X0306 4 2020-10-26 0 0001674365 Aptinyx Inc. APTX 0001703031 Bain Capital Life Sciences Investors, LLC 200 CLARENDON STREET BOSTON MA 02116 0 0 1 0 0001703030 Bain Capital Life Sciences Partners, LP 200 CLARENDON STREET BOSTON MA 02116 0 0 1 0 0001687968 Bain Capital Life Sciences Fund, L.P. 200 CLARENDON STREET BOSTON MA 02116 0 0 1 0 0001702921 BCIP Life Sciences Associates, LP 200 CLARENDON STREET BOSTON MA 02116 0 0 1 0 0001702957 Schwartz Jeffrey Lawrence 200 CLARENDON STREET BOSTON MA 02116 0 0 1 0 0001578965 Koppel Adam C/O BAIN CAPITAL LIFE SCIENCES INVESTORS 200 CLARENDON STREET BOSTON MA 02116 1 0 1 0 Common Stock 2020-10-26 4 P 0 3333333 3.00 A 8891758 I See footnotes On October 26, 2020, Bain Capital Life Sciences Fund, L.P. ("BCLS") and BCIP Life Sciences Fund, LP ("BCIPLS and, together with BCLS, the "Bain Capital Life Sciences Entities") purchased an aggregate of 3,333,333 shares of Common Stock in an underwritten public offering at a price per share of $3.00. BCLS purchased 3,023,816 of such shares and BCIPLS purchased 309,517 of such shares. Following such purchases, BCLS holds 8,066,113 shares of Common Stock and BCIPLS holds 825,645 shares of Common Stock. Bain Capital Life Sciences Partners, LP ("BCLSP") is the general partner of BCLS. As a result, BCLSP may be deemed to share voting and dispositive power with respect to the shares of Common Stock held by BCLS. BCLSP disclaims beneficial ownership of such securities except to the extent of its pecuniary interest therein. Bain Capital Life Sciences Investors, LLC ("BCLSI"), whose managers are Jeffrey Schwartz and Adam Koppel, is the general partner of BCLSP and governs the investment strategy and decision-making process with respect to investments held by BCIPLS, whose general partner is Boylston Coinvestors, LLC. As a result, each of BCLSI, Mr. Schwartz and Dr. Koppel may be deemed to share voting and dispositive power with respect to the shares of Common Stock held by the Bain Capital Life Sciences Entities. BCLSI, Mr. Schwartz and Dr. Koppel each disclaim beneficial ownership of such securities except to the extent of their pecuniary interest therein. Adam Koppel is a director of the Issuer. Bain Capital Life Sciences Investors, LLC, By: /s/ Adam Koppel, Title: Managing Director 2020-10-27 Bain Capital Life Sciences Partners, LP, By: Bain Capital Life Sciences Investors, LLC, its general partner, By: /s/ Adam Koppel, Title: Managing Director 2020-10-27 Bain Capital Life Sciences Fund, L.P., By: Bain Capital Life Sciences Partners, LP, its general partner, By: Bain Capital Life Sciences Investors, LLC, its general partner, By: /s/ Adam Koppel, Title: Managing Director 2020-10-27 BCIP Life Sciences Associates, LP, By: Boylston Coinvestors, LLC, its general partner, By: /s/ Adam Koppel, Title: Authorized Signatory 2020-10-27 /s/ Jeffrey Schwartz 2020-10-27 /s/ Adam Koppel 2020-10-27