<SEC-DOCUMENT>0001144204-17-009016.txt : 20170214
<SEC-HEADER>0001144204-17-009016.hdr.sgml : 20170214
<ACCEPTANCE-DATETIME>20170214173346
ACCESSION NUMBER:		0001144204-17-009016
CONFORMED SUBMISSION TYPE:	SC 13G/A
PUBLIC DOCUMENT COUNT:		1
FILED AS OF DATE:		20170214
DATE AS OF CHANGE:		20170214

SUBJECT COMPANY:	

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

	FILING VALUES:
		FORM TYPE:		SC 13G/A
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	005-51477
		FILM NUMBER:		17610826

	BUSINESS ADDRESS:	
		STREET 1:		11080 CIRCLEPOINT ROAD
		STREET 2:		SUITE 140
		CITY:			WESTMINSTER
		STATE:			CO
		ZIP:			80020
		BUSINESS PHONE:		720-940-2200

	MAIL ADDRESS:	
		STREET 1:		11080 CIRCLEPOINT ROAD
		STREET 2:		SUITE 140
		CITY:			WESTMINSTER
		STATE:			CO
		ZIP:			80020

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

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	HYSEQ INC
		DATE OF NAME CHANGE:	19970610

FILED BY:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			RA Capital Healthcare Fund LP
		CENTRAL INDEX KEY:			0001315082
		IRS NUMBER:				830406780
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		SC 13G/A

	BUSINESS ADDRESS:	
		STREET 1:		20 PARK PLAZA, SUITE 1200
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02116
		BUSINESS PHONE:		6177782500

	MAIL ADDRESS:	
		STREET 1:		20 PARK PLAZA, SUITE 1200
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02116

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	RA Capital Biotech Fund LP
		DATE OF NAME CHANGE:	20050121
</SEC-HEADER>
<DOCUMENT>
<TYPE>SC 13G/A
<SEQUENCE>1
<FILENAME>v459265_sc13ga.htm
<DESCRIPTION>SC 13G/A
<TEXT>
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<P STYLE="margin: 0">&nbsp;</P>

<P STYLE="font: bold 10pt Times New Roman, Times, Serif; margin: 0; text-align: center">UNITED STATES</P>

<P STYLE="font: bold 10pt Times New Roman, Times, Serif; margin: 0; text-align: center">SECURITIES AND EXCHANGE COMMISSION</P>

<P STYLE="font: bold 10pt Times New Roman, Times, Serif; margin: 0; text-align: center">Washington, D.C. 20549</P>

<P STYLE="font: bold 10pt Times New Roman, Times, Serif; margin: 0; text-align: center">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>SCHEDULE 13G</B></P>

<P STYLE="font: bold 10pt Times New Roman, Times, Serif; margin: 0; text-align: center">Under the Securities Exchange Act of 1934</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center; text-indent: 0in"><B>&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center; text-indent: 0in"><B>(Amendment No. 2)*</B></P>

<P STYLE="font: bold 10pt Times New Roman, Times, Serif; margin: 0; text-align: center">&nbsp;</P>

<P STYLE="font: bold 10pt Times New Roman, Times, Serif; margin: 0; text-align: center">ARCA biopharma, Inc.</P>

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<P STYLE="font: bold 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center">(Name of Issuer)</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>Common Stock, par value $0.001 per share
</B></P>

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<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center">(Title of Class of Securities)</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>00211Y407</B></P>

<!-- Field: Rule-Page --><DIV ALIGN="LEFT" STYLE="margin-top: 0; margin-bottom: 0"><DIV STYLE="font-size: 1pt; border-top: Black 1pt solid; width: 100%">&nbsp;</DIV></DIV><!-- Field: /Rule-Page -->

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center">(CUSIP Number)</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>December 31, 2016</B></P>

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<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center">(Date of Event Which Requires Filing of this
Statement)</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">Check the appropriate box to designate the rule pursuant to which
this Schedule is filed:</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<TABLE CELLPADDING="0" CELLSPACING="0" WIDTH="100%" STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 0"><TR STYLE="vertical-align: top">
<TD STYLE="width: 0.5in"></TD><TD STYLE="width: 0.5in"><FONT STYLE="font-family: Wingdings; font-size: 10pt">&uml;</FONT></TD><TD>Rule
                                         13d-1(b)</TD></TR></TABLE>

