Summit Therapeutics Inc. (Form: 8-K, Received: 07/18/2022 16:18:55)

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of The Securities Exchange Act of 1934

Date of Report (Date of Earliest Event Reported): July 18, 2022


Summit Therapeutics Inc.
(Exact Name of Registrant as Specified in Its Charter)

Delaware	001-36866	37-1979717
(State or Other Jurisdiction of Incorporation)	(Commission File Number)	(IRS Employer Identification No.)

2882 Sand Hill Road, Suite 106, Menlo Park, CA		94025
(Address of Principal Executive Offices)		(Zip Code)

Registrant’s Telephone Number, Including Area Code: 617-514-7149


Not applicable
(Former Name or Former Address, If Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:


Title of Each Class	Trading Symbol(s)	Name of Each Exchange on Which Registered
Common stock, $0.01 par value per share	SMMT	The Nasdaq Stock Market LLC

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐


Item 8.01			Other Events.

On July 18, 2022, Summit Therapeutics Inc. (the “Company”) issued a press release announcing the commencement of its previously-announced rights offering pursuant to a shelf registration statement filed on Form S-3 (File No. 333-249316) (the “Registration Statement”) with the Securities and Exchange Commission, which was declared effective October 15, 2020, and the prospectus supplement relating to the rights offering filed with the SEC on July 18, 2022 (the prospectus supplement together with the accompanying prospectus, the “Prospectus”).

In connection with the rights offering, the Company is filing certain ancillary documents as Exhibits 4.1, 99.1, 99.2, 99.3, 99.4, 99.5, 99.6, and 99.7 to this Current Report on Form 8-K for the purpose of incorporating such items by reference to the Registration Statement, of which the Prospectus forms a part. The Company is also filing as Exhibit 5.1 the opinion of Baker & Hostetler LLP in connection with the issuance of the subscription rights and the shares of the Company’s common stock, par value $0.01 per share (“Common Stock”), issuable upon exercise of such subscription rights.

This Current Report on Form 8-K does not constitute an offer to sell or the solicitation of an offer to buy the securities described herein, nor will there be any sale of such securities in any state or other jurisdiction in which such offer, solicitation, or sale would be unlawful prior to registration or qualification under the securities laws of any such state or jurisdiction. The rights offering will be made only by means of the Prospectus, copies of which will be mailed to all record holders entitled to participate in the rights offering, and can be accessed through the SEC’s website at www.sec.gov. A copy of the Prospectus may also be obtained by contacting the information agent for the rights offering, Broadridge Corporate Issuer Solutions, Inc., at (855) 793-5068.

A copy of the press release related to the matters set forth herein is attached hereto as Exhibit 99.7 and is incorporated herein by reference.


Item 9.01			Financial Statements and Exhibits.

(d) Exhibits


Exhibit Number			Description
4.1			Form of Subscription Rights Certificate
5.1			Legal Opinion of Baker & Hostetler LLP
23.2			Consent of Baker & Hostetler LLP (included in Exhibit 5.1 hereto)
99.1			Form of Instructions For Use of Non-Transferable Subscription Rights Certificates
99.2			Form of Letter to Stockholders who are Record Holders
99.3			Form of Letter to Brokers and other Nominee Holders
99.4			Form of Letter to Clients of Brokers and other Nominee Holders
99.5			Form of Nominee Holder Certification
99.6			Form of Beneficial Owner Election Form
99.7			Press Release, dated July 18, 2022
104			Cover Page Interactive Data File (embedded within the Inline XBRL document)

SIGNATURE

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, hereunto duly authorized.


	SUMMIT THERAPEUTICS INC.


Date: July 18, 2022	By:	/s/ Ankur Dhingra
		Chief Financial Officer

THE TERMS AND CONDITIONS OF THE RIGHTS OFFERING ARE SET FORTH IN THE COMPANY’S PROSPECTUS SUPPLEMENT DATED JULY 18, 2022 (THE “PROSPECTUS SUPPLEMENT”) AND ARE INCORPORATED HEREIN BY REFERENCE. COPIES OF THE PROSPECTUS AND PROSPECTUS SUPPLEMENT ARE AVAILABLE UPON REQUEST FROM BROADRIDGE CORPORATE ISSUER SOLUTIONS, INC., THE SUBSCRIPTION AGENT, BY CALLING (855) 793-5068.

SUMMIT THERAPEUTICS INC.
Incorporated under the laws of the State of Delaware

NON-TRANSFERABLE SUBSCRIPTION RIGHTS CERTIFICATE

Evidencing Non-Transferable Subscription Rights to Purchase Shares of
Common Stock, Par Value $0.01 per share, of Summit Therapeutics Inc.

Subscription Price: To be determined as set forth below

THE SUBSCRIPTION RIGHTS WILL EXPIRE IF NOT EXERCISED ON OR BEFORE
5:00 P.M., EASTERN TIME, ON AUGUST 8, 2022 (THE “EXPIRATION DATE”)

REGISTERED OWNER:

THIS CERTIFIES THAT the registered owner whose name is inscribed hereon is the owner of certain non-transferable subscription rights (each, a “Subscription Right”). The Subscription Right entitles the holder thereof to subscribe for and purchase shares of common stock, par value $0.01 per share (the “Common Stock”), of Summit Therapeutics Inc., a Delaware corporation (the “Company”), at a subscription price per full share equal to the lesser of (i) $1.08 per share (the “Initial Price”) and (ii) the volume weighted-average price of the Common Stock for the five (5) consecutive trading days through and including the Expiration Date (the “Alternate Price”), pursuant to a rights offering (the “Rights Offering”), on the terms and subject to the conditions set forth in the Prospectus Supplement, which supplements the Company’s prospectus dated October 15, 2020 (the “Prospectus”).

Each stockholder will receive one Subscription Right for each share of Common Stock owned as of 4:00 p.m., Eastern Time, on July 5, 2022 (the “Record Date”) and each Subscription Right will entitle its holder to purchase 0.9436442 shares of Common Stock at the Initial Price per full share.

The Subscription Rights represented by this Non-Transferable Subscription Rights Certificate may be exercised by completing Form 1 and any other appropriate forms on the reverse side hereof and by returning the full payment of the subscription price for each share of Common Stock in accordance with the instructions contained herein.

This Non-Transferable Subscription Rights Certificate is not valid unless countersigned by Broadridge Corporate Issuer Solutions, Inc., the Subscription Agent. Witness the seal of Summit Therapeutics Inc. and the signatures of its duly authorized officers.

DATED: July 18, 2022


/s/ Bob Duggan
Robert W. Duggan, Chief Executive Officer

DELIVERY OPTIONS FOR NON-TRANSFERABLE SUBSCRIPTION RIGHTS CERTIFICATE

Delivery other than in the manner or to the addresses listed below will not constitute valid delivery.


If delivering by hand or overnight courier:						If delivering by first class mail:

Broadridge Corporate Issuer Solutions, Inc. Attn: BCIS IWS 51 Mercedes Way Edgewood, NY 11717						Broadridge Corporate Issuer Solutions, Inc. Attn: BCIS Re-Organization Dept. P.O. Box 1317 Brentwood, NY 11717-0718

PLEASE PRINT ALL INFORMATION CLEARLY AND LEGIBLY.

SECTION 1 – EXERCISE OF SUBSCRIPTION RIGHTS

To subscribe for shares of Common Stock pursuant to your Subscription Right, please complete lines (a) and (b) and sign in part (c). If you do not indicate the number of Subscription Rights being exercised, or if you do not forward the full subscription payment for the number of Subscription Rights that you indicate are being exercised, then you will be deemed to have exercised the maximum number of Subscription Rights that may be exercised with the aggregate subscription payment you delivered to the Subscription Agent. Fractional shares of our Common Stock resulting from the exercise of the Subscription Rights will be eliminated by rounding down to the nearest whole share, with the total subscription payment being adjusted accordingly. Any excess subscription payments received by the Subscription Agent will be returned, without interest, as soon as practicable.

(a) EXERCISE OF SUBSCRIPTION RIGHT:


			(i)			Basic Subscription Right

I exercise

____________

0.9436442

______________________

$1.08

(No. of shares
owned)

(Initial ratio)

(No. of Basic Subscription

Shares Subscribed For)

(Initial Price)

(Amount Enclosed)


			(ii)			Over-Subscription Right: If you fully exercise your Basic Subscription Right, above, and wish to subscribe for additional shares, you may exercise your Over-Subscription Right below.

I exercise

____________________

$1.08

(No. of Over-Subscription
Shares
Subscribed For)

(Initial
Price)

(Amount Enclosed)

(b) PAYMENT:


	Amount Enclosed
Basic Subscription Right:	$	¨ Certified check drawn on a U.S. bank, or postal or express money order payable to Broadridge Corporate Issuer Solutions, Inc., as Subscription Agent.

Over-Subscription Right:	$	¨ Wire transfer directly to the escrow account maintained by Broadridge Corporate Issuer Solutions, Inc., as Subscription Agent.

