13D Filing: RA Capital Management and Dicerna Pharmaceuticals Inc (DRNA)

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of
1934

(Amendment No. 2)*

Dicerna Pharmaceuticals, Inc.

(Name of Issuer)

Common Stock, par value $0.0001 per share

(Title of Class of Securities)

253031108

(CUSIP Number)

RA Capital Management, LLC

20 Park Plaza, Suite 1200

Boston, MA 02116

Telephone: 617.778.2512

Attn: Peter Kolchinsky

(Name, Address and Telephone Number of Person
Authorized to
Receive Notices and Communications)

December 13, 2017

(Date of Event Which Requires Filing of
this Statement)

If the filing person has previously filed a statement on Schedule 13G
to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§240.13d-1(e),
240.13d-1(f) or 240.13d-1(g), check the following box. [ ]

Note: Schedules filed in paper format shall include a
signed original and five copies of the schedule, including all exhibits. See Rule 13d-7 for other parties to whom copies are to
be sent.

* 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 disclosures provided in a prior cover page.

The information required on 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).

_________________

¹ Represents 2,428,571 shares
of the common stock (“Common Stock”) of Dicerna Pharmaceuticals, Inc. (the “Issuer”) and 2,159,965 shares
of the Common Stock issuable upon conversion of Preferred Stock (as defined below) which constitute approximately 19.94% of the
class outstanding. The percentage calculation assumes that there are currently 20,848,503 outstanding shares of the Common Stock
of the Issuer, based on the Issuer’s Form 10-Q for the quarterly period ended September 30, 2017 as filed with the Securities
and Exchange Commission (“SEC”) on November 2, 2017.

 _________________

² Represents 2,428,571 shares
of the Common Stock of the Issuer and 2,159,965 shares of the Common Stock issuable upon conversion of Preferred Stock which constitute
approximately 19.94% of the class outstanding. The percentage calculation assumes that there are currently 20,848,503 outstanding
shares of the Common Stock of the Issuer, based on the Issuer’s Form 10-Q for the quarterly period ended September 30, 2017
as filed with the SEC on November 2, 2017.

_________________

³ Represents 2,256,071 shares
of the Common Stock of the Issuer and 1,762,532 shares of the Common Stock issuable upon conversion of Preferred Stock attributable
to the Fund which constitute approximately 17.47% of the class outstanding. The percentage calculation assumes that there are
currently 20,848,503 outstanding shares of the Common Stock of the Issuer, based on the Issuer’s Form 10-Q for the quarterly
period ended September 30, 2017 as filed with the SEC on November 2, 2017.

Explanatory Note

This Amendment No. 2 to
Schedule 13D (this “Amendment No. 2”) amends and supplements the Statement on Schedule 13D filed with the United
States Securities and Exchange Commission on February 5, 2014, as amended to date (the “Statement”) by (i) RA
Capital Management, LLC (the “RA Capital”), (ii) Peter Kolchinsky and (iii) RA Capital Healthcare Fund, L.P.
(“Fund” and together with each of the foregoing, the “Reporting Persons”), relating to the Common
Stock (the “Common Stock”) of Dicerna Pharmaceuticals, Inc. (the “Issuer”). Capitalized terms
used herein without definition shall have the meaning set forth in the Statement.

Item 4 of the Statement is hereby amended
and supplemented by adding the following:

On December 13, 2017,
in connection with a proposed underwritten follow-on public offering, the Issuer entered into a letter agreement (the “Letter
Agreement”) with the Fund, a separately managed account for which RA Capital serves as investment adviser (the “Account”)
and all other holders (together, the “Preferred Holders”) of all of the outstanding shares of the Issuer’s
redeemable convertible preferred stock (the “Preferred Stock”).

Pursuant to the Letter
Agreement, the Preferred Holders agreed, subject to the completion of the offering, to optionally convert all of their shares of
Preferred Stock—to the extent not subject to certain beneficial ownership limitations imposed by the Issuer’s Certificate
of Designation (the “Conversion Blockers”)—into Common Stock and consented, if applicable, to the repurchase
of the residual shares of Common Stock that would be issuable but for the Conversion Blockers (the “Residual Shares”)
for $0.0001 per share. After the conversion and redemption, no shares of Preferred Stock will remain outstanding.

The Letter Agreement also
provides for Preferred Holders to waive and amend certain provisions in an amended and restated registration rights agreement (the
“Registration Rights Agreement”) by and among the Issuer and the Preferred Holders party thereto, including
the Fund and the Account. In consideration for the Preferred Holders agreeing to the optional conversion of the Preferred Stock
and to a waiver under and certain amendments to the Registration Rights Agreement, the Issuer agreed to issue to the Preferred
Holders pre-funded warrants (the “Pre-Funded Warrants”) exercisable in part or in whole at any time upon grant
for shares of the Issuer’s Common Stock at a price per share of $0.0001 per share. Each Preferred Holder may elect to receive
shares of the Issuer’s Common Stock in lieu of the Pre-Funded Warrants that would otherwise be issued to such Preferred Holder
subject to any applicable Conversion Blockers. Under the Letter Agreement, the number of shares allocable to each Preferred Holder
will be calculated based on the sum of (i) the number of shares of Common Stock into which the additional dividend accruals on
the Preferred Stock that such Preferred Holders would have been entitled to receive up to and including March 31, 2018 are convertible,
calculated immediately prior to the effectiveness of the conversion, and (ii) any Residual Shares repurchased, or to be repurchased,
from such Preferred Holder by the Issuer as described above (collectively, the “Additional Investor Shares”).
The formula for the Additional Investor Shares assumes (1) a conversion price of $3.19 per share of Preferred Stock; (2) application
of a dividend rate of 12% per annum from April 11, 2017 to October 27, 2017, and (3) application of a dividend rate of 8% per annum
commencing from October 28, 2017 through March 31, 2018.

The foregoing description
of the Letter Agreement does not purport to be complete and is qualified in its entirety by the full text of the Letter Agreement,
a copy of which is filed as an exhibit to this Statement and is incorporated herein by reference.

Item 5 of the Statement is hereby amended
and restated in its entirety as follows:

(a)-(b) See Items 7-11 of the cover pages
and Item 2 of this Statement.

(c) Except for the transactions disclosed
in Item 4 herein, none of the Reporting Persons has effected any transactions in the Common Stock of the Issuer in the past 60
days.

(d) None.

(e) Not Applicable.

Item 6 of the Statement is hereby amended
and supplemented by adding the following:

Item 4 above summarizes
certain provisions of the Letter Agreement and is incorporated herein by reference. A copy of the Letter Agreement is attached
as an exhibit to this Statement and is incorporated herein by reference.

Except as set forth herein,
none of the Reporting Persons has any contracts, arrangements, understandings or relationships (legal or otherwise) with any person
with respect to any securities of the Issuer, including but not limited to any contracts, arrangements, understandings or relationships
concerning the transfer or voting of such securities, finder’s fees, joint ventures, loan or option arrangements, puts or
calls, guarantees of profits, division of profits or losses, or the giving or withholding of proxies.

Item 7 of
the Statement is amended and supplemented by adding the following:

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: December 15, 2017

RA CAPITAL MANAGEMENT, LLC

By: /s/ Rajeev Shah

————————————————-

Rajeev Shah

Authorized Signatory

PETER KOLCHINSKY

/s/ Peter Kolchinsky

————————————————-

RA CAPITAL HEALTHCARE FUND, L.P.

By: RA Capital Management, LLC

Its: General Partner

By: /s/ Rajeev Shah

————————————————-

Rajeev Shah

Authorized Signatory