<SEC-DOCUMENT>0001315797-25-000006.txt : 20251119
<SEC-HEADER>0001315797-25-000006.hdr.sgml : 20251119
<ACCEPTANCE-DATETIME>20251119210005
ACCESSION NUMBER:		0001315797-25-000006
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20251117
FILED AS OF DATE:		20251119
DATE AS OF CHANGE:		20251119

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Satter Muneer A
		CENTRAL INDEX KEY:			0001315797
		ORGANIZATION NAME:           	

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-39402
		FILM NUMBER:		251500815

	MAIL ADDRESS:	
		STREET 1:		C/O SATTER INVESTMENT MANAGEMENT, LLC
		STREET 2:		676 NORTH MICHIGAN AVENUE, SUITE 4000
		CITY:			CHICAGO
		STATE:			IL
		ZIP:			60611

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			Annexon, Inc.
		CENTRAL INDEX KEY:			0001528115
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		ORGANIZATION NAME:           	03 Life Sciences
		EIN:				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>form4-11192025_091101.xml
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2025-11-17</periodOfReport>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001315797</rptOwnerCik>
            <rptOwnerName>Satter Muneer A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ANNEXON, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>1400 SIERRA POINT PKWY, BLDG C, STE 200</rptOwnerStreet2>
            <rptOwnerCity>BRISBANE</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94005</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>true</isDirector>
            <isOfficer>false</isOfficer>
            <isTenPercentOwner>false</isTenPercentOwner>
            <isOther>false</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2025-11-17</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>500000</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>2.99</value>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>7906024</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>
            </securityTitle>
            <transactionDate>
                <value>2025-11-18</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>500000</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>3.18</value>
                    <footnoteId id="F4"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>8406024</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>
            </securityTitle>
            <transactionDate>
                <value>2025-11-19</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>500000</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>3.94</value>
                    <footnoteId id="F5"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>8906024</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See footnote</value>
                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">All shares were purchased by Alerce Medical Technology Partners, L.P. (&quot;Alerce Medical&quot;). The Reporting Person has sole voting and dispositive power over the shares held by Alerce Medical. The Reporting Person disclaims beneficial ownership of the shares except to the extent of his pecuniary interest therein.</footnote>
        <footnote id="F2">This transaction was executed in multiple trades in prices ranging from $2.695 to $3.115, inclusive. The price reported in Column 4 above reflects the weighted average purchase price. The Reporting Person hereby undertakes to provide to the Securities and Exchange Commission staff, the Issuer, or a security holder of the Issuer, upon request, full information regarding the number of shares purchased at each respective price within the range set forth in this footnote.</footnote>
        <footnote id="F3">As of November 19, 2025, includes (a) 240,000 shares that are held by the Muneer A. Satter Revocable Trust for which the Reporting Person serves as trustee and, in such capacity, has sole voting and dispositive power over all such shares, (b) 567,240 shares that are held by various other trusts and entities for which the Reporting Person serves as trustee, investment advisor or manager, as applicable, and, in each such capacity, has sole voting and dispositive power over all such shares, (c) 1,147,738 shares that are held by Satter Medical Technology Partners, L.P. for which the Reporting Person has sole voting and dispositive power over all such shares and (d) 6,951,046 shares that are held by Alerce Medical for which the Reporting Person has sole voting and dispositive power over all such shares. The Reporting Person disclaims beneficial ownership of all shares included under (b), (c) and (d) of this footnote, except to the extent of his pecuniary interest therein.</footnote>
        <footnote id="F4">This transaction was executed in multiple trades in prices ranging from $3.01 to $3.285, inclusive. The price reported in Column 4 above reflects the weighted average purchase price. The Reporting Person hereby undertakes to provide to the Securities and Exchange Commission staff, the Issuer, or a security holder of the Issuer, upon request, full information regarding the number of shares purchased at each respective price within the range set forth in this footnote.</footnote>
        <footnote id="F5">This transaction was executed in multiple trades in prices ranging from $3.57 to $4.19, inclusive. The price reported in Column 4 above reflects the weighted average purchase price. The Reporting Person hereby undertakes to provide to the Securities and Exchange Commission staff, the Issuer, or a security holder of the Issuer, upon request, full information regarding the number of shares purchased at each respective price within the range set forth in this footnote.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Muneer A. Satter</signatureName>
        <signatureDate>2025-11-19</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
