<SEC-DOCUMENT>0000950170-25-062123.txt : 20250501
<SEC-HEADER>0000950170-25-062123.hdr.sgml : 20250501
<ACCEPTANCE-DATETIME>20250501181657
ACCESSION NUMBER:		0000950170-25-062123
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20250429
FILED AS OF DATE:		20250501
DATE AS OF CHANGE:		20250501

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Harwin Peter Evan
		CENTRAL INDEX KEY:			0001663607
		ORGANIZATION NAME:           	

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-40544
		FILM NUMBER:		25904845

	MAIL ADDRESS:	
		STREET 1:		200 BARR HARBOR DRIVE
		STREET 2:		SUITE 400
		CITY:			WEST CONSHOHOCKEN
		STATE:			PA
		ZIP:			19428

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Fairmount Healthcare Fund II L.P.
		CENTRAL INDEX KEY:			0001769651
		ORGANIZATION NAME:           	
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-40544
		FILM NUMBER:		25904847

	BUSINESS ADDRESS:	
		STREET 1:		200 BARR HARBOR DRIVE
		STREET 2:		SUITE 400
		CITY:			WEST CONSHOHOCKEN
		STATE:			PA
		ZIP:			19428
		BUSINESS PHONE:		(267) 760-4066

	MAIL ADDRESS:	
		STREET 1:		200 BARR HARBOR DRIVE
		STREET 2:		SUITE 400
		CITY:			WEST CONSHOHOCKEN
		STATE:			PA
		ZIP:			19428

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Kiselak Tomas
		CENTRAL INDEX KEY:			0001830177
		ORGANIZATION NAME:           	

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-40544
		FILM NUMBER:		25904846

	MAIL ADDRESS:	
		STREET 1:		200 BARR HARBOR DRIVE
		STREET 2:		SUITE 400
		CITY:			WEST CONSHOHOCKEN
		STATE:			PA
		ZIP:			19428

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Fairmount Funds Management LLC
		CENTRAL INDEX KEY:			0001802528
		ORGANIZATION NAME:           	
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-40544
		FILM NUMBER:		25904848

	BUSINESS ADDRESS:	
		STREET 1:		200 BARR HARBOR DRIVE
		STREET 2:		SUITE 400
		CITY:			WEST CONSHOHOCKEN
		STATE:			PA
		ZIP:			19428
		BUSINESS PHONE:		267-262-5300

	MAIL ADDRESS:	
		STREET 1:		200 BARR HARBOR DRIVE
		STREET 2:		SUITE 400
		CITY:			WEST CONSHOHOCKEN
		STATE:			PA
		ZIP:			19428

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			Jade Biosciences, Inc.
		CENTRAL INDEX KEY:			0001798749
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		ORGANIZATION NAME:           	03 Life Sciences
		EIN:				831377888
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		221 CRESCENT ST.
		STREET 2:		BUILDING 23, SUITE 105
		CITY:			WALTHAM
		STATE:			MA
		ZIP:			02453
		BUSINESS PHONE:		(781) 312-3013

	MAIL ADDRESS:	
		STREET 1:		221 CRESCENT ST.
		STREET 2:		BUILDING 23, SUITE 105
		CITY:			WALTHAM
		STATE:			MA
		ZIP:			02453

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	Aerovate Therapeutics, Inc.
		DATE OF NAME CHANGE:	20200103
</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>2025-04-29</periodOfReport>

    <issuer>
        <issuerCik>0001798749</issuerCik>
        <issuerName>Jade Biosciences, Inc.</issuerName>
        <issuerTradingSymbol>JBIO</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001802528</rptOwnerCik>
            <rptOwnerName>Fairmount Funds Management LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>200 BARR HARBOR DRIVE, SUITE 400</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>WEST CONSHOHOCKEN</rptOwnerCity>
            <rptOwnerState>PA</rptOwnerState>
            <rptOwnerZipCode>19428</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>true</isDirector>
            <isOfficer>false</isOfficer>
            <isTenPercentOwner>true</isTenPercentOwner>
            <isOther>false</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001769651</rptOwnerCik>
            <rptOwnerName>Fairmount Healthcare Fund II L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>200 BARR HARBOR DRIVE SUITE 400</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>WEST CONSHOHOCKEN</rptOwnerCity>
            <rptOwnerState>PA</rptOwnerState>
            <rptOwnerZipCode>19428</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>true</isDirector>
            <isOfficer>false</isOfficer>
            <isTenPercentOwner>true</isTenPercentOwner>
            <isOther>false</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001830177</rptOwnerCik>
            <rptOwnerName>Kiselak Tomas</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>200 BARR HARBOR DRIVE SUITE 400</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>WEST CONSHOHOCKEN</rptOwnerCity>
            <rptOwnerState>PA</rptOwnerState>
            <rptOwnerZipCode>19428</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>true</isDirector>
            <isOfficer>false</isOfficer>
            <isTenPercentOwner>true</isTenPercentOwner>
            <isOther>false</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001663607</rptOwnerCik>
            <rptOwnerName>Harwin Peter Evan</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>200 BARR HARBOR DRIVE SUITE 400</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>WEST CONSHOHOCKEN</rptOwnerCity>
            <rptOwnerState>PA</rptOwnerState>
            <rptOwnerZipCode>19428</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>10.14</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2025-04-29</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>false</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>23017</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2035-04-29</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>23017</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>23017</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F2"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">This option represents a right to purchase 23,017 shares of the Issuer's common stock, which vests in full on the earlier of (i) April 29, 2026 or (ii) the date of the next annual meeting of the Issuer's stockholders, in each case, subject to the recipient's continued service to the Issuer.</footnote>
        <footnote id="F2">Under Mr. Kiselak's arrangement with Fairmount Funds Management LLC (&quot;Fairmount&quot;), Mr. Kiselak holds the option for one or more investment vehicles managed by Fairmount (each, a &quot;Fairmount Fund&quot;). Mr. Kiselak is obligated to turn over to Fairmount any net cash or stock received from the option for the benefit of such Fairmount Fund. Mr. Kiselak therefore disclaims beneficial ownership of the option and underlying common stock. Fairmount disclaims beneficial ownership of any of the reported securities, except to the extent of its pecuniary interest therein.</footnote>
    </footnotes>

    <remarks>Fairmount, Fairmount Healthcare Fund II LP and Fairmount Healthcare Co-Invest IV L.P. may each be deemed a director by deputization of the Issuer by virtue of the fact that Tomas Kiselak serves on the board of directors of the Issuer and is a manager of Fairmount.</remarks>

    <ownerSignature>
        <signatureName>/s/ Tomas Kiselak, Managing Member of Fairmount Funds Management LLC</signatureName>
        <signatureDate>2025-05-01</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Tomas Kiselak, Managing Member of Fairmount Healthcare Fund II L.P.</signatureName>
        <signatureDate>2025-05-01</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Tomas Kiselak</signatureName>
        <signatureDate>2025-05-01</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Peter Harwin</signatureName>
        <signatureDate>2025-05-01</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
