<SEC-DOCUMENT>0000874015-21-000068.txt : 20210302
<SEC-HEADER>0000874015-21-000068.hdr.sgml : 20210302
<ACCEPTANCE-DATETIME>20210302203409
ACCESSION NUMBER:		0000874015-21-000068
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20210226
FILED AS OF DATE:		20210302
DATE AS OF CHANGE:		20210302

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			O'NEIL PATRICK R.
		CENTRAL INDEX KEY:			0001564926

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-19125
		FILM NUMBER:		21706641

	MAIL ADDRESS:	
		STREET 1:		C/O ISIS PHARMACEUTICALS, INC.
		STREET 2:		2855 GAZELLE COURT
		CITY:			CARLSBAD
		STATE:			CA
		ZIP:			92010

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			IONIS PHARMACEUTICALS INC
		CENTRAL INDEX KEY:			0000874015
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		IRS NUMBER:				330336973
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		2855 GAZELLE COURT
		CITY:			CARLSBAD
		STATE:			CA
		ZIP:			92010
		BUSINESS PHONE:		7609319200

	MAIL ADDRESS:	
		STREET 1:		2855 GAZELLE COURT
		CITY:			CARLSBAD
		STATE:			CA
		ZIP:			92010

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	ISIS PHARMACEUTICALS INC
		DATE OF NAME CHANGE:	19930328
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2021-02-26</periodOfReport>

    <issuer>
        <issuerCik>0000874015</issuerCik>
        <issuerName>IONIS PHARMACEUTICALS INC</issuerName>
        <issuerTradingSymbol>IONS</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001564926</rptOwnerCik>
            <rptOwnerName>O'NEIL PATRICK R.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O IONIS PHARMACEUTICALS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>2855 GAZELLE CT.</rptOwnerStreet2>
            <rptOwnerCity>CARLSBAD,</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>92010</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>EVP &amp; General Counsel</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2021-02-26</value>
            </transactionDate>
            <deemedExecutionDate>
                <value>2021-02-26</value>
            </deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>197</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>44.54</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>26699</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Reporting 197 shares acquired under the Ionis Pharmaceuticals, Inc. Amended and Restated 2000 Employee Stock Purchase Plan on February 26, 2021.  These 197 shares may not be sold until August 26, 2021.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/Patrick R. O'Neil</signatureName>
        <signatureDate>2021-03-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
