UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

(Rule14a-101)

INFORMATION REQUIRED IN PROXY STATEMENT

SCHEDULE 14A INFORMATION

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

Check the appropriate box:

ARCA BIOPHARMA, INC.

(Name of Registrant as Specified inIn Its Charter)

(Name of Person(s) Filing Proxy Statement if Other Than the Registrant)

Payment of Filing Fee (Check the appropriate box)

ARCA BIOPHARMA, INC.

11080 CirclePoint Road, Suite 140

Westminster, Colorado 80020

April 18,, 2018

Dear Stockholders of ARCA biopharma, Inc.:

You are cordially invited to attend the AnnualSpecial Meeting (the “Special Meeting”) of Stockholders (the “Annual Meeting”) of ARCA biopharma, Inc., a Delaware corporation (the “Company” or “ARCA”). The meeting will be held on                 Thursday, May 31,, 2018 at 9:00 a.m.                  local time at the Renaissance Boulder Flatiron Hotel, 500 Flatiron Blvd, Broomfield, CO 80021.Company’s Headquarters, 11080 CirclePoint Road, Suite 140, Westminster, Colorado 80020.

The matters scheduled to be considered at the meeting are (1) to electapprove amendments to the nomineesCompany’s restated certificate of incorporation, as amended, and authorize the Company’s Board of Directors, (the “Boardif in their judgment it is necessary, to select and file one such amendment to effect a reverse stock split of Directors”), Dr. Raymond L. Woosleythe Company’s Common Stock, at a ratio of between1-for-3 and Mr. Daniel J. Mitchell,1-for-20, inclusive, such ratio to be determined at the Board of Directors to hold office until the 2021 Annual Meeting of Stockholders, (2) to ratify the selection by the Audit Committeediscretion of the Board of Directors (the “Audit Committee”) of KPMG LLP (“KPMG”) as the independent registered public accounting firm of the Company for its fiscal year ending December 31, 2018,Directors; and (3)(2) to conduct any other business properly brought before the meeting.Special Meeting. These items of business are more fully described in thisthe enclosed proxy statement, thatwhich you are encouraged to read in its entirety.

In accordance with the Securities and Exchange Commission (“SEC”) rule (“Notice and Access Rule”) that allows companies to furnish their proxy materials (including the form of proxy, this proxy statement and our Annual Report on Form10-K for the fiscal year ended December 31, 2017, filed with the SEC on March 22, 2018) over the Internet, we intend to send a Notice of Internet Availability of Proxy Materials (“Notice”) on or about April 20, 2018 to ourAll stockholders of record as of April 2, 2018. We will also provide access to our proxy materials over the Internet by April 20, 2018. As a result of the Notice and Access Rule, all stockholders receiving the Notice have the ability to access the proxy materials over the Internet and request to receive a paper copy of the proxy materials by mail. Instructions on how to access the proxy materials over the Internet or to request a paper copy may be found on the Notice. In addition, the Notice contains instructions on how stockholders may request to receive proxy materials electronically bye-mail.

All stockholdersARCA are cordially invited to attend the AnnualSpecial Meeting in person. Whether or not you expect to attend the AnnualSpecial Meeting, please vote your shares as promptly as possible using the enclosed proxy card, or via the Internet or telephone as instructed in the Notice of Internet Availability of Proxy Materials, via the Internet or the telephone, as promptly as possibleenclosed materials, in order to ensure your representation at the AnnualSpecial Meeting. Alternatively, you may follow the procedures outlined in the Notice of Internet Availability of Proxy Materials to request a paper proxy card to submit your vote by mail. Even if you have voted by proxy, you may still vote in person if you attend the Annualmeeting. Please note, however, that if your shares are held of record by a broker, bank or other nominee and you wish to vote at the meeting, you must obtain a proxy issued in your name from that record holder.

Sincerely,

CHRISTOPHER OZEROFF

Secretary, Senior Vice President and General Counsel

ARCA BIOPHARMA, INC.

11080 CirclePoint Road, Suite 140

Westminster, Colorado 80020

NOTICE OF SPECIAL MEETING OF STOCKHOLDERS

TO BE HELD ON                  , 2018

Notice is hereby given that the Special Meeting of Stockholders (the “Special Meeting”) of ARCA biopharma, Inc., a Delaware corporation (the “Company” or “ARCA”) will be held on                 , 2018 at                  local time at the headquarters of the Company, 11080 CirclePoint Road, Suite 140, Westminster, Colorado 80020, for the following purposes:

Please refer to the proxy materials accompanying this Notice for further information about the business to be transacted at the Special Meeting.

The record date for the Special Meeting is                 , 2018. Only stockholders of record at the close of business on that date may vote at the Special Meeting or any adjournment thereof.

By Order of the Board of Directors:

CHRISTOPHER OZEROFF

Secretary, Senior Vice President and General Counsel

WESTMINSTER, CO

                           , 2018

All stockholders are cordially invited to attend the Special Meeting in person. Whether or not you expect to attend the Special Meeting, please vote by proxy, as promptly as possible, to ensure your representation at the Special Meeting.

You may vote by proxy by completing and mailing the enclosed proxy card. If you submit a proxy card, we will vote your shares as you direct. If you submit a proxy card without giving specific voting instructions, those shares will be voted as recommended by our Board of Directors.

You may also vote by proxy via the Internet by going to the websitehttp://www.investorvote.com/ABIO, and following the instructions provided there, or by telephone, by calling the following number:1-800-652-VOTE (8683) using a touch-tone phone and follow the recorded instructions. You will be asked to provide the company number and control number found on the proxy card. Your proxy card, Internet or telephone vote must be received by                  Mountain Time on                 , 2018 to be counted.

We will make all of our proxy materials available on the Internet athttp://www.investorvote.com/ABIO, beginning on or about                 , 2018, and permit voting via the Internet and by telephone as of that date.

If your shares are held by a broker, bank, or other agent, you are considered the beneficial owner of those shares, and your shares are held in “street name.” If you hold your shares in “street name” you will receive instructions from your broker, bank or other agent describing how to vote your shares. If you hold shares in “street name” and do not receive instructions on how to vote your shares, you should contact your broker, bank or other agent promptly and request this information.

Even if you have voted by proxy via one of the procedures listed above, you may still vote in person if you attend the Special Meeting. Please note, however, that if your shares are held of record by a broker, bank or other agent and you wish to vote at the Annual Meeting, you must obtain a proxy issued in your name from that record holder.

ARCA BIOPHARMA, INC.

11080 CirclePoint Road, Suite 140

Westminster, Colorado 80020

NOTICE OF ANNUAL MEETING OF STOCKHOLDERS

TO BE HELD ON MAY 31, 2018

Notice is hereby given that the Annual Meeting of Stockholders (the “Annual Meeting”) of ARCA biopharma, Inc., a Delaware corporation (the “Company” or “ARCA”) will be held on Thursday, May 31, 2018, at 9:00 a.m. local time at the Renaissance Boulder Flatiron Hotel, 500 Flatiron Blvd, Broomfield, CO 80021, for the following purposes:

1.             To elect the Board of Directors’ nominees, Dr. Raymond L. Woosley and Dan J. Mitchell, to the Board of Directors to hold office until the 2021 Annual Meeting of Stockholders.

2.            To ratify the selection by the Audit Committee of the Board of Directors of KPMG LLP as independent registered public accounting firm of the Company for its fiscal year ending December 31, 2018.

3.            To conduct any other business properly brought before the meeting.

These items of business are more fully described in the proxy statement accompanying this Notice.

The record date for the Annual Meeting is April 2, 2018. Only stockholders of record at the close of business on that date may vote at the meeting or any adjournment thereof.

WESTMINSTER, CO

APRIL 18, 2018

Pursuant to the Internet proxy rules promulgated by the Securities and Exchange Commission, the Company has elected to provide access to its proxy materials over the Internet. Accordingly, stockholders of record at the close of business on April 2, 2018, will receive a Notice of Internet Availability of Proxy Materials and may vote at the Annual Meeting and any adjournment or postponement thereof. The Company expects to mail the Notice of Internet Availability of Proxy Materials on or about April 20, 2018.

All stockholders are cordially invited to attend the Annual Meeting in person. Whether or not you expect to attend the Annual Meeting, please vote, as instructed in the Notice of Internet Availability of Proxy Materials, via the Internet or the telephone, as promptly as possible in order to ensure your representation at the annual meeting. Alternatively, you may follow the procedures outlined in the Notice of Internet Availability of Proxy Materials to request a paper proxy card to submit your vote by mail. Even if you have voted by proxy, you may still vote in person if you attend the Annual Meeting. Please note, however, that if your shares are held of record by a broker, bank or other agent and you wish to vote at the AnnualSpecial Meeting, you must obtain a proxy issued in your name from that record holder.

ARCA BIOPHARMA, INC.

11080 CirclePoint Road, Suite 140

Westminster, Colorado 80020

PROXY STATEMENT

FOR THE 2018 ANNUALSPECIAL MEETING OF STOCKHOLDERS TO BE HELD ON

MAY 31,            , 2018

This proxy statement (this “Proxy Statement”) is being furnished to holders of ARCA biopharma, Inc. (sometimes referred to as the “Company,” “ARCA,” “we,” “us,” and “our”) common stock, par value $0.001 per share (the “Common Stock”). Proxies are being solicited on behalf of the Board of Directors of ARCA (the “Board of Directors” or the “Board”) to be used at the AnnualSpecial Meeting of Stockholders (the “Annual“Special Meeting”) to be held on                 Thursday, May 31,, 2018 at 9:00 a.m.                  local time at the Renaissance Boulder Flatiron Hotel, 500 Flatiron Boulevard, Broomfield, CO 80021,headquarters of the Company, 11080 CirclePoint Road, Suite 140, Westminster, Colorado 80020 and at any postponement or adjournment thereof, for the purposes set forth in the Notice of AnnualSpecial Meeting of Stockholders.

ARCA is using the Securities and Exchange Commission (the “SEC”) rule that allows companiesus to furnish theirdeliver a “full set” of our proxy materials over the Internet. As a result, we intend toby mail to all of our stockholders aof record as of                 , 2018 (the “Record Date”). Our proxy materials include the Notice of Internet Availability of Proxy MaterialsSpecial Meeting (the “Notice”) instead of a paper copy of the proxy materials (including the form of proxy,, this Proxy Statement and our Annual Report on Form10-K for the fiscal year ended December 31, 2017, filed with the SEC on March 22, 2018 (the “2017 Annual Report”), collectively,a proxy card (collectively, the “Proxy Materials”), and we will mail our Proxy Materials on or about                 April 20,, 2018. WeIn addition to mailing our Proxy Materials, we will also provide access to our Proxy Materials over the Internet, by                 April 20,, 2018. By furnishing theThe Notice to our stockholders of record, youwill not receive a printed copy ofand the Proxy Materials in the mail. Instead, the Notice instructsStatement instruct you on how to access and review all of the important information contained in the Proxy Statement and Annual Report electronically or to receive a printed version inMaterials via the mail.Internet. The Notice and the Proxy Statement also instructsinstruct you on how you may submit your proxy overvote by mail, the Internet, by toll-free number, or in person at the AnnualSpecial Meeting. After receiving the Notice, all stockholders can access the Proxy Materials over the Internet and request to receive a paper copy of the Proxy Materials by mail. Instructions on how to access the Proxy Materials over the Internet or to request a paper copy may be found on the Notice. In addition, the Notice contains instructions on how stockholders may request to receive Proxy Materials electronically bye-mail.

All stockholders may view and print ARCA’s proxy statement and the 2017 Annual Report, which are available at www.arcabio.com.

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QUESTIONS AND ANSWERS ABOUT THESE PROXY MATERIALS AND VOTING

Why didam I receive a notice regardingreceiving these materials?

We have sent you these proxy materials because the availability of the Proxy Materials on the Internet?

As described above, pursuant to rules adopted by the SEC, we have elected to provide access to the Proxy Materials over the Internet. Accordingly, on or about April 20, 2018, we expect to send the Notice to ARCA’s stockholders of record. The Board of Directors is soliciting your proxy to vote at the Annual Meeting. All stockholders can accessSpecial Meeting, including at any adjournments or postponements of the Proxy Materialsmeeting. You are invited to attend the annual meeting to vote on the website referredproposals described in this proxy statement. However, you do not need to inattend the Noticemeeting to vote your shares. Instead, you may simply complete, sign and return the enclosed proxy card, or requestfollow the instructions below to receive a printed or electronic set of the Proxy Materials. Instructions on how to access the Proxy Materialssubmit your proxy over the Internettelephone or through the Internet.

We intend to request a printed copy may be found inmail these proxy materials on or about                  , 2018 to all stockholders of record entitled to vote at the Notice.annual meeting.

How do I attend the AnnualSpecial Meeting?

The meeting will be held on                 Thursday, May 31,, 2018 at 9:00 a.m.                  local time at the Renaissance Boulder Flatiron Hotel, 500 Flatiron Blvd, Broomfield, CO 80021.Company’s headquarters, 11080 CirclePoint Road, Suite 140, Westminster, Colorado 80020. Directions to the AnnualSpecial Meeting may be found atwww.arcabio.com. Information on how to vote in person at the AnnualSpecial Meeting is discussed below.

Who can vote at the AnnualSpecial Meeting?

Only stockholders of record at the close of business on April 2, 2018,the Record Date will be entitled to vote at the AnnualSpecial Meeting. On this record date,the Record Date, there were 13,914,320                  shares of Common Stock outstanding and entitled to vote.

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Stockholder of Record: Shares Registered in Your Name

If on April 2, 2018,the Record Date, your shares of our Common Stock were registered directly in your name with ARCA’s transfer agent, Computershare Trust Company N.A., then you are a stockholder of record. As a stockholder of record, you may vote in person at the meetingSpecial Meeting or vote by proxy. Whether or not you plan to attend the meeting,Special Meeting, we urge you to fill out and return the enclosed proxy card or vote by proxy over the telephone or on the Internet (asas instructed below) or return the proxy card we may mail to youbelow to ensure your vote is counted.

Beneficial Owner: Shares Registered in the Name of a Broker or Bank

If, on April 2, 2018,the Record Date, your shares of our Common Stock were held, not in your name, but rather in an account at a brokerage firm, bank, dealer, or other similar organization, then you are the beneficial owner of shares held in “street name” and the Notice isProxy Materials are being forwarded to you by that organization. The organization holding your account is considered to be the stockholder of record for purposes of voting at the AnnualSpecial Meeting. As a beneficial owner, you have the right to direct your broker or other agent regarding how to vote the shares in your account. You are also invited to attend the AnnualSpecial Meeting. However, since you are not the stockholder of record, you may not vote your shares in person at the meeting unless you request and obtain a valid proxy from your broker or other agent.

What am I voting on?

