<SEC-DOCUMENT>0000950170-25-089072.txt : 20250623
<SEC-HEADER>0000950170-25-089072.hdr.sgml : 20250623
<ACCEPTANCE-DATETIME>20250623171129
ACCESSION NUMBER:		0000950170-25-089072
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20250623
FILED AS OF DATE:		20250623
DATE AS OF CHANGE:		20250623

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Burow Kristina
		CENTRAL INDEX KEY:			0001569248
		ORGANIZATION NAME:           	

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-41989
		FILM NUMBER:		251065835

	MAIL ADDRESS:	
		STREET 1:		8755 W. HIGGINS ROAD
		STREET 2:		SUITE 1025
		CITY:			CHICAGO
		STATE:			IL
		ZIP:			60631

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			Boundless Bio, Inc.
		CENTRAL INDEX KEY:			0001782303
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		ORGANIZATION NAME:           	03 Life Sciences
		EIN:				830751369
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		10955 ALEXANDRIA WAY
		STREET 2:		SUITE 100
		CITY:			SAN DIEGO
		STATE:			CA
		ZIP:			92121
		BUSINESS PHONE:		(858) 766-9912

	MAIL ADDRESS:	
		STREET 1:		10955 ALEXANDRIA WAY
		STREET 2:		SUITE 100
		CITY:			SAN DIEGO
		STATE:			CA
		ZIP:			92121
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>ownership.xml
<DESCRIPTION>4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2025-06-23</periodOfReport>

    <issuer>
        <issuerCik>0001782303</issuerCik>
        <issuerName>Boundless Bio, Inc.</issuerName>
        <issuerTradingSymbol>BOLD</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001569248</rptOwnerCik>
            <rptOwnerName>Burow Kristina</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O BOUNDLESS BIO, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>10955 ALEXANDRIA WAY, SUITE 100</rptOwnerStreet2>
            <rptOwnerCity>SAN DIEGO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>92121</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>true</isDirector>
            <isOfficer>false</isOfficer>
            <isTenPercentOwner>true</isTenPercentOwner>
            <isOther>false</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>false</aff10b5One>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Option (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>1.03</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2025-06-23</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>false</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>16000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2035-06-22</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>16000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>16000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The stock option shall vest in substantially equal monthly installments over the 12 months following June 23, 2025 (or, in the event the next annual meeting of the issuer's stockholders occurs prior to June 23, 2026, any remaining unvested portion of the stock option will vest on the date of such annual meeting), subject to the reporting person's continuing service on the issuer's board of directors through such vesting date.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Jessica Oien, Attorney-in-Fact for Kristina Burow</signatureName>
        <signatureDate>2025-06-23</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
