X0206 3 2020-06-02 0 0001746473 PLIANT THERAPEUTICS, INC. PLRX 0001569705 Third Rock Ventures III, L.P. C/O THIRD ROCK VENTURES, LLC, 29 NEWBURY STREET, 3RD FLOOR BOSTON MA 02116 0 0 1 0 0001637300 Third Rock Ventures GP III, L.P. 29 NEWBURY STREET, 3RD FLOOR BOSTON MA 02116 0 0 1 0 0001637299 TRV GP III, 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 0001192595 TEPPER ROBERT I C/O THIRD ROCK VENTURES, LLC 29 NEWBURY STREET, 3RD FLOOR BOSTON MA 02116 0 0 1 0 0001688327 Third Rock Ventures IV, L.P. 29 NEWBURY STREET, 3RD FLOOR BOSTON MA 02116 0 0 1 0 0001688326 Third Rock Ventures GP IV, L.P. 29 NEWBURY STREET, 3RD FLOOR BOSTON MA 02116 0 0 1 0 0001688325 TRV GP IV, LLC 29 NEWBURY STREET, 3RD FLOOR BOSTON MA 02116 0 0 1 0 Common Stock 279720 D Series A Preferred Stock Common Stock 5559440 D Series A Preferred Stock Common Stock 2132867 I See footnotes These shares are directly held by Third Rock Ventures III, L.P. ("TRV III"). 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 Mark Levin ("Levin"), Kevin Starr ("Starr") and Dr. Robert Tepper ("Tepper"). Each of TRV GP III, TRV GP III 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 A Preferred Stock is convertible on a 7.15-for-1 basis into Common Stock at any time at the election of the Reporting Person and will automatically convert upon the closing of the Issuer's initial public offering into the number of shares of the Issuer's Common Stock shown in column 3 without payment or further consideration. The Series A Preferred Stock has no expiration date. These shares are directly held by Third Rock Ventures IV, L.P. ("TRV IV").. The general partner of TRV IV is Third Rock Ventures GP IV, L.P. ("TRV GP IV"). The general partner of TRV GP IV is TRV GP IV, LLC ("TRV GP IV LLC"). Each of TRV GP IV and TRV GP IV LLC disclaims beneficial ownership of these shares except to the extent of its 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 of Reporting Persons disclaims the existence of a Section 13(d) "group" as between the TRV III related parties and the TRV IV related parties and this report shall not be deemed an admission that any of such parties is or may be part of such a group with any of the other parties. /s/ Kevin Gillis, Chief Operating Officer of TRV GP III, LLC, general partner of Third Rock Ventures GP III, L.P., general partner of Third Rock Ventures III, L.P. 2020-06-02 /s/ Kevin Gillis, Chief Operating Officer of TRV GP III, LLC, general partner of Third Rock Ventures GP III, L.P. 2020-06-02 /s/ Kevin Gillis, Chief Operating Officer of TRV GP III, LLC 2020-06-02 /s/ Kevin Gillis by power of attorney for Mark Levin 2020-06-02 /s/ Kevin Gillis by power of attorney for Kevin Starr 2020-06-02 /s/ Kevin Gillis by power of attorney for Dr. Robert Tepper 2020-06-02 /s/ Kevin Gillis, Chief Operating Officer of TRV GP IV, LLC, general partner of Third Rock Ventures GP IV, L.P., general partner of Third Rock Ventures IV, L.P. 2020-06-02 /s/ Kevin Gillis, Chief Operating Officer of TRV GP IV, LLC, general partner of Third Rock Ventures GP IV, L.P. 2020-06-02 /s/ Kevin Gillis, Chief Operating Officer of TRV GP IV, LLC 2020-06-02