Total Amount Enclosed	$

Method of Payment. All payments must be made in U.S. dollars by wire transfer of funds, U.S. Postal money order or certified check drawn upon a U.S. bank payable to “Broadridge Corporate Issuer Solutions, Inc. (acting as Subscription Agent for Summit Therapeutics Inc.)”. The Subscription Agent will not accept payment by any other means.

TO SUBSCRIBE: I acknowledge that I have received the Prospectus Supplement for the Rights Offering and I hereby irrevocably subscribe for the number of shares indicated above on the terms and conditions specified in the Prospectus Supplement. I hereby agree that if I fail to pay for the shares of Common Stock for which I have subscribed, Summit Therapeutics Inc. may exercise its legal remedies against me.

This form must be signed by the registered holder(s) exactly as their name(s) appear(s) on the certificate(s) or book entry or by person(s) authorized to sign on behalf of the registered holder(s) by documents transmitted herewith.


______________________________	_________________	_________________
Signature(s) of Subscriber(s)	Date	Daytime Telephone Number(s)

If signature is by trustee(s), executor(s), administrator(s), guardian(s), attorney(s)-in-fact, agent(s), officer(s) of a corporation or another acting in a fiduciary or representative capacity, please provide the following information (please print). See the instructions.


________________________	____________________	__________________	______________ ___________
Name(s)	Full Title	Taxpayer ID # or Social Security #	Date

SECTION 2 – SPECIAL ISSUANCE OR DELIVERY INSTRUCTIONS FOR SUBSCRIPTION RIGHTS HOLDERS


(a) To be completed ONLY if the book-entry representing the Common Stock is to be issued in a name other than that of the registered holder. (See the Instructions.) DO NOT FORGET TO COMPLETE THE GUARANTEE OF SIGNATURE(S) SECTION BELOW.						(b) To be completed ONLY if the book-entry representing the Common Stock is to be issued to an address other than that shown on the front of this certificate. (See the Instructions.) DO NOT FORGET TO COMPLETE THE GUARANTEE OF SIGNATURE(S) SECTION BELOW.


Print Full Name:	________________________	Print Full Name:	________________________
Print Full Address:	________________________	Print Full Address:	________________________
Taxpayer ID # or Social Security #:	________________________	Taxpayer ID # or Social Security #:	________________________

SIGNATURE GUARANTEE
This must be completed if you have completed any portion of Section 2.


Signature Guaranteed:
		(Name of Bank or Form)

____________________________
By:	_____________________
		(Signature of Officer)

IMPORTANT: The signature(s) should be guaranteed by an eligible guarantor institution (bank, stock broker, savings & loan association or credit union) with membership in an approved signature guarantee medallion program pursuant to Securities and Exchange Commission Rule 17Ad-15.

FOR INSTRUCTIONS ON THE USE OF NON-TRANSFERABLE SUBSCRIPTION RIGHTS CERTIFICATES, CONSULT BROADRIDGE CORPORATE ISSUER SOLUTIONS, INC., THE SUBSCRIPTION AGENT, AT (855) 793-5068 (TOLL-FREE). THE RIGHTS OFFERING EXPIRES AT 5:00 P.M., EASTERN TIME, ON AUGUST 8, 2022, AND THIS NON-TRANSFERABLE SUBSCRIPTION RIGHTS CERTIFICATE IS VOID THEREAFTER.

THE RIGHTS OFFERING HAS BEEN REGISTERED OR QUALIFIED OR IS BELIEVED TO BE EXEMPT FROM REGISTRATION OR QUALIFICATION ONLY UNDER THE FEDERAL LAWS OF THE UNITED STATES AND THE LAWS OF THE STATES IN THE UNITED STATES. RESIDENTS OF OTHER JURISDICTIONS MAY NOT PURCHASE THE SECURITIES OFFERED HEREBY UNLESS THEY CERTIFY THAT THEIR PURCHASES OF SUCH SECURITIES ARE EFFECTED IN ACCORDANCE WITH THE APPLICABLE LAWS OF SUCH JURISDICTIONS.

Exhibit 5.1

July 18, 2022

Summit Therapeutics Inc.
2882 Sand Hill Road, Suite 106

Menlo Park, California 94025

Ladies and Gentlemen:

We have acted as counsel to Summit Therapeutics Inc., a Delaware corporation (the “Company”), in connection with the filing by the Company with the Securities and Exchange Commission (the “Commission”) of a Prospectus Supplement, dated July 18, 2022 (the “Prospectus Supplement”), of the Company, filed pursuant to Rule 424(b)(4) promulgated under the Securities Act of 1933, as amended (the “Act”). The Prospectus Supplement forms a part of the Registration Statement on Form S-3 previously filed by the Company (Registration No. 333-249316) (the “Registration Statement”), which was declared effective on October 15, 2020.

The Prospectus Supplement relates to a rights offering (the “Rights Offering”) by the Company to the holders of its common stock, par value $0.01 per share (the “Common Stock”) as of 4:00 p.m., Eastern Time, on July 5, 2022 (the “Record Date”), as described in the Prospectus Supplement. Pursuant to the Rights Offering, the Company plans to distribute non-transferable subscription rights to purchase units (the “Rights”) to its stockholders as of the Record Date, entitling the holders of such Rights to purchase an aggregate of up to $100,000,000 of shares of Common Stock (the “Shares”). The Company is filing a Current Report on Form 8-K dated July 18, 2022 (the “Form 8-K”) relating to the Rights Offering, which includes this opinion letter as an exhibit. This opinion is being delivered at the request of the Company and in accordance with the requirements of Item 601(b)(5) of Regulation S-K promulgated by the Commission.

We have examined the Registration Statement, together with the documents incorporated by reference therein, the base prospectus contained in the Registration Statement (the “Base Prospectus”), the Prospectus Supplement (together with the Base Prospectus, the “Prospectus”), and the form of certificate representing the Rights. In addition, we have examined originals or copies, certified or otherwise identified to our satisfaction, of such other instruments, documents, certificates and records which we have deemed relevant and necessary for the basis of our opinions hereinafter expressed. In such examination, we have assumed: (i) the authenticity of original documents and the genuineness of all signatures; (ii) the conformity to the originals of all documents submitted to us as copies; (iii) the truth, accuracy and completeness of the information, representations and warranties contained in the instruments, documents, certificates and records we have reviewed; (iv) that the Shares will be issued and sold in compliance with applicable U.S. federal and state securities laws and in the manner stated in the Registration Statement and the Prospectus; (v) the legal capacity of all natural persons; and (vi) that there will be sufficient shares of Common Stock authorized under the Company’s organizational documents that are not otherwise reserved for issuance available for the issuance of the Shares. As to any facts material to the opinions expressed herein that were not independently established or verified, we have relied upon oral or written statements and representations of officers and other representatives of the Company.

We express no opinion herein as to the laws of any state or jurisdiction other than the General Corporation Law of the State of Delaware (including the statutory provisions and all applicable judicial decisions interpreting those laws) and the federal laws of the United States of America.

We express no opinion as to (i) the effect of any bankruptcy, insolvency, reorganization, arrangement, fraudulent conveyance, moratorium or other similar laws relating to or affecting the rights of creditors generally, (ii) rights to indemnification and contribution which may be limited by applicable law or equitable principles, or (iii) the effect of general principles of equity, including, without limitation, concepts of materiality, reasonableness, good faith and fair dealing, the effect of judicial discretion and the possible unavailability of specific performance, injunctive relief or other equitable relief, and the limitations on rights of acceleration, whether considered in a proceeding in equity or at law.

On the basis of the foregoing, we are of the opinion that:

1. the Rights, when issued, will be valid and binding obligations of the Company, enforceable against the Company in accordance with their terms.

2. The Shares, when issued and delivered as contemplated in the Prospectus, will be validly issued, fully paid and non-assessable.

We hereby consent to the filing of this opinion as Exhibit 5.1 to the Registration Statement and to the reference to our firm under the caption “Legal Matters” in the Prospectus. In giving such consent, we do not thereby admit that we are included in the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the Commission promulgated thereunder. We assume no obligation to update or supplement any of the opinion set forth herein to reflect any changes of law or fact that may occur following the date hereof.

Very truly yours,

/s/ Baker & Hostetler LLP

BAKER & HOSTETLER LLP

Exhibit 5.1

July 18, 2022

Summit Therapeutics Inc.
2882 Sand Hill Road, Suite 106

Menlo Park, California 94025

Ladies and Gentlemen:

On the basis of the foregoing, we are of the opinion that:

1. the Rights, when issued, will be valid and binding obligations of the Company, enforceable against the Company in accordance with their terms.

2. The Shares, when issued and delivered as contemplated in the Prospectus, will be validly issued, fully paid and non-assessable.

