<SEC-DOCUMENT>0000921895-21-001335.txt : 20210514
<SEC-HEADER>0000921895-21-001335.hdr.sgml : 20210514
<ACCEPTANCE-DATETIME>20210514163910
ACCESSION NUMBER:		0000921895-21-001335
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20210512
FILED AS OF DATE:		20210514
DATE AS OF CHANGE:		20210514

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			DUGGAN ROBERT W
		CENTRAL INDEX KEY:			0001055919

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-36866
		FILM NUMBER:		21925347

	MAIL ADDRESS:	
		STREET 1:		611 SOUTH FORT HARRISON AVE
		STREET 2:		SUITE 306
		CITY:			CLEARWATER
		STATE:			FL
		ZIP:			33756

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			Summit Therapeutics Inc.
		CENTRAL INDEX KEY:			0001599298
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		IRS NUMBER:				000000000
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		ONE BROADWAY
		STREET 2:		14TH FLOOR
		CITY:			CAMBRIDGE
		STATE:			MA
		ZIP:			02142
		BUSINESS PHONE:		617-514-7149

	MAIL ADDRESS:	
		STREET 1:		ONE BROADWAY
		STREET 2:		14TH FLOOR
		CITY:			CAMBRIDGE
		STATE:			MA
		ZIP:			02142

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	Summit Therapeutics plc
		DATE OF NAME CHANGE:	20150219

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	Summit Corp plc
		DATE OF NAME CHANGE:	20140205
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>form412566dug_05142021.xml
<DESCRIPTION>OWNERSHIP DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2021-05-12</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001599298</issuerCik>
        <issuerName>Summit Therapeutics Inc.</issuerName>
        <issuerTradingSymbol>SMMT</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001055919</rptOwnerCik>
            <rptOwnerName>DUGGAN ROBERT W</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>611 SOUTH FORT HARRISON AVE</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 306</rptOwnerStreet2>
            <rptOwnerCity>CLEARWATER</rptOwnerCity>
            <rptOwnerState>FL</rptOwnerState>
            <rptOwnerZipCode>33756</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chief Executive Officer</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2021-05-12</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>11365921</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>5.24</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>67662454</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Represents the number of shares of Common Stock that the Reporting Person purchased in the Issuer's rights offering.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Michael Paul Donaldson, Attorney-in-Fact</signatureName>
        <signatureDate>2021-05-14</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
