X0306 4 2020-11-19 0 0001640455 Jounce Therapeutics, Inc. JNCE 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 0001192603 STARR KEVIN P 29 NEWBURY STREET, 3RD FLOOR BOSTON MA 02116 0 0 1 0 0001192595 TEPPER ROBERT I 29 NEWBURY STREET, 3RD FLOOR BOSTON MA 02116 0 0 1 0 0001180428 LEVIN MARK J 29 NEWBURY STREET, 3RD FLOOR BOSTON MA 02116 0 0 1 0 Common Stock 2020-11-19 4 S 0 15000 7.005 D 9200349 D Common Stock 53597 D Common Stock 53592 D Common Stock 53599 D 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 the 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. Third Rock Ventures III, L.P. ("TRV III") directly holds 3,048,780 shares of the Issuer's Common Stock. The general partner of TRV III is Third Rock Ventures GP III, L.P. ("TRV GP III"). The general partner of TRV GP III is TRV GP III, LLC ("TRV GP III LLC"). The individual managers of TRV GP III LLC are Levin, Starr and Tepper. Each of TRV GP III, TRV GP III LLC, Levin, Starr and Tepper disclaims beneficial ownership of the 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. The shares are directly held by Levin. The shares are directly held by Starr. The shares are directly held by Tepper. /s/ Kevin Gillis, Chief Operating 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. 2020-11-23 /s/ Kevin Gillis, Chief Operating Officer of TRV GP II, LLC, general partner of Third Rock Ventures GP II, L.P. 2020-11-23 /s/ Kevin Gillis, Chief Operating Officer of TRV GP II, LLC 2020-11-23 /s/ Kevin Gillis, by power of attorney for Kevin Starr 2020-11-23 /s/ Kevin Gillis, by power of attorney for Dr. Robert Tepper 2020-11-23 /s/ Kevin Gillis, by power of attorney for Mark Levin 2020-11-23