<TABLE CELLPADDING="0" CELLSPACING="0" WIDTH="100%" STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 0"><TR STYLE="vertical-align: top">
<TD STYLE="width: 0.5in"></TD><TD STYLE="width: 0.5in"><FONT STYLE="font-family: Wingdings; font-size: 10pt">x</FONT></TD><TD>Rule
                                         13d-1(c)</TD></TR></TABLE>

<TABLE CELLPADDING="0" CELLSPACING="0" WIDTH="100%" STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 0"><TR STYLE="vertical-align: top">
<TD STYLE="width: 0.5in"></TD><TD STYLE="width: 0.5in"><FONT STYLE="font-family: Wingdings; font-size: 10pt">&uml;</FONT></TD><TD>Rule
                                         13d-1(d)</TD></TR></TABLE>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">*The remainder of this cover page shall be
filled out for a reporting person&rsquo;s initial filing on this form with respect to the subject class of securities, and for
any subsequent amendment containing information which would alter the disclosures provided in a prior cover page.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">The information required in the remainder
of this cover page shall not be deemed to be &ldquo;filed&rdquo; for the purpose of Section 18 of the Securities Exchange Act
of 1934 (&ldquo;<B><I>Act</I></B>&rdquo;) or otherwise subject to the liabilities of that section of the Act but shall be subject
to all other provisions of the Act (however, see the Notes).</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0"></P>

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    <DIV STYLE="page-break-before: always; margin-top: 6pt; margin-bottom: 12pt"><P STYLE="margin: 0pt">&nbsp;</P></DIV>
    <!-- Field: /Page -->

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 10pt Times New Roman, Times, Serif; width: 100%">
<TR>
    <TD STYLE="width: 70%; font-size: 10pt"><FONT STYLE="font-size: 10pt">CUSIP No. </FONT><B>00211Y407</B></TD>
    <TD STYLE="width: 30%; font-size: 10pt; text-align: center"><FONT STYLE="font-size: 12pt"><B>13G</B></FONT></TD></TR>
</TABLE>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 10pt Times New Roman, Times, Serif; width: 100%">
<TR>
    <TD STYLE="width: 5%; border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt">&nbsp;</TD>
    <TD STYLE="text-align: left; width: 6%; vertical-align: top; border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt"><FONT STYLE="font-size: 10pt">1.</FONT></TD>
    <TD STYLE="width: 89%; border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt"><P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">Names of Reporting Persons.</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">I.R.S. Identification Nos. of above persons (entities only).</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 0 12pt"><B>RA Capital Healthcare Fund, L.P.</B></P></TD></TR>
<TR>
    <TD>&nbsp;</TD>
    <TD STYLE="text-align: left; vertical-align: top">&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR>
    <TD STYLE="border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt">&nbsp;</TD>
    <TD STYLE="text-align: left; vertical-align: top; border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt"><FONT STYLE="font-size: 10pt">2. </FONT></TD>
    <TD STYLE="border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt"><FONT STYLE="font-size: 10pt">Check the Appropriate Box if a Member of a Group (See Instructions)</FONT></TD></TR>
<TR>
    <TD>&nbsp;</TD>
    <TD STYLE="text-align: left; vertical-align: top">&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">(a)&nbsp;&nbsp;&nbsp;<FONT STYLE="font-family: Wingdings">&uml;</FONT></FONT></TD></TR>
<TR>
    <TD>&nbsp;</TD>
    <TD STYLE="text-align: left; vertical-align: top">&nbsp;</TD>
    <TD><FONT STYLE="font-size: 10pt">(b)&nbsp;&nbsp;&nbsp;<FONT STYLE="font-family: Wingdings">&uml;</FONT></FONT></TD></TR>
<TR>
    <TD>&nbsp;</TD>
    <TD STYLE="text-align: left; vertical-align: top">&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR>
    <TD STYLE="border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt">&nbsp;</TD>
    <TD STYLE="text-align: left; vertical-align: top; border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt"><FONT STYLE="font-size: 10pt">3.</FONT></TD>
    <TD STYLE="border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt"><FONT STYLE="font-size: 10pt">SEC Use Only </FONT></TD></TR>
<TR>
    <TD>&nbsp;</TD>
    <TD STYLE="text-align: left; vertical-align: top">&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR>
    <TD STYLE="border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt">&nbsp;</TD>
    <TD STYLE="text-align: left; vertical-align: top; border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt"><FONT STYLE="font-size: 10pt">4.</FONT></TD>
    <TD STYLE="border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt"><FONT STYLE="font-size: 10pt">Citizenship or Place of Organization&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</FONT>&nbsp;<FONT STYLE="font-size: 10pt"><B>Delaware</B></FONT></TD></TR>
<TR>
    <TD>&nbsp;</TD>
    <TD STYLE="text-align: left; vertical-align: top">&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
</TABLE>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0"></P>

