X0206 3 2020-01-14 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 Common Stock 5558425 I See Footnotes Bain Capital Life Sciences Partners, LP ("BCLSP") is the general partner of Bain Capital Life Sciences Fund, L.P. ("BCLS"). As a result, BCLSP may be deemed to share voting and dispositive power with respect to the securities held by BCLS. BCLS holds 5,042,297 shares of Common Stock. BCLSP disclaims beneficial ownership of such securities except to the extent of its pecuniary interest therein. BCIP Life Sciences Associates, LP ("BCIP LS" and, together with BCLS, the "Bain Life Sciences Entities"), whose general partner is Boylston Coinvestors, LLC, holds 516,128 shares of Common Stock. 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 BCIP LS. As a result, each of BCLSI, Mr. Schwartz and Dr. Koppel may be deemed to share voting and dispositive power with respect to the securities held by the Bain 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. BAIN CAPITAL LIFE SCIENCES INVESTORS, LLC, By: /s/ Adam Koppel, Name: Adam Koppel, Title: Managing Director 2020-01-16 BAIN CAPITAL LIFE SCIENCES PARTNERS, LP, By: Bain Capital Life Sciences Investors, LLC, its general partner, By: /s/ Adam Koppel, Name: Adam Koppel, Title: Managing Director 2020-01-16 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, Name: Adam Koppel, Title: Managing Director 2020-01-16 BCIP LIFE SCIENCES ASSOCIATES, LP, By: Boylston Coinvestors, LLC, its general partner, By: /s/ Adam Koppel, Name: Adam Koppel, Title: Authorized Signatory 2020-01-16 /s/ Jeffrey Schwartz 2020-01-16