Very truly yours,

/s/ Baker & Hostetler LLP

BAKER & HOSTETLER LLP

FORM OF INSTRUCTIONS AS TO USE OF SUMMIT THERAPEUTICS INC. NON-TRANSFERABLE SUBSCRIPTION RIGHTS CERTIFICATES

PLEASE CONSULT THE SUBSCRIPTION AND INFORMATION AGENT,
YOUR BANK OR BROKER FOR ANY QUESTIONS

The following instructions relate to a rights offering by Summit Therapeutics Inc., a Delaware corporation (“we,” “us,” “our,” or the “Company”), to the stockholders (the “holder” or “you”) of its Common Stock, par value $0.01 per share (the “Common Stock”), as described in the Company’s prospectus dated October 15, 2020 (as supplemented by the Prospectus Supplement, the “Prospectus”). Holders of our Common Stock as of 4:00 p.m., Eastern Time, on July 5, 2022 (the “Record Date”) are receiving, at no charge, non-transferable subscription rights (each, a “Subscription Right”) to purchase up to an aggregate of $100,000,000 of shares of Common Stock at an initial price per share equal to the lesser of (i) $1.08 per share (the “Initial Price”) and (ii) the volume weighted-average price of the Common Stock for the five (5) consecutive trading days through and including the Expiration Date (as defined below) (the “Alternate Price”). Each stockholder will receive one Subscription Right for each share of Common Stock owned on the Record Date and each Subscription Right will entitle its holder to purchase 0.9436442 shares of Common Stock at the Initial Price (the “Basic Subscription Right”). To the extent the Alternate Price is lower than the Initial Price, we will issue additional shares in the rights offering to you.

The Subscription Rights will be evidenced by non-transferable subscription rights certificates (the “Non-Transferable Subscription Rights Certificate”). The number of Subscription Rights to which you are entitled is printed on the face of your Non-Transferable Subscription Rights Certificate.

Over-Subscription Right

If a holder purchases all of the shares of Common Stock available to it pursuant to its Basic Subscription Right, it may also exercise an over-subscription right (the “Over-Subscription Right”) to purchase a portion of any shares of Common Stock that are not purchased by other stockholders through the exercise of their Basic Subscription Rights (the “Unsubscribed Shares”), subject to the availability and pro rata allocation of the Unsubscribed Shares among all persons exercising their Over-Subscription Rights.

If you wish to exercise your Over-Subscription Right, you should indicate the number of additional shares that you would like to purchase in the space provided on your Non-Transferable Subscription Rights Certificate, as well as the number of shares that you beneficially own without giving effect to any shares to be purchased in this rights offering. When you send in your Non-Transferable Subscription Rights Certificate, you must also send the full purchase price in cash, as provided herein, for the number of additional shares that you have requested to purchase, at the Initial Price (in addition to the payment in cash, as provided herein, due for shares purchased through your Basic Subscription Right).

If the number of shares remaining after the exercise of all Basic Subscription Rights is not sufficient to satisfy all requests for shares pursuant to Over-Subscription Rights, you will be allocated additional shares (subject to elimination of fractional shares) in the proportion which the number of shares you purchased through the Basic Subscription Right bears to the total number of shares that all oversubscribing stockholders purchased through the Basic Subscription Right. Broadridge Corporate Issuer Solutions, Inc. (the “Subscription Agent”) will return any excess payments in the form in which made.

As soon as practicable after the Expiration Date, the Subscription Agent will determine the number of shares of Common Stock that you may purchase pursuant to the Over-Subscription Right. We will issue to you the shares in book-entry, or uncertificated, form as soon as practicable after the Expiration Date and after all allocations and adjustments have been effected. If you request and pay for more shares than are allocated to you, we will refund the overpayment in the form in which made. In connection with the exercise of the Over-Subscription Right, banks, brokers and other nominee holders of Subscription Rights who act on behalf of beneficial owners will be required to certify to us and to the Subscription Agent as to the aggregate number of Subscription Rights exercised, and the number of shares of Common Stock requested through the Over-Subscription Right, by each beneficial owner on whose behalf the nominee holder is acting.

We will not issue fractional shares, but rather will round down the aggregate number of shares you are entitled to receive to the nearest whole number, with the total exercise price being adjusted accordingly. If, on the Expiration Date, the Alternate Price is lower than the Initial Price, any excess subscription amounts paid by a subscriber (the “Excess Subscription Amount”) will be put towards the purchase of additional shares in the rights offering (either towards your Basic Subscription Right, if available, or towards the Over-Subscription Right if you have already exercised your Basic Subscription Right in full). Otherwise, any excess subscription payments received by the Subscription Agent will be returned, without interest, as soon as practicable.

You are not required to exercise any or all of your Subscription Rights. However, if you do not exercise your Subscription Rights and the rights offering is completed, the number of shares of our Common Stock you own will not change but your percentage ownership of our total outstanding voting stock will decrease because shares will be purchased by other stockholders in the rights offering. Your percentage ownership of our voting stock may also decrease if you do not exercise your Subscription Right in full. Please see the discussion of risk factors related to the rights offering, including dilution, under the heading “Risk Factors—Risks Related to The Rights Offering,” in the Prospectus Supplement.

Expiration Date

THE SUBSCRIPTION RIGHTS WILL EXPIRE AND WILL HAVE NO VALUE AT 5:00 P.M., EASTERN TIME, ON AUGUST 8, 2022, SUBJECT TO EXTENSION OR EARLIER TERMINATION (THE “EXPIRATION DATE”). YOUR NON-TRANSFERABLE SUBSCRIPTION RIGHTS CERTIFICATE AND SUBSCRIPTION PAYMENT FOR EACH RIGHT THAT IS EXERCISED PURSUANT TO THE SUBSCRIPTION RIGHT MUST BE RECEIVED BY THE SUBSCRIPTION AGENT ON OR BEFORE THE EXPIRATION DATE. ONCE YOU HAVE EXERCISED YOUR SUBSCRIPTION RIGHT, SUCH EXERCISE MAY NOT BE REVOKED, EVEN IF YOU LATER LEARN INFORMATION THAT YOU CONSIDER TO BE UNFAVORABLE TO THE EXERCISE OF YOUR SUBSCRIPTION RIGHTS. SUBSCRIPTION RIGHTS NOT EXERCISED PRIOR TO THE EXPIRATION DATE OF THE RIGHTS OFFERING WILL EXPIRE WITHOUT VALUE.

If you do not exercise your Subscription Rights prior to that time, your Subscription Rights will expire and will no longer be exercisable. We will not be required to issue shares of our Common Stock to you if the Subscription Agent receives your Non-Transferable Subscription Rights Certificate(s) or your subscription payment after the Expiration Date, regardless of when the Non-Transferable Subscription Rights Certificate(s) and subscription payment were sent. If you send your Non-Transferable Subscription Rights Certificate(s) and Initial Price payment by mail, we recommend that you send them by registered mail, properly insured, with return receipt requested, and that a sufficient number of days be allowed to ensure delivery to the Subscription Agent and clearance of payment before the expiration of the subscription period. See “The Rights Offering—Expiration of this rights offering and Extensions, Amendments and Termination” in the Prospectus Supplement.

The shares issued upon exercise of the Subscription Rights will be delivered as soon as practicable after the Expiration Date, and after all pro rata allocations and adjustments have been completed.

If you have any questions concerning the rights offering, please contact the Subscription Agent, Broadridge Corporate Issuer Solutions, Inc., at the following address and number:

Broadridge Corporate Issuer Solutions, Inc.
Attn: BCIS Re-Organization Dept.
P.O. Box 1317
Brentwood, NY 11717-0718
Holder Inquiries:
(855) 793-5068 (toll free)
shareholder@broadridge.com


			1.			Method of Subscription—Exercise of Subscription Rights.

To exercise your Subscription Rights, please: (1) complete Section 1 on your Non-Transferable Subscription Rights Certificate, attached to these instructions; (2) sign Section 1 of your Non-Transferable Subscription Rights Certificate; and (3) mail the properly completed and executed Non-Transferable Subscription Rights Certificate evidencing such Basic Subscription Rights and, if applicable, Over-Subscription Rights subscribed, together with payment in full of the Initial Price for each share of Common Stock subscribed for pursuant to the Basic Subscription Right and, if applicable, Over-Subscription Rights, to the Subscription Agent, on or prior to the Expiration Date.

Additionally, if the Common Stock to be issued pursuant to the Subscription Rights are to be issued in a name other than that of the registered holder, or sent to an address other than that shown on the front of the Non-Transferable Subscription Rights Certificate, please complete Section 2 of the Non-Transferable Subscription Rights Certificate and obtain a signature guarantee as described below prior to mailing the Non-Transferable Subscription Rights Certificate to the Subscription Agent, prior to the Expiration Date. Payment of the Initial Price will be held in a segregated account to be maintained by the Subscription Agent.


