X0306 4 2018-08-22 0 0001434418 CONSTELLATION PHARMACEUTICALS INC CNST 0001408591 THIRD ROCK VENTURES LP 29 NEWBURY STREET, 3RD FLOOR BOSTON MA 02116 0 0 1 0 0001578976 Third Rock Ventures GP, L.P. 29 NEWBURY STREET, 3RD FLOOR BOSTON MA 02116 0 0 1 0 0001578973 TRV GP, 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 Common Stock 2018-08-22 4 X 0 51032 1.55 A 3034083 D Warrant (right to buy) 1.55 2018-08-22 4 X 0 51032 0.00 D 2021-05-24 Common Stock 51032 0 D These securities are directly held by Third Rock Ventures, L.P. ("TRV"). The general partner of TRV is Third Rock Ventures GP, L.P. ("TRV GP"). The general partner of TRV GP is TRV GP, LLC ("TRV GP LLC"). The individual managers of TRV GP LLC are Mark Levin ("Levin"), Kevin Starr ("Starr") and Dr. Robert Tepper ("Tepper"). Each of TRV GP, TRV GP 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 warrant was fully exercisable upon grant. /s/ Kevin Gillis, Chief Financial Officer of TRV GP, LLC, general partner of Third Rock Ventures GP, L.P., general partner of Third Rock Ventures, L.P. 2018-08-24 /s/ Kevin Gillis, Chief Financial Officer of TRV GP, LLC, general partner of Third Rock Ventures GP, L.P. 2018-08-24 /s/ Kevin Gillis, Chief Financial Officer of TRV GP, LLC 2018-08-24 /s/ Kevin Gillis by power of attorney for Mark Levin 2018-08-24 /s/ Kevin Gillis by power of attorney for Kevin Starr 2018-08-24