SC 13G/A 1 abio-13g_20201231.txt UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 2)* ARCA BIOPHARMA, INC. ---------------------------------------------------------------------------- (Name of Issuer) Common Stock, par value $0.001 per share ---------------------------------------------------------------------------- (Title of Class of Securities) 00211Y506 ---------------------------------------------------------------------------- (CUSIP Number) December 31, 2020 ---------------------------------------------------------------------------- (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the rule pursuant to which this Schedule is filed: [X] Rule 13d-1(b) [_] Rule 13d-1(c) [_] Rule 13d-1(d) *The remainder of this cover page shall be filled out for a reporting person's initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page. The information required in the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes). ============================================================================= ----------------------------------------------------------------------------- CUSIP NO. 00211Y506 13G Page 2 of 8 Pages ----------------------------------------------------------------------------- (1) NAMES OF REPORTING PERSONS. I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (entities only). Renaissance Technologies LLC 26-0385758 ----------------------------------------------------------------------------- (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS): (a) [_] (b) [_] ----------------------------------------------------------------------------- (3) SEC USE ONLY ----------------------------------------------------------------------------- (4) CITIZENSHIP OR PLACE OF ORGANIZATION Delaware ----------------------------------------------------------------------------- (5) SOLE VOTING POWER NUMBER OF SHARES 79,612 BENEFICIALLY OWNED _____________________________ BY EACH REPORTING PERSON WITH: (6) SHARED VOTING POWER 0 _____________________________ (7) SOLE DISPOSITIVE POWER 205,500 _____________________________ (8) SHARED DISPOSITIVE POWER 0 ______________________________ (9) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 205,500 ------------------------------------------------------------------------------ (10) CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) [_] ------------------------------------------------------------------------------ (11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 2.20 % ------------------------------------------------------------------------------ (12) TYPE OF REPORTING PERSON (SEE INSTRUCTIONS) IA Page 2 of 8 pages ============================================================================= Page 3 of 8 pages ----------------------------------------------------------------------------- CUSIP NO. 00211Y506 13G Page 3 of 8 Pages ----------------------------------------------------------------------------- (1) NAMES OF REPORTING PERSONS. I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY). RENAISSANCE TECHNOLOGIES HOLDINGS CORPORATION 13-3127734 ----------------------------------------------------------------------------- (2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS) (a) [_] (b) [_] ----------------------------------------------------------------------------- (3) SEC USE ONLY ----------------------------------------------------------------------------- (4) CITIZENSHIP OR PLACE OF ORGANIZATION Delaware ----------------------------------------------------------------------------- (5) SOLE VOTING POWER NUMBER OF SHARES 79,612 BENEFICIALLY OWNED _____________________________ BY EACH REPORTING PERSON WITH: (6) SHARED VOTING POWER 0 _____________________________ (7) SOLE DISPOSITIVE POWER 205,500 _____________________________ (8) SHARED DISPOSITIVE POWER 0 _____________________________ (9) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 205,500 ----------------------------------------------------------------------------- (10) CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) [_] ----------------------------------------------------------------------------- (11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 2.20 % ----------------------------------------------------------------------------- (12) TYPE OF REPORTING PERSON (SEE INSTRUCTIONS) HC Page 3 of 8 pages ============================================================================= ----------------------------------------------------------------------------- CUSIP NO. 00211Y506 13G Page 4 of 8 Pages ----------------------------------------------------------------------------- Item 1. (a) Name of Issuer ARCA BIOPHARMA, INC. (b) Address of Issuer's Principal Executive Offices. 10170 Church Ranch Way, Suite 100, Westminster, CO 80021 Item 2. (a) Name of Person Filing: This Schedule 13G is being filed by Renaissance Technologies LLC ("RTC") and Renaissance Technologies Holdings Corporation ("RTHC"). (b) Address of Principal Business Office or, if none, Residence. The principal business address of the reporting persons is: 800 Third Avenue New York, New York 10022 (c) Citizenship. RTC is a Delaware limited liability company, and RTHC is a Delaware corporation. (d) Title of Class of Securities. Common Stock, par value $0.001 per share (e) CUSIP Number. 00211Y506 Page 4 of 8 pages ============================================================================= Item 3. If this statement is filed pursuant to Rule 13d-1(b) or 13-d-2(b) or (c),check whether the person filing is a: (a) [_] Broker or dealer registered under section 15 of the Act. (b) [_] Bank as defined in section 3(a)(6) of the Act. (c) [_] Insurance Company as defined in section 3(a)(19) of the Act. (d) [_] Investment Company registered under section 8 of the Investment Company Act. (e) [x] Investment Adviser in accordance with Sec.240.13d-1(b)(1)(ii)(E). (f) [_] Employee Benefit Plan or Endowment Fund in accordance with Sec. 240.13d-1(b)(1)(ii)(F). (g) [_] Parent holding company, in accordance with Sec.240.13d-1(b)(1)(ii)(G). (h) [_] A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act. (i) [_] A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940. (j) [_] Group, in accordance with Sec.240.13d-1(b)(1)(ii)(J). Item 4. Ownership. (a) Amount beneficially owned. RTC: 205,500 shares RTHC: 205,500 shares, comprising the shares beneficially owned by RTHC, because of RTHC's majority ownership of RTC. (b) Percent of Class. RTC: 2.20 % RTHC: 2.20 % (c) Number of shares as to which the person has: (i) sole power to vote or to direct the vote: RTC: 79,612 RTHC: 79,612 (ii) Shared power to vote or to direct the vote: 0 (iii) sole power to dispose or to direct the disposition of: RTC: 205,500 RTHC: 205,500 (iv) Shared power to dispose or to direct the disposition of: RTC: 0 RTHC: 0 Page 5 of 8 pages ============================================================================= Item 5. Ownership of Five Percent or Less of a Class. If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than five percent of the class of securities, check the following: [X] Item 6. Ownership of More than Five Percent on Behalf of Another Person. Certain funds and accounts managed by RTC have the right to receive dividends and proceeds from the sale of the securities which are the subject of this report. Item 7. Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company. Not applicable Item 8. Identification and Classification of Members of the Group. Not applicable Item 9. Notice of Dissolution of a Group. Not applicable Page 6 of 8 pages ============================================================================= Item 10. Certification By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect. SIGNATURE After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct. Date: February 10, 2021 Renaissance Technologies LLC By: /s/ James S. Rowen Chief Operating Officer Renaissance Technologies Holdings Corporation By: /s/ James S. Rowen Vice President Attention: Intentional misstatements or omissions of fact constitute Federal criminal violations (See 18 U.S.C. 1001). Page 7 of 8 Pages ============================================================================== EXHIBIT 99.1 AGREEMENT REGARDING JOINT FILING UNDER RULE 13D-1(K) OF THE EXCHANGE ACT In accordance with Rule 13d-1(k) under the Securities Exchange Act of 1934, as amended, each of the undersigned agrees to the filing on behalf of each of a Statement on Schedule 13G, and all amendments thereto, with respect to the shares of Common Stock, par value $0.001 per share of ARCA BIOPHARMA, INC. Date: February 10, 2021 Renaissance Technologies LLC By: /s/ James S. Rowen Chief Operating Officer Renaissance Technologies Holdings Corporation By: /s/ James S. Rowen Vice President Page 8 of 8 Pages

SEC Form SC 13G/A filed