			(a)			Method of Execution

(i) Execution by Registered Holder. Your signature on the Non-Transferable Subscription Rights Certificate must correspond with the name of the registered holder exactly as it appears on the face of the Non-Transferable Subscription Rights Certificate without any alteration or change whatsoever. Persons who sign the Non-Transferable Subscription Rights Certificate in a representative or other fiduciary capacity must indicate their capacity when signing and, unless waived by the Subscription Agent in its sole and absolute discretion, must present to the Subscription Agent satisfactory evidence of their authority to so act.

(ii) Execution by Person Other than Registered Holder. If the Non-Transferable Subscription Rights Certificate is executed by a person other than the holder named on the face of the Non-Transferable Subscription Rights Certificate, proper evidence of authority of the person executing the Non-Transferable Subscription Rights Certificate must accompany the same unless, for good cause, the Subscription Agent dispenses with proof of authority.

(iii) Signature Guarantees. If you completed any part of Section 2 of the Non-Transferable Subscription Rights Certificate to provide that the Common Stock sold pursuant to your exercise of Subscription Rights to be (x) issued in a name other than that of the registered holder, or (y) sent to an address other than that shown on the front of the Non-Transferable Subscription Rights Certificate, your signature in Section 1 must be guaranteed in Section 2 by an “Eligible Guarantor Institution,” as such term is defined in Rule 17Ad-15 of the Securities Exchange Act of 1934, such as a member firm of a registered national securities exchange or a member of the Financial Industry Regulatory Authority, Inc., or a commercial bank or trust company having an office or correspondent in the United States, or by a member of a Stock Transfer Association approved medallion program such as STAMP, SEMP or MSP, subject to standards and procedures adopted by the Subscription Agent.


			(b)			Method of Payment

Payments must be made in full in U.S. currency by:


			•·			wire transfer of immediately available funds to accounts maintained by the Subscription Agent for purposes of accepting subscription in the rights offering at:


Beneficiary Account Name: Broadridge Corporate Issuer Solutions Account Number: 153910728465 ABA/Routing number: 123000848 International/Swift Code: USBKUS44IMT Bank: U.S. Bank 800 Nicollet Mall Minneapolis, MN 55402 United States Reference: Summit Rights Offer For Further Credit Name: Summit Therapeutics Inc. For Further Credit Account Number: 153912031223


			•·			a certified check drawn against a U.S. bank payable to “Broadridge Corporate Issuer Solutions, Inc. (acting as Subscription Agent for Summit Therapeutics Inc.)”; or


			•·			U.S. Postal money order payable to “Broadridge Corporate Issuer Solutions, Inc. (acting as Subscription Agent for Summit Therapeutics Inc.)”.

Payments will be deemed to have been received upon (i) receipt by the Subscription Agent of any certified check drawn upon a U.S. bank or of any U.S. Postal money order or (ii) receipt of collected funds in the Subscription Account designated above. Payments submitted by means of uncertified personal check will not be accepted. Any wire transfer should clearly indicate the identity of the subscriber who is paying the Initial Price by wire transfer.

If you do not indicate the number of Subscription Rights being exercised, or if you do not forward the full subscription payment for the number of Subscription Rights that you indicate are being exercised, then you will be deemed to have exercised the maximum number of Subscription Rights that may be exercised with the aggregate subscription payment you delivered to the Subscription Agent. Any excess subscription payments received by the Subscription Agent will be returned to you by mail, without interest, as soon as practicable after completion of the rights offering and after all pro rata allocations and adjustments have been completed.

Fractional shares of our Common Stock resulting from the exercise of the Subscription Rights will be eliminated by rounding down to the nearest whole share, with the total subscription payment being adjusted accordingly. Any excess subscription payments received by the Subscription Agent will be returned, without interest, as soon as practicable.


			(c)			Method of Delivery

Non-Transferable Subscription Rights Certificate and payments of Initial Price must be delivered to the Subscription Agent by one of the methods described below:


If delivering by hand or overnight courier: Broadridge Corporate Issuer Solutions, Inc. Attn: BCIS IWS 51 Mercedes Way Edgewood, NY 11717			If delivering by first class mail: Broadridge Corporate Issuer Solutions, Inc. Attn: BCIS Re-Organization Dept. P.O. Box 1317 Brentwood, NY 11717-0718

Delivery to an address or by a method other than those above will not constitute valid delivery.

The method of delivery of Non-Transferable Subscription Rights Certificates and payment of the Initial Price to the Subscription Agent will be at the election and risk of the Subscription Rights holder. If you send a certified check drawn upon a U.S. bank, or a U.S. Postal money order directly to the Subscription Agent’s account, payment will be deemed to have been received by the Subscription Agent immediately upon receipt of such instruments.


			2.			Issuance of Common Stock.

The following deliveries and payments will be made and/or issued to the address shown on the face of your Non-Transferable Subscription Rights Certificate, unless you provide instructions to the contrary in your Non-Transferable Subscription Rights Certificate.


			(a)			Basic Subscription Right. As soon as practicable following the Expiration Date and the valid exercise of the Subscription Rights, we will issue to each exercising Subscription Rights holder shares in book-entry, or uncertificated, form representing shares of Common Stock purchased pursuant to the Basic Subscription Right.


			(b)			Over-Subscription Right. As soon as practicable following the Expiration Date and after all prorations and adjustments contemplated by the terms of the rights offering have been effected, we will issue to each Rights holder that validly exercises the Over-Subscription Right shares in book-entry, or uncertificated, form representing the number of shares of Common Stock, if any, allocated to such Rights holder pursuant to the Over-Subscription Right.


			(c)			Excess Cash Payments. As soon as practicable following the Expiration Date and after all prorations and adjustments contemplated by the terms of the rights offering have been effected, any excess subscription payments received in payment of the Initial Price will be mailed by the Subscription Agent to each Subscription Rights holder, without interest.


			3.			No Sale or Transfer of Subscription Rights.

The Subscription Rights granted to you are non-transferable and, therefore, you may not sell, transfer or assign your Subscription Rights to anyone.


			4.			Special Provisions Relating to the Delivery of Subscription Rights through the Depository Trust Company.

Banks, trust companies, securities dealers and brokers (each, a “Nominee”) that hold shares of our Common Stock on the Record Date as nominee for more than one beneficial owner may, upon proper showing to the Subscription Agent, exercise such beneficial owner’s Subscription Right through DTC on the same basis as if the beneficial owners were stockholders on the Record Date. Such Nominee may exercise the Subscription Rights on behalf of the exercising beneficial owner through DTC’s PSOP Function on the “agents subscription over PTS” procedure by (1) providing a certification as to the aggregate number of Subscription Rights exercised by the beneficial owner on whose behalf such Nominee is acting and (2) instruct DTC to charge the Nominee’s applicable DTC account for the subscription payment for the new shares to facilitate the delivery of the full subscription payment to the Subscription Agent. DTC must receive the subscription instructions and payment for the new shares no later than the Expiration Date.


			5.			Form W-9.

Each Subscription Rights holder who elects to exercise Subscription Rights should provide the Subscription Agent with a correct Taxpayer Identification Number (TIN) on IRS Form W-9. See “Material U.S. Federal Income Tax Consequences — Information Reporting and Backup Withholding” in the Prospectus Supplement. Failure to provide the information on the form may subject such holder to a $50 penalty for each such failure and to 24% federal income tax withholding with respect to dividends (including deemed dividends) that may be paid by the Company on shares of its Common Stock. Foreign Persons are generally required to provide an appropriate IRS Form W-8 rather than IRS Form W-9 and may be subject to withholding on dividends (including deemed dividends) at a rate of up to 30%.

FORM OF LETTER TO STOCKHOLDERS WHO ARE RECORD HOLDERS
SUMMIT THERAPEUTICS INC.
Shares of Common Stock
Offered Pursuant to Subscription Rights
Distributed to Stockholders
of Summit Therapeutics Inc.

July 18, 2022

Dear Stockholder:

Enclosed are materials relating to a rights offering by Summit Therapeutics Inc., a Delaware corporation (“we,” “us,” “our,” or the “Company”), including the prospectus dated October 15, 2020, as supplemented by the prospectus supplement dated July 18, 2022 (collectively, the “Prospectus”). Please carefully review the Prospectus, which describes how you can participate in the rights offering. You will be able to exercise your subscription rights to purchase shares of our common stock, par value $0.01 per share (the “Common Stock”), only during a limited period, pursuant to non-transferable subscription rights distributed to all stockholders of record of the Company at 4:00 p.m., Eastern Time, on July 5, 2022 (the “Record Date”). The subscription rights and shares of Common Stock are described in the Prospectus. Answers to some frequently asked questions about the rights offering can be found under the heading “Questions and Answers About the Rights Offering” in the Prospectus. Any prospective purchaser of shares of Common Stock pursuant to the exercise of the subscription rights should read the Prospectus, including without limitation the risk factors contained therein, prior to making any decision to invest in the Company.

In the rights offering, we are offering the rights to purchase an aggregate of up to $100,000,000 of shares of Common Stock, as described in the Prospectus.