There are two matters scheduled forApproval of amendments to the Company’s restated certificate of incorporation, as amended, and authorization of the Company’s Board of Directors, if in their judgment it is necessary, to select and file one such amendment to effect a vote:

reverse stock split of the Company’s Common Stock, at a ratio of between��1-for-3 Election of two directors; and

Ø1-for-20, Ratification of selection byinclusive, such ratio to be determined at the Audit Committee (the “Audit Committee”)discretion of the Board of Directors of KPMG LLP (“KPMG”(such proposal, “Proposal No. 1”) as independent registered public accounting firm of the Company for its fiscal year ending December 31, 2018;.

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What if another matter is properly brought before the meeting?

The Board of Directors knows of no other matters that will be presented for consideration at the AnnualSpecial Meeting. If any other matters are properly brought before the meeting, it is the intention of the persons named in the accompanying proxy to vote on those matters in accordance with their best judgment.

How do I vote?

You may either vote “For” each nominee to the Board of Directors or you may “Withhold” your vote for each nominee. For all other matters to be voted on, you may vote “For” or “Against” or abstain from voting. The procedures for voting are fairly simple:

Stockholder of Record: Shares Registered in Your Name

If you are a stockholder of record, you may vote in person at the AnnualSpecial Meeting, vote by proxy over the telephone, vote by proxy through the Internet or vote by proxy using athe enclosed proxy card that you may request or that we may elect to deliver at a later time.card. Whether or not you plan to attend the meeting, we urge you to vote by proxy to ensure your vote is counted. You may still attend the meeting and vote in person even if you have already voted by proxy.

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Beneficial Owner: Shares Registered in the Name of Broker or Bank

If you are a beneficial owner of shares registered in the name of your broker, bank, or other agent, you should have received a Notice containing voting instructionsfrominstruction form with these proxy materialsfrom that organization rather than from ARCA. Simply followcomplete and mail the voting instructions in the Noticetoinstruction formto ensure that your vote is counted. Alternatively, you may vote by telephone or over the Internet as instructed by your broker or bank. To vote in person at the AnnualSpecial Meeting, you must obtain a valid proxy from your broker, bank, or other agent. Follow the instructions from your broker or bank included with these proxy materials, or contact your broker or bank to request a proxy form.

We provide Internet proxy voting to allow you to vote your shares online, with procedures designed to ensure the authenticity and correctness of your proxy vote instructions. However, please be aware that you must bear any costs associated with your access to the Internet, such as usage charges from Internet access providers and telephone companies.

How many votes do I have?

On each matter to be voted upon, you have one vote for each share of Company Common Stock you ownedown as of April 2, 2018.the Record Date.

What if I return a proxy card or otherwise vote but do not make specific choices?

If you return a signed and dated proxy card or otherwise vote without marking voting selections, your shares will be voted, as applicable, “For” the election of each nominee for director and “For” Proposal 2.approval to effect the reverse stock split. If any

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other matter is properly presented at the meeting, your proxy holder (one of the individuals named on your proxy card) will vote your shares using his or her best judgment.

Who is paying for this proxy solicitation?

We will pay for the entire cost of soliciting proxies. In addition to these proxy materials, the directors and employees may also solicit proxies in person, by telephone, or by other means of communication. Directors and employees will not be paid any additional compensation for soliciting proxies. We may also reimburse brokerage firms, banks and other agents for the cost of forwarding proxy materials to beneficial owners.

What does it mean if I receive more than one Notice?set of Proxy Materials?

If you receive more than one Notice,set of Proxy Materials, your shares may be registered in more than one name or in different accounts. Please follow the voting instructions on each Noticethe proxy cards in the Proxy Materials to ensure that all of your shares are voted.

Can I change my vote after submitting my proxy?

Yes. You can revoke your proxy at any time before the final vote at the meeting. If you are the record holder of your shares, you may revoke your proxy in any one of the following ways:

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Your most current proxy card or telephone or the Internet proxy is the one that is counted.

If your shares are held by your broker or bank as a nominee or agent, you should follow the instructions provided by your broker or bank.

WhenHow are votes counted?

Votes will be counted by the inspector of election appointed for the meeting, who will separately count “For” and “Against” votes, abstentions and brokernon-votes. Abstentions will be counted towards the vote total for Proposal No. 1, and will have the same effect as “Against” votes. As described in more detail below, as a “routine” matter, we do not expect a substantial number of brokernon-votes.

What are “brokernon-votes”?

Brokernon-votes occur when banks, brokers or others who hold shares in “street name” for a beneficial owner return a proxy but provide no instruction as to how the sharesshould be voted on a particular matter. Generally, if shares are held in street name, the beneficial owner of the shares is entitled to give voting instructions to the broker or nominee holding the shares. If the beneficial owner does not provide voting instructions, the broker or nomineecan still vote the shares with respect to matters that are considered to be “routine,” but not with respect to“non-routine” matters. Under the rules and interpretations of the New York Stock Exchange,“non-routine” matters are matters that may substantially affect the rights or privileges of stockholders, such as mergers, stockholder proposals dueand elections of directors, even if not contested. Approval of the stock split contemplated in Proposal No. 1 is considered a “routine” matter upon which a broker or nominee may vote without instruction from the beneficial owner.

How many votes are needed to approve this proposal?

The affirmative vote of a majority of the Company’s outstanding Common Stock is required to pass Proposal No. 1 to approve the amendments of the Company’s restated certificate of incorporation, as amended, and authorize the Board of Directors, if in their judgment it is necessary, to select and file one such amendment to effect a reverse stock split of the Company’s Common Stock at a ratio of between1-for-3 and1-for-20, inclusive, such ratio to be determined at the discretion of the Board of Directors. Brokerage firms have authority to vote their customers’ unvoted shares held by the firms in street name on this proposal. If a broker does not exercise this authority, such brokernon-votes, as well as any abstentions, will be treated as votes against this proposal.

How does the Board of Directors recommend that I vote?

The Board of Directors recommends that you voteFOR Proposal No. 1.

What is the quorum requirement?

A quorum of stockholders is necessary to hold a valid meeting. A quorum will be present if stockholders holding a majority of the outstanding shares entitled to vote are present at the meeting in person or represented by proxy. On the Record Date, there were                  shares outstanding and entitled to vote. Thus, the holders of                 shares must be present in person or represented by proxy at the meeting to have a quorum.

Your shares will be counted towards the quorum only if you submit a valid proxy (or one is submitted on your behalf by your broker, bank or other nominee) or if you vote in person at the meeting. Abstentions and brokernon-votes, if any, will be counted towards the quorum requirement. If there is no quorum, the holders of a majority of shares present at the meeting in person or represented by proxy may adjourn the meeting to another date.

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How can I find out the results of the voting at the Special Meeting?

Preliminary voting results will be announced at the Special Meeting. In addition, final voting results will be published in a current report onForm 8-K that we expect to file within four business days after the Special Meeting. If final voting results are not available to us in time to file aForm 8-K within four business days after the meeting, we intend to file aForm 8-K to publish preliminary results and, within four business days after the final results are known to us, file an additionalForm 8-K to publish the final results.

What proxy materials are available on the internet?

We will make all of the Proxy Materials available on the Internet athttp://www.investorvote.com/ABIO, beginning on or about                 , 2018, and permit voting via the Internet and by telephone as of that date.

What are the deadlines for next year’ssubmitting stockholder proposals for the 2019 annual meeting?

To be considered for inclusion in next year’s proxy materials, your proposal must be submitted in writing by December 19, 2018, to ARCA’s Secretary at 11080 CirclePoint Road, Suite 140, Westminster, Colorado, 80020. If you wish to submit a proposal that is not to be included in next year’s proxy materials or nominate a director, you must do so by no earlier than March 2, 2019, and no later than April 1, 2019. You are also advised to review the Company’s Bylaws, which contain additional requirements about advance notice of stockholder proposals and director nominations.

How

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PROPOSAL NO. 1

APPROVAL OF CERTIFICATES OF AMENDMENT TO THE COMPANY’S

RESTATED CERTIFICATE OF INCORPORATION TO EFFECT A REVERSE STOCK SPLIT

Introduction

The Board has adopted a resolution approving, and recommending to the Company’s stockholders for their approval, a series of proposed certificates of amendment to the Company’s Restated Certificate of Incorporation (as amended, the “Restated Certificate of Incorporation”) to effect a reverse split of the shares of the Company’s Common Stock at a ratio of between1-for-3 and1-for-20, inclusive, (the “Reverse Stock Split”). The texts of the forms of the proposed certificates of amendment to the Restated Certificate of Incorporation are votes counted?

Votes will be counted byannexed to this proxy statement as AnnexesA-1 toA-18. Assuming the inspector of election appointed forstockholders approve the meeting. For Proposal 1, to elect new directors, votes “For” and “Withhold” will be counted. For Proposal 2, votes “For” and “Against”, abstentions and brokernon-votes will be counted. Abstentions will be counted towardsproposal, the vote total for Proposal 2, andBoard will have the samesole discretion under Section 242(c) of the General Corporation Law of the State of Delaware (the “DGCL”), as it determines to be in the best interest of the Company and its stockholders, both to select the specific exchange ratio within the designated range of between1-for-3 and1-for-20, inclusive, and also to decide whether or not to proceed to effect as “Against” votes. Brokernon-votes have noa Reverse Stock Split or instead to abandon the proposed certificates of amendment altogether. If a certificate of amendment is filed with the Secretary of State of the State of Delaware, the certificate of amendment to the Restated Certificate of Incorporation will effect the Reverse Stock Split by reducing the outstanding number of shares of the Company’s Common Stock by the ratio to be determined by the Board, but will not increase the par value of the Company’s Common Stock, and will not be counted towardschange the vote total for any proposal.

What are “brokernon-votes”?

Brokernon-votes occur when a beneficial ownernumber of authorized shares held in “street name”of the Company’s Common Stock. If the Board does not give instructionsimplement an approved Reverse Stock Split prior to the broker or nominee holdingone-year anniversary of this meeting, the sharesasBoard will seek stockholder approval before implementing any Reverse Stock Split after that time.

By approving Proposal No. 1 and the Reverse Stock Split, stockholders will approve each of a series of certificates of amendment to howthe Restated Certificate of Incorporation pursuant to vote. Generally, ifwhich any whole number of outstanding shares, are held in street name, the beneficial ownerbetween and including three and twenty, would be combined into one share of the shares is entitledCompany’s Common Stock, and authorize the Board to give voting instructionsfile only one such certificate of amendment, as determined by the Board in the manner described herein, and to abandon each certificate of amendment not selected by the Board. If approved, the Board may also elect not to effect any Reverse Stock Split and consequently not to file any certificate of amendment to the broker or nominee holding the shares. If the beneficial owner does not provide voting instructions, the broker or nomineecan still vote the shares with respect to mattersRestated Certificate of Incorporation. The Board believes that are considered to be “routine,” but not with respect to“non-routine” matters. Under the rules and interpretationsstockholder approval of the New Yorkseries of certificates of amendment granting the Board this discretion, rather than approval of a specified exchange ratio, provides the Board with maximum flexibility to react to then-current market conditions and, therefore, is in the best interests of the Company and its stockholders.

The Company’s Nasdaq Listing Compliance

The Company’s Common Stock Exchange,“non-routine” matters are matters that may substantially affect

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is listed on the rights or privilegesNasdaq Capital Market under the symbol “ABIO.” To maintain a listing on the Nasdaq Capital Market, the Company must satisfy the applicable listing maintenance standards established by Nasdaq Stock Market LLC (“Nasdaq”). Among other things, the Company is required to comply with the continued listing requirements of stockholders, such as mergers, stockholder proposals and electionsthe Nasdaq Capital Market (the “Nasdaq Capital Requirements”). To comply with the Nasdaq Capital Requirements, the Company must meet each of directors, even if not contested.

How many votes are needed to approve each proposal?the following requirements:

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To comply with the Nasdaq Capital Requirements, the Company must also meet at least one of the following requirements:

WhatCurrently, the Company meets the Nasdaq Capital Requirements, except the $1.00 minimum bid price. Assuming the stockholders approve Proposal No. 1, the Board will determine whether to effect a Reverse Stock Split in the range of between1-for-3 and1-for-20, inclusive, at the ratio determined by the Board to be most likely sufficient to allow the Company to meet and maintain the $1.00 minimum bid price requirement.

Reasons for the Reverse Stock Split

On April 11, 2018, Nasdaq notified us that the bid price of our Common Stock had closed below the required $1.00 per share for 30 consecutive trading days, and, accordingly, that we did not comply with the applicable Nasdaq minimum bid price requirement. We have been provided 180 calendar days by Nasdaq to regain compliance with this requirement. We may be eligible for an additional 180 day extension from Nasdaq.

The Board has considered the potential harm to us of a delisting of our Common Stock and has determined that, if our Common Stock continues to trade below $1.00 per share, the consummation of the Reverse Stock Split is the quorum requirement?

A quorumbest way to maintain liquidity by achieving compliance with the Nasdaq Capital Requirements. Approval of stockholders is necessary to hold a valid meeting. A quorumProposal No. 1 will be present if stockholders holding a majority of the outstanding shares of Common Stock entitled to vote are present at the meeting in person or represented by proxy. On the record date, April 2, 2018, there were 13,914,320 shares of Common Stock outstanding and entitled to vote. Thus, the holders of 6,957,161 shares of Common Stock must be present in person or represented by proxy at the meeting to have a quorum.

Your shares will be counted towards the quorum only if you submit a valid proxy (or one is submitted on your behalf by your broker, bank or other nominee) or if you vote in person at the meeting. Abstentions and brokernon-votes will be counted towards the quorum requirement. If there is no quorum, the holders of a majority of shares present at the meeting in person or represented by proxy may adjourn the meeting to another date.

How can I find out the results of the voting at the Annual Meeting?

Preliminary voting results will be announced at the Annual Meeting. In addition, final voting results will be published in a current report on Form8-K that we expectpermit us to file within four business days afterone certificate of amendment to the Annual Meeting. If final voting results are not available to us in time to file aForm 8-K within four business days after the meeting, we intend to file aForm 8-K to publish preliminary results and, within four business days after the final results are known to us, file an additionalForm 8-K to publish the final results.

NO PERSON IS AUTHORIZED TO GIVE ANY INFORMATION OR TO MAKE ANY REPRESENTATION OTHER THAN THOSE CONTAINED IN THIS PROXY STATEMENT, AND, IF GIVEN OR MADE, SUCH INFORMATION MUST NOT BE RELIED UPON AS HAVING BEEN AUTHORIZED. THE DELIVERY OF THIS PROXY STATEMENT SHALL, UNDER NO CIRCUMSTANCES, CREATE ANY IMPLICATION THAT THERE HAS BEEN NO CHANGE IN THE AFFAIRS OF ARCA SINCE THE DATE OF THIS PROXY STATEMENT.

