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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
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 Z4dEa8ZIvHa+BcxWHlhwEw==

<SEC-DOCUMENT>0001181431-09-059205.txt : 20091230
<SEC-HEADER>0001181431-09-059205.hdr.sgml : 20091230
<ACCEPTANCE-DATETIME>20091230170456
ACCESSION NUMBER:		0001181431-09-059205
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20091228
FILED AS OF DATE:		20091230
DATE AS OF CHANGE:		20091230

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			INVESTOR GROWTH CAPITAL LTD
		CENTRAL INDEX KEY:			0001237710
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-33095
		FILM NUMBER:		091266994

	BUSINESS ADDRESS:	
		STREET 1:		C/O INVESTOR GROWTH INC
		STREET 2:		12 E 49TH STREET 27 FL
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10017
		BUSINESS PHONE:		2125159000

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			ACHILLION PHARMACEUTICALS INC
		CENTRAL INDEX KEY:			0001070336
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		IRS NUMBER:				000000000

	BUSINESS ADDRESS:	
		STREET 1:		300 GEORGE STREET
		CITY:			NEW HAVEN
		STATE:			CT
		ZIP:			06511
		BUSINESS PHONE:		203-624-7000

	MAIL ADDRESS:	
		STREET 1:		300 GEORGE STREET
		CITY:			NEW HAVEN
		STATE:			CT
		ZIP:			06511

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			INVESTOR AB
		CENTRAL INDEX KEY:			0000889232

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-33095
		FILM NUMBER:		091266995

	BUSINESS ADDRESS:	
		STREET 1:		ARAENALSGATAN SC
		STREET 2:		S-103 32
		CITY:			STOCKHOLM SWEDEN
		STATE:			V7
		ZIP:			00000
		BUSINESS PHONE:		310 2291000

	MAIL ADDRESS:	
		STREET 1:		ARAENALSGATAN SC
		STREET 2:		S-103 32
		CITY:			STOCKHOLM
		STATE:			V7
		ZIP:			15222
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>rrd261185.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2009-12-28</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001070336</issuerCik>
        <issuerName>ACHILLION PHARMACEUTICALS INC</issuerName>
        <issuerTradingSymbol>ACHN</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000889232</rptOwnerCik>
            <rptOwnerName>INVESTOR AB</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>ARSENALSGATAN 8C S-103</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>STOCKHOLM</rptOwnerCity>
            <rptOwnerState>V7</rptOwnerState>
            <rptOwnerZipCode></rptOwnerZipCode>
            <rptOwnerStateDescription>SWEDEN</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001237710</rptOwnerCik>
            <rptOwnerName>INVESTOR GROWTH CAPITAL LTD</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>CANADA COURT</rptOwnerStreet1>
            <rptOwnerStreet2>UPLAND ROAD, ST. PETER PORT</rptOwnerStreet2>
            <rptOwnerCity>GUERNSEY, CHANNEL ISLANDS</rptOwnerCity>
            <rptOwnerState>X0</rptOwnerState>
            <rptOwnerZipCode>GY1 3BQ</rptOwnerZipCode>
            <rptOwnerStateDescription>UNITED KINGDOM</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <transactionDate>
                <value>2009-12-28</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>42446</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>3.1842</value>
                    <footnoteId id="F5"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2281214</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnote</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
                <footnoteId id="F2"/>
            </securityTitle>
            <transactionDate>
                <value>2009-12-28</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>29712</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>3.1842</value>
                    <footnoteId id="F5"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1596860</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
                <footnoteId id="F3"/>
            </securityTitle>
            <transactionDate>
                <value>2009-12-29</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>105500</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>3.15</value>
                    <footnoteId id="F6"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2175714</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnote</value>
                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
                <footnoteId id="F4"/>
            </securityTitle>
            <transactionDate>
                <value>2009-12-29</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>73850</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>3.15</value>
                    <footnoteId id="F6"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1523010</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">29,712 shares of Common Stock, par value $0.001 (the &quot;Common Stock&quot;), were sold by Investor Growth Capital Limited and 12,734 shares of Common Stock were sold by Investor Group, L.P. The shares of Common Stock reported in Column 5 are held directly by Investor Growth Capital Limited and Investor Group, L.P. Investor Growth Capital Limited is an indirect wholly-owned subsidiary of Investor AB. Investor Group, L.P. is a limited partnership of which Investor AB is the indirect general partner. Investor AB may be deemed to beneficially own the securities held by Investor Growth Capital Limited and Investor Group, L.P. Investor AB disclaims beneficial ownership of such securities except to the extent of its pecuniary interest in such securities.</footnote>
        <footnote id="F2">These shares of Common Stock were sold by Investor Growth Capital Limited.</footnote>
        <footnote id="F3">73,850 shares of Common Stock were sold by Investor Growth Capital Limited and 31,650 shares of Common Stock were sold by Investor Group, L.P. The shares of Common Stock reported in Column 5 are held directly by Investor Growth Capital Limited and Investor Group, L.P. Investor Growth Capital Limited is an indirect wholly-owned subsidiary of Investor AB. Investor Group, L.P. is a limited partnership of which Investor AB is the indirect general partner. Investor AB may be deemed to beneficially own the securities held by Investor Growth Capital Limited and Investor Group, L.P. Investor AB disclaims beneficial ownership of such securities except to the extent of its pecuniary interest in such securities.</footnote>
        <footnote id="F4">These shares of Common Stock were sold by Investor Growth Capital Limited.</footnote>
        <footnote id="F5">The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $3.18 to $3.202. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote.</footnote>
        <footnote id="F6">The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $3.10 to $3.20. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Michael Oporto</signatureName>
        <signatureDate>2009-12-30</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Stephen Campe</signatureName>
        <signatureDate>2009-12-30</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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