The subscription rights will expire if not exercised prior to 5:00 p.m., Eastern Time, on August 8, 2022 (the “Expiration Date,” and such time, the “Expiration Time”).

As described in the Prospectus, you will receive one subscription right to purchase 0.9436442 shares of Common Stock for each share of Common Stock (each, a “Basic Subscription Right”) owned at 4:00 p.m., Eastern Time, on July 5, 2022 (the “Record Date”). Each Basic Subscription Right will allow you to subscribe for 0.9436442 shares of Common Stock (rounded down to the nearest whole share of Common Stock, with the total subscription payment being adjusted accordingly, as discussed below) at a cash price per share equal to the lesser of (i) $1.08 (the “Initial Price”) and (ii) the volume weighted average price of the Common Stock for the five trading day period through and including the Expiration Date (the “Alternate Price”). For example, if you owned 100 shares of Common Stock as of 4:00 p.m., Eastern Time, on the Record Date, you would receive 100 Basic Subscription Rights and would have the right to purchase 943 shares of Common Stock at the Initial Price. If, on the Expiration Date, the Alternate Price is lower than the Initial Price, any excess subscription amounts paid by a subscriber (the “Excess Subscription Amount”) will be put towards the purchase of additional shares of Common Stock in the rights offering (either towards your Basic Subscription Rights, if available, or towards the Over-Subscription Right if you have already exercised your Basic Subscription Rights in full), but fractional shares will not be sold.

In the event that you purchase all shares of Common Stock available to you pursuant to your Basic Subscription Rights, you may also exercise an over-subscription right (the “Over-Subscription Right,” collectively with the Basic Subscription Rights, the “Subscription Rights”) to purchase a portion of shares that are not purchased by stockholders through the exercise of their Basic Subscription Rights (the “Unsubscribed Shares”), subject to the availability and pro rata allocation of the Unsubscribed Shares among all persons exercising this Over-Subscription Right. To the extent the Unsubscribed Shares are not sufficient to satisfy all of the properly exercised Over-Subscription Rights, then the Unsubscribed Shares will be prorated among those who properly exercised Over-Subscription Right based on the number of shares each person subscribed for under the Basic Subscription Rights. If this pro rata allocation results in any person receiving a greater number of Unsubscribed Shares than the person subscribed for pursuant to the exercise of the Over-Subscription Right, then such person will be allocated only that number of Unsubscribed Shares for which the person oversubscribed, and the remaining Unsubscribed Shares will be allocated among all other persons exercising the Over-Subscription Right on the same pro rata basis described above. The proration process will be repeated until all Unsubscribed Shares have been allocated or all Over-Subscription Rights have been fulfilled, whichever occurs earlier.

You will be required to submit payment in full for all the shares of Common Stock you wish to buy with your Over-Subscription Right. Because we will not know the total number of Unsubscribed Shares prior to the Expiration Time, if you wish to maximize the number of shares of Common Stock you may purchase pursuant to your Over-

Subscription Right, you will need to deliver payment in an amount equal to the aggregate Initial Price (the “Subscription Price”) for the maximum number of shares available to you, assuming that no stockholder other than you has purchased any shares pursuant to the Basic Subscription Rights and Over-Subscription Right. The Company will eliminate fractional shares resulting from the exercise of the Over-Subscription Right by rounding down to the nearest whole number, with the total subscription payment being adjusted accordingly. Any excess subscription payments received by the Broadridge Corporate Issuer Solutions, Inc. (the “Subscription Agent”) will be returned, without interest, as soon as practicable.

The Company can provide no assurances that you will actually be entitled to purchase the number of shares of Common Stock subscribed for pursuant to the exercise of your Over-Subscription Right in full at the expiration of the rights offering. The Company will not be able to satisfy your exercise of the Over-Subscription Right if all of our stockholders exercise their Basic Subscription Rights in full, and we will only honor an Over-Subscription Right to the extent sufficient shares of Common Stock are available following the exercise of Subscription Rights under the Basic Subscription Rights.


•			To the extent the aggregate Initial Price of the maximum number of Unsubscribed Shares available to you pursuant to the Over-Subscription Right is less than the amount you actually paid in connection with the exercise of the Over-Subscription Right, you will be allocated only the number of Unsubscribed Shares available to you as soon as practicable after the Expiration Time, and your excess subscription payment received by the Subscription Agent will be returned, without interest, as soon as practicable.


•			To the extent the amount you actually paid in connection with the exercise of the Over-Subscription Right is less than the aggregate Initial Price of the maximum number of Unsubscribed Shares available to you pursuant to the Over-Subscription Right, you will be allocated the number of Unsubscribed Shares for which you actually paid in connection with the Over-Subscription Right. If, on the Expiration Date, the Alternate Price is lower than the Initial Price, any Excess Subscription Amount will be put towards the purchase of additional shares of Common Stock (either towards your Basic Subscription Rights, if available, or towards the Over-Subscription Right if you have already exercised your Basic Subscription Rights in full). See the discussion under the heading “The Rights Offering — Subscription Rights — Over-Subscription Rights” in the Prospectus.

You are not required to exercise any or all of your Subscription Rights. If you do not exercise your Subscription Rights and the rights offering is completed, the number of shares of our Common Stock you own will not change but your percentage ownership of our total outstanding voting stock may decrease because shares may be purchased by other stockholders in the rights offering. Your percentage ownership of our voting stock may also decrease if you do not exercise your Subscription Right in full. Please see the discussion of risk factors related to the rights offering, including dilution, under the heading “Risk Factors—Risks Related to the Rights Offering” in the Prospectus.

The Subscription Rights will be evidenced by a Non-Transferable Subscription Rights Certificate issued to stockholders of record and will cease to have any value after the Expiration Time.

Enclosed are copies of the following documents:


1.			Prospectus;


2.			Non-Transferable Subscription Rights Certificate;


3.			Instructions as to Use of Summit Therapeutics Inc. Non-Transferable Subscription Rights Certificates; and


4.			A return envelope addressed to Broadridge Corporate Issuer Solutions, Inc., the Subscription Agent.

Your prompt action is requested. To exercise the Subscription Rights, as indicated in the Prospectus, you should deliver to the Subscription Agent the properly completed and signed Non-Transferable Subscription Rights Certificate with payment of the Subscription Price in full for each share of Common Stock subscribed for pursuant to the Subscription Right. The Subscription Agent must receive the Non-Transferable Subscription Rights Certificate with payment of the Subscription Price prior to the Expiration Time. If you send your Non-Transferable Subscription Rights Certificate(s) and Subscription Price payment by mail, we recommend that you send them by registered mail, properly insured, with return receipt requested. We will not be required to sell shares of Common

Stock to you if the Subscription Agent receives your Non-Transferable Subscription Rights Certificate or your subscription payment after the Expiration Time, regardless of when the Non-Transferable Subscription Rights Certificate and subscription payment were sent. See the discussion under the heading “The Rights Offering—Expiration Date and Amendments” in the Prospectus.

Once you have exercised your Subscription Rights, such exercise may not be revoked, even if you later learn information that you consider to be unfavorable to the exercise of your Subscription Rights.

Additional copies of the enclosed materials may be obtained from Broadridge Corporate Issuer Solutions, Inc., the Subscription Agent for this rights offering, by calling (855) 793-5068 (toll-free). Any questions or requests for assistance concerning the rights offering should be directed to the Subscription Agent.



Very truly yours, Summit Therapeutics Inc.

FORM OF LETTER TO BROKERS AND OTHER NOMINEE HOLDERS
SUMMIT THERAPEUTICS INC.

Subscription Rights to Purchase Shares of Common Stock
Offered Pursuant to Subscription Rights
Distributed to Stockholders
of Summit Therapeutics Inc.

July 18, 2022

To Securities Dealers, Commercial Banks, Trust Companies and Other Nominees:

This letter is being distributed to securities dealers, commercial banks, trust companies and other nominees in connection with the rights offering by Summit Therapeutics Inc., a Delaware corporation (“we,” “us,” “our,” or the “Company”), of shares of common stock, pursuant to non-transferable subscription rights distributed to all stockholders of record (the “Record Holders”) of shares of our common stock, par value $0.01 per share (the “Common Stock”), at 4:00 p.m., Eastern Time, on July 5, 2022 (the “Record Date”). The subscription rights and Common Stock are described in the Company’s prospectus dated October 15, 2020 (the “Prospectus”), as supplemented by the prospectus supplement dated July 18, 2022 (the “Prospectus Supplement”).

In the rights offering, we are offering an aggregate of $100,000,000 of shares of Common Stock, as described in the Prospectus Supplement.

The subscription rights will expire if not exercised prior to 5:00 p.m., Eastern Time, on August 8, 2022 (the “Expiration Date”).

