X0306 4 2020-01-14 0 0001674365 Aptinyx Inc. APTX 0001578965 Koppel Adam C/O BAIN CAPITAL LIFE SCIENCES INVESTORS LLC, 200 CLARENDON STREET BOSTON MA 02116 1 0 1 0 Common Stock 2020-01-14 4 P 0 3333333 3.00 A 5558425 I See Footnotes On January 14, 2020, the Bain Capital Life Sciences Fund, L.P. ("BCLS") and BCIP Life Sciences Associates, LP ("BCIP LS" and, collectively, the "Bain Life Sciences Entities") purchased, in the aggregate, 3,333,333 shares of Common Stock of the Issuer at a price of $3.00 per share, pursuant to an underwritten public offering. Represents shares of Common Stock held directly by the Bain Life Sciences Entities. Bain Capital Life Sciences Investors, LLC ("BCLSI") is the ultimate general partner of BCLS and governs the investment strategy and decision making process with respect to investments held by BCIP LS. Dr. Koppel is a manager of BCLSI. By virtue of the relationships described in this footnote, 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 except to the extent of his pecuniary interest therein. /s/ Adam Koppel 2020-01-16