<SEC-DOCUMENT>0001280776-18-000071.txt : 20180611
<SEC-HEADER>0001280776-18-000071.hdr.sgml : 20180611
<ACCEPTANCE-DATETIME>20180611192321
ACCESSION NUMBER:		0001280776-18-000071
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20180609
FILED AS OF DATE:		20180611
DATE AS OF CHANGE:		20180611

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Ashley Robert A.
		CENTRAL INDEX KEY:			0001591017

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-36201
		FILM NUMBER:		18893242

	MAIL ADDRESS:	
		STREET 1:		C/O VITAL THERAPIES, INC.
		STREET 2:		15010 AVENUE OF SCIENCE, SUITE 200
		CITY:			SAN DIEGO
		STATE:			CA
		ZIP:			92128

	FORMER NAME:	
		FORMER CONFORMED NAME:	Ashley Rob
		DATE OF NAME CHANGE:	20131104

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			VITAL THERAPIES INC
		CENTRAL INDEX KEY:			0001280776
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		IRS NUMBER:				000000000
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		15010 AVENUE OF SCIENCE
		STREET 2:		STE. 200
		CITY:			SAN DIEGO
		STATE:			CA
		ZIP:			92128
		BUSINESS PHONE:		858-673-6840

	MAIL ADDRESS:	
		STREET 1:		15010 AVENUE OF SCIENCE
		STREET 2:		STE. 200
		CITY:			SAN DIEGO
		STATE:			CA
		ZIP:			92128
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wf-form4_152875938337968.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2018-06-09</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001280776</issuerCik>
        <issuerName>VITAL THERAPIES INC</issuerName>
        <issuerTradingSymbol>VTL</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001591017</rptOwnerCik>
            <rptOwnerName>Ashley Robert A.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O VITAL THERAPIES, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>15010 AVENUE OF SCIENCE, SUITE 200</rptOwnerStreet2>
            <rptOwnerCity>SAN DIEGO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>92128</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chief Technical Officer, EVP</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable></nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Option (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>5.0</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2018-06-09</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>75000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2028-06-08</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>75000.0</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>75000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">One forty-eighth (1/48th) of the shares of common stock subject to the option shall vest monthly beginning on July 9, 2018, such that all of the shares of common stock subject to the option are vested by June 9, 2022, subject to the reporting person's continuing to be a Service Provider (as defined in the 2014 Equity Incentive Plan (the &quot;Plan&quot;)) through each vesting date; provided, that, 100% of the unvested portion of the option, if any, shall vest in the event of a termination without cause following a Change in Control (as defined in the Plan).</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Michael V. Swanson, by power of attorney</signatureName>
        <signatureDate>2018-06-11</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
