Additional Proxy Soliciting Materials (definitive) (defa14a)

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of
the Securities Exchange Act of 1934 (Amendment No. )

Filed by the Registrant x

Filed by a Party other than the Registrant o

Check the appropriate box:
o	Preliminary Proxy Statement
o	Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2))
o	Definitive Proxy Statement
x	Definitive Additional Materials
o	Soliciting Material under §240.14a-12

Aptinyx Inc.
(Name of Registrant as Specified In Its Charter)


(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

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*** Exercise Your Right to Vote *** Important Notice Regarding the Availability of Proxy Materials for the Shareholder Meeting to Be Held on May 20, 2020. APTINYX INC. Location: Meeting live via the Internet-please visit XXXX XXXX XXXX XXXX (located on the following page). APTINYX INC. 909 DAVIS STREET, SUITE 600 EVANSTON, IL 60201 You are receiving this communication because you hold shares in the company named above. This is not a ballot. You cannot use this notice to vote these shares. This communication presents only an overview of the more complete proxy materials that are available to you on the Internet. You may view the proxy materials online at www.proxyvote.com or easily request a paper copy (see reverse side). We encourage you to access and review all of the important information contained in the proxy materials before voting. proxy materials and voting instructions. D01862-P34419 See the reverse side of this notice to obtain Meeting Information Meeting Type:Annual Meeting For holders as of:March 23, 2020 Date: May 20, 2020Time: 9:00 AM Eastern Time, 8:00 AM Central Time www.virtualshareholdermeeting.com/APTX2020. The company will be hosting the meeting live via the Internet this year. To attend the meeting via the Internet please visit www.virtualshareholdermeeting.com/APTX2020 and be sure to have the information that is printed in the box marked by the arrow

Before You Vote How to Access the Proxy Materials How To Vote Please Choose One of the Following Voting Methods D01863-P34419 Vote By Internet: Before The Meeting: Go to www.proxyvote.com. Have the information that is printed in the box marked by the arrow (located on the following page) available and follow the instructions. During The Meeting: Go to www.virtualshareholdermeeting.com/APTX2020. Have the information that is printed in the box marked by the arrow(located on the following page) available and follow the instructions. Vote By Mail: You can vote by mail by requesting a paper copy of the materials, which will include a proxy card. XXXX XXXX XXXX XXXX XXXX XXXX XXXX XXXX Proxy Materials Available to VIEW or RECEIVE: NOTICE AND PROXY STATEMENTFORM 10-K How to View Online: Have the information that is printed in the box marked by the arrow(located on the following page) and visit: www.proxyvote.com. How to Request and Receive a PAPER or E-MAIL Copy: If you want to receive a paper or e-mail copy of these documents, you must request one. There is NO charge for requesting a copy. Please choose one of the following methods to make your request: 1) BY INTERNET:www.proxyvote.com 2) BY TELEPHONE:1-800-579-1639 3) BY E-MAIL*:sendmaterial@proxyvote.com * If requesting materials by e-mail, please send a blank e-mail with the information that is printed in the box marked by the arrow(located on the following page) in the subject line. Requests, instructions and other inquiries sent to this e-mail address will NOT be forwarded to your investment advisor. Please make the request as instructed above on or before May 6, 2020 to facilitate timely delivery. XXXX XXXX XXXX XXXX XXXX XXXX XXXX XXXX

The Board of Directors recommends you vote FOR the following: 1. Election of Class II Directors Nominees: To be elected for a three-year term expiring in 2023. 01) Patrick G. Enright 02) Adam M. Koppel, M.D., Ph.D. The Board of Directors recommends you vote FOR proposal 2: 2.To ratify the appointment of Deloitte & Touche LLP as Aptinyx Inc.'s Independent Registered Public Accounting firm for the fiscal year ending December 31, 2020. NOTE: In their discretion, the proxies are authorized to vote upon any other matters that are properly brought by or at the direction of the Board of Directors before the Annual Meeting and at any adjournments or postponements thereof. D01864-P34419 Voting Items