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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 TMSLy7eynuIAKWYmxfKgLgrYpAO8jj7OhpREpZfSDgShGxiDx/ZgGmrbDil0MBS6
 a4ZCd5Ly/RWsInkK9autDw==

<SEC-DOCUMENT>0001179110-08-006077.txt : 20080317
<SEC-HEADER>0001179110-08-006077.hdr.sgml : 20080317
<ACCEPTANCE-DATETIME>20080317175405
ACCESSION NUMBER:		0001179110-08-006077
CONFORMED SUBMISSION TYPE:	3
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20080307
FILED AS OF DATE:		20080317
DATE AS OF CHANGE:		20080317

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			AVANT IMMUNOTHERAPEUTICS INC
		CENTRAL INDEX KEY:			0000744218
		STANDARD INDUSTRIAL CLASSIFICATION:	IN VITRO & IN VIVO DIAGNOSTIC SUBSTANCES [2835]
		IRS NUMBER:				133191702
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		119 FOURTH AVE
		CITY:			NEEDHAM
		STATE:			MA
		ZIP:			02494
		BUSINESS PHONE:		7814330771

	MAIL ADDRESS:	
		STREET 1:		119 FOURTH AVE
		CITY:			NEEDHAM
		STATE:			MA
		ZIP:			021942725

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	T CELL SCIENCES INC
		DATE OF NAME CHANGE:	19920703

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			MEDAREX INC
		CENTRAL INDEX KEY:			0000874255
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-COMMERCIAL PHYSICAL & BIOLOGICAL RESEARCH [8731]
		STATE OF INCORPORATION:			NJ
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		3
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-15006
		FILM NUMBER:		08694354

	BUSINESS ADDRESS:	
		STREET 1:		707 STATE ROAD 206
		CITY:			PRINCETON
		STATE:			NJ
		ZIP:			08540
		BUSINESS PHONE:		9087136001

	MAIL ADDRESS:	
		STREET 1:		707 STATE ROAD 206
		CITY:			PRINCETON
		STATE:			NJ
		ZIP:			08540
</SEC-HEADER>
<DOCUMENT>
<TYPE>3
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>FORM 3 -
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2008-03-07</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0000744218</issuerCik>
        <issuerName>AVANT IMMUNOTHERAPEUTICS INC</issuerName>
        <issuerTradingSymbol>AVAN</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000874255</rptOwnerCik>
            <rptOwnerName>MEDAREX INC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>707 STATE ROAD</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>PRINCETON</rptOwnerCity>
            <rptOwnerState>NJ</rptOwnerState>
            <rptOwnerZipCode>08540</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>5312539</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">The Board of Directors of AVANT Immunotherapeutics, Inc., approved a 1-for 12 reverse stock split of AVANT's common stock, which became effective as of March 7, 2008.  As a result of the reverse stock split, each twelve shares of AVANT common stock were combined and reclassified into one share of AVANT common stock.  The number of shares reported on this form is reflected on a post-split basis.  The common stock will trade under the symbol &quot;AVAND&quot; for 20 trading days beginning on March 10, 2008 to designate that it is trading on a post-reverse split basis, and will remain trading under the symbol &quot;AVAN&quot; after the 20-day period has expired.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/Christian Scade, CFO on behalf of Medarex, Inc.</signatureName>
        <signatureDate>2008-03-14</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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