As described in the Prospectus Supplement, each beneficial owner of shares of Common Stock registered in your name or the name of your nominee is entitled to one subscription right for each share of Common Stock (each, a “Basic Subscription Right”) owned by such beneficial owner at 5:00 p.m., Eastern Time, on the Record Date. Each Basic Subscription Right will allow the holder thereof to subscribe for 0.9436442 shares of Common Stock at a cash price equal to the lesser of (i) $1.08 per share (the “Initial Price”) and (ii) the volume weighted-average price of the Common Stock for the five (5) consecutive trading days through and including the Expiration Date (the “Alternate Price”). For example, if a Record Holder owned 1,000 shares of Common Stock as of 5:00 p.m., Eastern Time, on the Record Date, it would receive one Basic Subscription Right for each share and would have the right to purchase 943 shares of Common Stock (rounded down to the nearest whole share, with the total subscription payment being adjusted accordingly, as discussed below) at the Initial Price. If, on the Expiration Date, the Alternate Price is lower than the Initial Price, any excess subscription amounts paid by a subscriber (the “Excess Subscription Amount”) will be put towards the purchase of additional shares in the rights offering (either towards the Record Holder’s Basic Subscription Right, if available, or towards the Over-Subscription Right if the Record Holder has already exercised its Basic Subscription Right in full).

In the event that a Record Holder purchases all of the shares of Common Stock available to it pursuant to its Basic Subscription Right, Record Holder may also exercise an over-subscription right (the “Over-Subscription Right”, collectively with the Basic Subscription Right, the “Subscription Rights”) to purchase a portion of any shares of Common Stock that are not purchased by other Record Holders through the exercise of their Basic Subscription Rights (the “Unsubscribed Shares”), subject to the availability and pro rata allocation of the Unsubscribed Shares among all persons exercising this Over-Subscription Right. To the extent the Unsubscribed Shares are not sufficient to satisfy all of the properly exercised Over-Subscription Rights, then the Unsubscribed Shares will be prorated among those who properly exercised the Over-Subscription Right based on the number of shares each person subscribed for under the Basic Subscription Right. If this pro rata allocation results in any person receiving a greater number of Unsubscribed Shares than the person subscribed for pursuant to the exercise of the Over-Subscription Right, then such person will be allocated only that number of Unsubscribed Shares for which the person oversubscribed, and the remaining Unsubscribed Shares will be allocated among all other persons exercising the Over-Subscription Right on the same pro rata basis described above. The proration process will be repeated until all Unsubscribed Shares have been allocated or all Over-Subscription Rights have been fulfilled, whichever occurs earlier.

Each Record Holder will be required to submit payment in full for all the shares it wishes to buy with its Over-Subscription Right. Because we will not know the total number of Unsubscribed Shares prior to the Expiration Date, if Record Holder wishes to maximize the number of shares Record Holder may purchase pursuant to its Over-Subscription Right, the Record Holder will need to deliver payment in an amount equal to the aggregate Initial Price for the maximum number of shares of Common Stock available to Record Holder, assuming that no stockholders other than the Record Holder has purchased any shares of Common Stock pursuant to the Basic Subscription Right

and Over-Subscription Right. The Company will eliminate fractional shares of Common Stock resulting from the exercise of the Over-Subscription Right by rounding down to the nearest whole share, with the total subscription payment being adjusted accordingly. Any excess subscription payments received by the Broadridge Corporate Issuer Solutions, Inc. (the “Subscription Agent”) will be returned, without interest, as soon as practicable.

The Company can provide no assurances that each Record Holder will actually be entitled to purchase the number of shares of Common Stock issuable upon the exercise of its Over-Subscription Right in full at the expiration of the rights offering. The Company will not be able to satisfy its exercise of the Over-Subscription Right if all of our Record Holders exercise their Basic Subscription Rights in full, and we will only honor an Over-Subscription Right to the extent sufficient shares of Common Stock are available following the exercise of Subscription Rights under the Basic Subscription Rights.


			•·			To the extent the aggregate Initial Price of the maximum number of Unsubscribed Shares available to Record Holder pursuant to the Over-Subscription Right is less than the amount Record Holder actually paid in connection with the exercise of the Over-Subscription Right, Record Holder will be allocated only the number of Unsubscribed Shares available to Record Holder as soon as practicable after the Expiration Date, and the Record Holder’s excess subscription payment received by the Subscription Agent will be returned, without interest, as soon as practicable.


			•·			To the extent the amount Record Holder actually paid in connection with the exercise of the Over-Subscription Right is less than the aggregate Initial Price of the maximum number of Unsubscribed Shares available to Record Holder pursuant to the Over-Subscription Right, Record Holder will be allocated the number of Unsubscribed Shares for which the Record Holder actually paid in connection with the Over-Subscription Right. If, on the Expiration Date, the Alternate Price is lower than the Initial Price, any Excess Subscription Amount will be put towards the purchase of additional shares in the rights offering (either towards the Record Holder’s Basic Subscription Right, if available, or towards the Over-Subscription Right if the Record Holder has already exercised its Basic Subscription Right in full). See “The Rights Offering—Subscription Rights—Over-Subscription Rights” in the Prospectus Supplement.

The Subscription Rights will be evidenced by a Non-Transferable Subscription Rights Certificate registered in the Record Holder’s name or its nominee and will cease to have any value at the Expiration Date.

We are asking persons who hold shares of Common Stock beneficially and who have received the Subscription Rights distributable with respect to those shares through a broker, dealer, commercial bank, trust company or other nominee, as well as persons who hold certificates of Common Stock directly and prefer to have such institutions effect transactions relating to the Subscription Rights on their behalf, to contact the appropriate institution or nominee and request it to effect the transactions for them. In addition, we are asking beneficial owners who wish to obtain a separate Non-Transferable Subscription Rights Certificate to contact the appropriate nominee as soon as possible and request that a separate Non-Transferable Subscription Rights Certificate be issued.

All commissions, fees and other expenses (including brokerage commissions and transfer taxes), other than fees and expenses of the Subscription Agent, incurred in connection with the exercise of the Subscription Rights will be for the account of the holder of the Subscription Rights, and none of such commissions, fees or expenses will be paid by the Company or the Subscription Agent.

Enclosed are copies of the following documents:


			1.			Prospectus and Prospectus Supplement;


			2.			Instructions as to Use of Summit Therapeutics Inc. Non-Transferable Subscription Rights Certificates;


			3.			A form of letter which may be sent to your clients for whose accounts you hold shares of our Common Stock registered in your name or the name of your nominee;


			4.			Beneficial Owner Election;


			5.			Nominee Holder Certification; and


			6.			A return envelope addressed to Broadridge Corporate Issuer Solutions, Inc., the Subscription Agent.

Your prompt action is requested. To exercise the Subscription Rights, as indicated in the Prospectus Supplement, you should deliver to the Subscription Agent the properly completed and signed Non-Transferable Subscription Rights Certificate with payment of the Initial Price in full for each share of Common Stock subscribed for pursuant to the Subscription Right. The Subscription Agent must receive the Non-Transferable Subscription Rights Certificate with payment of the Initial Price prior to the Expiration Date. Once a Record Holder has exercised its Subscription Right, such exercise may not be revoked, even if the Record Holder later learns information that it considers to be unfavorable to the exercise of its Subscription Rights.

Very truly yours,

Summit Therapeutics Inc.

FORM OF LETTER TO CLIENTS OF BROKERS AND OTHER NOMINEE HOLDERS SUMMIT THERAPEUTICS INC.

Subscription Rights to Purchase Shares of Common Stock
Offered Pursuant to Subscription Rights
Distributed to Stockholders
of Summit Therapeutics Inc.

July 18, 2022

To Our Clients:

Enclosed for your consideration are a prospectus dated October 15, 2020 (the “Prospectus”), as supplemented by the prospectus supplement dated July 18, 2022 (the “Prospectus Supplement”), and the “Instructions as to Use of Summit Therapeutics Inc. Non-Transferable Subscription Rights Certificates” relating to the rights offering by Summit Therapeutics Inc., a Delaware corporation (the “Company”), of shares of its common stock, par value $0.01 per share (the “Common Stock”), pursuant to non-transferable subscription rights distributed to all stockholders of record of the Company at 4:00 p.m., Eastern Time, on July 5, 2022 (the “Record Date”). The subscription rights and Common Stock are described in the Prospectus Supplement.

In the rights offering, the Company is offering the rights to purchase an aggregate of up to $100,000,000 of shares of its Common Stock, as described in the Prospectus Supplement.

The subscription rights will expire if not exercised prior to 5:00 p.m., Eastern Time, on August 8, 2022 (the “Expiration Date”).