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PROPOSAL 1

ELECTIONOF BOARDOF DIRECTORS

The Company’s Amended and Restated Certificate of Incorporation provides thatand the Boardcertificate of Directors is divided into three classes to provide for staggered terms and that each directoramendment filed thereby will serve for a termcontain the number of three years or less, depending on the class to which the Board of Directors has assigned a director not previously elected by the stockholders. There are currently no vacancies on the Board of Directors. Vacancies on the Board of Directors may be filled only by persons elected by a majority of the remaining directors. A director electedshares selected by the Board within the limits set forth in Proposal No. 1 to be combined into one share of DirectorsCommon Stock.

The Board also believes that the current low per share market price of our Common Stock has a negative effect on the marketability of our existing shares. The Board believes there are several reasons for this effect. First, certain institutional investors have internal policies preventing the purchase oflow-priced stocks. Second, a variety of policies and practices of broker-dealers discourage individual brokers within those firms from dealing inlow-priced stocks. Third, because the brokers’ commissions onlow-priced stocks generally represent a higher percentage of the stock price than commissions on higher priced stocks, the current share price of our Common Stock can result in individual stockholders paying transaction costs (commissions, markups or markdowns) that are a higher percentage of their total share value than would be the case if the share price of the Common Stock were substantially higher. This factor is also believed to filllimit the willingness of some institutions to purchase the Common Stock. The Board anticipates that a vacancyReverse Stock Split will result in a class, including vacancies createdhigher bid price for our Common Stock, which may help to alleviate some of these problems.

If Proposal No. 1 is approved by the holders of our Common Stock and the Board decides to implement the Reverse Stock Split, the Board will determine the ratio of the Reverse Stock Split, in the range of between1-for-3 and1-for-20, inclusive, as determined in the judgment of the Board to be most likely sufficient to allow us to achieve and maintain compliance with the minimum $1.00 per share requirement for listing on the Nasdaq Capital Market for the longest period of time while retaining sufficient number of outstanding, tradeable shares to facilitate an adequate market. By way of illustration, assuming a per share price of $                , which represents the closing price of our Common Stock on the Nasdaq Capital Market on the Record Date, immediately prior to the filing of the appropriate certificate of amendment to the Restated Certificate of Incorporation, the Board may determine that we should effect a1-for-3 or1-for-20 reverse stock split, with the goal of achieving a bid price of $                 or $                 per share, respectively. Please refer to the section entitled “Effects of the Reverse Stock Split” below for more

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detailed examples of the effects of the range of ratios.

We believe that maintaining listing on the Nasdaq Capital Market will provide us with a market for the Common Stock that is more accessible than if our Common Stock were traded on the OTC Bulletin Board or in the “pink sheets” maintained by the OTC Markets Group, Inc. Such alternative markets are generally considered to be less efficient than, and not as broad as, the Nasdaq Capital Market. Among other factors, trading on the Nasdaq Capital Market increases liquidity and may potentially minimize the spread between the “bid” and “asked” prices quoted by Market Makers (as defined in Nasdaq Rule 5005). Further, a Nasdaq Capital Market listing may enhance our access to capital, increase our flexibility in responding to anticipated capital requirements and facilitate the use of our Common Stock in any strategic or financing transactions that it may undertake. We believe that prospective investors will view an investment in us more favorably if our shares qualify for listing on the Nasdaq Capital Market as compared with the OTC markets.

We expect that a Reverse Stock Split of our Common Stock will increase the market price of the Common Stock so that we are able to maintain compliance with the Nasdaq minimum bid price listing standard. However, the effect of a Reverse Stock Split on the market price of the Common Stock cannot be predicted with any certainty, and the history of similar stock split combinations for companies in like circumstances is varied. It is possible that the per share price of the Common Stock after the Reverse Stock Split will not rise in proportion to the reduction in the number of directors,shall serve for the remaindershares of the full term ofCommon Stock outstanding resulting from the Reverse Stock Split, effectively reducing our market capitalization, and there can be no assurance that class and until the director’s successor is duly elected and qualified.The Company may reducemarket price per post-reverse split share will either exceed or increase the sizeremain in excess of the $1.00 minimum bid price for a sustained period of time. The market price of our Common Stock may vary based on other factors that are unrelated to the number of shares outstanding, including our future performance.

In order to maintain the listing on the Nasdaq Capital Market, we must maintain compliance with the Nasdaq Capital Requirements. As of June 30, 2018, the Company’s Market Value (as defined in Nasdaq Rule 5005) of Listed Securities (as defined in Nasdaq Rule 5005) was $7,741,647, our market value of Publicly Held Shares (as defined in Nasdaq Rule 5005) was $7,650,869 and our stockholders’ equity was $8,998,000. Even if we meet the bid price requirement, if we are unable to comply with the other Nasdaq Capital Requirements, Nasdaq may determine to delist the Company’s Common Stock from the Nasdaq Capital Market.

The Board does not intend for this transaction to be the first step in a series of Directors by resolution adopted by the affirmative voteplans or proposals of a majority of the directors.

There are currently two Class III directors whose terms expire at the annual stockholders’ meeting in 2018, two Class I directors whose terms expire at the annual stockholders’ meeting in 2019 and two Class II directors whose terms expire at the annual meeting in 2020. The Board of Directors has nominated two Class III directors, Dr. Raymond L. Woosley and Dan J. Mitchell, for election to the Board of Directors, for a three-year term ending on the date of the annual meeting in 2021 or until their successors are duly elected and qualified or appointed.

If elected at the Annual Meeting, Dr. Woosley and Mr. Mitchell would serve until the 2021 annual meeting and until their successors have been duly elected and qualified, or, if sooner, until the director’s death, resignation or removal. It is the Company’s policy to encourage directors and nominees for director to attend the Annual Meeting. Four of the Company’s directors then on the Board of Directors attended the 2017 Annual Meeting of Stockholders in person, and one attended by telephone.

Directors are elected by a plurality of the votes of the holders of shares present in person or represented by proxy and entitled to vote on the election of directors. The two nominees receiving the highest number of affirmative votes will be elected. Each person nominated for election has agreed to serve if elected. The Company’s management has no reason to believe that either nominee will be unable to serve.

Director Qualifications and Diversity

The below paragraphs provide information, as of the date of this proxy statement, about each nominee and current members of the Board of Directors, including age, all positions currently held, principal occupation and business experience for the past five years. In addition to the information presented regarding each nominee’s specific experience, qualifications, attributes and skills that led the Board of Directors to conclude that such director or nominee should be able to serve as a director, the Board of Directors also believes that all of the directors and nominees have a reputation of integrity, honesty and adherence to high ethical standards. They each have demonstrated business acumen and an ability to exercise sound judgment as well as a commitment to service to ARCA and the Board of Directors.

Our Nominating and Corporate Governance Committee of the Board of Directors (the “Nominating and Corporate Governance Committee”) considers diversity in the director identification and nomination process. The Nominating and Corporate Governance Committee seeks nominees with a broad diversity of experience, professions, skills, geographic representation and backgrounds. The Nominating and Corporate Governance Committee does not assign specific weights to particular criteria and no particular criterion is necessarily applicable to all prospective nominees. ARCA believes that the backgrounds and qualifications of the directors, considered as a group, should provide a significant composite mix of experience, knowledge and abilities that will allow the Board of Directors to fulfill its responsibilities. Nominees are not discriminated against on the basis of race, religion, national origin, sexual orientation, disability or any other basis proscribed by law.

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NOMINEEFOR ELECTIONFORA THREE-YEAR TERM EXPIRINGATTHE 2020 ANNUAL MEETING

THE BOARD OF DIRECTORS RECOMMENDS

A VOTE IN FAVOR OF THE NAMED NOMINEES.

Raymond L. Woosley, M.D., Ph.D.

Dr. Woosley, age 75, was appointed to the Board of Directors in July 2013. Dr. Woosley is currently Professor of Medicine andCo-Director of the Division for Data Analytics and Decision Support in the Department of Medicine of the University of Arizona, College of Medicine in Phoenix. Since 2012, Dr. Woosley has served as the Director of the Arizona Center for Education and Research on Therapeutics (AzCERT), an independent, nonprofit research and education organization. He is also President Emeritus of the Critical Path Institute(C-Path), anon-profit, public-private partnership with the U.S. Food and Drug Administration, of which he was a founder in November 2004, and where he served as President, Chief Executive Officer and Chairman of the board of directors from 2005 to 2011. Since 2001, Dr. Woosley has also been a Professor of Medicine and Pharmacology at The University of Arizona Health Sciences Center in Tucson, AZ, and, since 2012, Professor Emeritus, where he was also Vice President for Health Sciences from 2001 to 2005, and Dean of the College of Medicine from 2001 to 2002. From 1988 to 2001, Dr. Woosley was a professor of medicine at the Georgetown University School of Medicine, where he was also Director of the Institute of Cardiovascular Sciences from 1994 to 2000, and Division Chief, Clinical Pharmacology, in the Department of Medicine from 1988 to 1994. From 1976 to 1988 he was a member of the faculty of Vanderbilt University where he rose to the rank of Professor of Medicine and Pharmacology and Associate Director of the NIH funded General Clinical Research Center. Dr. Woosley earned his Ph.D. in Pharmacology from the University of Louisville and his M.D. from the University of Miami. Dr. Woosley’s research has been published in over 312 peer-reviewed publications and 52 book chapters. We believe Dr. Woosley is an appropriate member of the Board of Directors, given his expertise and experience in cardiovascular medicine and clinical pharmacology, arrhythmia therapeutics, pharmacogenetic drug development and therapeutic regulatory science.

Dan J. Mitchell

Mr. Mitchell, age 61, was appointed to the Board of Directors in February 2014. He founded, and is a manager of Sequel Venture Partners, L.L.C., a venture capital firm formed in January 1997. Prior to founding Sequel Venture Partners, Mr. Mitchell was a founder of Capital Health Venture Partners, a health care focused venture capital firm, where he was a General Partner from October 1986 until 2006, and he was in the Venture Capital Division of the Trust Department of the First National Bank of Chicago from 1983 to 1985. He currently serves on the board of directors of several“going private companies. Mr. Mitchell holds a B.S. from the University of Illinois and an M.B.A. from the University of California at Berkeley. We believe Mr. Mitchell is an appropriate member of the Board of Directors given his expertise and experience in the pharmaceutical industry, pharmaceutical development, and in corporate finance and governance.

DIRECTORS CONTINUINGIN OFFICE UNTILTHE 2019 ANNUAL MEETING

Linda Grais, M.D.

Dr. Grais, age 61, has served as a member of the Board of Directors since May 2007. Dr. Grais has been a director of Ocera Therapeutics, Inc., a public biopharmaceutical company, since January 2008 and became President and Chief Executive Officer of Ocera in June 2012. Dr. Grais served as a Managing Member at InterWest Partners, a venture capital firm from has served as a member of the Board of Directors since May 2007. Dr. Grais has been a director of Ocera Therapeutics, Inc., a public biopharmaceutical company, since January 2008 and became President and Chief Executive Officer of Ocera in June 2012, and served in that role until Ocera’s acquisition by Mallinckrodt Pharmaceuticals in December 2017. Dr. Grais served as a Managing Member at InterWest Partners, a venture capital firm from May 2005 until February 2011. From July 1998 to July 2003, Dr. Grais was a founder and executive vice president of SGX Pharmaceuticals Inc., a drug discovery company. Prior to that, she was a corporate attorney at Wilson Sonsini Goodrich & Rosati, where she practiced in such areas as venture financings, public offerings and

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strategic partnerships. Before practicing law, Dr. Grais worked as an assistant clinical professor of Internal Medicine and Critical Care at the University of California, San Francisco. Dr. Grais received a B.A. from Yale University, magna cum laude, and Phi Beta Kappa, an M.D. from Yale Medical School and a J.D. from Stanford Law School. Since September 2015, Dr. Grais has served on the board of PRA Health Sciences, a public contract research organization. We believe Dr. Grais is an appropriate member of the Board of Directors because of her diverse training and experience as both a medical doctor and a lawyer, her experience as a founder and senior executive of a pharmaceutical company, and her experience as an investor in new life sciences companies. She also has extensive experience with and knowledge of the Company’s business from her service on the Board of Directors of the Company since 2007.

Anders Hove, M.D.

Dr. Hove, age 52, has served as a member of the Board of Directors since February 2017. Dr. Hove owns Acorn Capital Advisors and is a managing partner at Majalin/Amzak Health, a partnership focusing on long-term investments in biotech, specialty pharma and medical device companies. Dr. Hove was most recently a general partner of Venrock Associates, a venture capital firm, which he joined in January 2004 and remained at through December 2016. In 2008, Dr. Hove was a founder of Venrock Healthcare Capital Partners, Venrock’s public funds focused on small capitalization biotech companies and late-stage private companies. From 1996 to 2004, Dr. Hove was a fund manager at BB Biotech Fund, an investment firm, and from 2002 to 2003 he also served as Chief Executive Officer of Bellevue Asset Management, LLC, an investment company. Dr. Hove previously held senior level positions in the medical, clinical and business operations of the pharmaceuticals division of Ciba-Geigy. Mr. Hove was a member of the boards of directors of Anacor Pharmaceuticals, a publicly traded pharmaceutical company, from 2005 until its acquisition by Pfizer in June 2016, and Edge Therapeutics, a publicly traded biotechnology company, from 2015 to 2016. In addition, Dr. Hove is a member of the board of directors of MC2 Therapeutics. He received a M.Sc. in Biotechnology Engineering from the Technical University of Denmark, an M.D. from the University of Copenhagen and an M.B.A. from the Institut Européen d’Administration des Affaires. We believe Dr. Hove is an appropriate member of the Company’s Board of Directors, given his extensive training and experience as a medical doctor and masters of business administration, an executive in the pharmaceutical industry, and as an investor in biotechnology companies.

DIRECTORS CONTINUINGIN OFFICE UNTILTHE 2020 ANNUAL MEETING

Michael R. Bristow, M.D., Ph.D.

Dr. Bristow, age 73, was one of the founders of ARCA in September 2004, and has served as a Director since that time. Dr. Bristow has also served as the Company’s President and Chief Executive Officer since July 2009. Previously, Dr. Bristow served as the President and Chief Executive Officer of the Company from September 2004 to November 2006, and as the Company’s Chief Science and Medical Officer from November 2006 to July 2009. Dr. Bristow is a Professor of Medicine and the former Head of Cardiology at the University of Colorado Health Sciences Center, where he has been since October 1991. Dr. Bristow was one of the founders of Myogen, Inc. and served as Myogen’s Chief Science and Medical Officer from October 1996 to February 2006 and as a Scientific Advisor to Myogen from February 2006 until the acquisition of Myogen by Gilead Sciences, Inc. in November 2006. We believe Dr. Bristow is an appropriate member of the Company’s Board of Directors given his extensive experience and expertise as a cardiologist, medical researcher and drug developer in the field of cardiovascular medicine, and heart failure specifically, and his experience as a founder and manager of cardiovascular-focused, public pharmaceutical company. Dr. Bristow also has extensive experience with, and knowledge of, ARCA’s business, as the founder and former Chief Science and Medical Officer of the Company, and the current President and Chief Executive Officer of ARCA, and as a member of the Board of Directors of ARCA since the founding of the Company. Dr. Bristow holds a M.D. and Ph.D. from the University of Illinois.

