<SEC-DOCUMENT>0001140361-15-034452.txt : 20150904
<SEC-HEADER>0001140361-15-034452.hdr.sgml : 20150904
<ACCEPTANCE-DATETIME>20150904142400
ACCESSION NUMBER:		0001140361-15-034452
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20150902
FILED AS OF DATE:		20150904
DATE AS OF CHANGE:		20150904

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			Synthetic Biologics, Inc.
		CENTRAL INDEX KEY:			0000894158
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		IRS NUMBER:				133808303
		STATE OF INCORPORATION:			NV
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		617 DETROIT STREET, SUITE 100
		CITY:			ANN ARBOR
		STATE:			MI
		ZIP:			48104
		BUSINESS PHONE:		(734) 332-7800

	MAIL ADDRESS:	
		STREET 1:		155 GIBBS STREET
		STREET 2:		SUITE 412
		CITY:			ROCKVILLE
		STATE:			MD
		ZIP:			20850

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	ADEONA PHARMACEUTICALS, INC.
		DATE OF NAME CHANGE:	20081027

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	PIPEX PHARMACEUTICALS, INC.
		DATE OF NAME CHANGE:	20061214

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	SHEFFIELD PHARMACEUTICALS INC
		DATE OF NAME CHANGE:	19970730

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			INTREXON CORP
		CENTRAL INDEX KEY:			0001356090
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-COMMERCIAL PHYSICAL & BIOLOGICAL RESEARCH [8731]
		STATE OF INCORPORATION:			VA
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-12584
		FILM NUMBER:		151094322

	BUSINESS ADDRESS:	
		STREET 1:		1750 KRAFT DRIVE
		STREET 2:		SUITE 1400
		CITY:			BLACKSBURG
		STATE:			VA
		ZIP:			24060
		BUSINESS PHONE:		301-556-9809

	MAIL ADDRESS:	
		STREET 1:		1750 KRAFT DRIVE
		STREET 2:		SUITE 1400
		CITY:			BLACKSBURG
		STATE:			VA
		ZIP:			24060

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			KIRK RANDAL J
		CENTRAL INDEX KEY:			0001091823

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-12584
		FILM NUMBER:		151094323

	MAIL ADDRESS:	
		STREET 1:		1881 GROVE AVENUE
		CITY:			RADFORD
		STATE:			VA
		ZIP:			24141
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>doc1.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2015-09-02</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000894158</issuerCik>
        <issuerName>Synthetic Biologics, Inc.</issuerName>
        <issuerTradingSymbol>SYN</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001091823</rptOwnerCik>
            <rptOwnerName>KIRK RANDAL J</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O THIRD SECURITY, LLC</rptOwnerStreet1>
            <rptOwnerStreet2>1881 GROVE AVENUE</rptOwnerStreet2>
            <rptOwnerCity>RADFORD</rptOwnerCity>
            <rptOwnerState>VA</rptOwnerState>
            <rptOwnerZipCode>24141</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>0001356090</rptOwnerCik>
            <rptOwnerName>INTREXON CORP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O LEGAL DEPARTMENT</rptOwnerStreet1>
            <rptOwnerStreet2>20374 SENECA MEADOWS PARKWAY</rptOwnerStreet2>
            <rptOwnerCity>GERMANTOWN</rptOwnerCity>
            <rptOwnerState>MD</rptOwnerState>
            <rptOwnerZipCode>20876</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</value>
            </securityTitle>
            <transactionDate>
                <value>2015-09-02</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>937500</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>3.20</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>9613268</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>by Intrexon</value>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3625000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>by NRM VII Holdings</value>
                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">On September 2, 2015 and pursuant to a Stock Issuance Agreement between the issuer and Intrexon Corporation (&quot;Intrexon&quot;) dated August 10, 2015, the issuer issued 937,500 shares of its Common Stock to Intrexon in consideration for the execution and delivery of an Exclusive Channel Collaboration Agreement dated August 10, 2015 between the issuer and Intrexon.</footnote>
        <footnote id="F2">Randal J. Kirk, directly and through certain affiliates, has voting and dispositive power over a majority of the outstanding capital stock of Intrexon. Mr. Kirk may therefore be deemed to have voting and dispositive power over the shares of the issuer owned by Intrexon. Shares held by Intrexon may be deemed to be indirectly beneficially owned (as defined under Rule 13d-3 promulgated under the Securities Exchange Act of 1934, as amended) by Mr. Kirk. Mr. Kirk disclaims beneficial ownership of such shares, except to the extent of any pecuniary interest therein.</footnote>
        <footnote id="F3">Randal J. Kirk controls NRM VII Holdings I, LLC (&quot;NRM VII Holdings&quot;). Shares held by this entity may be deemed to be indirectly beneficially owned (as defined under Rule 13d-3 promulgated under the Securities Exchange Act of 1934, as amended) by Mr. Kirk. Mr. Kirk disclaims beneficial ownership of such shares, except to the extent of any
pecuniary interest therein.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/  Randal J. Kirk</signatureName>
        <signatureDate>2015-09-04</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/  Randal J. Kirk , CEO Intrexon Corporation</signatureName>
        <signatureDate>2015-09-04</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