As described in the Prospectus Supplement, you will receive one subscription right for each share of Common Stock (each, a “Basic Subscription Right”) owned at 5:00 p.m., Eastern Time, on the Record Date. Each Basic Subscription Right will allow you to subscribe for 0.9436442 shares of Common Stock at a cash price equal to the lesser of (i) $1.08 per share (the “Initial Price”) and (ii) the volume weighted-average price of the Common Stock for the ten (10) consecutive trading days through and including the Expiration Date (the “Alternate Price”). For example, if you owned 1,000 shares of Common Stock as of 5:00 p.m., Eastern Time, on the Record Date, you would receive one Basic Subscription Right for each share and would have the right to purchase 943 shares of Common Stock (rounded down to the nearest whole share, with the total subscription payment being adjusted accordingly, as discussed below) at the Initial Price. If, on the Expiration Date, the Alternate Price is lower than the Initial Price, any excess subscription amounts paid by a subscriber (the “Excess Subscription Amount”) will be put towards the purchase of additional shares in the rights offering (either towards your Basic Subscription Right, if available, or towards the Over-Subscription Right if you have already exercised your Basic Subscription Right in full).

In the event that you purchase all of the shares of Common Stock available to you pursuant to your Basic Subscription Right, you may also exercise an over-subscription right (the “Over-Subscription Right”, collectively with the Basic Subscription Right, the “Subscription Rights”) to purchase a portion of any shares of Common Stock that are not purchased by stockholders through the exercise of their Basic Subscription Rights (the “Unsubscribed Shares”), subject to the availability and pro rata allocation of the Unsubscribed Shares among all persons exercising this Over-Subscription Right. To the extent the Unsubscribed Shares are not sufficient to satisfy all of the properly exercised Over-Subscription Rights, then the Unsubscribed Shares will be prorated among those who properly exercised the Over-Subscription Rights based on the number of shares each person subscribed for under the Basic Subscription Right. If this pro rata allocation results in any person receiving a greater number of Unsubscribed Shares than the person subscribed for pursuant to the exercise of the Over-Subscription Right, then such person will be allocated only that number of Unsubscribed Shares for which the person oversubscribed, and the remaining Unsubscribed Shares will be allocated among all other persons exercising the Over-Subscription Right on the same pro rata basis described above. The proration process will be repeated until all Unsubscribed Shares have been allocated or all Over-Subscription Rights have been fulfilled, whichever occurs earlier.

You will be required to submit payment in full for all the shares you wish to buy with your Over-Subscription Right. Because we will not know the total number of Unsubscribed Shares prior to the Expiration Date, if you wish to maximize the number of shares you may purchase pursuant to your Over-Subscription Right, you will need to deliver payment in an amount equal to the aggregate Initial Price for the maximum number of shares of Common Stock available to you, assuming that no stockholder other than you has purchased any shares of Common Stock pursuant to the Basic Subscription Right and Over-Subscription Right. The Company will eliminate fractional shares of Common Stock resulting from the exercise of the Over-Subscription Right by rounding down to the nearest whole share, with the total subscription payment being adjusted accordingly. Any excess subscription

payments received by the Broadridge Corporate Issuer Solutions, Inc. (the “Subscription Agent”) will be returned, without interest, as soon as practicable.

The Company can provide no assurances that each of you will actually be entitled to purchase the number of shares of Common Stock issuable upon the exercise of your Over-Subscription Right in full at the expiration of the rights offering. The Company will not be able to satisfy your exercise of the Over-Subscription Right if all of our stockholders exercise their Basic Subscription Rights in full, and we will only honor an Over-Subscription Right to the extent sufficient shares of Common Stock are available following the exercise of Subscription Rights under the Basic Subscription Rights.


			•			To the extent the aggregate Initial Price of the maximum number of Unsubscribed Shares available to you pursuant to the Over-Subscription Right is less than the amount you actually paid in connection with the exercise of the Over-Subscription Right, you will be allocated only the number of Unsubscribed Shares available to you as soon as practicable after the Expiration Date, and your excess subscription payment received by the Subscription Agent will be returned, without interest, as soon as practicable.


			•			To the extent the amount you actually paid in connection with the exercise of the Over-Subscription Right is less than the aggregate Initial Price of the maximum number of Unsubscribed Shares available to you pursuant to the Over-Subscription Right, you will be allocated the number of Unsubscribed Shares for which you actually paid in connection with the Over-Subscription Right. If, on the Expiration Date, the Alternate Price is lower than the Initial Price, any Excess Subscription Amount will be put towards the purchase of additional shares in the rights offering (either towards your Basic Subscription Right, if available, or towards the Over-Subscription Right if you have already exercised your Basic Subscription Right in full). See “The Rights Offering — Subscription Rights — Over-Subscription Rights” in the Prospectus Supplement.

The Subscription Rights are evidenced by a Non-Transferable Subscription Rights Certificate issued to stockholders of record and will cease to have any value at the Expiration Date.

THE MATERIALS ENCLOSED ARE BEING FORWARDED TO YOU AS THE BENEFICIAL OWNER OF COMMON STOCK CARRIED BY US IN YOUR ACCOUNT BUT NOT REGISTERED IN YOUR NAME. THE SUBSCRIPTION RIGHTS MAY BE EXERCISED ONLY BY US AS THE RECORD OWNER AND PURSUANT TO YOUR INSTRUCTIONS.

Accordingly, we request instructions as to whether you wish us to elect to subscribe for any shares of Common Stock to which you are entitled pursuant to the terms and subject to the conditions set forth in the Prospectus Supplement. However, we urge you to read the document carefully before instructing us to exercise your Subscription Rights.

If you wish to have us, on your behalf, exercise the Subscription Rights for any shares of Common Stock to which you are entitled, please so instruct us by completing, executing and returning to us the Beneficial Owner Election form.

Your Beneficial Owner Election form should be forwarded to us as promptly as possible in order to permit us to exercise your Subscription Rights on your behalf in accordance with the provisions of the rights offering. The rights offering will expire at the Expiration Date. Please contact us for our deadline with respect to your submission of the Beneficial Owner Election form. Once you have exercised your Subscription Rights, such exercise may not be revoked, even if you later learn information that you consider to be unfavorable to the exercise of your Subscription Rights.

Additional copies of the enclosed materials may be obtained from Broadridge Corporate Issuer Solutions, Inc., the Subscription Agent for this rights offering, by calling (855) 793-5068 (toll free). Any questions or requests for assistance concerning the rights offering should be directed to the Subscription Agent.

Very truly yours,

Summit Therapeutics Inc.

THE TERMS AND CONDITIONS OF THE RIGHTS OFFERING ARE SET FORTH IN THE COMPANY’S PROSPECTUS SUPPLEMENT DATED JULY 18, 2022 (THE “PROSPECTUS SUPPLEMENT”) AND ARE INCORPORATED HEREIN BY REFERENCE. COPIES OF THE PROSPECTUS AND PROSPECTUS SUPPLEMENT ARE AVAILABLE UPON REQUEST FROM BROADRIDGE CORPORATE ISSUER SOLUTIONS INC., THE SUBSCRIPTION AGENT, BY CALLING (855) 793-5068.

SUMMIT THERAPEUTICS INC.

SHARES OF COMMON STOCK
ISSUABLE UPON EXERCISE OF SUBSCRIPTION RIGHTS

NOMINEE HOLDER CERTIFICATION

The undersigned, a bank, broker, trustee, depository or other nominee holder of subscription rights (the “Subscription Rights”) to purchase shares of common stock, par value $0.01 per share (“Common Stock”), of Summit Therapeutics Inc., a Delaware corporation (the “Company”), pursuant to the rights offering described in Company’s prospectus dated October 15, 2020 (as supplemented by the Prospectus Supplement, the “Prospectus”), hereby certifies to the Company and Broadridge Corporate Issuer Solutions, Inc., the subscription agent for the rights offering, that (1) the undersigned has exercised on behalf of the beneficial owners thereof (which may include the undersigned), the number of Subscription Rights specified below pursuant to the basic subscription right (as defined in the Prospectus Supplement), and on behalf of beneficial owners of Subscription Rights who have subscribed for the purchase of additional shares of Common Stock pursuant to the over-subscription right (as defined in the Prospectus Supplement), listing separately below each such exercised basic subscription right and the corresponding over-subscription right (without identifying any such beneficial owner), and (2) each such beneficial owner’s basic subscription right has been exercised in full:


	NUMBER OF SHARES OWNED ON RECORD DATE	NUMBER OF SHARES SUBSCRIBED FOR PURSUANT TO BASIC SUBSCRIPTION RIGHT	NUMBER OF SHARES SUBSCRIBED FOR PURSUANT TO OVER-SUBSCRIPTION RIGHT
1.
2.
3.
4.
5.


Name of Bank, Broker, Trustee, Depository or Other Nominee:

By:______________________________ Authorized Signature


Name:____________________________
(Please print or type)

Title: ____________________________ (Please print or type)


Provide the following information if applicable:


Depository Trust Company (“DTC”) Participant Number


Participant:

By:______________________________ Authorized Signature


Name:____________________________
(Please print or type)

Title: ____________________________ (Please print or type)


DTC Subscription Confirmation Number(s)

SUMMIT THERAPEUTICS INC.

