<SEC-DOCUMENT>0001104659-18-048863.txt : 20180801
<SEC-HEADER>0001104659-18-048863.hdr.sgml : 20180801
<ACCEPTANCE-DATETIME>20180801192201
ACCESSION NUMBER:		0001104659-18-048863
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20180730
FILED AS OF DATE:		20180801
DATE AS OF CHANGE:		20180801

REPORTING-OWNER:	

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

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-37990
		FILM NUMBER:		18986197

	MAIL ADDRESS:	
		STREET 1:		C/O TOLERRX INC
		STREET 2:		300 TECHNOLOGY SQUARE
		CITY:			CAMBRIDGE
		STATE:			MA
		ZIP:			02139

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
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>a4.xml
<DESCRIPTION>4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2018-07-30</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <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, GC, Treasurer &amp; Secretary</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Warrant (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>6.085</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2018-07-30</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
                <footnoteId id="F2"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>21369</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2017-11-14</value>
            </exerciseDate>
            <expirationDate>
                <value>2024-11-14</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>21369</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>21369</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnote</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Pro rata distribution from HealthCare Ventures IX, L.P. (&quot;HCV IX&quot;) to its limited partner, Nine Capital Partners, LLC.  Christopher K. Mirabelli, Douglas E. Onsi and Augustine Lawlor are the Managing Members of Nine Capital Partners, LLC, and as such, beneficially own and share voting and dispositive power with respect to all of the securities owned by Nine Capital Partners, LLC.  Mr. Onsi disclaims beneficial ownership of these shares except to the extent of his proportionate pecuniary interest in these securities. The reporting person is also (i) a Managing Director of HealthCare Partners IX, LLC, which is the General Partner of HealthCare Partners IX, L.P., which is the General Partner of HCV IX and (ii) a Managing Director of HCV Strategic LLC, which is the General Partner of HealthCare Ventures Strategic Fund, L.P. (&quot;HCV SF&quot;).</footnote>
        <footnote id="F2">HCV IX continues to hold 3,573,376 shares of common stock and HCV SF continues to hold 343,889 shares of common stock, representing 24.3% and 2.3% respectively, and 26.6% in the aggregate, of the outstanding shares of common stock.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Douglas E. Onsi</signatureName>
        <signatureDate>2018-08-01</signatureDate>
    </ownerSignature>
</ownershipDocument>
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</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
