<SEC-DOCUMENT>0001104659-25-096678.txt : 20251003
<SEC-HEADER>0001104659-25-096678.hdr.sgml : 20251003
<ACCEPTANCE-DATETIME>20251003162325
ACCESSION NUMBER:		0001104659-25-096678
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20251001
FILED AS OF DATE:		20251003
DATE AS OF CHANGE:		20251003

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Arbet-Engels Christophe
		CENTRAL INDEX KEY:			0001802615
		ORGANIZATION NAME:           	

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-32587
		FILM NUMBER:		251374226

	MAIL ADDRESS:	
		STREET 1:		ALTIMMUNE, INC.
		STREET 2:		910 CLOPPER ROAD, SUITE 201S
		CITY:			GAITHERSBURG
		STATE:			MD
		ZIP:			20878

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			Altimmune, Inc.
		CENTRAL INDEX KEY:			0001326190
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		ORGANIZATION NAME:           	03 Life Sciences
		EIN:				202726770
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		910 CLOPPER ROAD
		STREET 2:		SUITE 201S
		CITY:			GAITHERSBURG
		STATE:			MD
		ZIP:			20878
		BUSINESS PHONE:		2406541450

	MAIL ADDRESS:	
		STREET 1:		910 CLOPPER ROAD
		STREET 2:		SUITE 201S
		CITY:			GAITHERSBURG
		STATE:			MD
		ZIP:			20878

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	PHARMATHENE, INC
		DATE OF NAME CHANGE:	20071016

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	HEALTHCARE ACQUISITION CORP
		DATE OF NAME CHANGE:	20050505
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>tm2527887-2_4seq1.xml
<DESCRIPTION>OWNERSHIP DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2025-10-01</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001326190</issuerCik>
        <issuerName>Altimmune, Inc.</issuerName>
        <issuerTradingSymbol>ALT</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001802615</rptOwnerCik>
            <rptOwnerName>Arbet-Engels Christophe</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ALTIMMUNE, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>910 CLOPPER ROAD, SUITE 201S</rptOwnerStreet2>
            <rptOwnerCity>GAITHERSBURG</rptOwnerCity>
            <rptOwnerState>MD</rptOwnerState>
            <rptOwnerZipCode>20878</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chief Medical Officer</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Options (option to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>3.87</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2025-10-01</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>450000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.00</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2035-10-01</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, par value $0.0001</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>450000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>450000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>Restricted Stock Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F2"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2025-10-01</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>150000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.00</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F3"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, par value $0.0001</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>150000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>150000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The shares underlying the option become vested and exercisable over four (4) years with 25% of the shares vesting on October 1, 2026, with the remainder vesting in equal monthly installments for the following thirty-six (36) months, subject to the reporting person's continued service on each applicable vesting date.</footnote>
        <footnote id="F2">Each Restricted Stock Unit (&quot;RSU&quot;) represents a contingent right to receive one share of Common Stock, par value $0.0001, when vested</footnote>
        <footnote id="F3">The RSUs become vested over four (4) years with 25% of the shares vesting October 1, 2026, with the remainder vesting in equal annual installments for the following three (3) years, subject to the reporting person's continued service through the applicable vesting date, and have no expiration date.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Gregory Weaver, as Attorney-in-Fact</signatureName>
        <signatureDate>2025-10-03</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