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Robert E. Conway

Mr. Conway, age 64, was appointed to the Board of Directors in September 2013, and has served as the Chairman of our Board of Directors since 2014. Mr. Conway served as the Chief Executive Officer and member of the board of directors of Array Biopharma, a publicly traded pharmaceutical company, from 1999 to 2012. Prior to joining Array, Mr. Conway was the Chief Operating Officer and Executive Vice President of Hill Top Research, Inc., from 1996 to 1999. From 1979 until 1996, Mr. Conway held various executive positions for Corning Inc. including Corporate Vice President and General Manager of Corning Hazleton, Inc., a contract research organization. From 2004 to 2013, he served on the board of directors of PRA International, Inc., which was a public company for a portion of his tenure there, from 2012 to the present, he has served on the board of directors of eResearch Technology, Inc., a private company, and from 2015 to July 2017, he has served on the board of directors of Nivalis Therapeutics, Inc. a public, clinical stage pharmaceutical company. In July 2017, Nivalis Therapeutics, Inc. combined with Alpine Immune Sciences, Inc., a public, clinical stage pharmaceutical company, and Mr. Conway continues to serve on the board of directors following such combination. Mr. Conway also serves as the Chairman of Wall Family Enterprise, a leading library and educational supplies company. In addition, Mr. Conway is a member of the Strategic Advisory Committee of Genstar Capital, LLC and is a member of the board of directors of Bracket, Inc. Mr. Conway received a B.S. in accounting from Marquette University in 1976. We believe Mr. Conway is an appropriate member of the Board of Directors given his experience and expertise in the pharmaceutical industry, in pharmaceutical development and clinical trials, and in corporate finance, governance, accounting and public company compliance.

INFORMATION REGARDINGTHE BOARDOF DIRECTORSAND CORPORATE GOVERNANCE

INDEPENDENCEOF THE BOARDOF DIRECTORS

As required under the Nasdaq Stock Market (“Nasdaq”)listing standards, a majority of the members of a listed company’s board of directors must qualify as “independent,” as affirmatively determined by the board of directors. Our Board of Directors consults with the Company’s counsel to ensure that the Board of Directors’ determinations are consistent with relevant securities and other laws and regulations regarding the definition of “independent,” including those set forth in pertinent listing standards of the Nasdaq, as in effect from time to time.

Consistent with these considerations, after review of all relevant identified transactions or relationships between each director, or any of his or her family members, and the Company, its senior management and its independent registered public accounting firm, the Board of Directors has affirmatively determined that the following five directors are independent directorstransaction” within the meaning of the applicable Nasdaqlisting standards: Mr. Conway, Dr. Grais, Mr. Mitchell, Dr. Hove and Dr. Woosley. In making this determination, the Board of Directors found that none of the directors or nominees for director had a material or other disqualifying relationship with the Company. Dr. Bristow, the Company’s President and Chief Executive Officer, is not anindependent director by virtue of his employment relationship with the Company.

BOARD LEADERSHIP STRUCTURE

The Company has structured its Board of Directors in a way that the Company believes effectively serves its objectives of corporate governance and management oversight. The Company separates the roles of Chief Executive Officer and Chairman of the Board of Directors in recognition of the differences between the two roles. The Company believes that the Chief Executive Officer should be responsible for the day to day leadership and performance of the Company, while the Chairman of the Board of Directors should work with the Chief Executive Officer and the rest of the Board of Directors to set the strategic direction for the Company and provide guidance to, and oversight of the Chief Executive Officer. The Chairman also sets the agenda for meetings of the Board of Directors and presides over them.

Mr. Conway, who is an independent director, was elected Chairman of the Board of Directors in 2014. In this capacity, Mr. Conway, among other things, calls and presides over Board meetings, including meetings of the independent directors, and sets meeting agendas. In this role, Mr. Conway can effectively coordinate between the Board and management regarding risk management issues and the implementation of appropriate responses, and can help ensure the effective independent functioning of the Board of Directors in its oversight responsibilities. Accordingly, the Chairman has substantial ability to shape the work of the Board of Directors.

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ROLEOFTHE BOARDOF DIRECTORSIN RISK OVERSIGHTAND RISK MANAGEMENT

One of the Board of Directors’ key functions is informed oversight of the Company’s risk management process. The Board of Directors does not have a standing risk management committee, but rather administers this oversight function directly through the Board of Directors as a whole, as well as through various standing committees of the Board of Directors that address risks inherent in their respective areas of oversight. In particular, while the Board of Directors is responsible for monitoring and assessing strategic risk exposure, the Audit Committee has the responsibility to consider and discuss the major financial risk exposures and the steps management has taken to monitor and control these exposures, including guidelines and policies to govern the process by which risk assessment and management is undertaken. The Audit Committee also monitors compliance with legal and regulatory requirements, in addition to oversight of the performance of ARCA’s accounting and financial reporting processes. The Nominating and Corporate Governance Committee monitors the effectiveness of the corporate governance guidelines, including whether they are successful in preventing illegal or improper liability-creating conduct. The compensation committee of the Board of Directors (the “Compensation Committee”) assesses and monitors whether any compensation policies and programs have the potential to encourage excessive risk-taking. The entire Board of Directors and its committees address risk management issues fromtime-to-timeRule 13e-3 and at least annually meet with the employees responsible for risk management in the committees’ respective areas of oversight. Both the Board of Directors as a whole and the various standing committees receive periodic reports from the employees responsible for risk management, as well as incidental reports as matters may arise. It is the responsibility of the committee chairs to report findings regarding material risk exposures to the Board of Directors as quickly as possible.

MEETINGSOF THE BOARDOF DIRECTORS

The Board of Directors met seven times during the 2017 fiscal year. The independent members of the Board of Directors met separately as a group at four of the board meetings in 2017. All members of the Board of Directors, other than Dr. Woosley, attended at least 75% of the meetings of the Board of Directors and at least 75% the meeting of the committees of the Board of Directors of which each director was a member.

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INFORMATION REGARDING COMMITTEESOFTHE BOARDOF DIRECTORS

The Board of Directors has three standing committees:The Audit Committee, the Compensation Committee, and the Nominating and Corporate Governance Committee. The following table provides membership and meeting information for the fiscal year ended December 31, 2017, for each of the committees of the Board of Directors:

Dr. Hove was appointed to our Board of Directors in February 2017. Upon Dr. Hove’s appointment to the Board of Directors, he joined our Nominating and Corporate Governance Committee. At the same time, Dr. Woosley left our Audit Committee, and Dr. Grais left our Nominating and Corporate Governance Committee and joined our Audit Committee.

Below is a description of each committee of the Board of Directors. Each of the committees has authority to engage legal counsel or other experts or consultants, as it deems appropriate to carry out its responsibilities.The Board of Directors has determined that each member of each committee meets the applicable Nasdaq rules and regulations regarding “independence” and that each member is free of any relationship that would impair his or her individual exercise of independent judgment regarding the Company.

Audit Committee

The Audit Committee was established by the Board of Directors in accordance with Section 3(a)(58)(A) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”),.

Board Discretion to overseeImplement the Company’s corporate accounting and financial reporting processes and audits of its financial statements. For this purpose,Reverse Stock Split

If the Audit Committee performs several functions. The Audit Committee evaluatesBoard determines to effect the performance of and assessesReverse Stock Split, it will consider certain factors in selecting the qualificationsspecific exchange ratio, including prevailing market conditions, the trading price of the independent registered public accounting firm; determinesCommon Stock and approves the engagementsteps that we will need to take in order to achieve compliance with the bid price requirement and other listing regulations of the independent registered public accounting firm; determines whether to retain or terminateNasdaq Capital Market. Based in part on the existing independent registered public accounting firm or to appoint and engage a new independent registered public accounting firm; reviews and approves the retentionprice of the independent registered public accounting firmCommon Stock on the days leading up to perform any proposed permissiblenon-audit services; monitors the rotation of partnersfiling of the independent registered public accounting firmcertificate of amendment to the Restated Certificate of Incorporation effecting the Reverse Stock Split, the Board will determine the ratio of the Reverse Stock Split, in the range of1-for-3 to1-for-20, inclusive, that, in the judgment of the Board, is the reverse split ratio most likely to allow us to achieve and maintain compliance with the minimum $1.00 per share requirement for listing on the Company’s audit engagement team as requiredNasdaq Capital Market for the longest period of time, while retaining a sufficient number of outstanding, tradeable shares to facilitate an adequate market.

Notwithstanding approval of the Reverse Stock Split by law; reviewsthe stockholders, the Board may, in its sole discretion, abandon all of the proposed certificates of amendment and approves or rejects transactions between the company and any related persons; confers with management and the independent registered public accounting firm regardingdetermine prior to the effectiveness of internal controls over financial reporting; establishes procedures,any filing with the Secretary of State of the State of Delaware not to effect the Reverse Stock Split prior to the one year anniversary of this Special Meeting of stockholders, as permitted under Section 242(c) of the DGCL. If the Board fails to implement any of the certificates of amendment prior to the one year anniversary of this meeting of stockholders, stockholder approval would again be required under applicable law,prior to implementing any Reverse Stock Split.

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Consequences if Stockholder Approval for Proposal Is Not Obtained

If stockholder approval for Proposal No. 1 is not obtained, we will not be able to file a certificate of amendment to the Restated Certificate of Incorporation to effect the Reverse Stock Split. Unless the bid price for the receipt, retentionCommon Stock increases to greater than $1.00 for ten consecutive business days prior to October 8, 2018, then we will not meet the listing requirements for the Nasdaq Capital Market. If compliance is not achieved by October 8, 2018, and treatmentNasdaq does not grant us an additional 180 day extension, then our stock would be delisted from the Nasdaq Capital Market. If we were unable to qualify for the additional compliance period, or if we were unable to regain compliance during any such period, the Common Stock would likely be transferred to the OTC Bulletin Board or OTC Market.

If we fail to meet all applicable Nasdaq Capital Requirements and Nasdaq determines to delist the Common Stock, the delisting could adversely affect the market liquidity of complaints received by the Company regarding accounting, internal accounting controls or auditing mattersCommon Stock and the confidential and anonymous submission by employees of concerns regarding questionable accounting or auditing matters; and meets to review the Company’s annual audited financial statements and quarterly financial statements with management and the independent registered public accounting firm, including a reviewmarket price of the Company’s disclosures underCommon Stock could decrease. Delisting could also adversely affect our ability to obtain financing for the “Management’s Discussioncontinuation of our operations and/or result in the loss of confidence by investors, suppliers, commercial partners and Analysisemployees. In addition, the limited number of Financial Condition and Results of Operations” discussion in its Annual Reports on Form10-K and Quarterly Reports on Form10-QThe Audit Committee is currently composed of threedirectors: Mr. Conway (chair), Mr. Mitchell and Dr. Grais. The Audit Committee met five times during the fiscal year. The Board of Directors has adopted a written charterauthorized shares of the Audit CommitteeCommon Stock that is availableare neither outstanding nor reserved for issuance could adversely affect the ability of us to stockholderson the Company’s website at www.arcabio.com.

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The Board of Directors reviews the Nasdaq listing standards definition of independence for audit committee members on an annual basis and has determined that all membersEffects of the Audit Committee are independent (as independence is currently defined in Rule 5605(c)(2)(A)(i) and (ii)Reverse Stock Split

The following table sets forth the number of shares of our Common Stock that would be outstanding immediately after the Nasdaq listing standards).The Board of Directors has also determined that Mr. Conway qualifies as an “audit committee financial expert,” as defined in applicable SEC rules.The Board of Directors made a qualitative assessment of Mr. Conway’s level of knowledge and experienceReverse Stock Split at various exchange ratios, based on several factors, including his prior experience, business acumen and independence.

Reportthe 13,923,825 shares of the Audit CommitteeCommon Stock outstanding as of the Board of Directors¹

June 30, 2018. The Audit Committee has reviewed and discussed the audited financial statementstable does not account for the fiscal year ended December 31, 2017, with management of the Company. The Audit Committee has discussed with the independent registered public accounting firm the matters required tofractional shares that will be discussed by Public Company Accounting Oversight Board (“PCAOB”) Auditing Standard No. 1301, Communications with Audit Committees. The Audit Committee has also received the written disclosures and the letter from the independent registered public accounting firm required by applicable requirements of the PCAOB regarding the independent registered public accounting firm’s communications with the Audit Committee concerning independence, and has discussed with the independent registered public accounting firm the accounting firm’s independence. Based on the foregoing, the Audit Committee has recommended to the Board of Directors that the audited financial statements be includedpaid in the Company’s Annual Report on Form10-K for the fiscal year ended December 31, 2017.cash.

Compensation Committee

The Compensation Committee is currently composed of three directors: Mr. Conway, Dr. Grais (chair) and Dr. Woosley. All members of the Compensation Committee are independent, as independence is currently defined in Rule 5605(a)(2) of the Nasdaq listing standards. The Compensation Committee met onetime during the fiscal year. The Compensation Committee has adopted a written charter that is available to stockholders on the Company’s website at www.arcabio.com.

The Compensation Committee of the Board of Directors acts on behalf of the Board of Directors to review, adopt and oversee the Company’s compensation strategy, policies, plans and programs, including:

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Compensation Committee ProcessesIf a stockholder owns 10,000 shares of Common Stock prior to the Reverse Stock Split, after the Reverse Stock Split that same stockholder would own 3,333 shares in the case of a Reverse Stock Split at the ratio of1-for-3, 2,500 shares in the case of a Reverse Stock Split at the ratio of1-for-4, 2,000 shares in the case of a Reverse Stock Split at the ratio of1-for-5, 1,666 shares in the case of a Reverse Stock Split at the ratio of1-for-6, 1,428 shares in the case of a Reverse Stock Split at the ratio of1-for-7, 1,250 shares in the case of a Reverse Stock Split at the ratio of1-for-8, 1,111 shares in the case of a Reverse Stock Split at the ratio of1-for-9, 1,000 shares in the case of a Reverse Stock Split at the ratio of1-for-10, 909 shares in the case of a Reverse Stock Split at the ratio of1-for-11, 833 shares in the case of a Reverse Stock Split at the ratio of1-for-12, 769 shares in the case of a Reverse Stock Split at the ratio of1-for-13, 714 shares in the case of a Reverse Stock Split at the ratio of1-for-14, 666 shares in the case of a Reverse Stock Split at the ratio of1-for-15, 625 shares in the case of a Reverse Stock Split at the ratio of1-for-16, 588 shares in the case of a Reverse Stock Split at the ratio of1-for-17, 555 shares in the case of a Reverse Stock Split at the ratio of1-for-18, 526 shares in the case of a Reverse Stock Split at the ratio of1-for-19, and Procedures500 shares in the case of a Reverse Stock Split at the ratio of1-for-20.

