X0206 3 2017-11-01 0 0001624658 Allena Pharmaceuticals, Inc. ALNA 0001488495 Third Rock Ventures II, L.P. C/O THIRD ROCK VENTURES, LLC 29 NEWBURY STREET, 3RD FLOOR BOSTON MA 02116 0 0 1 0 0001614061 Third Rock Ventures GP II, L.P. 29 NEWBURY STREET, 3RD FLOOR BOSTON MA 02116 0 0 1 0 0001614073 TRV GP II, LLC 29 NEWBURY STREET, 3RD FLOOR BOSTON MA 02116 0 0 1 0 0001180428 LEVIN MARK J C/O THIRD ROCK VENTURES, LLC 29 NEWBURY STREET, 3RD FLOOR BOSTON MA 02116 0 0 1 0 0001192603 STARR KEVIN P C/O THIRD ROCK VENTURES, LLC 29 NEWBURY STREET, 3RD FLOOR BOSTON MA 02116 0 0 1 0 Series A Preferred Stock Common Stock 1466805 D Series B Preferred Stock Common Stock 1109159 D Each share of Series A Preferred Stock is convertible into Common Stock on a 4.174-for-one basis at any time at the holder's election, and automatically upon the closing of the Issuer's initial public offering, and has no expiration date. These shares are directly held by Third Rock Ventures II, L.P. ("TRV II"). The general partner of TRV II is Third Rock Ventures GP II, L.P. ("TRV GP II"). The general partner of TRV GP II is TRV GP II, LLC ("TRV GP II LLC"). The individual managers of TRV GP II LLC are Mark Levin ("Levin"), Kevin Starr ("Starr") and Dr. Robert Tepper ("Tepper"). Each of TRV GP II, TRV GP II LLC, Levin, Starr and Tepper disclaims beneficial ownership of these shares except to the extent of its or his pecuniary interest therein, if any, and this report shall not be deemed an admission that it or he is the beneficial owner of such shares. Each share of Series B Preferred Stock is convertible into Common Stock on a 4.174-for-one basis at any time at the holder's election, and automatically upon the closing of the Issuer's initial public offering, and has no expiration date. /s/ Kevin Gillis, Chief Financial Officer of TRV GP II, LLC, general partner of Third Rock Ventures GP II, L.P., general partner of Third Rock Ventures II, L.P. 2017-11-01 /s/ Kevin Gillis, Chief Financial Officer of TRV GP II, LLC, general partner of Third Rock Ventures GP II, L.P. 2017-11-01 /s/ Kevin Gillis, Chief Financial Officer of TRV GP II, LLC 2017-11-01 /s/ Kevin Gillis by power of attorney for Mark Levin 2017-11-01 /s/ Kevin Gillis by power of attorney for Kevin Starr 2017-11-01