Sec Form 4 Filing - MOTT DAVID M @ Nightstar Therapeutics plc - 2019-06-07

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 MOTT DAVID M 2. Issuer Name and Ticker or Trading Symbol Nightstar Therapeutics plc [ NITE] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 1954 GREENSPRING DRIVE, SUITE 600 3. Date of Earliest Transaction (MM/DD/YY) 06/07/2019 (Street) TIMONIUM, MD21093 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ 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 Ordinary Shares ( 1 ) 06/07/2019 D 6,662,532 D $ 25.5 0 I See Note 2 ( 2 )

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 Stock Option (Right to Buy) $ 12.27 06/07/2019 D 36,400 ( 3 ) 02/27/2028 Ordinary Shares ( 1 ) 36,400 $ 13.23 ( 4 ) 0 D Stock Option (Right to Buy) $ 13.57 06/07/2019 D 21,000 ( 3 ) 01/24/2029 Ordinary Shares ( 1 ) 21,000 $ 11.93 ( 4 ) 0 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other MOTT DAVID M 1954 GREENSPRING DRIVE SUITE 600 TIMONIUM, MD21093 X X Signatures /s/ Sasha Keough, attorney-in-fact 06/07/2019 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The ordinary shares, nominal value GBP 0.01 per share, of Nightstar Therapeutics plc (the "Issuer") may be represented by American Depositary Shares ("ADSs"). Each ADS represents one ordinary share of the Issuer. ( 2 )The Reporting Person is a manager of NEA 15 GP, LLC, ("NEA 15 GP") which is the sole general partner of NEA Partners 15, L.P. ("NEA Partners 15"). NEA Partners 15 is the sole general partner of New Enterprise Associates 15, L.P. ("NEA 15"), which is the direct beneficial owner of the shares. The Reporting Person disclaims beneficial ownership within the meaning of Section 16 of the Securities Exchange Act of 1934, as amended, or otherwise of such portion of the shares held by NEA 15 in which the Reporting Person has no pecuniary interest. ( 3 )In connection with the acquisition by Tungsten Bidco Limited of the entire issued and to be issued share capital of the Issuer on June 7, 2019 by means of a scheme of arrangement under Part 26 of the UK Companies Act 2006, all stock options were cancelled in exchange for a payment equal to $25.50 with respect to each ordinary share subject to the option award, less the applicable exercise price. ( 4 )Represents the payment per share received in exchange for the cancellation of each option of $25.50, less the applicable exercise price.

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

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