-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
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 4hybbFvsK0M5e9aMQjxjrA==

<SEC-DOCUMENT>0001140361-10-016109.txt : 20100412
<SEC-HEADER>0001140361-10-016109.hdr.sgml : 20100412
<ACCEPTANCE-DATETIME>20100412161958
ACCESSION NUMBER:		0001140361-10-016109
CONFORMED SUBMISSION TYPE:	4/A
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20100408
FILED AS OF DATE:		20100412
DATE AS OF CHANGE:		20100412

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			KLARMAN SETH A
		CENTRAL INDEX KEY:			0000899869
		STATE OF INCORPORATION:			MA
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4/A
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-34154
		FILM NUMBER:		10745117

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		6172108300

	MAIL ADDRESS:	
		STREET 1:		10 ST JAMES AVENUE
		STREET 2:		STE 1700
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02116

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			FACET BIOTECH CORP
		CENTRAL INDEX KEY:			0001441848
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		IRS NUMBER:				263070657
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		1500 SEAPORT BLVD.
		CITY:			REDWOOD CITY
		STATE:			CA
		ZIP:			94063
		BUSINESS PHONE:		650-454-1000

	MAIL ADDRESS:	
		STREET 1:		1500 SEAPORT BLVD.
		CITY:			REDWOOD CITY
		STATE:			CA
		ZIP:			94063

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	Biotech Spinco, Inc.
		DATE OF NAME CHANGE:	20080804

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			SAK CORP
		CENTRAL INDEX KEY:			0001061088
		STATE OF INCORPORATION:			MA

	FILING VALUES:
		FORM TYPE:		4/A
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-34154
		FILM NUMBER:		10745118

	BUSINESS ADDRESS:	
		STREET 1:		10 ST JAMES AVENUE
		STREET 2:		STE 1700
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02116
		BUSINESS PHONE:		6172108300

	MAIL ADDRESS:	
		STREET 1:		10 ST JAMES AVENUE
		STREET 2:		STE 1700
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02116

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			BAUPOST GROUP LLC/MA
		CENTRAL INDEX KEY:			0001061768

	FILING VALUES:
		FORM TYPE:		4/A
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-34154
		FILM NUMBER:		10745119

	BUSINESS ADDRESS:	
		STREET 1:		10 ST JAMES AVE
		STREET 2:		SUITE 1700
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02116
		BUSINESS PHONE:		617-210-8300

	MAIL ADDRESS:	
		STREET 1:		10 ST JAMES AVE
		STREET 2:		SUITE 1700
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02116
</SEC-HEADER>
<DOCUMENT>
<TYPE>4/A
<SEQUENCE>1
<FILENAME>doc1.xml
<DESCRIPTION>FORM 4/A
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2010-04-08</periodOfReport>

    <dateOfOriginalSubmission>2009-09-08</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001441848</issuerCik>
        <issuerName>FACET BIOTECH CORP</issuerName>
        <issuerTradingSymbol>FACT</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001061768</rptOwnerCik>
            <rptOwnerName>BAUPOST GROUP LLC/MA</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>10 ST JAMES AVE</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 1700</rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02116</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001061088</rptOwnerCik>
            <rptOwnerName>SAK CORP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>10 ST JAMES AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2>STE 1700</rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02116</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000899869</rptOwnerCik>
            <rptOwnerName>KLARMAN SETH A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>10 ST. JAMES AVE.</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 1700</rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02116</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, $0.01 par value per share</value>
            </securityTitle>
            <transactionDate>
                <value>2010-04-08</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>500000</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>26.96</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1500000</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                    <footnoteId id="F1"/>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnote</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">This statement on Form 4 is being jointly filed by The Baupost Group, L.L.C. (Baupost), SAK Corporation and Seth A. Klarman. Baupost is a registered investment adviser under the Investment Advisers Act of 1940, as amended, and acts as an investment adviser to certain investment limited partnerships. Securities reported on this Form 4 as being beneficially owned by Baupost include securities held by such investment limited partnerships, for which Baupost is the general partner and investment adviser. SAK Corporation is the manager of Baupost. Mr. Klarman is the sole director and sole officer of SAK Corporation and a controlling person of Baupost. The reporting persons disclaim beneficial ownership of the securities except to the extent of their pecuniary interests therein.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>The Baupost Group, LLC, by /s/ Seth A. Klarman</signatureName>
        <signatureDate>2010-04-12</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>SAK Corporation, by /s/ Seth A. Klarman</signatureName>
        <signatureDate>2010-04-12</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Seth A. Klarman</signatureName>
        <signatureDate>2010-04-12</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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