X0206 3 2018-06-20 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 Series B Convertible Preferred Stock Common Stock 1825092 I See footnotes 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. 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 convertible preferred 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. /s/ Adam Koppel 2018-06-20