Sec Form 4 Filing - TEPPER ROBERT I @ Neon Therapeutics, Inc. - 2018-06-29

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 TEPPER ROBERT I 2. Issuer Name and Ticker or Trading Symbol Neon Therapeutics, Inc. [ NTGN] 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) C/O THIRD ROCK VENTURES, LLC, 29 NEWBURY STREET, 3RD FLOOR 3. Date of Earliest Transaction (MM/DD/YY) 06/29/2018 (Street) BOSTON, MA02116 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 Common Stock 06/29/2018 C 0 ( 1 ) A 0 ( 4 ) I See footnote ( 5 ) Common Stock 06/29/2018 C 0 ( 2 ) A 0 ( 6 ) I See footnote ( 5 )

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 Series A Preferred Stock ( 3 ) 06/29/2018 C 0 ( 1 ) ( 3 ) ( 3 ) Common Stock 0 ( 1 ) ( 3 ) 0 I See footnote ( 5 ) Series B Preferred Stock ( 3 ) 06/29/2018 C 0 ( 2 ) ( 3 ) ( 3 ) Common Stock 0 ( 2 ) ( 3 ) 0 I See footnote ( 5 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other TEPPER ROBERT I C/O THIRD ROCK VENTURES, LLC 29 NEWBURY STREET, 3RD FLOOR BOSTON, MA02116 X X Signatures /s/ Yasir B. Al-Wakeel, attorney-in-fact for Robert Tepper 07/03/2018 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Third Rock Ventures III, L.P. ("TRV III") received 8,999,999 shares of Common Stock of the Issuer upon conversion of 45,000,000 shares of Series A Preferred Stock in connection with the closing of the Issuer's initial public offering. ( 2 )TRV III received 341,637 shares of Common Stock of the Issuer upon conversion of 1,708,185 shares of Series B Preferred Stock in connection with the closing of the Issuer's initial public offering. ( 3 )All series of Preferred Stock automatically converted into the Issuer's Common Stock on a 5-for-1 basis upon the closing of the Issuer's initial public offering on June 29, 2018 and had no expiration date. ( 4 )After the above transaction, TRV III owned 9,399,999 shares of Common Stock of the Issuer. ( 5 )These shares are directly held by TRV III. The general partner of TRV III is Third Rock Ventures GP III, L.P. ("TRV GP III"). The general partner of TRV GP III is TRV GP III, LLC ("TRV GP III LLC"). The individual managers of TRV GP III LLC are Mark Levin ("Levin"), Kevin Starr ("Starr") and Dr. Robert Tepper ("Tepper"). Each of TRV GP III, TRV GP III LLC, Levin, Starr and Tepper disclaims beneficial ownership of the shares except to the extent of its or his pecuniary interest therein, if any, and this report shall not be deemed an admission that it or he is the beneficial owner of such shares. ( 6 )After the above transaction, TRV III owned 9,741,636 shares of Common Stock of the Issuer.

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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