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 10pt Times New Roman, Times, Serif; width: 100%">
<TR>
    <TD ROWSPAN="7" STYLE="width: 17%; border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt"><P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">Number of</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">Shares</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">Beneficially</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">Owned by</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">Each Reporting</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">Person With</P></TD>
    <TD STYLE="width: 5%; text-align: left; vertical-align: top; border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt"><FONT STYLE="font-size: 10pt">5.</FONT></TD>
    <TD STYLE="width: 25%; border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt"><FONT STYLE="font-size: 10pt">Sole Voting Power</FONT></TD>
    <TD STYLE="width: 53%; border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt"><FONT STYLE="font-size: 10pt"><B>0 shares</B></FONT></TD></TR>
<TR>
    <TD STYLE="text-align: left; vertical-align: top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR>
    <TD STYLE="text-align: left; vertical-align: top; border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt"><FONT STYLE="font-size: 10pt">6.</FONT></TD>
    <TD STYLE="border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt"><FONT STYLE="font-size: 10pt">Shared Voting Power</FONT></TD>
    <TD STYLE="border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt"><FONT STYLE="font-size: 10pt"><B>0 shares</B></FONT></TD></TR>
<TR>
    <TD STYLE="text-align: left; vertical-align: top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR>
    <TD STYLE="text-align: left; vertical-align: top; border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt"><FONT STYLE="font-size: 10pt">7.</FONT></TD>
    <TD STYLE="border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt"><FONT STYLE="font-size: 10pt">Sole Dispositive Power</FONT></TD>
    <TD STYLE="border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt"><FONT STYLE="font-size: 10pt"><B>0 shares</B></FONT></TD></TR>
<TR>
    <TD STYLE="text-align: left; vertical-align: top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR>
    <TD STYLE="text-align: left; vertical-align: top; border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt"><FONT STYLE="font-size: 10pt">8.</FONT></TD>
    <TD STYLE="border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt"><FONT STYLE="font-size: 10pt">Shared Dispositive Power</FONT><BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</TD>
    <TD STYLE="border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt"><FONT STYLE="font-size: 10pt"><B>0 shares</B></FONT><BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</TD></TR>
</TABLE>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0"></P>

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 10pt Times New Roman, Times, Serif; width: 100%">
<TR>
    <TD STYLE="width: 5%; border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt">&nbsp;</TD>
    <TD STYLE="width: 6%; text-align: left; vertical-align: top; border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt"><FONT STYLE="font-size: 10pt">9.</FONT></TD>
    <TD STYLE="width: 69%; border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt"><P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">Aggregate Amount Beneficially Owned by Each Reporting Person</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 0 12pt"><B>0 shares</B></P></TD>
    <TD STYLE="width: 20%; border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt">&nbsp;</TD></TR>
<TR>
    <TD>&nbsp;</TD>
    <TD STYLE="text-align: left; vertical-align: top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR>
    <TD STYLE="border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt">&nbsp;</TD>
    <TD STYLE="text-align: left; vertical-align: top; border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt"><FONT STYLE="font-size: 10pt">10.</FONT></TD>
    <TD STYLE="border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt"><P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">Check
if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions)</P></TD>
    <TD STYLE="border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt"><FONT STYLE="font-family: Wingdings; font-size: 10pt">&uml;</FONT></TD></TR>
<TR>
    <TD>&nbsp;</TD>
    <TD STYLE="text-align: left; vertical-align: top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR>
    <TD STYLE="border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt">&nbsp;</TD>
    <TD STYLE="text-align: left; vertical-align: top; border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt"><FONT STYLE="font-size: 10pt">11.</FONT></TD>
    <TD STYLE="border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt"><P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">Percent of Class Represented by Amount in Row (9)</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 0 12pt"><B>0.0%</B></P></TD>
    <TD STYLE="border-top: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt">&nbsp;</TD></TR>
<TR>
    <TD>&nbsp;</TD>
    <TD STYLE="text-align: left; vertical-align: top">&nbsp;</TD>
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR>
    <TD STYLE="border-top: Black 1pt solid; border-bottom: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt">&nbsp;</TD>
    <TD STYLE="text-align: left; vertical-align: top; border-top: Black 1pt solid; border-bottom: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt"><FONT STYLE="font-size: 10pt">12.</FONT></TD>
    <TD STYLE="border-top: Black 1pt solid; border-bottom: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt"><P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">Type of Reporting Person (See Instructions)</P>
        <P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 0 12pt"><B>PN (Limited Partnership)</B></P>&nbsp;&nbsp;&nbsp;</TD>
    <TD STYLE="border-top: Black 1pt solid; border-bottom: Black 1pt solid; padding-top: 3pt; padding-bottom: 3pt">&nbsp;</TD></TR>
</TABLE>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>


