Sec Form 4 Filing - RA CAPITAL MANAGEMENT, LLC @ Dicerna Pharmaceuticals Inc - 2017-12-18

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person RA CAPITAL MANAGEMENT, LLC 2. Issuer Name and Ticker or Trading Symbol Dicerna Pharmaceuticals Inc [ DRNA] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 20 PARK PLAZA, SUITE 1200 3. Date of Earliest Transaction (MM/DD/YY) 12/18/2017 (Street) BOSTON, MA02116 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 12/18/2017 M 2,645,442 A 5,074,013 I See Note ( 2 ) ( 3 ) ( 4 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Redeemable Convertible Preferred Stock ( 1 ) 12/18/2017 M 76,500 ( 1 ) ( 1 ) Common Stock 2,645,442 $ 3.19 0 I See Note ( 2 ) ( 3 ) ( 4 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other RA CAPITAL MANAGEMENT, LLC 20 PARK PLAZA, SUITE 1200 BOSTON, MA02116 X RA Capital Healthcare Fund LP 20 PARK PLAZA, SUITE 1200 BOSTON, MA02116 X Signatures /s/ Peter Kolchinsky, Manager of RA Capital Management, LLC 12/20/2017 Signature of Reporting Person Date /s/ Peter Kolchinsky, Manager of RA Capital Management, LLC, the General Partner of RA Capital Healthcare Fund, L.P. 12/20/2017 Signature of Reporting Person Date

Explanation of Responses:

( 1 )On December 18, 2017, in consideration for the holders of the Issuer's redeemable convertible preferred stock (the "Preferred Stock") waiving certain rights, the Issuer automatically converted each outstanding share of Preferred Stock into Common Stock for no additional consideration. ( 2 )Peter Kolchinsky is a director of the Issuer and the sole manager of RA Capital Management, LLC (the "Adviser") which is the general partner RA Capital Healthcare Fund, L.P. (the "Fund"). The Fund is a shareholder. ( 3 )4,414,752 of the aggregate common stock beneficially held after transaction is held directly by the Fund. The Adviser and Mr. Kolchinsky may be deemed indirect beneficial owners of the securities. The Adviser and Mr. Kolchinsky disclaim beneficial ownership of the reported securities in reliance on Rule 16a-1(a)(1)(v) and (vii) and disclaim any obligation to file reports under Section 16 other than, in the case of Mr. Kolchinsky, as a director. Pursuant to Rule 16a-1 under the Securities Exchange Act of 1934, as amended (the "Act"), each of the Reporting Persons disclaims beneficial ownership of the securities reported herein except to the extent of their respective pecuniary interests therein. The filing of this Form 4 shall not be construed as an admission that Mr. Kolchinsky or the Adviser is or was for the purposes of Section 16(a) of the Act, or otherwise, the beneficial owner of any of securities reported herein. ( 4 )659,261 of the common stock beneficially held after the transaction are held in a separately managed account for which the Advisor serves as investment adviser (the "Account"). The Adviser, the Fund and Mr. Kolchinsky have no pecuniary interest in the reported securities held in the Account and disclaim: (A) beneficial ownership thereof for purposes of Rule 16a-1(a)(2) and (B) beneficial ownership of securities held by the Fund, for purposes of Rule 16a-1(a)(2), except to the extent of their pecuniary interest therein.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

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