<SEC-DOCUMENT>0001437749-24-027344.txt : 20240820
<SEC-HEADER>0001437749-24-027344.hdr.sgml : 20240820
<ACCEPTANCE-DATETIME>20240820142317
ACCESSION NUMBER:		0001437749-24-027344
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20240816
FILED AS OF DATE:		20240820
DATE AS OF CHANGE:		20240820

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			JANUS HENDERSON GROUP PLC
		CENTRAL INDEX KEY:			0001274173
		STANDARD INDUSTRIAL CLASSIFICATION:	INVESTMENT ADVICE [6282]
		ORGANIZATION NAME:           	02 Finance
		STATE OF INCORPORATION:			Y9
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-22873
		FILM NUMBER:		241224512

	BUSINESS ADDRESS:	
		STREET 1:		201 BISHOPSGATE
		CITY:			LONDON
		STATE:			X0
		ZIP:			EC2M 3AE
		BUSINESS PHONE:		442078181818

	MAIL ADDRESS:	
		STREET 1:		201 BISHOPSGATE
		CITY:			LONDON
		STATE:			X0
		ZIP:			EC2M 3AE

	FORMER NAME:	
		FORMER CONFORMED NAME:	HENDERSON GROUP PLC
		DATE OF NAME CHANGE:	20050511

	FORMER NAME:	
		FORMER CONFORMED NAME:	HHG PLC
		DATE OF NAME CHANGE:	20031223

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Janus Henderson Biotech Innovation Master Fund Ltd
		CENTRAL INDEX KEY:			0002030299
		ORGANIZATION NAME:           	
		STATE OF INCORPORATION:			E9
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-22873
		FILM NUMBER:		241224511

	BUSINESS ADDRESS:	
		STREET 1:		151 DETROIT STREET
		CITY:			DENVER
		STATE:			CO
		ZIP:			80206
		BUSINESS PHONE:		3033364030

	MAIL ADDRESS:	
		STREET 1:		151 DETROIT STREET
		CITY:			DENVER
		STATE:			CO
		ZIP:			80206

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			ARCA biopharma, Inc.
		CENTRAL INDEX KEY:			0000907654
		STANDARD INDUSTRIAL CLASSIFICATION:	IN VITRO & IN VIVO DIAGNOSTIC SUBSTANCES [2835]
		ORGANIZATION NAME:           	03 Life Sciences
		IRS NUMBER:				363855489
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		10170 CHURCH RANCH WAY
		STREET 2:		SUITE 100
		CITY:			WESTMINSTER
		STATE:			CO
		ZIP:			80021
		BUSINESS PHONE:		7209402200

	MAIL ADDRESS:	
		STREET 1:		10170 CHURCH RANCH WAY
		STREET 2:		SUITE 100
		CITY:			WESTMINSTER
		STATE:			CO
		ZIP:			80021

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	NUVELO INC
		DATE OF NAME CHANGE:	20030203

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	HYSEQ INC
		DATE OF NAME CHANGE:	19970610
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>rdgdoc.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2024-08-16</periodOfReport>

    <issuer>
        <issuerCik>0000907654</issuerCik>
        <issuerName>ARCA biopharma, Inc.</issuerName>
        <issuerTradingSymbol>ABIO</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001274173</rptOwnerCik>
            <rptOwnerName>JANUS HENDERSON GROUP PLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>201 BISHOPGATE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>LONDON</rptOwnerCity>
            <rptOwnerState>X0</rptOwnerState>
            <rptOwnerZipCode>EC2M 3AE</rptOwnerZipCode>
            <rptOwnerStateDescription>UNITED KINGDOM</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isTenPercentOwner>1</isTenPercentOwner>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0002030299</rptOwnerCik>
            <rptOwnerName>Janus Henderson Biotech Innovation Master Fund Ltd</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>201 BISHOPGATE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>LONDON</rptOwnerCity>
            <rptOwnerState>X0</rptOwnerState>
            <rptOwnerZipCode>EC2M 3AE</rptOwnerZipCode>
            <rptOwnerStateDescription>UNITED KINGDOM</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isTenPercentOwner>1</isTenPercentOwner>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2024-08-16</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>5390</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>2.93</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2116785</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Fund</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2024-08-16</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>428</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>2.9768</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2117213</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Fund</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The securities reported are beneficially owned directly by Janus Henderson Biotech Innovation Master Fund Ltd. (the &quot;Fund&quot;). Janus Henderson Group plc has a 100% ownership stake in Janus Henderson Investors US LLC, which serve as the investment advisor to the Fund, and may therefore be deemed a beneficial owner of the securities reported herein. Each Reporting Person disclaims beneficial ownership of the securities reported herein except to the extent of its pecuniary interest therein, if any.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Michelle Rosenberg, CAO, General Counsel &amp; Company Secretary</signatureName>
        <signatureDate>2024-08-20</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Janus Henderson Biotech Innovation Master Fund Ltd., By: Janus Henderson Investors US LLC, By: Kristin Mariani, Head of North America Compliance, CCO</signatureName>
        <signatureDate>2024-08-20</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
