Nightstar Announces Pricing of Initial Public Offering

Nightstar Therapeutics plc (“Nightstar” or the “Company”), a clinical-stage gene therapy company developing treatments for rare inherited retinal diseases, today announced the pricing of its initial public offering in the United States of 5,360,000 American Depositary Shares (“ADSs”) representing 5,360,000 ordinary shares at an initial public offering price of $14.00 per ADS for total gross proceeds of approximately $75.0 million. All ADSs sold in the offering were offered by Nightstar. The shares are expected to begin trading on The NASDAQ Global Select Market on September 28, 2017 under the ticker symbol “NITE.” In addition, Nightstar has granted the underwriters a 30-day option to purchase up to an additional 804,000 ADSs at the initial public offering price, less underwriting discounts and commissions. The offering is expected to close on October 2, 2017, subject to customary closing conditions.

Jefferies LLC, Leerink Partners LLC and BMO Capital Markets Corp. are acting as joint book-running managers for the offering. Wedbush Securities Inc. and Chardan are acting as co-managers.

The offering will be made only by means of a prospectus. When available, copies of the final prospectus related to the offering can be obtained from Jefferies LLC, Attention: Equity Syndicate Prospectus Department, 520 Madison Avenue, 2nd Floor, New York, NY 10022, or by telephone at [phone], or by email at [e-mail]; Leerink Partners LLC, Attention: Syndicate Department, One Federal Street, 37th Floor, Boston, MA 02110, or by telephone at [phone] ext. 6132, or by email at [e-mail]; or BMO Capital Markets Corp., Attention: Equity Syndicate Department, 3 Times Square, New York, NY 10036, or by telephone at [phone], or by email at [e-mail].

A registration statement relating to these securities has been filed with, and declared effective by, the U.S. Securities and Exchange Commission (the “SEC”). Copies of the registration statement can be accessed through the SEC’s website at www.sec.gov. This press release does not constitute an offer to sell or the solicitation of an offer to buy securities, and shall not constitute an offer, solicitation or sale in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of that jurisdiction.

About Nightstar

Nightstar is a leading clinical-stage gene therapy company focused on developing and commercializing novel one-time treatments for patients suffering from rare inherited retinal diseases including choroideremia, X-linked retinitis pigmentosa and Best vitelliform macular dystrophy.

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THRUST IRAlicia Davis, [e-mail]