Typically,The lasting effect of the Compensation Committee meets onproposed Reverse Stock Split upon the market price for our Common Stock cannot be predicted, and the history of similar reverse stock splits for companies in like circumstances is varied. We cannot assure you that the market price per new share of our Common Stock after the Reverse Stock Split (which we refer to as “New Shares”) will rise in proportion to the reduction in the number of old shares of our Common Stock outstanding (which we refer to as “Old Shares”) as a regular basisresult of the Reverse Stock Split. We also cannot assure you that the market price per New Share will either exceed or remain in excess of the $1.00 minimum bid price as it deems appropriate. The agenda for each meeting is usually developedrequired by the ChairNasdaq Capital Requirements, or that we will otherwise continue to meet the Nasdaq Capital Requirement, including, for example, the applicable minimum Market Value (as defined in Nasdaq Rule 5005) of Listed Securities (as defined in Nasdaq Rule 5005) requirements. For instance, in 2015 and 2013 we executed a reverse split of our Common Stock in order to maintain compliance with the Nasdaq Capital Requirements. We cannot assure you that another reverse split of our Common Stock will not be necessary in the future. The market price of our Common Stock is dependent on our financial condition, performance, prospects and a number of other factors, many of which are unrelated to the number of shares outstanding. If our efforts to meet the Nasdaq Capital Requirements are unsuccessful, our Common Stock would remain subject to delisting.

The liquidity of our Common Stock could be adversely affected by the reduced number of shares that would be outstanding after the Reverse Stock Split, and the reduced number of shares may make it more difficult to trade shares of the Compensation Committee. The Compensation Committee meets regularlyCommon Stock. In addition, the Reverse Stock Split will increase the number of our stockholders who own odd lots (less than 100 shares). Stockholders who hold odd lots typically will experience an increase in executive session. However, from time to time, various membersthe cost of management and other employeesselling their shares, as well as outside advisorspossible greater difficulty in effecting those sales.

The Reverse Stock Split will affect all of our holders of Common Stock uniformly and will not affect any stockholder’s percentage ownership interests in the Company or consultants may be invited byproportionate voting power, except to the Compensation Committee to make presentations, to provide financial or other background information or advice or to otherwise participateextent that the Reverse Stock Split results in Compensation Committee meetings.any of our stockholders owning a fractional share, in which case such stockholders will receive a cash payment in lieu of such fractional share. The Chief Executive Officer mayCompany’s issued Common Stock will remain fully paid andnon-assessable.

The Reverse Stock Split will not participate in, or be present during, any deliberations or determinationsaffect the par value of our Common Stock. As a result, upon the effectiveness of the Compensation Committee regarding his compensation or individual performance objectives. The Compensation Committee hasReverse Stock Split, the sole authoritystated capital on our balance sheet attributable to retain compensation consultants to assist in its evaluation of executive and director compensation, including the authority to approve the consultant’s reasonable fees and other retention terms.

In June 2013, the Company’s Compensation Committee reviewed the Company’s executive compensation considering general market conditions in the life science industry. As part of this review process, the Compensation Committee identified a peer group of biotechnology companies that it viewed as having a similar profile to ARCA at that time.

In setting 2017 base salary and cash bonus award amounts for the Company’s named executive officers, the Compensation Committee considered peer group data and factors specific to the Company, and targeted cash compensation toour Common Stock will be consistent with these metrics. The Compensation Committee recommended, and the Board of Directors approved, a base salary of $295,359 for Dr. Bristow, the Company’s President and Chief Executive Officer, a base salary of $294,170 for Mr. Keuer, the Company’s Chief Operating Officer, and a base salary of $288,683 for Mr. Ozeroff, the Company’s Senior Vice President and General Counsel, for the fiscal year ended December 31, 2016. In early 2017, the Compensation Committee recommended and the Board of Directors approved cash bonusesreduced proportionately based on previous performance for the Named Executive Officers (as defined below), and also approved increases to Named Executive Officer salaries for the fiscal year 2017 as described in below under “Executive Compensation.” There were no changes to the Company’s named executive officers’ salaries for 2018.

Historically, the Compensation Committee has made most of the significant adjustments to annual compensation, determined bonus and equity awards and established new performance objectives at one or more meetings held during the first quarter of the year. However, the Compensation Committee also considers matters related to individual compensation, such as compensation for new executive hires, as well as high-level strategic issues, such as the efficacy of the Company’s compensation strategy, potential modifications to that strategy and new trends, plans or approaches to compensation, at various meetings throughout the year. Generally, the Compensation Committee’s process comprises two related elements: the determination of compensation levels and the establishment of performance objectives for the current year.

The Compensation Committee reviews and approves the compensation of the Chief Executive Officer and the other executive officers of the Company, including annual base salaries, annual and long-term incentive or bonus awards, employment agreements, and severance and change in control agreements/provisions, in each case as, when and if appropriate, and any special or supplemental benefits. For executives other than the Chief Executive Officer, the Compensation Committee solicits and considers evaluations and recommendations submitted to the Compensation Committee by the Chief Executive Officer. The Compensation Committee evaluates the performance of the Chief Executive Officer in light of Company and individual goals and objectives, and makes appropriate recommendations for improving performance. In performing the evaluation, the Chair of the Compensation Committee may solicit comments from theother non-employee members of the Board of Directors and lead the Board of Directors in an overall review of the Chief Executive Officer’s performance in an executive sessionof non-employee members of the Board of Directors. If the compensation for the Chief Executive Officer or any other executive officer is governed by an employment agreement, the Compensation Committee approves such employment agreement and any amendments thereto.

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For all executives as part of its deliberations, the Compensation Committee may review and consider, as appropriate, materials such as financial reports and projections, operational data, tax and accounting information, tally sheets that set forth the total compensation that may become payable to executives in various hypothetical scenarios, executive and director stock ownership information, company stock performance data, analyses of historical executive compensation levels and current Company-wide compensation levels.

The Compensation Committee also considers the results ofany “say-on-pay” vote of the Company’s stockholders with regard to the compensation of the Company’s executive officers when making compensation decisions. At the 2016 annual meeting of stockholders, the Company’s stockholders approved, on an advisory basis, the compensation of the Company’s named executive officers as described in the proxy statement for such annual meeting. The Compensation Committee believes that this advisory vote supports that the Company’s current compensation practices are aligned with the best interests of stockholders and anticipates taking into account any subsequent advisory vote when making compensation decisions in the future.

Nominating and Corporate Governance Committee

The Nominating and Corporate Governance Committee is responsible for identifying, reviewing and evaluating candidates to serve as directors of the Company (consistent with criteria approvedexchange ratio selected by the Board for the Reverse Stock Split, and the additionalpaid-in capital account will be credited with the amount by which the stated capital is reduced. The per share net income or loss and net book value of Directors), reviewing and evaluating incumbent directors, recommendingour Common Stock will be increased because there will be fewer shares of our Common Stock outstanding. In addition, proportionate adjustments will be made to the Board of Directors candidates for election to the Board of Directors, making recommendations to the Board of Directors regarding compensation for service on the Board of Directorsper share exercise price and the committees thereof, making recommendationsnumber of shares issuable upon the exercise or settlement of all outstanding options, restricted stock units and warrants to the Boardpurchase or acquire, as applicable, shares of Directors regarding the membership of the committees of the Board of Directors, assessing the performance of the Board of Directors, developing a set of corporate governance principles for the Company and endeavoring to ensure that the Company’s Board and Board Committees are operating in accord with best practices of corporate governance. The Nominating and Corporate Governance Committee is currently composed of three directors: Dr. Hove, Mr. Mitchell and Dr. Woosley (chair). All members of the Nominating and Corporate Governance Committee in 2017 were independent (as independence is currently defined in Rule 5605(a)(2) of the Nasdaq listing standards). The Nominating and Corporate Governance Committee met four times during the 2017 fiscal year. The Nominating and Corporate Governance Committee has adopted a written charter that is available to stockholders on the Company’s website at www.arcabio.com.

The Nominating and Corporate Governance Committee periodically reviews the compensationof non-employee Directors for service on the Board of Directors and committees thereof. In 2015, the Nominating and Corporate Governance Committee began a review of its Director compensation levels considering general market conditions in the life science industry, and in comparison to other clinical stage biopharmaceutical companies similarly situated to the Company, and in early 2016, the Committee recommended, and the Board of Directors approved, revised compensationfor non-employee Directors, discussed in “Director Compensation” below.

The Board of Directors has adopted a process for identifying and evaluating director nominees, including stockholder nominees. Before recommending an individual to the Board of Directors for membership on the Board of Directors, the Nominating and Corporate Governance Committee canvasses its members and the Company’s management team for potential candidates for the Board of Directors. The Nominating and Corporate Governance Committee also uses its network of contacts to identify potential candidates and, if it deems appropriate, may also engage a professional search firm. The Nominating and Corporate Governance Committee will consider stockholders’ recommendations for nominees to serve as director if notice is timely received by the Secretary of the Company. Candidates nominated by stockholders will be evaluated in the same manner as other candidates. The Nominating and Corporate Governance Committee keeps the Board of Directors apprised of its discussions with potential nominees, and the names of potential nominees received from its current directors, management, and stockholders, if the stockholder notice of nomination is timely made.

Although the Board of Directors has not adopted a fixed set of minimum qualifications for candidates for membership on the Board of Directors, the Nominating and Corporate Governance Committee generally considers several factors in its evaluation of a potential member, such as the candidate’s education, professional background and field of expertise including industry or academic experience in the pharmaceutical, biotechnology and cardiovascular fields, experience in corporate governance and management, the reasonable availability of the potential member to devote time to the affairs of the Company, as well as any other criteria deemed relevant by the Board of Directors or the Nominating and Corporate Governance Committee. However, the Nominating and

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Corporate Governance Committee retains the right to modify these qualifications from time to time. Candidates for director nominees are reviewed in the context of the current composition of the Board of Directors, the operating requirementsCommon Stock of the Company, and the long-term interestsnumber of stockholders. In conductingshares reserved for issuance pursuant to our existing equity incentive, stock option and employee stock purchase plans will be reduced proportionately based on the exchange ratio selected by the Board for the Reverse Stock Split.

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The Reverse Stock Split will have no effect on the total number of shares of Common Stock we are authorized to issue under the Restated Certificate of Incorporation. Therefore, upon effectiveness of the Reverse Stock Split, the number of shares of Common Stock that are authorized and unissued will increase relative to the number of issued and outstanding shares. We may use the additional authorized and unissued shares of our Common Stock resulting from the Reverse Stock Split to issue additional shares of our Common Stock from time to time in equity financings, under our equity compensation plans or in connection with other matters. The Board currently has no plans, arrangements or understandings regarding the issuance of such additional authorized and unissued shares of the Company’s Common Stock.

Our Common Stock is currently registered under Section 12(b) of the Exchange Act, and we are subject to the periodic reporting and other requirements of the Exchange Act. The proposed Reverse Stock Split will not affect the registration of the Common Stock under the Exchange Act. If the proposed Reverse Stock Split is implemented, the Common Stock will continue to be reported on the Nasdaq Capital Market under the symbol “ABIO.”

Potential Anti-Takeover Effect of the Reverse Stock Split

Upon effectiveness of the Reverse Stock Split, the number of authorized shares of Common Stock that are not issued or outstanding will increase relative to the number of shares of Common Stock that are issued and outstanding prior to the Reverse Stock Split. Although this assessment,increase could, under certain circumstances, have an anti-takeover effect (for example, by permitting issuances that would dilute the Nominating and Corporate Governance Committee typically considers diversity, age, skills and such other factors as it deems appropriate givenstock ownership of a person seeking to effect a change in the current needscomposition of the Board or contemplating a tender offer or other transaction for the combination of Directorsthe Company with another company), Proposal No. 1 is not being proposed in response to any effort of which we are aware to accumulate shares of our Common Stock or to obtain control of the Company.

Effective Date

The Reverse Stock Split will be effected at 5:01 p.m. Eastern time, on the date that the certificate of amendment to the Restated Certificate of Incorporation is filed with the Secretary of State of the State of Delaware. Beginning at the effective time of the Reverse Stock Split, each certificate representing Old Shares will be deemed for all corporate purposes to represent New Shares. The texts of the proposed certificates of amendment to the Restated Certificate of Incorporation are in the forms annexed to this proxy statement asAnnexes A-1 throughA-18.

Exchange of Stock Certificates

The transfer agent for the Company will act as the “exchange agent” for purposes of implementing the exchange of stock certificates. Holders of Old Shares will be asked to surrender to the exchange agent certificates representing Old Shares in exchange for certificates representing New Shares in accordance with the procedures to be set forth in a letter of transmittal to be sent by the exchange agent. No new certificates will be issued to a stockholder until the stockholder has surrendered the stockholder’s outstanding certificate(s) together with the properly completed and executed letter of transmittal to the exchange agent. Stockholders should not destroy any stock certificates and should not submit any certificates until requested to do so.

Fractional Shares

No fractional shares of Common Stock will be issued as a result of the proposed Reverse Stock Split. Instead, stockholders who otherwise would be entitled to receive fractional shares will, upon surrender to the exchange agent of certificates representing their fractional shares, be entitled to receive cash in an amount equal to the product obtained by multiplying (i) the closing sales price of our Common Stock as reported on the Nasdaq Capital Market on the effective date of the certificate of amendment to the Restated Certificate of Incorporation by (ii) the number of shares of our Common Stock held by such stockholder before the Reverse Stock Split that would otherwise have been exchanged for such fractional share interest. Holders of as many as nineteen shares (if we were to implement a1-for-20 Reverse Stock Split) of our Common Stock would be eliminated as a result of the cash payment in lieu of any issuance of fractional shares or interests in connection with the Reverse Stock Split. The exact number by which the number of

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holders of our Common Stock would be reduced will depend on the Reverse Stock Split ratio adopted and the Company,number of stockholders that hold less than the Reverse Stock Split ratio as of the effective date of the Reverse Stock Split. As of the Record Date, there were approximately         holders of record of our Common Stock, of which                 were holders of less than 20 shares of our Common Stock. As a result of the Reverse Stock Split, assuming the maximum Reverse Stock Split ratio of1-for-20 were selected, we estimate that cashing out fractional stockholders would potentially reduce that number of stockholders of record to         maintain.

