X0306 4 2018-06-25 0 0001674365 Aptinyx Inc. APTX 0001578965 Koppel Adam C/O/ BAIN CAPITAL LIFE SCIENCES INVESTORS LLC, 200 CLARENDON STREET BOSTON MA 02116 1 0 0 0 Common Stock 2018-06-25 4 C 0 1825092 A 1825092 I See Footnotes Common Stock 2018-06-25 4 P 0 400000 16.00 A 2225092 I See Footnotes Series B Convertible Preferred Stock 2018-06-25 4 C 0 50347397 D Common Stock 1825092 0 I See footnotes Represents shares held directly by Bain Capital Life Sciences Fund, L.P. and BCIP Life Sciences Associates, LP (collectively, the "Bain Life Sciences Entities"). The governance, investment strategy and decision-making process with respect to investments held by the Bain Life Sciences Entities is directed by Bain Capital Life Sciences Investors, LLC, whose managers are Jeffrey Schwartz and Adam Koppel. By virtue of the relationships described in these footnotes, Dr. Koppel may be deemed to share voting and dispositive power with respect to all of the shares of Common Stock held by the Bain Life Sciences Entities. Dr. Koppel disclaims beneficial ownership of such securities except to the extent of his pecuniary interest therein. Each share of Series B Convertible Preferred Stock automatically converted into shares of Common Stock on a 27.58621-for-one basis immediately prior to the closing of the Issuer's initial public offering without payment or additional consideration. The shares of Series B Convertible Preferred Stock had no expiration date. On June 25, 2018, the Bain Life Sciences Entities purchased, in aggregate, 400,000 shares of Common Stock of the Issuer at a price of $16.00 per share, pursuant to an underwritten public offering. /s/ Adam Koppel 2018-06-26