam Zanganeh and Manmeet S. Soni, or either of them, as proxies, each with the power to appoint his or her substitute, and hereby authorize(s) them to represent and to vote, as designated on the reverse side of this ballot, all of the shares of Common Stock of Summit Therapeutics Inc. that the stockholder(s) is/are entitled to vote at the Special Meeting of Stockholders to be held at 11:00 a.m. Eastern Time on November 4, 2026, to be conducted virtually via live webcast at www.virtualshareholdermeeting.com/SMMT2026SM, and any adjournment or postponement thereof.

THIS PROXY, WHEN PROPERLY EXECUTED, WILL BE VOTED AS DIRECTED BY THE STOCKHOLDER(S). IF NO SUCH DIRECTIONS ARE MADE, THIS PROXY WILL BE VOTED “FOR” ITEM 1; AND AT THE DISCRETION OF THE PROXY HOLDERS WITH REGARD TO ANY OTHER MATTER THAT MAY PROPERLY COME BEFORE THE MEETING OR ANY ADJOURNMENT OR POSTPONEMENT THEREOF.

PLEASE MARK, SIGN, DATE AND RETURN THIS PROXY CARD PROMPTLY USING THE ENCLOSED REPLY ENVELOPE.

CONTINUED AND TO BE SIGNED ON REVERSE SIDE