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    <DIV STYLE="margin-top: 12pt; margin-bottom: 6pt; border-bottom: Black 1pt solid"><P STYLE="margin: 0pt">&nbsp;</P></DIV>
    <DIV STYLE="page-break-before: always; margin-top: 6pt; margin-bottom: 12pt"><P STYLE="margin: 0pt">&nbsp;</P></DIV>
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<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 10pt Times New Roman, Times, Serif; width: 100%">
<TR>
    <TD STYLE="width: 70%"><FONT STYLE="font-size: 10pt">CUSIP No. </FONT><B>00211Y407</B></TD>
    <TD STYLE="width: 30%; text-align: center"><FONT STYLE="font-size: 12pt"><B>13G</B></FONT></TD></TR>
</TABLE>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0"><B>Item 1.</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">(a)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<B>Name
of Issuer:</B> ARCA biopharma, Inc. (the &ldquo;Issuer&rdquo;).</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">(b)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<B>Address
of the Issuer&rsquo;s Principal Executive Offices:</B> 11080 CirclePoint Road, Suite 140, Westminster, CO 80020.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0"><B>&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0"><B>Item 2.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0in">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0in">(a)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<B>Name
of Person Filing: </B> This statement on Schedule 13G is being filed by and RA Capital Healthcare Fund, L.P. (the &ldquo;Fund&rdquo;).
The Fund is referred to herein as the &ldquo;Reporting Person.&rdquo;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0in">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0in">(b)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<B>Address
of Principal Business Office:</B> The principal business office of the Reporting Person is c/o RA Capital Management, LLC, 20
Park Plaza, Suite 1200, Boston, MA 02116.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0in">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0in">(c) &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<B>Citizenship:
</B>The Fund is a Delaware limited partnership.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0in">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0in">(d)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<B>Title
and Class of Securities: </B>Common stock (&ldquo;Common Stock&rdquo;)</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0in">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0in">(e)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<B>CUSIP
Number: </B>00211Y407</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify"><B>&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify"><B>Item 3.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;If
this statement is filed pursuant to &sect;&sect;240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">Not applicable.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify"><B>Item 4. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Ownership:</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">Provide the following information regarding
the aggregate number and percentage of the class of securities of the issuer identified in Item 1.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">&nbsp;</P>

<TABLE CELLPADDING="0" CELLSPACING="0" WIDTH="100%" STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 0"><TR STYLE="vertical-align: top">
<TD STYLE="width: 0"></TD><TD STYLE="width: 0.5in">(a)</TD><TD>Amount Beneficially Owned:</TD></TR></TABLE>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 0 0.5in">See the response(s) to Item 9 on the attached cover page(s).</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<TABLE CELLPADDING="0" CELLSPACING="0" WIDTH="100%" STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 0"><TR STYLE="vertical-align: top">
<TD STYLE="width: 0"></TD><TD STYLE="width: 0.5in">(b)</TD><TD>Percent of Class:</TD></TR></TABLE>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 0 0.5in">See the response(s) to Item 11 on the attached cover
page(s).</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<TABLE CELLPADDING="0" CELLSPACING="0" WIDTH="100%" STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 0"><TR STYLE="vertical-align: top">
<TD STYLE="width: 0"></TD><TD STYLE="width: 0.5in">(c)</TD><TD>Number of shares as to which such person has:</TD></TR></TABLE>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 0 1in; text-indent: -0.5in">&nbsp;</P>

<TABLE CELLPADDING="0" CELLSPACING="0" WIDTH="100%" STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 0"><TR STYLE="vertical-align: top">
<TD STYLE="width: 0.5in"></TD><TD STYLE="width: 0.5in">(i)</TD><TD>sole power to vote or to direct the vote:</TD></TR></TABLE>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 0 1in">See the response(s) to Item 5 on the attached cover page(s).</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>


