INCY: amended insider filing

<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0609</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2026-05-06</periodOfReport>

    <dateOfOriginalSubmission>2026-04-17</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000879169</issuerCik>
        <issuerName>INCYTE CORP</issuerName>
        <issuerTradingSymbol>INCY</issuerTradingSymbol>
        <issuerForeignTradingSymbol></issuerForeignTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001673776</rptOwnerCik>
            <rptOwnerName>Stein Steven H</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerNonUSAddressFlag>false</rptOwnerNonUSAddressFlag>
            <rptOwnerStreet1>1801 AUGUSTINE CUT-OFF</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>WILMINGTON</rptOwnerCity>
            <rptOwnerState>DE</rptOwnerState>
            <rptOwnerZipCode>19803</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>CMO &amp; Head of Late-Stage Dev.</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2026-05-06</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>44124</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>78327</value>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Represents the shares of common stock underlying performance shares earned upon the achievement of performance criteria determined to be satisfied on May 6, 2026. The earned shares will vest on the third anniversary of the July 14, 2023 grant date, subject to the Reporting Person's continued service with the Issuer. Each performance share represents the right to receive one or more shares of common stock based on, and subject to, specified development, revenue and market-based (relative total shareholder returns compared to the Nasdaq Biotechnology Index) performance goals determined by the Issuer's Compensation Committee in January 2023 as set forth in the Performance Share Award Agreement. The number of shares of common stock that the Reporting Person is entitled to receive over the three-year performance period ranges from 0% to 150% of the number of performance shares awarded.</footnote>
        <footnote id="F2">This Form 4/A amends the original Form 4, filed on April 17, 2026, to reflect the Compensation Committee's determination on May 6, 2026 relating to the achievement of the performance criteria, which superseded the Compensation Committee's initial determination on April 15, 2026.</footnote>
        <footnote id="F3">Including this certification of performance shares, this includes an aggregate of 78,327 shares of common stock issuable pursuant to previously reported restricted stock units and earned performance shares that have not vested.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Elizabeth Feeney, Attorney-In-Fact</signatureName>
        <signatureDate>2026-05-20</signatureDate>
    </ownerSignature>
</ownershipDocument>