<SEC-DOCUMENT>0001567619-21-005004.txt : 20210226
<SEC-HEADER>0001567619-21-005004.hdr.sgml : 20210226
<ACCEPTANCE-DATETIME>20210226160915
ACCESSION NUMBER:		0001567619-21-005004
CONFORMED SUBMISSION TYPE:	4/A
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20210212
FILED AS OF DATE:		20210226
DATE AS OF CHANGE:		20210226

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			EcoR1 Capital, LLC
		CENTRAL INDEX KEY:			0001587114
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4/A
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-35676
		FILM NUMBER:		21688801

	BUSINESS ADDRESS:	
		STREET 1:		357 TEHAMA STREET #3
		CITY:			SAN FRANCISCO
		STATE:			CA
		ZIP:			94103
		BUSINESS PHONE:		415-448-6534

	MAIL ADDRESS:	
		STREET 1:		357 TEHAMA STREET #3
		CITY:			SAN FRANCISCO
		STATE:			CA
		ZIP:			94103

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			PROTHENA CORP PUBLIC LTD CO
		CENTRAL INDEX KEY:			0001559053
		STANDARD INDUSTRIAL CLASSIFICATION:	PHARMACEUTICAL PREPARATIONS [2834]
		IRS NUMBER:				000000000
		STATE OF INCORPORATION:			L2
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		77 SIR JOHN ROGERSON'S QUAY, BLOCK C
		STREET 2:		GRAND CANAL DOCKLANDS
		CITY:			DUBLIN 2
		STATE:			L2
		ZIP:			D02 T804
		BUSINESS PHONE:		011-353-1-236-2500

	MAIL ADDRESS:	
		STREET 1:		77 SIR JOHN ROGERSON'S QUAY, BLOCK C
		STREET 2:		GRAND CANAL DOCKLANDS
		CITY:			DUBLIN 2
		STATE:			L2
		ZIP:			D02 T804

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	Prothena Corp plc
		DATE OF NAME CHANGE:	20121102

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	Neotope Corp Ltd
		DATE OF NAME CHANGE:	20120926
</SEC-HEADER>
<DOCUMENT>
<TYPE>4/A
<SEQUENCE>1
<FILENAME>doc1.xml
<DESCRIPTION>FORM 4/A
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2021-02-12</periodOfReport>

    <dateOfOriginalSubmission>2021-02-17</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001559053</issuerCik>
        <issuerName>PROTHENA CORP PUBLIC LTD CO</issuerName>
        <issuerTradingSymbol>PRTA</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001587114</rptOwnerCik>
            <rptOwnerName>EcoR1 Capital, LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>357 TEHAMA STREET #3</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94103</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable></nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Call Option</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>30</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2021-02-17</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>2500</value>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>3.6758</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2021-02-17</value>
            </exerciseDate>
            <expirationDate>
                <value>2021-06-18</value>
                <footnoteId id="F3"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Ordinary Shares</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>250000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2500</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Note 1</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The filing persons (the &quot;Filers&quot;) are EcoR1 Capital, LLC (&quot;EcoR1&quot;), Oleg Nodelman and EcoR1 Capital Fund Qualified, L.P. (&quot;Qualified Fund&quot;). EcoR1 is the general partner and investment adviser of private funds, including Qualified Fund (collectively, the &quot;Funds&quot;). Mr. Nodelman is the manager and controlling owner of EcoR1. EcoR1 is filing this Form 3 for itself, Mr. Nodelman and Qualified Fund. The Filers are filing this Form 4 jointly, but not as a group, and each expressly disclaims membership in a group, within the meaning of Rule 13d-5(b) under the Securities Exchange Act of 1934, as amended. The Funds hold these securities directly for the benefit of their investors. EcoR1 indirectly beneficially owns them as the investment adviser to the Funds, and Mr. Nodelman indirectly beneficially owns them as the control person of EcoR1. The Filers disclaim beneficial ownership of such securities except to the extent of their pecuniary interest therein.</footnote>
        <footnote id="F2">2,099 of the options purchased in this transaction were purchased by Qualified Fund.  After this transaction, Qualified Fund owned 2,099 options to acquire 209,900 Ordinary Shares.</footnote>
        <footnote id="F3">The Filers are filing this amendment to correct the expiration date of the options, which was reported as 6/30/2021 in the Form 4 filed on 2/17/2021.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Oleg Nodelman, Manager of EcoR1 Capital, LLC</signatureName>
        <signatureDate>2021-02-26</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