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<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 10pt Times New Roman, Times, Serif; width: 100%">
<TR>
    <TD STYLE="width: 70%"><FONT STYLE="font-size: 10pt">CUSIP No. </FONT><B>00211Y407</B></TD>
    <TD STYLE="width: 30%; text-align: center"><FONT STYLE="font-size: 12pt"><B>13G</B></FONT></TD></TR>
</TABLE>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<TABLE CELLPADDING="0" CELLSPACING="0" WIDTH="100%" STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 0"><TR STYLE="vertical-align: top">
<TD STYLE="width: 0.5in"></TD><TD STYLE="width: 0.5in">(ii)</TD><TD>shared power to vote or to direct the vote</TD></TR></TABLE>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 0 1in">See the response(s) to Item 6 on the attached cover page(s).</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 0 0.5in">&nbsp;</P>

<TABLE CELLPADDING="0" CELLSPACING="0" WIDTH="100%" STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 0"><TR STYLE="vertical-align: top">
<TD STYLE="width: 0.5in"></TD><TD STYLE="width: 0.5in">(iii)</TD><TD>sole power to dispose or to direct the disposition of</TD></TR></TABLE>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 0 1in">See the response(s) to Item 7 on the attached cover page(s).</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 0 0.5in">&nbsp;</P>

<TABLE CELLPADDING="0" CELLSPACING="0" WIDTH="100%" STYLE="font: 10pt Times New Roman, Times, Serif; margin-top: 0; margin-bottom: 0"><TR STYLE="vertical-align: top">
<TD STYLE="width: 0.5in"></TD><TD STYLE="width: 0.5in">(iv)</TD><TD>shared power to dispose or to direct the disposition of</TD></TR></TABLE>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 0 1in">See the response(s) to Item 8 on the attached cover page(s).</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify"><B>Item 5.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Ownership
of Five Percent or Less of a Class:</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">If this statement is being filed to report the fact that as of
the date hereof the Reporting Person has ceased to be the beneficial owner of more than five percent of the class of securities,
check the following <FONT STYLE="font-family: Wingdings; font-size: 10pt">x</FONT>.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 0 1in; text-align: justify; text-indent: -1in"><B>&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0 0 0 1in; text-align: justify; text-indent: -1in"><B>Item 6.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Ownership
of More than Five Percent on Behalf of Another Person:</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">Not applicable.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify"><B>&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify"><B>Item 7. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Identification
and Classification of the Subsidiary Which Acquired the Security Being Reported on By the Parent Holding Company or Control Person:</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">Not applicable.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify"><B>&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify"><B>Item 8.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Identification
and Classification of Members of the Group:</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">Not applicable.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify"><B>&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify"><B>Item 9.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Notice
of Dissolution of Group:</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">Not applicable.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify"><B>&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify"><B>Item 10.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Certification:</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">By signing below I hereby certify that, to
the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or
with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held
in connection with or as a participant in any transaction having that purpose or effect.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify">&nbsp;</P>


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<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>&nbsp;</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: center"><B>SIGNATURE</B></P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0.5in">&nbsp;</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0.5in">After reasonable inquiry
and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.</P>

<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify; text-indent: 0.5in">&nbsp;</P>

<TABLE CELLSPACING="0" CELLPADDING="0" STYLE="font: 10pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse">
<TR STYLE="vertical-align: top">
    <TD STYLE="width: 50%">&nbsp;</TD>
    <TD STYLE="width: 50%; text-decoration: none"><FONT STYLE="text-transform: uppercase">Date: F</FONT>ebruary 14<FONT STYLE="text-transform: uppercase">,
    2017</FONT></TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>RA CAPITAL HEALTHCARE FUND, L.P.</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>By: RA Capital Management, LLC</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>Its: General Partner</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>&nbsp;</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD STYLE="border-bottom: Black 1pt solid">By: /s/ Rajeev Shah</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>Rajeev Shah</TD></TR>
<TR STYLE="vertical-align: top">
    <TD>&nbsp;</TD>
    <TD>Authorized Signatory</TD></TR>
</TABLE>
<P STYLE="font: 10pt Times New Roman, Times, Serif; margin: 0"><FONT STYLE="text-transform: uppercase">&nbsp;</FONT></P>


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