BENEFICIAL OWNER ELECTION FORM

I (We), the beneficial owner(s) of shares of common stock, par value $0.01 per share (the “Common Stock”), of Summit Therapeutics Inc., a Delaware corporation (the “Company”), acknowledge receipt of your letter, the Company’s prospectus dated October 15, 2020 (as supplemented by the Prospectus Supplement, the “Prospectus”), and the other enclosed materials relating to the offering of shares of Common Stock issuable upon the exercise of subscription rights (“Subscription Rights”) as described in the Prospectus Supplement.

In this form, I (we) instruct you whether to exercise Subscription Rights to purchase shares of Common Stock distributed with respect to the Common Stock held by you for my (our) account, pursuant to the terms and subject to the conditions set forth in the Prospectus Supplement and the related “Form of Instructions for Use of Summit Therapeutics Inc. Non-Transferable Subscription Rights Certificates.”

I (We) hereby instruct you as follow:

(CHECK THE APPLICABLE BOXES AND PROVIDE ALL REQUIRED INFORMATION)


Box 1.	☐	Please DO NOT EXERCISE SUBSCRIPTION RIGHTS for shares of Common Stock.

		If you checked Box 1, please sign and date this form and mail it to your broker, custodian bank or your other nominee that holds your shares.

Box 2.	☐	Please EXERCISE SUBSCRIPTION RIGHTS for shares of Common Stock as set forth below.

		If you checked Box 2, please fill out the table shown below. Next, please check Box 3 and/or Box 4, as applicable, and fill out the information indicated under Box 3 and/or Box 4, as applicable. Please then sign and date this form and mail it to your broker, custodian bank or other nominee that holds your shares.

		The number of Subscription Rights for which the undersigned gives instructions for exercise under the subscription privilege should not exceed the number of Subscription Rights that the undersigned is entitled to exercise.

Number
of
Shares
Owned

Initial
Ratio

Number of
Shares of
Common
Stock
Subscribed
For

Per Share
Initial
Subscription
Price (the
“Initial
Price”)

Payment

Basic Subscription Right:

0.9436442

$ 1.08

$_________ (Line 1)

Over-Subscription Right:

$ 1.08

$_________ (Line 2)

Total Payment Required:

$_________
(Sum of Lines 1 and 2)


Box 3.	☐	Payment in the following amount is enclosed: $__________.

Box 4.	☐	Please deduct payment of $__________ from the following account maintained by you:

		The total of Box 3 and 4, together, must equal the sum of lines 1 and 2 from Box 2 above.

		Type of Account: _________________ Account No.: ____________________

I (We) on my (our) behalf, or on behalf of any other person(s) on whose behalf, or under whose directions, I am (we are) signing this form:


			•			irrevocably elect to purchase the number of shares of Common Stock indicated above upon the terms and conditions specified in the Prospectus Supplement;


			•			understands that if the volume weighted-average price of the Common Stock for the five (5) consecutive trading days at 4:00 p.m., Eastern Time, on July 5, 2022 (the “Alternate Price”) is lower than the Initial Price, any excess subscription amounts paid by me (us) will be put towards the purchase of additional shares in the rights offering (either towards my (our) Basic Subscription Right, if available, or towards the Over-Subscription Right if I (we) have already exercised my (our) Basic Subscription Right in full); and


			•			agree that if I (we) fail to pay for the shares of Common Stock I (we) have elected to purchase, you may exercise any remedies available to you under law.


Name of beneficial owner(s): ____________________

Signature of beneficial owner(s): ______________________

Date: ________________________

If you are signing in your capacity as a trustee, executor, administrator, guardian, attorney-in-fact, agent, officer of a corporation or another acting in a fiduciary or representative capacity, please provide the following information:


Name: __________________________

Capacity: ________________________

Address (including Zip Code): _________________________


Telephone Number: ________________________

PLEASE MAKE SURE THAT YOU USE THE CORRECT ADDRESS. You may want to check this address with your broker.

Summit Therapeutics Announces Commencement of

$100 Million Rights Offering

Menlo Park, California, July 18, 2022 - Summit Therapeutics Inc. (NASDAQ: SMMT) today announced that it has commenced its previously-announced rights offering of up to $100 million of the Company’s common stock. The subscription rights will expire and have no value if they are not exercised prior to 5:00 pm Eastern Time on August 8, 2022, the expiration date (the “Expiration Date”).

Pursuant to the rights offering, Summit is distributing, at no charge to the holders of its common stock as of the close of trading on July 5, 2022 (the “Stockholders”), non-transferable subscription rights to purchase shares of the Company’s common stock, par value $0.01 (“Shares,” and each, a “Share”). The subscription price per Share shall be equal to the lesser of (i) $1.08 per share (the “Initial Price”) or (ii) the volume weighted-average price of the Company’s common stock for the five consecutive trading days through and including the Expiration Date (the “Alternate Price”).

The subscription price per Share will determine the final number of Shares issuable, and subsequently the pro rata number of Shares to which Stockholders can subscribe.

Stockholders wishing to exercise their subscription rights must timely pay $1.08 per Share, the Initial Price, for the number of Shares they wish to acquire. If the Alternate Price is lower than the Initial Price as of the Expiration Date, any excess subscription amounts paid by a subscribing holder will be applied towards the purchase of additional Shares in the rights offering. Stockholders who fully exercise their basic subscription rights will be entitled to subscribe for additional Shares that are not purchased by other Stockholders on a pro rata basis and subject to availability.

A prospectus supplement relating to the offering was filed with the US Securities and Exchange Commission (the “SEC”) on July 18, 2022 and is available on the SEC’s website. Questions about the offering and requests for copies of the prospectus relating to the rights offering may be directed to Broadridge Corporate Issuers Solutions, Inc., the Company’s information and subscription agent for the rights offering, at the email address and/or telephone number provided at the end of the release.

This press release does not constitute an offer to sell or the solicitation of an offer to buy these securities, nor will there be any sale of these securities in any state or other jurisdiction in which such offer, solicitation, or sale would be unlawful prior to registration or qualification under the securities laws of any such state or jurisdiction. The rights offering is made pursuant to the Company’s shelf registration statement on Form S-3, which became effective on October 15, 2020, and the prospectus supplement containing the detailed terms of the rights offering filed with the SEC. Any offer will be made only by means of a prospectus forming part of the registration statement.

Contact Summit Investor Relations:

Dave Gancarz

Head of Stakeholder Relations & Corporate Strategy

david.gancarz@summitplc.com

General Inquiries:

investors@summitplc.com

Rights Offering Information and Subscription Agent:

Broadridge Corporate Issuer Solutions, Inc.

+1 855 793 5068

shareholder@broadridge.com

Summit Forward-looking Statements

Any statements in this press release about the Company’s future expectations, plans and prospects, including but not limited to, statements about the clinical and preclinical development of the Company’s product candidates, the therapeutic potential of the Company’s product candidates, the potential commercialization of the Company’s product candidates, the timing of initiation, completion and availability of data from clinical trials, the potential submission of applications for marketing approvals, the impact of the COVID-19 pandemic on the Company’s operations and clinical trials, potential acquisitions and other statements containing the words "anticipate," "believe," "continue," "could," "estimate," "expect," "intend," "may," "plan," "potential," "predict," "project," "should," "target," "would," and similar expressions, constitute forward-looking statements within the meaning of The Private Securities Litigation Reform Act of 1995. Actual results may differ materially from those indicated by such forward-looking statements as a result of various important factors, including the results of our evaluation of the underlying data in connection with the topline results of our Phase III Ri-CoDIFy study evaluating ridinilazole, the outcome of discussions with regulatory authorities, including the Food and Drug Administration, the uncertainties inherent in the initiation of future clinical trials, availability and timing of data from ongoing and future clinical trials, the results of such trials, and their success, and global public health crises, including the coronavirus COVID-19 outbreak, that may affect timing and status of our clinical trials and operations, whether preliminary results from a clinical trial will be predictive of the final results of that trial or whether results of early clinical trials or preclinical studies will be indicative of the results of later clinical trials, whether business development opportunities to expand the Company’s pipeline of drug candidates, including without limitation, through potential acquisitions of, and/or collaborations with, other entities occur, expectations for regulatory approvals, laws and regulations affecting government contracts and funding awards, availability of funding sufficient for the Company’s foreseeable and unforeseeable operating expenses and capital expenditure requirements and other factors discussed in the "Risk Factors" section of filings that the Company makes with the Securities and Exchange Commission. Any change to our ongoing trials could cause delays, affect our future expenses, and add uncertainty to our commercialization efforts, as well as to affect the likelihood of the successful completion of clinical development of ridinilazole. Accordingly, readers should not place undue reliance on forward-looking statements or information. In addition, any forward-looking statements included in this press release represent the Company’s views only as of the date of this release and should not be relied upon as representing the Company’s views as of any subsequent date. The Company specifically disclaims any obligation to update any forward-looking statements included in this press release.