Federal Income Tax Consequences of the Reverse Stock Split

The following is a balancesummary of knowledge, experiencecertain material federal income tax consequences of the Reverse Stock Split to certain holders of Old Shares, but does not purport to be a complete discussion of all of the potential tax considerations relating thereto. This summary is based on the provisions of the United States federal income tax law (including the Internal Revenue Code of 1986, as amended (the “Code”), Treasury Regulations promulgated thereunder, and capability.judicial and administrative interpretations thereof) as of the date hereof, all of which are subject to change retroactively as well as prospectively. Our views regarding the tax consequences of the Reverse Stock Split are not binding upon the Internal Revenue Service or the courts, and there can be no assurance that the Internal Revenue Service or the courts will accept the positions expressed below. This summary assumes that the Old Shares were, and the New Shares will be, held as a “capital asset,” as defined in the Code (i.e., generally, property held for investment). Further, it does not discuss any state, local, foreign or other tax consequences. In addition, this summary does not address the tax consequences applicable to a holder’s particular circumstances or to holders that are subject to special tax rules, including without limitation banks, insurance companies, regulated investment companies, personal holding companies, foreign entities, nonresident alien individuals, broker-dealers, traders,tax-exempt entities and persons who hold Old Shares as a position in a hedging transaction, “straddle,” “conversion transaction” or other risk reduction transaction. THIS SUMMARY OF CERTAIN MATERIAL U.S. FEDERAL TAX CONSIDERATIONS IS FOR GENERAL INFORMATION ONLY AND IS NOT TAX ADVICE. EACH STOCKHOLDER IS URGED TO CONSULT WITH SUCH STOCKHOLDER’S OWN TAX ADVISOR WITH RESPECT TO THE TAX CONSEQUENCES OF THE REVERSE STOCK SPLIT.

Other than the cash payments, if any, received by a stockholder in lieu of fractional shares as discussed below, no gain or loss should be recognized by a stockholder upon such stockholder’s exchange of Old Shares for New Shares pursuant to the Reverse Stock Split. The Nominatingaggregate tax basis of the New Shares received pursuant to the Reverse Stock Split will be the same as the stockholder’s aggregate tax basis in the Old Shares exchanged therefor, less any basis attributable to fractional share interests. Stockholders who receive cash in lieu of fractional share interests in the New Shares as a result of the Reverse Stock Split will be treated as having received the fractional shares pursuant to the Reverse Stock Split and Corporate Governance Committee believes it is essential that Board of Directors members come fromthen as having exchanged the fractional shares for cash in a variety of backgrounds and experiences.

In the case of incumbent directors whose terms of office are set to expire, the Nominating and Corporate Governance Committee reviews these directors’ overall contributions toredemption by the Company, and the Board of Directors during their terms, including level of attendance, level of participation, quality of performance and contributionwill generally recognize gain or loss equal to the Boarddifference between the amount of Directors’ responsibilitiescash received in lieu of a fractional share and actions, and any relationships and transactions that might impairtheir adjusted basis allocable to the directors’ independence. Infractional share interests redeemed. Such gain or loss will be long term capital gain or loss if the case of new director candidates,Old Shares were held for more than one year. The stockholder’s holding period for the Nominating and Corporate Governance Committee also determines whetherNew Shares will include the nominee is independent for Nasdaq and SEC purposes,period during which determination is based upon applicable Nasdaq listing standards, applicable SEC rules and regulations and the advice of counsel, if necessary. The Nominating and Corporate Governance Committee conducts any appropriate and necessary inquiries intostockholder held the backgrounds and qualifications of possible candidates after consideringOld Shares surrendered in the function and needsReverse Stock Split.

No gain or loss will be recognized by us as a result of the Board of Directors. The Nominating and Corporate Governance Committee meetsReverse Stock Split.

No Dissenters’ Rights

Under applicable Delaware law, the Company’s stockholders are not entitled to discuss and consider the candidates’ qualifications and then determines whether to recommend a nomineedissenters’ or appraisal rights with respect to the Board of Directors by majority vote.

Stockholders who wish to recommend individuals for consideration by the Nominating and Corporate Governance Committee to become nominees for electionproposed amendment to the BoardRestated Certificate of Directors may do so by delivering a written recommendationIncorporation to effect the Nominating and Corporate Governance Committee addressed to the Corporate Secretary, between 60 and 90 days before theone-year anniversary date of ARCA’s last annual meeting of stockholders. Recommendations must include the full name of the proposed nominee, a description of the proposed nominee’s business experience for at least the previous five years, complete biographical information, a description of the proposed nominee’s qualifications as a director, and a representation that the recommending stockholder is a beneficial or record owner of ARCA’s stock. AnyReverse Stock Split. We will not independently provide our stockholders with any such submission must be accompanied by the written consent of the proposed nominee to be named as a nominee and to serve as a director if elected. To date, the Nominating and Corporate Governance Committee has not rejected a timely director nominee from a stockholder.

In 2017, the Nominating and Corporate Governance Committee did not pay any fees to assist in the process of identifying or evaluating director candidates.

STOCKHOLDER COMMUNICATIONS WITH THE BOARD OF DIRECTORS

Stockholders who wish to communicate with the Board of Directors may do so bye-mail by using the following email address: directors@arcabio.com; or by mail by following the directions as set forth on ARCA’s website at www.arcabio.com, under the section titled “Corporate Governance” and the subsection titled ��Governance Documents”.

CODEOF BUSINESS CONDUCTAND ETHICS

The Company has adopted the ARCA biopharma, Inc. Code of Business Conduct and Ethics that applies to all officers, directors and employees. The Code of Business Conduct and Ethics is available on the Company’s website at www.arcabio.com. If the Company makes any substantive amendments to the Code of Business Conduct and Ethics or grants any waiver from a provision of the Code of Business Conduct and Ethics to any executive officer or director, the Company will promptly disclose the nature of the amendment or waiver on its website and file any current report on Form8-K required by applicable law or NASDAQ listing standards.

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PROPOSAL 2

RATIFICATIONOF SELECTIONOFTHE INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

The Audit Committee has selected KPMG as the Company’s independent registered public accounting firm for the fiscal year ending December 31, 2018, and has further directed that management submit the selection of the independent registered public accounting firm for ratification by the stockholders at the Annual Meeting. KPMG has audited the Company’s fiscal year financial statements since 2006. Representatives of KPMG are expected to be present at the Annual Meeting. They will have an opportunity to make a statement if they so desire and will be available to respond to appropriate questions.

Neither the Company’s Bylaws nor other governing documents or law require stockholder ratification of the selection of KPMG as the Company’s independent registered public accounting firm. However, the Board of Directors is submitting the selection of KPMG to the stockholders for ratification as a matter of good corporate practice. If the stockholders fail to ratify the selection, the Audit Committee will reconsider whether to retain that firm. Even if the selection is ratified, the Audit Committee in its discretion may direct the appointment of a different independent registered public accounting firm at any time during the year if they determine that such a change would be in the best interests of the Company and its stockholders.Vote Required

The affirmative vote of the holders of a majority of all outstanding shares of the shares presentCompany’s Common Stock on the record date is required for approval of the proposed certificates of amendment to the Restated Certificate of Incorporation set forth in person or represented by proxyProposal No. 1 and included as AnnexesA-1 throughA-18. Brokernon-votes with respect to Proposal No. 1 will be treated as votes “against” the proposal because they represent shares entitled to vote atthat have not been voted in the Annual Meetingaffirmative. Abstentions will be requiredalso have the same effect as votes “against” the proposal because they represent shares entitled to ratifyvote that have not been voted in the selection of KPMG. Brokernon-votes are counted towards a quorum, but are not counted for any purpose in determining whether this matter has been approved.affirmative.

PRINCIPALTHE BOARD UNANIMOUSLY RECOMMENDS ACCOUNTANT FEESAND SERVICES

The following table represents aggregate fees billed, or expected to be billed, to the Company for the fiscal year ended December 31, 2017, and December 31, 2016, by KPMG, the Company’s independent registered public accounting firm.

All fees described above were approved by the Audit Committee.

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SECURITY OWNERSHIPOF

CERTAIN BENEFICIAL OWNERSAND MANAGEMENT

Principal Stockholders

The following table sets forth certain information regarding the ownership of the Company’s Common Stock as of April 4,the August 31, 2018, by: (i) each director and nominee for director, (ii) each of our named executive officers, (iii) all executive officers and directors of the Company as a group, and (iv) all those known by the Company to be beneficial owners of more than five percent of its Common Stock. Unless otherwise noted below, the address of each beneficial owner listed on the table is c/o ARCA biopharma, Inc., 11080 CirclePoint Road, Suite 140, Westminster, Colorado, 80020.

We have determined beneficial ownership in accordance with the rules of the SEC. Except as indicated by the footnotes below, we believe, based on the information furnished to us, that the persons and entities named in the table below have sole voting and investment power with respect to all shares of Common Stock that they beneficially own, subject to applicable community property laws. The table is based upon information supplied by officers, directors and principal stockholders and Schedules 13G or 13D, Form 4s or other ownership reports filed with the SEC. For purposes of this table, certain of our outstanding warrants that may be exercisable for fractional shares have been rounded down to the nearest whole number.

In computing the number of shares of Common Stock beneficially owned by a person and the percentage ownership of that person, we deemed outstanding shares of Common Stock subject to options, restricted stock units, or warrants held by that person that are currently exercisable or exercisable within 60 days of April 4,August 31, 2018. We did not deem these shares outstanding, however, for the purpose of computing the percentage ownership of any other person.

The percentages below are based on 13,923,825 shares of our Common Stock outstanding as of April 4,August 31, 2018.

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SECTION 16(A) BENEFICIAL OWNERSHIP REPORTING COMPLIANCE

Section 16 of the Exchange Act requires the Company’s directors and executive officers, and persons who own more than 10% of its Common Stock, to file with the SEC initial reports of ownership and reports of changes in ownership of Common Stock of the Company. Such persons are required by SEC regulation to furnish us with copies of all Section 16(a) forms that they file.

To the Company’s knowledge, based solely upon its review of the copies of such reports furnished to it and written representations that no other reports were required, during the fiscal year ended December 31, 2017, all Section 16(a) filing requirements applicable to its officers, directors and ten percent beneficial owners were complied with.

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EXECUTIVE OFFICERS

Set forth below is information regarding each of the executive officers as of March 31, 2018.

Michael R. Bristow, M.D., Ph.D. See Mr. Bristow’s biography in Proposal Number 1 – Election of Directors.15

Brian L. Selby. Mr. Selby has served as the Company’s Vice President, Finance and Chief Accounting Officer since December 2014. Previously, Mr. Selby served as the Company’s Controller from 2007 to 2014. Prior to joining the Company, Mr. Selby served as the Controller for Myogen, Inc., a publicly traded pharmaceutical company subsequently acquired by Gilead, from 2004 to 2007. Prior to Myogen, Mr. Selby served as the Controller for several private and publicly traded companies and earlier in his career was an audit professional with Deloitte. Mr. Selby received his M.S. in Accounting from the University of Colorado and received his B.S., in Business Administration and Finance from Colorado State University, and is a certified public accountant.

Thomas A. Keuer. Mr. Keuer has served as the Company’s Chief Operating Officer since December 2014. Mr. Keuer served as the Company’s Executive Vice President, Pharmaceutical Operations from 2006 to 2014. Prior to joining the Company, Mr. Keuer served as the SVP of Operations for Insmed, Inc. from 2004 to 2006. Prior to Insmed, Mr. Keuer served as the VP of Engineering for Baxter Healthcare from 1998 to 2004. Prior to Baxter, Mr. Keuer served as the VP of Operations for Somatogen, Inc. Mr. Keuer received his M.S. in Biochemical Engineering from Rice University and received his B.S. in Chemical Engineering from the University of Texas, Austin.

Christopher D. Ozeroff. Mr. Ozeroff is aco-founder of ARCA. Mr. Ozeroff has served as the Company’s Senior Vice President, General Counsel and Secretary since 2009, has served as the Company’s General Counsel and Secretary since the Company’s founding, and has also served as Executive Vice President, Business Development from 2004 to 2009. Prior to joining the Company, Mr. Ozeroff was a partner with the law firm of Hogan & Hartson L.L.P., where he practiced in such areas as finance, acquisitions, public offerings, and licensing. Mr. Ozeroff completed his undergraduate degree at Stanford University and his law degree at the University of Chicago Law School.

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HOUSEHOLDINGOF PROXY MATERIALS

The SEC has adopted rules that permit companies and intermediaries (e.g., brokers) to satisfy the delivery requirements for Notices of Internet Availability ofthe Proxy Materials or other Annual Meeting materials with respect to two or more stockholders sharing the same address by delivering a single Noticeset of Internet Availability ofthe Proxy Materials or other Annual Meeting materials addressed to those stockholders. This process, which is commonly referred to as “householding,” potentially means extra convenience for stockholders and cost savings for companies.

This year,In connection with the Special Meeting, a number of brokers with account holders who are ARCA biopharma, Inc. stockholders will be “householding” the Company’s proxy materials.Proxy Materials. A single Noticeset of Internet Availability ofthe Proxy Materials will be delivered to multiple stockholders sharing an address unless contrary instructions have been received from the affected stockholders. Once you have received notice from your broker that they will be “householding” communications to your address, “householding” will continue until you are notified otherwise or until you revoke your consent. If, at any time, you no longer wish to participate in “householding” and would prefer to receive a separate Noticeset of Internet Availability ofthe Proxy Materials, please notify your broker or ARCA biopharma, Inc.ARCA. Direct your written request to Secretary, ARCA biopharma, Inc., 11080 CirclePoint Road, Suite 140, Westminster, Colorado, 80020 or contact Investor Relations at720-940-2100. The Company undertakes to promptly deliver a separate copyoffset of the Notice of Internet Availability of Proxy Materials promptly upon receiving your written request. Stockholders who currently receive multiple copies of the Notices of Internet Availability of Proxy Materials at their addresses and would like to request “householding” of their communications should contact their brokers.

OTHER MATTERS

The Board of Directors knows of no other matters that will be presented for consideration at the AnnualSpecial Meeting. If any other matters are properly brought before the meeting, it is the intention of the persons named in the accompanying proxy to vote on such matters in accordance with their best judgment.

		By Order of the Board of Directors
				Christopher Ozeroff
		Christopher Ozeroff
		Secretary, Senior Vice President and General Counsel

April 18,                        , 2018

AWe will provide without charge to each person, including any beneficial owner, to whom a copy of the Company’s Annual Report to the Securities and Exchange Commission on Form10-K for the fiscal year ended December 31, 2017, is available without chargethis proxy statement has been delivered, upon written or oral request, to:a copy of any or all of the documents referred to above that have been or may be incorporated in this proxy statement by reference. Requests for copies should be directed to: Corporate Secretary, ARCA biopharma, Inc., 11080 CirclePoint Road, Suite 140, Westminster, Colorado 8002080020.

