<SEC-DOCUMENT>0001280776-17-000053.txt : 20170525
<SEC-HEADER>0001280776-17-000053.hdr.sgml : 20170525
<ACCEPTANCE-DATETIME>20170525174100
ACCESSION NUMBER:		0001280776-17-000053
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20170523
FILED AS OF DATE:		20170525
DATE AS OF CHANGE:		20170525

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

REPORTING-OWNER:	

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

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-36201
		FILM NUMBER:		17871120

	MAIL ADDRESS:	
		STREET 1:		C/O SATTER INVESTMENT MANAGEMENT, LLC
		STREET 2:		676 NORTH MICHIGAN AVENUE, SUITE 4000
		CITY:			CHICAGO
		STATE:			IL
		ZIP:			60611
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wf-form4_149574844517420.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2017-05-23</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001315797</rptOwnerCik>
            <rptOwnerName>Satter Muneer 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>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable></nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Option (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>3.2</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2017-05-23</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>63031</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2027-05-22</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>63031.0</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>63031</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Subject to the reporting person's continuing to be a Service Provider (as defined in the 2014 Equity Incentive Plan) through the vesting date, 100% of the shares will vest upon the earlier of the one (1) year anniversary from May 23, 2017 or the day prior to the Company's 2018 annual meeting of stockholders.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Jon-Micheal A. Wheat, by power of attorney</signatureName>
        <signatureDate>2017-05-25</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
