<SEC-DOCUMENT>0000899243-23-014139.txt : 20230530
<SEC-HEADER>0000899243-23-014139.hdr.sgml : 20230530
<ACCEPTANCE-DATETIME>20230530215416
ACCESSION NUMBER:		0000899243-23-014139
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20230525
FILED AS OF DATE:		20230530
DATE AS OF CHANGE:		20230530

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			BCIP Life Sciences Associates, LP
		CENTRAL INDEX KEY:			0001702921
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-39402
		FILM NUMBER:		23978781

	BUSINESS ADDRESS:	
		STREET 1:		200 CLARENDON STREET
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02116
		BUSINESS PHONE:		6175162878

	MAIL ADDRESS:	
		STREET 1:		200 CLARENDON STREET
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02116

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Bain Capital Life Sciences Fund, L.P.
		CENTRAL INDEX KEY:			0001687968
		STATE OF INCORPORATION:			E9
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-39402
		FILM NUMBER:		23978783

	BUSINESS ADDRESS:	
		STREET 1:		200 CLARENDON STREET
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02116
		BUSINESS PHONE:		617-516-2000

	MAIL ADDRESS:	
		STREET 1:		200 CLARENDON STREET
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02116

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Bain Capital Life Sciences Investors, LLC
		CENTRAL INDEX KEY:			0001703031
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-39402
		FILM NUMBER:		23978784

	BUSINESS ADDRESS:	
		STREET 1:		200 CLARENDON STREET
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02116
		BUSINESS PHONE:		6175162878

	MAIL ADDRESS:	
		STREET 1:		200 CLARENDON STREET
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02116

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Bain Capital Life Sciences Partners, LP
		CENTRAL INDEX KEY:			0001703030
		STATE OF INCORPORATION:			E9
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-39402
		FILM NUMBER:		23978782

	BUSINESS ADDRESS:	
		STREET 1:		200 CLARENDON STREET
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02116
		BUSINESS PHONE:		6175162878

	MAIL ADDRESS:	
		STREET 1:		200 CLARENDON STREET
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02116

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			Annexon, Inc.
		CENTRAL INDEX KEY:			0001528115
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		IRS NUMBER:				275414423
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		1400 SIERRA POINT PARKWAY
		STREET 2:		BLDG C, SUITE 200
		CITY:			BRISBANE
		STATE:			CA
		ZIP:			94005
		BUSINESS PHONE:		(650)-822-5500

	MAIL ADDRESS:	
		STREET 1:		1400 SIERRA POINT PARKWAY
		STREET 2:		BLDG C, SUITE 200
		CITY:			BRISBANE
		STATE:			CA
		ZIP:			94005
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>doc4.xml
<DESCRIPTION>FORM 4 SUBMISSION
<TEXT>
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<ownershipDocument>

    <schemaVersion>X0407</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2023-05-25</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001528115</issuerCik>
        <issuerName>Annexon, Inc.</issuerName>
        <issuerTradingSymbol>ANNX</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001703031</rptOwnerCik>
            <rptOwnerName>Bain Capital Life Sciences Investors, LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>200 CLARENDON STREET</rptOwnerStreet1>
            <rptOwnerStreet2></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>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001687968</rptOwnerCik>
            <rptOwnerName>Bain Capital Life Sciences Fund, L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>200 CLARENDON STREET</rptOwnerStreet1>
            <rptOwnerStreet2></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>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001703030</rptOwnerCik>
            <rptOwnerName>Bain Capital Life Sciences Partners, LP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>200 CLARENDON STREET</rptOwnerStreet1>
            <rptOwnerStreet2></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>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001702921</rptOwnerCik>
            <rptOwnerName>BCIP Life Sciences Associates, LP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>200 CLARENDON STREET</rptOwnerStreet1>
            <rptOwnerStreet2></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>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2023-05-25</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>300000</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>2.1324</value>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>5701926</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See footnotes</value>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                    <footnoteId id="F5"/>
                    <footnoteId id="F6"/>
                    <footnoteId id="F7"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Represents 300,000 shares of Common Stock purchased by BCLS I Investco, LP (&quot;BCLS I Investco&quot;) on May 25, 2023.</footnote>
        <footnote id="F2">The price reported in Column 4 is a weighted average price. The shares were purchased in multiple transactions at prices ranging from $2.08 to $2.25, inclusive. The reporting persons undertake to provide to the Issuer, any securityholder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each separate price within the range set forth herein.</footnote>
        <footnote id="F3">Represents shares of Common Stock held by Bain Capital Life Sciences Fund, L.P. (&quot;BCLS Fund I&quot;), BCLS I Investco and BCIP Life Sciences Associates, LP (&quot;BCIPLS&quot; and, together with BCLS Fund I and BCLS I Investco, the &quot;Bain Capital Life Sciences Entities&quot;). Following the completion of the transactions reported in footnote (1) above, BCLS Fund I, BCLS I Investco and BCIPLS each holds 2,940,627, 2,460,298 and 301,001 shares of Common Stock, respectively.</footnote>
        <footnote id="F4">Bain Capital Life Sciences Partners, LP (&quot;BCLSP&quot;) is the general partner of BCLS Fund I. As a result, BCLSP may be deemed to share voting and dispositive power with respect to the securities held by BCLS Fund I. BCLSP disclaims beneficial ownership of such securities except to the extent of its pecuniary interest therein.</footnote>
        <footnote id="F5">BCLS I Investco GP, LLC (&quot;BCLS I Investco GP&quot;), whose manager is BCLS Fund I, is the general partner of BCLS I Investco. As a result, each of BCLSP, BCLS Fund I and BCLS I Investco GP may be deemed to share voting and dispositive power with respect to the securities held by BCLS I Investco. Each of BCLSP, BCLS Fund I and BCLS I Investco GP disclaims beneficial ownership of such securities except to the extent of its pecuniary interest therein.</footnote>
        <footnote id="F6">Boylston Coinvestors, LLC is the general partner of BCIPLS.</footnote>
        <footnote id="F7">Bain Capital Life Sciences Investors, LLC (&quot;BCLSI&quot;) is the general partner of BCLSP and governs the investment strategy and decision making process with respect to investments held by BCIPLS. As a result, BCLSI may be deemed to share voting and dispositive power with respect to the securities held by the Bain Capital Life Sciences Entities. BCLSI disclaims beneficial ownership of such securities except to the extent of its pecuniary interest therein.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Bain Capital Life Sciences Investors, LLC, By: /s/ Ricky Sun, Title: Partner</signatureName>
        <signatureDate>2023-05-30</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Bain Capital Life Sciences Fund, L.P., By: Bain Capital Life Sciences Partners, LP, its general partner, By: Bain Capital Life Sciences Investors, LLC, its general partner, By: /s/ Ricky Sun, Title: Partner</signatureName>
        <signatureDate>2023-05-30</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Bain Capital Life Sciences Partners, LP, By: Bain Capital Life Sciences Investors, LLC, its general partner, By: /s/ Ricky Sun, Title: Partner</signatureName>
        <signatureDate>2023-05-30</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>BCIP Life Sciences Associates, LP, By: Boylston Coinvestors, LLC, its general partner, By: /s/ Ricky Sun, Title: Authorized Signatory</signatureName>
        <signatureDate>2023-05-30</signatureDate>
    </ownerSignature>
</ownershipDocument>
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</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