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16

ANNEXA-1

CERTIFICATE OF AMENDMENT

OF

AMENDED AND RESTATED CERTIFICATE OF INCORPORATION

OF

ARCA BIOPHARMA, INC.

ARCABIOPHARMA, INC., a corporation organized and existing under and by virtue of the General Corporation Law of the State of Delaware (the “DGCL”), does hereby certify:

FIRST:               The name of the corporation is ARCA biopharma, Inc. (the “Corporation”).

SECOND:           The date of filing of its original Certificate of Incorporation with the Secretary of State of the State of Delaware was March 16, 2004 under the name “Nuvelo Merger Sub, Inc.”

THIRD:              The Board of Directors (the “Board”) of the Corporation, acting in accordance with the provisions of Sections 141 and 242 of the DGCL, adopted resolutions amending its Amended and Restated Certificate of Incorporation, as amended, as follows:

1.                         Article IV of the Amended and Restated Certificate of Incorporation of the Corporation is hereby amended to add the following provisions in their entirety to the existing provisions of Article IV:

“Effective at 5:01 p.m. Eastern time, on the date of the filing of this Certificate of Amendment to the Amended and Restated Certificate of Incorporation with the Secretary of State of the State of Delaware (the “Effective Time”), the shares of the Corporation’s Common Stock, par value $0.001 per share, issued and outstanding immediately prior to the Effective Time and the shares of Common Stock issued and held in the treasury of the Corporation immediately prior to the Effective Time shall be combined into a smaller number of shares such that each 3 shares of issued and outstanding Common Stock immediately prior to the Effective Time are combined into one validly issued, fully paid and nonassessable share of Common Stock, par value $0.001 per share. Notwithstanding the immediately preceding sentence, no fractional shares shall be issued and, in lieu thereof, upon surrender after the Effective Time of a certificate which formerly represented shares of Common Stock that were issued and outstanding immediately prior to the Effective Time, any person who would otherwise be entitled to a fractional share of Common Stock as a result of the combination, following the Effective Time (after taking into account all fractional shares of Common Stock otherwise issuable to such holder), shall be entitled to receive a cash payment equal to the fraction to which such holder would otherwise be entitled multiplied by the fair value of the Common Stock on the date of the Effective Time, as determined by the Board of Directors.

Each stock certificate that, immediately prior to the Effective Time, represented shares of Common Stock that were issued and outstanding immediately prior to the Effective Time shall, from and after the Effective Time, automatically and without the necessity of presenting the same for exchange, represent that number of whole shares of Common Stock after the Effective Time into which the shares of Common Stock formerly represented by such certificate shall have been combined (as well as the right to receive cash in lieu of fractional shares of Common Stock after the Effective Time), provided however, that each person of record holding a certificate that represented shares of Common Stock that were issued and outstanding immediately prior to the Effective Time shall receive, upon surrender of such certificate, a new certificate evidencing and representing the number of whole shares of Common Stock after the Effective Time into which the shares of Common Stock formerly represented by such certificate shall have been combined.”

FOURTH:           Thereafter, pursuant to a resolution by the Board, this Certificate of Amendment was submitted to the stockholders of the Corporation for their approval in accordance with the provisions of Section 211 and 242 of the DGCL. Accordingly, said proposed amendment has been adopted in accordance with Section 242 of the DGCL.

IN WITNESS WHEREOF,ARCABIOPHARMA, INC. has caused this Certificate of Amendment to be signed by its duly authorized officer this ______ day of ________, 2018.

					Electronic Voting Instructions
					Available 24 hours a day, 7 days a week!
					Instead of mailing your proxy, you may choose one of the voting methods outlined below to vote your proxy.
					VALIDATION DETAILS ARE LOCATED BELOW IN THE TITLE BAR.
					Proxies submitted by the Internet or telephone must be received by 1:00 a.m.ARCABIOPHARMA, Mountain Time, on May 31, 2018.
								Vote by Internet
								• Go towww.investorvote.com/ABIOINC.
								• Or scan the QR code with your smartphone
								• Follow the steps outlined on the secure website
						Vote by telephone
						•   Call toll free 1-800-652-VOTE (8683) within the USA, US territories & Canada on a touch tone telephone •   Follow the instructions provided by the recorded message
Using ablack ink pen, mark your votes with anX as shown in this example. Please do not write outside the designated areas.		☒

q IF YOU HAVE NOT VOTED VIA THE INTERNETOR TELEPHONE, FOLD ALONG THE PERFORATION, DETACH AND RETURN THE BOTTOM PORTION IN THE ENCLOSED ENVELOPE.q

ANNEXA-2

CERTIFICATE OF AMENDMENT

OF

AMENDED AND RESTATED CERTIFICATE OF INCORPORATION

OF

ARCA BIOPHARMA, INC.

ARCABIOPHARMA, INC., a corporation organized and existing under and by virtue of the General Corporation Law of the State of Delaware (the “DGCL”), does hereby certify:

FIRST:               The name of the corporation is ARCA biopharma, Inc. (the “Corporation”).

SECOND:           The date of filing of its original Certificate of Incorporation with the Secretary of State of the State of Delaware was March 16, 2004 under the name “Nuvelo Merger Sub, Inc.”

THIRD:              The Board of Directors (the “Board”) of the Corporation, acting in accordance with the provisions of Sections 141 and 242 of the DGCL, adopted resolutions amending its Amended and Restated Certificate of Incorporation, as amended, as follows:

1.                         Article IV of the Amended and Restated Certificate of Incorporation of the Corporation is hereby amended to add the following provisions in their entirety to the existing provisions of Article IV:

“Effective at 5:01 p.m. Eastern time, on the date of the filing of this Certificate of Amendment to the Amended and Restated Certificate of Incorporation with the Secretary of State of the State of Delaware (the “Effective Time”), the shares of the Corporation’s Common Stock, par value $0.001 per share, issued and outstanding immediately prior to the Effective Time and the shares of Common Stock issued and held in the treasury of the Corporation immediately prior to the Effective Time shall be combined into a smaller number of shares such that each 4 shares of issued and outstanding Common Stock immediately prior to the Effective Time are combined into one validly issued, fully paid and nonassessable share of Common Stock, par value $0.001 per share. Notwithstanding the immediately preceding sentence, no fractional shares shall be issued and, in lieu thereof, upon surrender after the Effective Time of a certificate which formerly represented shares of Common Stock that were issued and outstanding immediately prior to the Effective Time, any person who would otherwise be entitled to a fractional share of Common Stock as a result of the combination, following the Effective Time (after taking into account all fractional shares of Common Stock otherwise issuable to such holder), shall be entitled to receive a cash payment equal to the fraction to which such holder would otherwise be entitled multiplied by the fair value of the Common Stock on the date of the Effective Time, as determined by the Board of Directors.

Each stock certificate that, immediately prior to the Effective Time, represented shares of Common Stock that were issued and outstanding immediately prior to the Effective Time shall, from and after the Effective Time, automatically and without the necessity of presenting the same for exchange, represent that number of whole shares of Common Stock after the Effective Time into which the shares of Common Stock formerly represented by such certificate shall have been combined (as well as the right to receive cash in lieu of fractional shares of Common Stock after the Effective Time), provided however, that each person of record holding a certificate that represented shares of Common Stock that were issued and outstanding immediately prior to the Effective Time shall receive, upon surrender of such certificate, a new certificate evidencing and representing the number of whole shares of Common Stock after the Effective Time into which the shares of Common Stock formerly represented by such certificate shall have been combined.”

FOURTH:           Thereafter, pursuant to a resolution by the Board, this Certificate of Amendment was submitted to the stockholders of the Corporation for their approval in accordance with the provisions of Section 211 and 242 of the DGCL. Accordingly, said proposed amendment has been adopted in accordance with Section 242 of the DGCL.

IN WITNESS WHEREOF,ARCABIOPHARMA, INC.has caused this Certificate of Amendment to be signed by its duly authorized officer this ______ day of ________, 2018.

ANNEXA-3

CERTIFICATE OF AMENDMENT

OF

AMENDED AND RESTATED CERTIFICATE OF INCORPORATION

OF

ARCA BIOPHARMA, INC.

ARCABIOPHARMA, INC.,a corporation organized and existing under and by virtue of the General Corporation Law of the State of Delaware (the “DGCL”), does hereby certify:

FIRST:               The name of the corporation is ARCA biopharma, Inc. (the “Corporation”).

SECOND:           The date of filing of its original Certificate of Incorporation with the Secretary of State of the State of Delaware was March 16, 2004 under the name “Nuvelo Merger Sub, Inc.”

THIRD:              The Board of Directors (the “Board”) of the Corporation, acting in accordance with the provisions of Sections 141 and 242 of the DGCL, adopted resolutions amending its Amended and Restated Certificate of Incorporation, as amended, as follows:

1.                         Article IV of the Amended and Restated Certificate of Incorporation of the Corporation is hereby amended to add the following provisions in their entirety to the existing provisions of Article IV:

“Effective at 5:01 p.m. Eastern time, on the date of the filing of this Certificate of Amendment to the Amended and Restated Certificate of Incorporation with the Secretary of State of the State of Delaware (the “Effective Time”), the shares of the Corporation’s Common Stock, par value $0.001 per share, issued and outstanding immediately prior to the Effective Time and the shares of Common Stock issued and held in the treasury of the Corporation immediately prior to the Effective Time shall be combined into a smaller number of shares such that each 5 shares of issued and outstanding Common Stock immediately prior to the Effective Time are combined into one validly issued, fully paid and nonassessable share of Common Stock, par value $0.001 per share. Notwithstanding the immediately preceding sentence, no fractional shares shall be issued and, in lieu thereof, upon surrender after the Effective Time of a certificate which formerly represented shares of Common Stock that were issued and outstanding immediately prior to the Effective Time, any person who would otherwise be entitled to a fractional share of Common Stock as a result of the combination, following the Effective Time (after taking into account all fractional shares of Common Stock otherwise issuable to such holder), shall be entitled to receive a cash payment equal to the fraction to which such holder would otherwise be entitled multiplied by the fair value of the Common Stock on the date of the Effective Time, as determined by the Board of Directors.

Each stock certificate that, immediately prior to the Effective Time, represented shares of Common Stock that were issued and outstanding immediately prior to the Effective Time shall, from and after the Effective Time, automatically and without the necessity of presenting the same for exchange, represent that number of whole shares of Common Stock after the Effective Time into which the shares of Common Stock formerly represented by such certificate shall have been combined (as well as the right to receive cash in lieu of fractional shares of Common Stock after the Effective Time), provided however, that each person of record holding a certificate that represented shares of Common Stock that were issued and outstanding immediately prior to the Effective Time shall receive, upon surrender of such certificate, a new certificate evidencing and representing the number of whole shares of Common Stock after the Effective Time into which the shares of Common Stock formerly represented by such certificate shall have been combined.”

FOURTH:           Thereafter, pursuant to a resolution by the Board, this Certificate of Amendment was submitted to the stockholders of the Corporation for their approval in accordance with the provisions of Section 211 and 242 of the DGCL. Accordingly, said proposed amendment has been adopted in accordance with Section 242 of the DGCL.

IN WITNESS WHEREOF,ARCABIOPHARMA, INC. has caused this Certificate of Amendment to be signed by its duly authorized officer this ______ day of ________, 2018.

Date (mm/dd/yyyy) — Please print date below.						Signature 1 — Please keep signature within the box.				Signature 2 — Please keep signature within the box.
/      /

---

Important notice regarding the Internet availability of

proxy materials for the Annual Meeting of Stockholders.

The ARCA biopharma, Inc. Annual Report

and ARCA biopharma, Inc. Notice of Annual Meeting are available at:

www.edocumentview.com/ABIO

q IF YOU HAVE NOT VOTED VIA THE INTERNETOR TELEPHONE, FOLD ALONG THE PERFORATION, DETACH AND RETURN THE BOTTOM PORTION IN THE ENCLOSED ENVELOPE. ARCABIOPHARMA, INC.q

Proxy — ARCA BIOPHARMA, INC.

PROXY SOLICITED BY THE BOARD OF DIRECTORS OF ARCA BIOPHARMA, INC.

FOR THE ANNUAL MEETING OF STOCKHOLDERS TO BE HELD ON MAY 31, 2018

The undersigned hereby acknowledges receipt of the Notice of Annual Meeting of Stockholders and Proxy Statement of ARCA biopharma, Inc. (the “Company”) in connection with the Company’s Annual Meeting of Stockholders to be held at the Renaissance Boulder Flatiron Hotel, 500 Flatiron Blvd., Broomfield, Colorado 80021 at 9:00 a.m., Mountain Time, on Thursday, May 31, 2018, and does hereby appoint Michael R. Bristow, M.D., Ph.D., Thomas A. Keuer and Christopher D. Ozeroff, and each of them (with full power to act alone), as proxies of the undersigned with all the powers the undersigned would possess if personally present and with full power of substitution in each of them, to appear and vote all shares of Common Stock of the Company which the undersigned would be entitled to vote if personally present at the 2018 Annual Meeting of Stockholders, and at any postponement or adjournment thereof.

The shares represented hereby will be voted as directed herein.IN EACH CASE, IF NO DIRECTION IS INDICATED, SUCH SHARES WILL BE VOTED “FOR” THE NOMINEES LISTED AND “FOR” PROPOSAL 2. AS TO ANY OTHER MATTER THAT MAY PROPERLY COME BEFORE THE MEETING OR ANY POSTPONEMENT OR ADJOURNMENT THEREOF, SAID PROXY HOLDERS WILL VOTE IN ACCORDANCE WITH THEIR BEST JUDGMENT. THIS PROXY MAY BE REVOKED IN WRITING AT ANY TIME PRIOR TO THE VOTING THEREOF.

PLEASE VOTE, DATE AND SIGN ON THE REVERSE SIDE AND RETURN PROMPTLY IN THE ENCLOSED ENVELOPE.

Please be sure to sign and date this Proxy.

---

By:
		Using ablack ink pen, mark your votes with anX as shown in this example. Please do not write outside the designated areas.		☒

q PLEASE FOLD ALONG THE PERFORATION, DETACH AND RETURN THE BOTTOM PORTION IN THE ENCLOSED ENVELOPE.q

A		Proposals — The Board of Directors recommends a voteFOR the nominees listed andFOR Proposal 2.

1. Election of two directors to hold office until the 2021 Annual Meeting of Stockholders.

+

For

Withhold

For

Withhold

01 - Raymond L. Woosley

☐

☐

02 - Daniel J. Mitchell

☐

☐

ANNEXA-4

CERTIFICATE OF AMENDMENT

OF

AMENDED AND RESTATED CERTIFICATE OF INCORPORATION

OF

ARCA BIOPHARMA, INC.

ARCABIOPHARMA, INC., a corporation organized and existing under and by virtue of the General Corporation Law of the State of Delaware (the “DGCL”), does hereby certify:

FIRST:               The name of the corporation is ARCA biopharma, Inc. (the “Corporation”).

