Sec Form 3 Filing - New Leaf Venture Management III, L.L.C. @ Aptinyx Inc. - 2018-06-20

FORM 3 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 New Leaf Venture Management III, L.L.C. 2. Issuer Name and Ticker or Trading Symbol Aptinyx Inc. [ APTX] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O NEW LEAF VENTURES, 7 TIMES SQUARE, SUITE 3502 3. Date of Earliest Transaction (MM/DD/YY) 06/20/2018 (Street) NEW YORK, NY10036 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ 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

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-1 Convertible Preferred Stock ( 1 ) ( 1 ) ( 1 ) Common Stock 1,047,450 I See footnotes ( 2 ) ( 3 ) Series A-2 Convertible Preferred Stock ( 1 ) ( 1 ) ( 1 ) Common Stock 1,197,076 I See footnotes ( 2 ) ( 3 ) Series B Convertible Preferred Stock ( 1 ) ( 1 ) ( 1 ) Common Stock 552,208 I See footnotes ( 2 ) ( 3 ) Series B Convertible Preferred Stock ( 1 ) ( 1 ) ( 1 ) Common Stock 243,345 I See footnote ( 4 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other New Leaf Venture Management III, L.L.C. C/O NEW LEAF VENTURES 7 TIMES SQUARE, SUITE 3502 NEW YORK, NY10036 X New Leaf Venture Associates III, L.P. C/O NEW LEAF VENTURES 7 TIMES SQUARE, SUITE 3502 NEW YORK, NY10036 X New Leaf Ventures III, L.P. C/O NEW LEAF VENTURES 7 TIMES SQUARE, SUITE 3502 NEW YORK, NY10036 X New Leaf Biopharma Opportunities I, L.P. C/O NEW LEAF VENTURES 7 TIMES SQUARE, SUITE 3502 NEW YORK, NY10036 X New Leaf BPO Associates I, L.P. C/O NEW LEAF VENTURES 7 TIMES SQUARE, SUITE 3502 NEW YORK, NY10036 X Signatures New Leaf Venture Management III, L.L.C. /s/ Craig Slutzkin By: Craig Slutzkin Its: Chief Financial Officer 06/20/2018 Signature of Reporting Person Date New Leaf Venture Associates III, L.P. By: New Leaf Venture Management III, L.L.C., its general partner /s/ Craig Slutzkin By: Craig Slutzkin Its: Chief Financial Officer 06/20/2018 Signature of Reporting Person Date New Leaf Ventures III, L.P. By: New Leaf Venture Associates III, L.P. By: New Leaf Venture Management III, L.L.C., its general partner /s/ Craig Slutzkin By: Craig Slutzkin Its: Chief Financial Officer 06/20/2018 Signature of Reporting Person Date New Leaf Ventures Biopharma Opportunities I, L.P. By: New Leaf BPO Associates I, L.P. By: New Leaf Venture Management III, L.L.C., its general partner /s/ Craig Slutzkin By: Craig Slutzkin Its: Chief Financial Officer 06/20/2018 Signature of Reporting Person Date New Leaf BPO Associates I, L.P. By: New Leaf Venture Management III, L.L.C., its general partner /s/ Craig Slutzkin By: Craig Slutzkin Its: Chief Financial Officer 06/20/2018 Signature of Reporting Person Date

Explanation of Responses:

( 1 )All series of convertible preferred stock will automatically convert into the number of shares of the Issuer's common stock on a 27.58621-for-1 basis immediately prior to the closing of the Issuer's initial public offering and have no expiration date. ( 2 )These shares are held directly by New Leaf Ventures III, L.P. ("NLV-III"). The general partner of NLV-III is New Leaf Venture Associates III, L.P. ("NLVA-III"). The general partner of NLVA-III is New Leaf Venture Management III, L.L.C. ("Management-III"). Each of NLVA-III and Management-III disclaim beneficial ownership of these securities and this report shall not be deemed an admission that NLVA-III or Management-III are beneficial owners of such securities for purposes of Section 16 or any other purpose, except to the extent of their respective pecuniary interests therein. Ronald M. Hunt, Vijay K. Lathi, and Liam T. Ratcliffe, a member of the Issuer's board of directors, are the managers of Management-III (each, a "Manager" and collectively, the "Managers") and may each be deemed to have shared voting and investment power with respect to these securities. ( 3 )Each of the Managers disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein. ( 4 )These shares are held directly by New Leaf Ventures Biopharma Opportunities I, L.P. ("NLV Biopharma"). The general partner of NLV Biopharma is New Leaf BPO Associates I, L.P. ("NLBA-I"). The general partner of NLBA-I is Management-III. Each of NLVB-I and Management-III disclaim beneficial ownership of these securities and this report shall not be deemed an admission that NLVB-I or Management-III are beneficial owners of such securities for purposes of Section 16 or any other purpose, except to the extent of their respective pecuniary interests therein. The Managers may be deemed to have shared voting and investment power with respect to these securities. Each of the Managers disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any of them is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of their respective pecuniary interests therein.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

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