Dicerna Announces Proposed Follow-On Public Offering of Common Stock

Dicerna Pharmaceuticals, Inc. DRNA, a leading developer of investigational ribonucleic acid interference (RNAi) therapeutics, today announced the commencement of a proposed underwritten registered public offering of 6,150,000 shares of its common stock. In connection with this offering, Dicerna expects to grant the underwriters a 30-day option to purchase up to an additional 922,500 shares of its common stock on the same terms and conditions. The offering is subject to market and other conditions, and there can be no assurance as to whether or when the offering may be completed, or as to the actual size or terms of the offering.

Dicerna intends to use the net proceeds from this offering for preclinical studies and clinical trials, and to use the remainder of any net proceeds for continued technology platform development, working capital and general corporate purposes.

Citigroup, Leerink Partners and Stifel are acting as the joint book-running managers for the offering. H.C. Wainwright & Co. and SunTrust Robinson Humphrey are acting as the lead co-managers for the offering.

The shares will be issued pursuant to Dicerna's shelf registration statement on Form S-3 previously filed with and declared effective by the Securities and Exchange Commission ("SEC"). The offering may be made only by means of a prospectus supplement and the accompanying prospectus, copies of which may be obtained free of charge on the SEC website at www.sec.gov or by sending a request to: Citigroup, c/o Broadridge Financial Solutions, 1155 Long Island Avenue, Edgewood, NY 11717 (Tel: 800-831-9146); Leerink Partners LLC, Attention: Syndicate Department, One Federal Street, 37th Floor, Boston, MA 02110, by telephone at (800) 808-7525 ext. 6132 or by email at Syndicate@Leerink.com; or Stifel at Attention: Syndicate, One Montgomery Street, Suite 3700, San Francisco, CA 94104, or by telephone at (415) 364-2720, or by email at syndprospectus@stifel.com.

This press release shall not constitute an offer to sell or the solicitation of an offer to buy any securities of Dicerna, nor shall there be any sale of these securities in any state or other jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state or jurisdiction.

About Dicerna Pharmaceuticals, Inc.

Dicerna Pharmaceuticals, Inc., is a biopharmaceutical company focused on the discovery and development of innovative, subcutaneously delivered RNAi-based therapeutics for the treatment of diseases involving the liver, including rare diseases, viral infectious diseases, chronic liver diseases, and cardiovascular diseases. Dicerna is leveraging its proprietary GalXC™ RNAi technology platform to build a broad pipeline in these core therapeutic areas, focusing on target genes where connections between target gene and diseases are well understood and documented. Dicerna intends to discover, develop and commercialize novel therapeutics either on its own or in collaboration with pharmaceutical partners.

About GalXC^™ RNAi Technology Platform

GalXC^TM is a proprietary technology platform invented by Dicerna to discover and develop RNAi-based therapies designed to silence disease-driving genes in the liver. Compounds produced via GalXC are intended to be broadly applicable across multiple therapeutic areas, including rare diseases, viral infectious diseases, chronic liver diseases, and cardiovascular diseases. Using GalXC, Dicerna scientists attach N-acetylgalactosamine sugars directly to the extended region of our proprietary RNAi molecules, yielding multiple proprietary conjugate delivery configurations. Many of the conjugates produced via GalXC incorporate a folded motif known as a tetraloop in the extended region. The tetraloop configuration, which is unique to Dicerna's GalXC compounds, allows flexible and efficient conjugation to the targeting ligands, and stabilizes the RNAi duplex which the Company believes will enable subcutaneous delivery of its RNAi therapies to hepatocytes in the liver, where they are designed to specifically bind to receptors on target cells, potentially leading to internalization and access to the RNAi machinery within the cells. The technology may offer several distinct benefits, as suggested by strong preclinical data. The benefits seen in preclinical studies include: potency that is on par with or better than comparable platforms; highly specific binding to gene targets; long duration of action; and an infrequent subcutaneous dosing regimen.

Cautionary Note on Forward-Looking Statements

This press release includes forward-looking statements. Such forward-looking statements are subject to risks and uncertainties that could cause actual results to differ materially from those expressed or implied in such statements. Examples of forward-looking statements in this release include Dicerna's expectations regarding the offering (including the actual size or terms of the offering, the size of the underwriter's option to purchase additional shares of common stock, whether or when the offering may be completed and its anticipated use of proceeds from the offering). Applicable risks and uncertainties include those relating to the offering and other risks identified under the heading "Risk Factors" included in our most recent Form 10-Q filing and in other future filings with the SEC including any prospectus related to the offering. The forward-looking statements contained in this press release reflect Dicerna's current views with respect to future events, and Dicerna does not undertake and specifically disclaims any obligation to update any forward-looking statements.

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