<SEC-DOCUMENT>0001104659-17-003599.txt : 20170123
<SEC-HEADER>0001104659-17-003599.hdr.sgml : 20170123
<ACCEPTANCE-DATETIME>20170123180304
ACCESSION NUMBER:		0001104659-17-003599
CONFORMED SUBMISSION TYPE:	3
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20170120
FILED AS OF DATE:		20170123
DATE AS OF CHANGE:		20170123

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			LEAP THERAPEUTICS, INC.
		CENTRAL INDEX KEY:			0001509745
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		IRS NUMBER:				274412575
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		47 THORNDIKE STREET
		STREET 2:		SUITE B1-1
		CITY:			CAMBRIDGE
		STATE:			MA
		ZIP:			02142
		BUSINESS PHONE:		617 252 4343

	MAIL ADDRESS:	
		STREET 1:		47 THORNDIKE STREET
		STREET 2:		SUITE B1-1
		CITY:			CAMBRIDGE
		STATE:			MA
		ZIP:			02142

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	Dekkun Corp
		DATE OF NAME CHANGE:	20110107

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			ONSI DOUGLAS E
		CENTRAL INDEX KEY:			0001270185

	FILING VALUES:
		FORM TYPE:		3
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-37990
		FILM NUMBER:		17542119

	MAIL ADDRESS:	
		STREET 1:		C/O TOLERRX INC
		STREET 2:		300 TECHNOLOGY SQUARE
		CITY:			CAMBRIDGE
		STATE:			MA
		ZIP:			02139
</SEC-HEADER>
<DOCUMENT>
<TYPE>3
<SEQUENCE>1
<FILENAME>a3.xml
<DESCRIPTION>3
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0206</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2017-01-20</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0001509745</issuerCik>
        <issuerName>LEAP THERAPEUTICS, INC.</issuerName>
        <issuerTradingSymbol>LPTX</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001270185</rptOwnerCik>
            <rptOwnerName>ONSI DOUGLAS E</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O LEAP THERAPEUTICS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>47 THORNDIKE STREET SUITE B1-1</rptOwnerStreet2>
            <rptOwnerCity>CAMBRIDGE</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02141</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>CFO,Gen Counsel,Treas, Sec.</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2859496</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnotes</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Consists of (i) 2,515,607 held by HealthCare Ventures IX, L.P. and (ii) 343,889 shares held by HealthCare Ventures Strategic Fund, L.P. Christopher K. Mirabelli, Douglas E. Onsi and Augustine Lawlor (collectively, the &quot;HCVIX Directors&quot;) are the Managing Directors of HealthCare Partners IX, LLC (&quot;HCPIX LLC&quot;), which is the General Partner of HealthCare Partners IX, L.P. (&quot;HCPIX&quot;), which is the General Partner of HealthCare Ventures IX, L.P. Each of the HCVIX Directors, HCPIX LLC and HCPIX beneficially own and share voting and dispositive power with respect to all of the securities owned by HealthCare Ventures IX, L.P. Douglas E. Onsi disclaims beneficial ownership of these shares except to the extent of his proportionate pecuniary interest in these securities.</footnote>
        <footnote id="F2">Christopher K. Mirabelli, Douglas E. Onsi and Augustine Lawlor (collectively, the &quot;HCSP Directors&quot;) are the Managing Directors of HealthCare Strategic Partners, LLC (&quot;HCV Strategic LLC&quot;), which is the General Partner of HealthCare Ventures Strategic Fund, L.P. Each of the HCSP Directors, and HCV Strategic LLC beneficially own and share voting and dispositive power with respect to all of the securities owned by HCV Strategic Fund, L.P. Douglas E. Onsi disclaims beneficial ownership of these shares except to the extent of his proportionate pecuniary interest in these securities.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Douglas E. Onsi</signatureName>
        <signatureDate>2017-01-23</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
