SEC Form 3

FORM 3

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person* Longitude Capital Partners II, LLC (Last) (First) (Middle) 2740 SAND HILL RD 2ND FLOOR (Street) MENLO PARK CA 94025 (City) (State) (Zip)	2. Date of Event Requiring Statement (Month/Day/Year) 06/20/2018	3. Issuer Name and Ticker or Trading Symbol Aptinyx Inc. [ APTX ]
		4. Relationship of Reporting Person(s) to Issuer (Check all applicable) Director X 10% Owner Officer (give title below) Other (specify below)	5. If Amendment, Date of Original Filed (Month/Day/Year)
			6. Individual or Joint/Group Filing (Check Applicable Line) Form filed by One Reporting Person X Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Beneficially Owned
1. Title of Security (Instr. 4)	2. Amount of Securities Beneficially Owned (Instr. 4)	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	4. Nature of Indirect Beneficial Ownership (Instr. 5)

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Series A-1 Convertible Preferred Stock	(1)	(1)	Common Stock	1,047,450	(1)	I	By: Longitude Venture Partners II, L.P.(2)
Series A-2 Convertible Preferred Stock	(1)	(1)	Common Stock	1,197,076	(1)	I	By: Longitude Venture Partners II, L.P.(2)
Series B Convertible Preferred Stock	(1)	(1)	Common Stock	795,553	(1)	I	By: Longitude Venture Partners II, L.P.(2)

1. Name and Address of Reporting Person* Longitude Capital Partners II, LLC (Last) (First) (Middle) 2740 SAND HILL RD 2ND FLOOR (Street) MENLO PARK CA 94025 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* Tammenoms Bakker Juliet (Last) (First) (Middle) 2740 SAND HILL RD 2ND FLOOR (Street) MENLO PARK CA 94025 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* Longitude Venture Partners II, L.P. (Last) (First) (Middle) 2740 SAND HILL RD 2ND FLOOR (Street) MENLO PARK CA 94025 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

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. This report is filed jointly by Longitude Capital Partners II, LLC ("Longitude Capital II"), Longitude Venture Partners II, L.P. ("Longitude Venture II"), and Juliet Tammenoms Bakker ("Ms. Bakker"), all of whom share beneficial ownership of more than 10% of the capital stock of the Issuer. Longitude Capital II as general partner of Longitude Venture II maybe deemed to have shared voting, investment and dispositive power over the shares held by Longitude Venture II. Patrick G. Enright ("Mr. Enright") and Ms. Bakker are each managing members of Longitude Capital II and in their capacity as such, may be deemed to exercise shared voting and investment power over the shares held by Reporting Persons. Each of Longitude Capital II, Mr. Enright and Ms. Bakker disclaims beneficial ownership of such shares except to the extent of its, his or her pecuniary interest therein. Mr. Enright is filing a separate form 3 in his capacity as a director of the Issuer.

	LONGITUDE CAPITAL PARTNERS II, LLC, a Delaware limited liability company, By: /s/ Patrick G. Enright, Managing Member	06/20/2018
	LONGITUDE VENTURE PARTNERS II, L.P., By: Longitude Capital Partners II, LLC, a Delaware limited liability company, Its General Partner, By: /s/ Patrick G. Enright, Managing Member	06/20/2018
	/s/ Juliet Tammenoms Bakker	06/20/2018
	** Signature of Reporting Person	Date
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 5 (b)(v).
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