X0306 4 2021-03-23 0 0001707502 Solid Biosciences Inc. SLDB 0001578965 Koppel Adam C/O BAIN CAPITAL LIFE SCIENCES INVESTORS LLC, 200 CLARENDON STREET BOSTON MA 02116 1 0 0 0 Common Stock 2021-03-23 4 A 0 869565 5.75 A 7929918 I See footnotes Represents shares of common stock held directly by BCLS SB Investco, LP ("BCLS"). Bain Capital Life Sciences Investors, LLC, whose managers are Jeffrey Schwartz and Adam Koppel, is the general partner of Bain Capital Life Sciences Partners, LP, which is the general partner of BCLS. As a result, Dr. Koppel may be deemed to share voting and dispositive power with respect to the shares of common stock held by BCLS. Dr. Koppel disclaims beneficial ownership of such securities except to the extent of his pecuniary interest therein. On March 23, 2021, BCLS purchased 869,565 shares of common stock of the Issuer at a price per share of $5.75, pursuant to an underwritten public offering. /s/ Adam Koppel 2021-03-25