SECOND:           The date of filing of its original Certificate of Incorporation with the Secretary of State of the State of Delaware was March 16, 2004 under the name “Nuvelo Merger Sub, Inc.”

THIRD:              The Board of Directors (the “Board”) of the Corporation, acting in accordance with the provisions of Sections 141 and 242 of the DGCL, adopted resolutions amending its Amended and Restated Certificate of Incorporation, as amended, as follows:

1.                         Article IV of the Amended and Restated Certificate of Incorporation of the Corporation is hereby amended to add the following provisions in their entirety to the existing provisions of Article IV:

“Effective at 5:01 p.m. Eastern time, on the date of the filing of this Certificate of Amendment to the Amended and Restated Certificate of Incorporation with the Secretary of State of the State of Delaware (the “Effective Time”), the shares of the Corporation’s Common Stock, par value $0.001 per share, issued and outstanding immediately prior to the Effective Time and the shares of Common Stock issued and held in the treasury of the Corporation immediately prior to the Effective Time shall be combined into a smaller number of shares such that each 6 shares of issued and outstanding Common Stock immediately prior to the Effective Time are combined into one validly issued, fully paid and nonassessable share of Common Stock, par value $0.001 per share. Notwithstanding the immediately preceding sentence, no fractional shares shall be issued and, in lieu thereof, upon surrender after the Effective Time of a certificate which formerly represented shares of Common Stock that were issued and outstanding immediately prior to the Effective Time, any person who would otherwise be entitled to a fractional share of Common Stock as a result of the combination, following the Effective Time (after taking into account all fractional shares of Common Stock otherwise issuable to such holder), shall be entitled to receive a cash payment equal to the fraction to which such holder would otherwise be entitled multiplied by the fair value of the Common Stock on the date of the Effective Time, as determined by the Board of Directors.

Each stock certificate that, immediately prior to the Effective Time, represented shares of Common Stock that were issued and outstanding immediately prior to the Effective Time shall, from and after the Effective Time, automatically and without the necessity of presenting the same for exchange, represent that number of whole shares of Common Stock after the Effective Time into which the shares of Common Stock formerly represented by such certificate shall have been combined (as well as the right to receive cash in lieu of fractional shares of Common Stock after the Effective Time), provided however, that each person of record holding a certificate that represented shares of Common Stock that were issued and outstanding immediately prior to the Effective Time shall receive, upon surrender of such certificate, a new certificate evidencing and representing the number of whole shares of Common Stock after the Effective Time into which the shares of Common Stock formerly represented by such certificate shall have been combined.”

FOURTH:           Thereafter, pursuant to a resolution by the Board, this Certificate of Amendment was submitted to the stockholders of the Corporation for their approval in accordance with the provisions of Section 211 and 242 of the DGCL. Accordingly, said proposed amendment has been adopted in accordance with Section 242 of the DGCL.

IN WITNESS WHEREOF,ARCABIOPHARMA, INC. has caused this Certificate of Amendment to be signed by its duly authorized officer this ______ day of ________, 2018.

ANNEXA-5

CERTIFICATE OF AMENDMENT

Important notice regarding the Internet availability ofOF

proxy materials for the Annual Meeting of Stockholders.AMENDED AND RESTATED CERTIFICATE OF INCORPORATION

The ARCA biopharma, Inc. Annual ReportOF

and ARCA biopharma, Inc. Notice of Annual Meeting are available at:

www.edocumentview.com/ABIO

q PLEASE FOLD ALONG THE PERFORATION, DETACH AND RETURN THE BOTTOM PORTION IN THE ENCLOSED ENVELOPE. q

Proxy — ARCA BIOPHARMA, INC.

PROXY SOLICITED BY THE BOARD OF DIRECTORS OF ARCABIOPHARMA INC.

FOR THE ANNUAL MEETING OF STOCKHOLDERS TO BE HELD ON MAY 31, 2018

The undersigned hereby acknowledges receipt, INC., a corporation organized and existing under and by virtue of the NoticeGeneral Corporation Law of Annual Meetingthe State of Stockholders and Proxy StatementDelaware (the “DGCL”), does hereby certify:

FIRST:               The name of the corporation is ARCA biopharma, Inc. (the “Company”“Corporation”) in connection.

SECOND:           The date of filing of its original Certificate of Incorporation with the Company’s Annual MeetingSecretary of Stockholders to be held at the Renaissance Boulder Flatiron Hotel, 500 Flatiron Blvd., Broomfield, Colorado 80021 at 9:00 a.m., Mountain Time, on Thursday, May 31, 2018, and does hereby appoint Michael R. Bristow, M.D., Ph.D., Thomas A. Keuer and Christopher D. Ozeroff, and each of them (with full power to act alone), as proxiesState of the undersignedState of Delaware was March 16, 2004 under the name “Nuvelo Merger Sub, Inc.”

THIRD:              The Board of Directors (the “Board”) of the Corporation, acting in accordance with all the powersprovisions of Sections 141 and 242 of the undersigned would possess if personally presentDGCL, adopted resolutions amending its Amended and Restated Certificate of Incorporation, as amended, as follows:

1.                         Article IV of the Amended and Restated Certificate of Incorporation of the Corporation is hereby amended to add the following provisions in their entirety to the existing provisions of Article IV:

“Effective at 5:01 p.m. Eastern time, on the date of the filing of this Certificate of Amendment to the Amended and Restated Certificate of Incorporation with full powerthe Secretary of substitution in eachState of them,the State of Delaware (the “Effective Time”), the shares of the Corporation’s Common Stock, par value $0.001 per share, issued and outstanding immediately prior to appearthe Effective Time and vote allthe shares of Common Stock issued and held in the treasury of the CompanyCorporation immediately prior to the Effective Time shall be combined into a smaller number of shares such that each 7 shares of issued and outstanding Common Stock immediately prior to the Effective Time are combined into one validly issued, fully paid and nonassessable share of Common Stock, par value $0.001 per share. Notwithstanding the immediately preceding sentence, no fractional shares shall be issued and, in lieu thereof, upon surrender after the Effective Time of a certificate which formerly represented shares of Common Stock that were issued and outstanding immediately prior to the undersignedEffective Time, any person who would otherwise be entitled to vote if personally presenta fractional share of Common Stock as a result of the combination, following the Effective Time (after taking into account all fractional shares of Common Stock otherwise issuable to such holder), shall be entitled to receive a cash payment equal to the fraction to which such holder would otherwise be entitled multiplied by the fair value of the Common Stock on the date of the Effective Time, as determined by the Board of Directors.

Each stock certificate that, immediately prior to the Effective Time, represented shares of Common Stock that were issued and outstanding immediately prior to the Effective Time shall, from and after the Effective Time, automatically and without the necessity of presenting the same for exchange, represent that number of whole shares of Common Stock after the Effective Time into which the shares of Common Stock formerly represented by such certificate shall have been combined (as well as the right to receive cash in lieu of fractional shares of Common Stock after the Effective Time), provided however, that each person of record holding a certificate that represented shares of Common Stock that were issued and outstanding immediately prior to the Effective Time shall receive, upon surrender of such certificate, a new certificate evidencing and representing the number of whole shares of Common Stock after the Effective Time into which the shares of Common Stock formerly represented by such certificate shall have been combined.”

FOURTH:           Thereafter, pursuant to a resolution by the Board, this Certificate of Amendment was submitted to the stockholders of the Corporation for their approval in accordance with the provisions of Section 211 and 242 of the DGCL. Accordingly, said proposed amendment has been adopted in accordance with Section 242 of the DGCL.

IN WITNESS WHEREOF,ARCABIOPHARMA, INC. has caused this Certificate of Amendment to be signed by its duly authorized officer this ______ day of ________, 2018.

ANNEXA-6

CERTIFICATE OF AMENDMENT

OF

AMENDED AND RESTATED CERTIFICATE OF INCORPORATION

OF

ARCA BIOPHARMA, INC.

ARCABIOPHARMA, INC., a corporation organized and existing under and by virtue of the General Corporation Law of the State of Delaware (the “DGCL”), does hereby certify:

FIRST:               The name of the corporation is ARCA biopharma, Inc. (the “Corporation”).

SECOND:           The date of filing of its original Certificate of Incorporation with the Secretary of State of the State of Delaware was March 16, 2004 under the name “Nuvelo Merger Sub, Inc.”

THIRD:              The Board of Directors (the “Board”) of the Corporation, acting in accordance with the provisions of Sections 141 and 242 of the DGCL, adopted resolutions amending its Amended and Restated Certificate of Incorporation, as amended, as follows:

1.                         Article IV of the Amended and Restated Certificate of Incorporation of the Corporation is hereby amended to add the following provisions in their entirety to the existing provisions of Article IV:

“Effective at 5:01 p.m. Eastern time, on the 2018 Annual Meetingdate of Stockholders,the filing of this Certificate of Amendment to the Amended and Restated Certificate of Incorporation with the Secretary of State of the State of Delaware (the “Effective Time”), the shares of the Corporation’s Common Stock, par value $0.001 per share, issued and outstanding immediately prior to the Effective Time and the shares of Common Stock issued and held in the treasury of the Corporation immediately prior to the Effective Time shall be combined into a smaller number of shares such that each 8 shares of issued and outstanding Common Stock immediately prior to the Effective Time are combined into one validly issued, fully paid and nonassessable share of Common Stock, par value $0.001 per share. Notwithstanding the immediately preceding sentence, no fractional shares shall be issued and, in lieu thereof, upon surrender after the Effective Time of a certificate which formerly represented shares of Common Stock that were issued and outstanding immediately prior to the Effective Time, any person who would otherwise be entitled to a fractional share of Common Stock as a result of the combination, following the Effective Time (after taking into account all fractional shares of Common Stock otherwise issuable to such holder), shall be entitled to receive a cash payment equal to the fraction to which such holder would otherwise be entitled multiplied by the fair value of the Common Stock on the date of the Effective Time, as determined by the Board of Directors.

Each stock certificate that, immediately prior to the Effective Time, represented shares of Common Stock that were issued and outstanding immediately prior to the Effective Time shall, from and after the Effective Time, automatically and without the necessity of presenting the same for exchange, represent that number of whole shares of Common Stock after the Effective Time into which the shares of Common Stock formerly represented by such certificate shall have been combined (as well as the right to receive cash in lieu of fractional shares of Common Stock after the Effective Time), provided however, that each person of record holding a certificate that represented shares of Common Stock that were issued and outstanding immediately prior to the Effective Time shall receive, upon surrender of such certificate, a new certificate evidencing and representing the number of whole shares of Common Stock after the Effective Time into which the shares of Common Stock formerly represented by such certificate shall have been combined.”

FOURTH:           Thereafter, pursuant to a resolution by the Board, this Certificate of Amendment was submitted to the stockholders of the Corporation for their approval in accordance with the provisions of Section 211 and 242 of the DGCL. Accordingly, said proposed amendment has been adopted in accordance with Section 242 of the DGCL.

IN WITNESS WHEREOF,ARCABIOPHARMA, INC. has caused this Certificate of Amendment to be signed by its duly authorized officer this ______ day of ________, 2018.

ANNEXA-7

CERTIFICATE OF AMENDMENT

OF

AMENDED AND RESTATED CERTIFICATE OF INCORPORATION

OF

ARCA BIOPHARMA, INC.

ARCABIOPHARMA, INC., a corporation organized and existing under and by virtue of the General Corporation Law of the State of Delaware (the “DGCL”), does hereby certify:

FIRST:               The name of the corporation is ARCA biopharma, Inc. (the “Corporation”).

SECOND:           The date of filing of its original Certificate of Incorporation with the Secretary of State of the State of Delaware was March 16, 2004 under the name “Nuvelo Merger Sub, Inc.”

THIRD:              The Board of Directors (the “Board”) of the Corporation, acting in accordance with the provisions of Sections 141 and 242 of the DGCL, adopted resolutions amending its Amended and Restated Certificate of Incorporation, as amended, as follows:

1.                         Article IV of the Amended and Restated Certificate of Incorporation of the Corporation is hereby amended to add the following provisions in their entirety to the existing provisions of Article IV:

“Effective at 5:01 p.m. Eastern time, on the date of the filing of this Certificate of Amendment to the Amended and Restated Certificate of Incorporation with the Secretary of State of the State of Delaware (the “Effective Time”), the shares of the Corporation’s Common Stock, par value $0.001 per share, issued and outstanding immediately prior to the Effective Time and the shares of Common Stock issued and held in the treasury of the Corporation immediately prior to the Effective Time shall be combined into a smaller number of shares such that each 9 shares of issued and outstanding Common Stock immediately prior to the Effective Time are combined into one validly issued, fully paid and nonassessable share of Common Stock, par value $0.001 per share. Notwithstanding the immediately preceding sentence, no fractional shares shall be issued and, in lieu thereof, upon surrender after the Effective Time of a certificate which formerly represented shares of Common Stock that were issued and outstanding immediately prior to the Effective Time, any postponement or adjournment thereof.person who would otherwise be entitled to a fractional share of Common Stock as a result of the combination, following the Effective Time (after taking into account all fractional shares of Common Stock otherwise issuable to such holder), shall be entitled to receive a cash payment equal to the fraction to which such holder would otherwise be entitled multiplied by the fair value of the Common Stock on the date of the Effective Time, as determined by the Board of Directors.

Each stock certificate that, immediately prior to the Effective Time, represented shares of Common Stock that were issued and outstanding immediately prior to the Effective Time shall, from and after the Effective Time, automatically and without the necessity of presenting the same for exchange, represent that number of whole shares of Common Stock after the Effective Time into which the shares of Common Stock formerly represented by such certificate shall have been combined (as well as the right to receive cash in lieu of fractional shares of Common Stock after the Effective Time), provided however, that each person of record holding a certificate that represented shares of Common Stock that were issued and outstanding immediately prior to the Effective Time shall receive, upon surrender of such certificate, a new certificate evidencing and representing the number of whole shares of Common Stock after the Effective Time into which the shares of Common Stock formerly represented by such certificate shall have been combined.”

FOURTH:           Thereafter, pursuant to a resolution by the Board, this Certificate of Amendment was submitted to the stockholders of the Corporation for their approval in accordance with the provisions of Section 211 and 242 of the DGCL. Accordingly, said proposed amendment has been adopted in accordance with Section 242 of the DGCL.

IN WITNESS WHEREOF,ARCABIOPHARMA, INC. has caused this Certificate of Amendment to be signed by its duly authorized officer this ______ day of ________, 2018.

ANNEXA-8

CERTIFICATE OF AMENDMENT

OF

AMENDED AND RESTATED CERTIFICATE OF INCORPORATION

OF

ARCA BIOPHARMA, INC.

ARCABIOPHARMA, INC., a corporation organized and existing under and by virtue of the General Corporation Law of the State of Delaware (the “DGCL”), does hereby certify: