<SEC-DOCUMENT>0000315066-21-001812.txt : 20211028
<SEC-HEADER>0000315066-21-001812.hdr.sgml : 20211028
<ACCEPTANCE-DATETIME>20211028154521
ACCESSION NUMBER:		0000315066-21-001812
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20211026
FILED AS OF DATE:		20211028
DATE AS OF CHANGE:		20211028

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			FMR LLC
		CENTRAL INDEX KEY:			0000315066
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-40925
		FILM NUMBER:		211357900

	BUSINESS ADDRESS:	
		STREET 1:		245 SUMMER STREET
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02210
		BUSINESS PHONE:		6175706339

	MAIL ADDRESS:	
		STREET 1:		245 SUMMER STREET
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02210

	FORMER NAME:	
		FORMER CONFORMED NAME:	FMR CORP
		DATE OF NAME CHANGE:	19920717

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			Xilio Therapeutics, Inc.
		CENTRAL INDEX KEY:			0001840233
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		IRS NUMBER:				851623397
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		828 WINTER STREET
		CITY:			WALTHAM
		STATE:			MA
		ZIP:			02451
		BUSINESS PHONE:		617-833-1027

	MAIL ADDRESS:	
		STREET 1:		828 WINTER STREET
		CITY:			WALTHAM
		STATE:			MA
		ZIP:			02451
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
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    <periodOfReport>2021-10-26</periodOfReport>

    <notSubjectToSection16>1</notSubjectToSection16>

    <issuer>
        <issuerCik>0001840233</issuerCik>
        <issuerName>Xilio Therapeutics, Inc.</issuerName>
        <issuerTradingSymbol>XLO</issuerTradingSymbol>
    </issuer>

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        <reportingOwnerId>
            <rptOwnerCik>0000315066</rptOwnerCik>
            <rptOwnerName>FMR LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>245 SUMMER STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02210</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
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        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>1</isOther>
            <otherText>See Remark 1</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

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                    <value>F-Prime Capital Partners Healthcare Fund IV LP</value>
                </natureOfOwnership>
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        <nonDerivativeTransaction>
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                <value>Common Stock</value>
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                <sharesOwnedFollowingTransaction>
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                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Impresa Fund III Limited Partnership</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2021-10-26</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>C</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
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            <transactionTimeliness>
                <value></value>
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                    <value>4465</value>
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                    <footnoteId id="F1"/>
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                <directOrIndirectOwnership>
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                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>F-Prime Capital Partners Healthcare Advisors Fund IV LP</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
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    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Series A Preferred Stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
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            <transactionDate>
                <value>2021-10-26</value>
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            </transactionTimeliness>
            <transactionAmounts>
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                    <value>7500000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F1"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>789473</value>
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            </underlyingSecurity>
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                </directOrIndirectOwnership>
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                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
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                <equitySwapInvolved>0</equitySwapInvolved>
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            <transactionTimeliness>
                <value></value>
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            <transactionAmounts>
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                <transactionPricePerShare>
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                <transactionAcquiredDisposedCode>
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                <underlyingSecurityTitle>
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                <directOrIndirectOwnership>
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                </directOrIndirectOwnership>
                <natureOfOwnership>
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            <securityTitle>
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            <transactionAmounts>
                <transactionShares>
                    <value>42421</value>
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                <transactionPricePerShare>
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                <footnoteId id="F1"/>
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                <footnoteId id="F1"/>
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                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>4465</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
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                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
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            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>F-Prime Capital Partners Healthcare Advisors Fund IV LP</value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">On October 26, 2021, in connection with the completion of the issuer's initial public offering, each share of  Series A, A-1, and B Preferred Stock converted on a 1-for-9.5 basis into shares of Common Stock.</footnote>
    </footnotes>

    <remarks>Remark 1: Abigail P. Johnson is a Director, the Chairman and the Chief Executive Officer of FMR LLC. Members of the Johnson family, including Abigail P. Johnson, are the predominant owners, directly or through trusts, of Series B voting common shares of FMR LLC, representing 49% of the voting power of FMR LLC. The Johnson family group and all other Series B shareholders have entered into a shareholders' voting agreement under which all Series B voting common shares will be voted in accordance with the majority vote of Series B voting common shares. Accordingly, through their ownership of voting common shares and the execution of the shareholders' voting agreement, members of the Johnson family may be deemed, under the Investment Company Act of 1940, to form a controlling group with respect to FMR LLC. The address of Abigail P. Johnson is c/o FMR LLC, 245 Summer Street, Boston, MA 02110.
Remark 2: The filing of this statement shall not be deemed to be an admission that, for purposes of Section 16 of the Securities Exchange Act of 1934 or otherwise, the undersigned are the beneficial owners of any securities reported herein.
Remark 3: F-Prime Capital Partners Healthcare Advisors Fund IV LP (FPCPHA) is the general partner of F-Prime Capital Partners Healthcare Fund IV LP.  FPCPHA is solely managed by Impresa Management LLC, the managing member of its general partner and its investment manager.  Impresa Fund III Limited Partnership is solely managed by Impresa Management LLC, its general partner and investment manager. Impresa Management LLC is owned, directly or indirectly, by various shareholders and employees of FMR LLC, including certain members of the Johnson family.</remarks>

    <ownerSignature>
        <signatureName>Kevin M. Meagher, Duly authorized under Powers of Attorney, by and on behalf of FMR LLC and its direct and indirect subsidiaries, and Abigail P. Johnson</signatureName>
        <signatureDate>2021-10-28</signatureDate>
    </ownerSignature>
</ownershipDocument>
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</SEC-DOCUMENT>
